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Sample records for air bubble formation

  1. 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. PMID:26382942

  2. 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.

  3. 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.

  4. Blood platelet-derived microparticles release and bubble formation after an open-sea air dive.

    PubMed

    Pontier, Jean-Michel; Gempp, Emmanuel; Ignatescu, Mihaela

    2012-10-01

    Bubble-induced platelet aggregation offers an index for evaluating decompression severity in humans and in a rat model of decompression sickness. Endothelial cells, blood platelets, or leukocytes shed microparticles (MP) upon activation and during cell apoptosis. The aim was to study blood platelet MP (PMP) release and bubble formation after a scuba-air dive in field conditions. Healthy, experienced divers were assigned to 1 experimental group (n = 10) with an open-sea air dive to 30 msw for 30 min and 1 control group (n = 5) during head-out water immersion for the same period. Bubble grades were monitored with a pulsed doppler according to Kissman Integrated Severity Score (KISS). Blood samples for platelet count (PC) and PMP (annexin V and CD41) were taken 1 h before and after exposure in both groups. The result showed a decrease in post-dive PC compared with pre-dive values in experimental group with no significant change in the control group. We observed a significant increase in PMP values after the dive while no change was revealed in the control group. There was a significant positive correlation between the PMP values after the dive and the KISS bubble score. The present study highlighted a relationship between the post-dive decrease in PC, platelet MP release, and bubble formation. Release of platelet MPs could reflect bubble-induced platelet aggregation and could play a key role in alteration of the coagulation. Further studies must investigate endothelial and leukocyte MP release in the same field conditions.

  5. 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

  6. Simulation study on the effect of air distribution on the bed height and bubble formation in bubbling fluidization reactor

    NASA Astrophysics Data System (ADS)

    bin Ibrahim, Muhamad Hilmee; Mohd Najib, Nur Khadijah; Karuppanan, Saravanan; Sinnathambi, Chandra Mohan

    2012-09-01

    This paper describes the numerical study on the effect of inlet air distribution in the Bubbling Fluidized Bed (BFB) riser of diameter 0.18 m and 1.44 m of length using a 3-hole orifice plate. A 2D model has been developed and meshed using Gambit software version 2.4.6 and was simulated using CFD code, fluent version 6.3. Laminar model has been used for the modeling and Eulerian-Eulerian multiphase model coupled with kinetic theory of granular flow was employed. For the drag, Gidaspow Drag Model was used to calculate the phase interaction between the gas and solid particles. The simulation results obtained for the validation purpose showed good agreement with the results available in the literature. The model with orifice plate gives a better and clear bubble shape with improved turbulent and better mixing compared to the model without the orifice plate. The model with orifice plate is also more realistic and ideal as compared to the model without the orifice plate.

  7. Numerical Simulation of Air Bubble Characteristics in Stationary Water

    NASA Astrophysics Data System (ADS)

    Zhang, C. X.; Wang, Y. X.

    The motion of air bubble in water plays a key role in such diverse aspects as air bubble curtain breakwater, air curtain drag reduction, air cushion isolation, weakening the shock wave in water by air bubble screen, etc. At present, the research on air bubble behaviors can be subdivided into several processes: air bubble formation from submerged orifices; interaction and coalescence during the ascending. The work presented in this paper focuses on numerical simulation of air bubble characteristics in stationary water, for example, air bubble formation, the ascending speed, the departing period, and so on. A series of models to simulate the characteristics of air bubble are developed by the VOF method in the two phase flow module of FLUENT. The numerical simulation results are consistent with the theoretical characteristics of air bubble in many aspects. So it is concluded that numerical simulation of air bubble characteristics in stationary water based on FLUENT is feasible. Due to the fact that the characteristics of air bubble are complicated questions, it is important that study on the air bubble behaviors in stationary water should be conducted on deeply.

  8. Bubble formation in microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1994-01-01

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

  9. Bubble formation in additive manufacturing of glass

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  10. Bubble formation in microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1996-01-01

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

  11. Shock formation within sonoluminescence bubbles

    SciTech Connect

    Vuong, V.Q.; Szeri, A.J.; Young, D.A.

    1999-01-01

    A strong case has been made by several authors that sharp, spherically symmetric shocks converging on the center of a spherical bubble driven by a strong acoustic field give rise to rapid compression and heating that produces the brief flash of light known as sonoluminescence. The formation of such shocks is considered. It is found that, although at the main collapse the bubble wall does indeed launch an inwardly-traveling compression wave, and although the subsequent reflection of the wave at the bubble center produces a very rapid temperature peak, the wave is prevented from steepening into a sharp shock by an adverse gradient in the sound speed caused by heat transfer. It is shown that the mathematical characteristics of the flow can be prevented from accumulating into a shock front by this adverse sound speed gradient. A range of results is presented for a variety of bubble ambient radii and sound field amplitudes suggested by experiments. The time scale of the peak temperature in the bubble is set by the dynamics of the compression wave: this is typically in the range 100{endash}300 ps (FWHM) in concert with recent measurements of the sonoluminescence pulse width. {copyright} {ital 1999 American Institute of Physics.}

  12. Air bubble bursting effect of lotus leaf.

    PubMed

    Wang, Jingming; Zheng, Yongmei; Nie, Fu-Qiang; Zhai, Jin; Jiang, Lei

    2009-12-15

    In this paper, a phenomenon of air bubbles quickly bursting within several milliseconds on a "self-cleaning" lotus leaf was described. This observation prompted the synthesis of artificial surfaces similar to that of the lotus leaf. The artificial leaf surfaces, prepared by photolithography and wet etching, showed a similar air bubble bursting effect. Smooth and rough silicon surfaces with an ordered nanostructure or patterned microstructure were utilized to study the contribution of the micro/nano hierarchical structures to this phenomenon of air bubble bursting. Air bubbles were found to burst on some superhydrophobic surfaces with microstructure (within 220 ms). However, air bubbles burst much more rapidly (within 13 ms) on similar surfaces with micro/nanostructure. The height, width, and spacing of hierarchical structures could also affect air bubble bursting, and the effect of the height was more obvious. When the height of hierarchical structures was around the height found in natural lotus papillae, the width and spacing were significant for air bubble bursting. An original model was proposed to further evaluate the reason why the micro/nano hierarchical rough structures had an excellent air bubble bursting effect, and the validity of the model was theoretically demonstrated.

  13. Body fat does not affect venous bubble formation after air dives of moderate severity: theory and experiment.

    PubMed

    Schellart, Nico A M; van Rees Vellinga, Tjeerd P; van Hulst, Rob A

    2013-03-01

    For over a century, studies on body fat (BF) in decompression sickness and venous gas embolism of divers have been inconsistent. A major problem is that age, BF, and maximal oxygen consumption (Vo2max) show high multicollinearity. Using the Bühlmann model with eight parallel compartments, preceded by a blood compartment in series, nitrogen tensions and loads were calculated with a 40 min/3.1 bar (absolute) profile. Compared with Haldanian models, the new model showed a substantial delay in N2 uptake and (especially) release. One hour after surfacing, an increase of 14-28% in BF resulted in a whole body increase of the N2 load of 51%, but in only 15% in the blood compartment. This would result in an increase in the bubble grade of only 0.01 Kisman-Masurel (KM) units at the scale near KM = I-. This outcome was tested indirectly by a dry dive simulation (air breathing) with 53 male divers with a small range in age and Vo2max to suppress multicollinearity. BF was determined with the four-skinfold method. Precordial Doppler bubble grades determined at 40, 80, 120, and 160 min after surfacing were used to calculate the Kisman Integrated Severity Score and were also transformed to the logarithm of the number of bubbles/cm(2) (logB). The highest of the four scores yielded logB = -1.78, equivalent to KM = I-. All statistical outcomes of partial correlations with BF were nonsignificant. These results support the model outcomes. Although this and our previous study suggest that BF does not influence venous gas embolism (Schellart NAM, van Rees Vellinga TP, van Dijk FH, Sterk W. Aviat Space Environ Med 83: 951-957, 2012), more studies with different profiles under various conditions are needed to establish whether BF remains (together with age and Vo2max) a basic physical characteristic or will become less important for the medical examination and for risk assessment.

  14. Understanding air-gun bubble behavior

    SciTech Connect

    Johnson, D.T. )

    1994-11-01

    An air-gun bubble behaves approximately as a spherical bubble of an ideal gas in an infinite volume of practically incompressible water. With this simplification, the equation of bubble motion and its far-field signature is more understandable than with the more exact theory commonly cited in the literature. The terms of the equation of bubble motion are explained using elementary physics and mathematics, computation of numerical results is outlined, and an example signature is shown. An air-gun bubble is analogous to a simple harmonic oscillator consisting of a mass on a spring, with an equivalent mass equal three times that of the water displaced by the bubble, and air pressure following an ideal gas law corresponding to a spring. With this understanding, one is prepared to deal with the effects of interactions among air guns and with the high-order terms and other features that must be included to model the air-gun signature of actual seismic source arrays.

  15. Plasma formation in underwater gas bubbles

    NASA Astrophysics Data System (ADS)

    Sommers, B. S.; Foster, J. E.

    2014-02-01

    The generation of plasma in underwater gas bubbles offers the potential to produce large volume plasma in water while minimizing electrode erosion. Such attributes are desirable for the design of plasma-based water purification systems. In this work, gas bubbles of diameter 0.4-0.7 mm were trapped in the node of a 26.4 kHz underwater acoustic standing wave and pulsed with voltages in the range 10-14 kV. Plasma formation in trapped, isolated bubbles was observed to occur through two separate pathways: (1) plasma generated in the bubble through impact by a liquid streamer and (2) plasma generated in the bubble due solely to the applied electric field. The former case demonstrates the mechanism of so-called streamer hopping in which the discharge transitions from a water streamer to a gaseous surface streamer. Perturbations of the bubble's fluid boundary due to the streamer are also discussed.

  16. Interaction between Air Bubbles and Superhydrophobic Surfaces in Aqueous Solutions.

    PubMed

    Shi, Chen; Cui, Xin; Zhang, Xurui; Tchoukov, Plamen; Liu, Qingxia; Encinas, Noemi; Paven, Maxime; Geyer, Florian; Vollmer, Doris; Xu, Zhenghe; Butt, Hans-Jürgen; Zeng, Hongbo

    2015-07-01

    Superhydrophobic surfaces are usually characterized by a high apparent contact angle of water drops in air. Here we analyze the inverse situation: Rather than focusing on water repellency in air, we measure the attractive interaction of air bubbles and superhydrophobic surfaces in water. Forces were measured between microbubbles with radii R of 40-90 μm attached to an atomic force microscope cantilever and submerged superhydrophobic surfaces. In addition, forces between macroscopic bubbles (R = 1.2 mm) at the end of capillaries and superhydrophobic surfaces were measured. As superhydrophobic surfaces we applied soot-templated surfaces, nanofilament surfaces, micropillar arrays with flat top faces, and decorated micropillars. Depending on the specific structure of the superhydrophobic surfaces and the presence and amount of entrapped air, different interactions were observed. Soot-templated surfaces in the Cassie state showed superaerophilic behavior: Once the electrostatic double-layer force and a hydrodynamic repulsion were overcome, bubbles jumped onto the surface and fully merged with the entrapped air. On nanofilaments and micropillar arrays we observed in addition the formation of sessile bubbles with finite contact angles below 90° or the attachment of bubbles, which retained their spherical shape.

  17. EXPERIMENTAL BUBBLE FORMATION IN A LARGE SCALE SYSTEM FOR NEWTONIAN AND NONNEWTONIAN FLUIDS

    SciTech Connect

    Leishear, R; Michael Restivo, M

    2008-06-26

    The complexities of bubble formation in liquids increase as the system size increases, and a photographic study is presented here to provide some insight into the dynamics of bubble formation for large systems. Air was injected at the bottom of a 28 feet tall by 30 inch diameter column. Different fluids were subjected to different air flow rates at different fluid depths. The fluids were water and non-Newtonian, Bingham plastic fluids, which have yield stresses requiring an applied force to initiate movement, or shearing, of the fluid. Tests showed that bubble formation was significantly different in the two types of fluids. In water, a field of bubbles was formed, which consisted of numerous, distributed, 1/4 to 3/8 inch diameter bubbles. In the Bingham fluid, large bubbles of 6 to 12 inches in diameter were formed, which depended on the air flow rate. This paper provides comprehensive photographic results related to bubble formation in these fluids.

  18. Effect of an entrained air bubble on the acoustics of an ink channel.

    PubMed

    Jeurissen, Roger; de Jong, Jos; Reinten, Hans; van den Berg, Marc; Wijshoff, Herman; Versluis, Michel; Lohse, Detlef

    2008-05-01

    Piezo-driven inkjet systems are very sensitive to air entrapment. The entrapped air bubbles grow by rectified diffusion in the ink channel and finally result in nozzle failure. Experimental results on the dynamics of fully grown air bubbles are presented. It is found that the bubble counteracts the pressure buildup necessary for the droplet formation. The channel acoustics and the air bubble dynamics are modeled. For good agreement with the experimental data it is crucial to include the confined geometry into the model: The air bubble acts back on the acoustic field in the channel and thus on its own dynamics. This two-way coupling limits further bubble growth and thus determines the saturation size of the bubble.

  19. Dew and bubble point properties of air

    NASA Astrophysics Data System (ADS)

    Penoncello, S. G.; Jacobsen, R. T.; Lemmon, E. W.

    Four new ancillary functions for the calculation of pressures and densities of states at the bubble and dew points of air are presented. These functions were developed using experimental data and calculated values. The experimental data for the bubble and dew point pressures and densities of air are summarized and evaluated. In the absence of experimental data at high-pressure phase equilibrium states, a Leung-Griffiths model modified for ternary mixtures was used to calculate pseudo-data. This ternary mixture model was also used to calculate new values for the critical point, maxcondenbar and maxcondentherm for air. The calculated properties at the maxcondentherm were used as reducing parameters in the ancillary functions. Graphical comparisons of the ancillary equations to the experimental data and pseudo-data are presented to justify the estimated accuracies of the new ancillary functions. The equations presented here have been used to calculate dew and bubble point pressures and densities for the determination of the phase boundary for a wide-range equation of state for air treated as a pseudo-pure fluid.

  20. Decompression-induced bubble formation in salmonids: comparison to gas bubble disease.

    PubMed

    Beyer, D L; D'Aoust, B G; Smith, L S

    1976-12-01

    The relationship of gas bubble disease (GBD) in fish to decompression-induced bubble formation was investigated with salmonids. Acute bioassays were used to determine equilibration times for critical effects in fish decompressed from depths to 200 fsw. It was found that equilibration of critical tissues was complete in 60-90 min. Salmonids and air-breathers are sensitive to decompressions at similar levels of supersaturation if elimination of excess gas following decompression is unrestricted. However, if elimination is restricted, bubble formation and growth increase accordingly. Tests with mixtures of He-O2, Ar-O2, N2-O2 (80% inert gas: 20% O2) and pure oxygen demonstrated that gas solubility as well as supersaturation (delta P), pressure ratio (initial pressure: final pressure), and absolute pressure must be considered in setting tolerance limits for any decompression. Gases with higher solubility are more likely to produce bubbles upon decompression. Oxygen, however, does not follow this relationship until higher pressures are reached, probably owing to its function in metabolism and in binding with hemoglobin. Tissue responses observed in both GBD and decompressed fish involved similar pathological effects at acute exposures. The circulatory system was consistently affected by bubbles that occluded vessels and blocked flow through the heart.

  1. Freeze/Thaw-induced embolism: probability of critical bubble formation depends on speed of ice formation.

    PubMed

    Sevanto, Sanna; Holbrook, N Michele; Ball, Marilyn C

    2012-01-01

    Bubble formation in the conduits of woody plants sets a challenge for uninterrupted water transportation from the soil up to the canopy. Freezing and thawing of stems has been shown to increase the number of air-filled (embolized) conduits, especially in trees with large conduit diameters. Despite numerous experimental studies, the mechanisms leading to bubble formation during freezing have not been addressed theoretically. We used classical nucleation theory and fluid mechanics to show which mechanisms are most likely to be responsible for bubble formation during freezing and what parameters determine the likelihood of the process. Our results confirm the common assumption that bubble formation during freezing is most likely due to gas segregation by ice. If xylem conduit walls are not permeable to the salts expelled by ice during the freezing process, osmotic pressures high enough for air seeding could be created. The build-up rate of segregated solutes in front of the ice-water interface depends equally on conduit diameter and freezing velocity. Therefore, bubble formation probability depends on these variables. The dependence of bubble formation probability on freezing velocity means that the experimental results obtained for cavitation threshold conduit diameters during freeze/thaw cycles depend on the experimental setup; namely sample size and cooling rate. The velocity dependence also suggests that to avoid bubble formation during freezing trees should have narrow conduits where freezing is likely to be fast (e.g., branches or outermost layer of the xylem). Avoidance of bubble formation during freezing could thus be one piece of the explanation why xylem conduit size of temperate and boreal zone trees varies quite systematically.

  2. In Vitro Observation of Air Bubbles during Delivery of Various Detachable Aneurysm Embolization Coils

    PubMed Central

    Hwang, Seon Moon; Lim, Ok Kyun; Kim, Jae Kyun

    2012-01-01

    Objective Device- or technique-related air embolism is a drawback of various neuro-endovascular procedures. Detachable aneurysm embolization coils can be sources of such air bubbles. We therefore assessed the formation of air bubbles during in vitro delivery of various detachable coils. Materials and Methods A closed circuit simulating a typical endovascular coiling procedure was primed with saline solution degassed by a sonification device. Thirty commercially available detachable coils (7 Axium, 4 GDCs, 5 MicroPlex, 7 Target, and 7 Trufill coils) were tested by using the standard coil flushing and delivery techniques suggested by each manufacturer. The emergence of any air bubbles was monitored with a digital microscope and the images were captured to measure total volumes of air bubbles during coil insertion and detachment and after coil pusher removal. Results Air bubbles were seen during insertion or removal of 23 of 30 coils (76.7%), with volumes ranging from 0 to 23.42 mm3 (median: 0.16 mm3). Air bubbles were observed most frequently after removal of the coil pusher. Significantly larger amounts of air bubbles were observed in Target coils. Conclusion Variable volumes of air bubbles are observed while delivering detachable embolization coils, particularly after removal of the coil pusher and especially with Target coils. PMID:22778562

  3. Simple method for high-performance stretchable composite conductors with entrapped air bubbles.

    PubMed

    Hwang, Hyejin; Kim, Dae-Gon; Jang, Nam-Su; Kong, Jeong-Ho; Kim, Jong-Man

    2016-12-01

    We integrate air bubbles into conductive elastic composite-based stretchable conductors to make them mechanically less stiff and electrically more robust against physical deformations. A surfactant facilitates both the formation and maintenance of air bubbles inside the elastic composites, leading to a simple fabrication of bubble-entrapped stretchable conductors. Based on the unique bubble-entrapped architecture, the elastic properties are greatly enhanced and the resistance change in response to tensile strains can clearly be controlled. The bubble-entrapped conductor achieves ~80 % elongation at ~3.4 times lower stress and ~44.8 % smaller change in the electrical resistance at 80 % tensile strain, compared to bare conductor without air bubbles.

  4. Air bubble migration rates as a proxy for bubble pressure distribution in ice cores

    NASA Astrophysics Data System (ADS)

    Dadic, Ruzica; Schneebeli, Martin; Bertler, Nancy

    2015-04-01

    Air bubble migration can be used as a proxy to measure the pressure of individual bubbles and can help constrain the gradual close-off of gas bubbles and the resulting age distribution of gases in ice cores. The close-off depth of single bubbles can vary by tens of meters, which leads to a distribution of pressures for bubbles at a given depth. The age distribution of gases (along with gas-age-ice-age differences) decreases the resolution of the gas level reconstructions from ice cores and limits our ability to determine the phase relationship between gas and ice, and thus, the impact of rapid changes of greenhouse gases on surface temperatures. For times of rapid climate change, including the last 150 years, and abrupt climate changes further back in the past, knowledge of the age distribution of the gases trapped in air bubbles will enable us to refine estimates of atmospheric changes. When a temperature gradient is applied to gas bubbles in an ice sample, the bubbles migrate toward warmer ice. This motion is caused by sublimation from the warm wall and subsequent frost deposition on the cold wall. The migration rate depends on ice temperature and bubble pressure and is proportional to the temperature gradient. The spread in migration rates for bubbles in the same samples at given temperatures should therefore reflect the variations in bubble pressures within a sample. Air bubbles with higher pressures would have been closed off higher in the firn column and thus have had time to equilibrate with the surrounding ice pressure, while air bubbles that have been closed off recently would have pressures that are similar to todays atmospheric pressure above the firn column. For ice under pressures up to ~13-16 bar, the pressure distribution of bubbles from a single depth provides a record of the trapping function of air bubbles in the firn column for a certain time in the past. We will present laboratory experiments on air bubble migration, using Antarctic ice core

  5. Skin formation and bubble growth during drying process of polymer solution.

    PubMed

    Arai, S; Doi, M

    2012-07-01

    When a polymer solution with volatile solvent is dried, skins are often formed at the surface of the solution. It has been observed that after the skin is formed, bubbles often appear in the solution. We conducted experiments to clarify the relation between the skin formation and the bubble formation. We measured the time dependence of the thickness of the skin layer, the size of the bubbles, and the pressure in the solution. From our experiments, we concluded that i) the gas in the bubble is a mixture of solvent vapor and air dissolved in the solution, ii) the bubble nucleation is assisted by the pressure decrease in the solution covered by the skin layer, and iii) the growth of the bubbles is diffusion limited, mainly limited by the diffusion of air molecules dissolved in the solution.

  6. Computer simulation of bubble formation.

    SciTech Connect

    Insepov, Z.; Bazhirov, T.; Norman, G.; Stegailov, V.; Mathematics and Computer Science; Institute for High Energy Densities of Joint Institute for High Temperatures of RAS

    2007-01-01

    Properties of liquid metals (Li, Pb, Na) containing nanoscale cavities were studied by atomistic Molecular Dynamics (MD). Two atomistic models of cavity simulation were developed that cover a wide area in the phase diagram with negative pressure. In the first model, the thermodynamics of cavity formation, stability and the dynamics of cavity evolution in bulk liquid metals have been studied. Radial densities, pressures, surface tensions, and work functions of nano-scale cavities of various radii were calculated for liquid Li, Na, and Pb at various temperatures and densities, and at small negative pressures near the liquid-gas spinodal, and the work functions for cavity formation in liquid Li were calculated and compared with the available experimental data. The cavitation rate can further be obtained by using the classical nucleation theory (CNT). The second model is based on the stability study and on the kinetics of cavitation of the stretched liquid metals. A MD method was used to simulate cavitation in a metastable Pb and Li melts and determine the stability limits. States at temperatures below critical (T < 0.5Tc) and large negative pressures were considered. The kinetic boundary of liquid phase stability was shown to be different from the spinodal. The kinetics and dynamics of cavitation were studied. The pressure dependences of cavitation frequencies were obtained for several temperatures. The results of MD calculations were compared with estimates based on classical nucleation theory.

  7. Insertion and confinement of air bubbles inside a liquid marble.

    PubMed

    Sun, Guanqing; Sheng, Yifeng; Ngai, To

    2016-01-14

    Nanoparticles at the air/liquid interface can serve as solid separating barriers to form stable foams or liquid marbles depending on the wettability of the nanoparticles. This paper presents an effect that enables the insertion and confinement of air bubbles inside a liquid marble, based on encapsulating an air bubble surrounded by surfactant molecules or hydrophilic particles. We have demonstrated that more than one bubble can be inserted and trapped inside one liquid marble so that liquid marbles can be divided into several separate compartments. The findings presented here may stimulate fundamental studies of this novel bubble-marble phenomenon, as well as developments of various practical applications.

  8. Influence of artificially generated air bubbles on a wave breaking

    NASA Astrophysics Data System (ADS)

    Merkoune, D.; Ezersky, A.; Abcha, N.; Amine, F.; Mouazé, D.

    2011-12-01

    We report experimental results on influence of air bubbles curtain on wave breaking. It was found that position of wave breaking point depends on bubble concentration in water. It was revealed that the effect of wave breaking is very sensitive to the concentration of air bubbles which are situated near free surface of water. We showed that small concentration of artificially created bubbles do not lead to additional dissipation of energy in surface waves but change sufficiently the position of breaking point. This phenomenon could synchronize the breaking of irregular surface waves in the ocean and lead to the generation of spatially inhomogeneous turbulence in the upper layer of the ocean.

  9. Cascades of popping bubbles along air/foam interfaces.

    PubMed

    Vandewalle, N; Lentz, J F

    2001-08-01

    We report image analysis of popping bubbles during the collapsing of two-dimensional (2D) and 3D aqueous foams. Although temporal and spatial correlations between successive popping bubbles within avalanches are emphasized, the breaking of a soap film at the air/foam interface seems to be independent of (i) the topology, (ii) the local curvature, and (iii) the size of the popping bubble. Possible mechanisms for cascades of pops are proposed and discussed. PMID:11497589

  10. 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.

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

    PubMed

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

    2013-05-01

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

  12. Electric Field Effects on an Injected Air Bubble at Detachment in a Low Gravity Environment

    NASA Technical Reports Server (NTRS)

    Iacona, Estelle; Herman, Cila; Chang, Shinan

    2002-01-01

    The objective of the study is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static and uniform electric field. Bubble formation and detachment were visualized and recorded in microgravity using a high-speed video camera. Bubble volume, dimensions and contact angle at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. Measured data and model predictions show good agreement, and indicate that the level of gravity and the electric field magnitude significantly affect bubble shape, volume and dimensions.

  13. Period adding cascades: experiment and modeling in air bubbling.

    PubMed

    Pereira, Felipe Augusto Cardoso; Colli, Eduardo; Sartorelli, José Carlos

    2012-03-01

    Period adding cascades have been observed experimentally/numerically in the dynamics of neurons and pancreatic cells, lasers, electric circuits, chemical reactions, oceanic internal waves, and also in air bubbling. We show that the period adding cascades appearing in bubbling from a nozzle submerged in a viscous liquid can be reproduced by a simple model, based on some hydrodynamical principles, dealing with the time evolution of two variables, bubble position and pressure of the air chamber, through a system of differential equations with a rule of detachment based on force balance. The model further reduces to an iterating one-dimensional map giving the pressures at the detachments, where time between bubbles come out as an observable of the dynamics. The model has not only good agreement with experimental data, but is also able to predict the influence of the main parameters involved, like the length of the hose connecting the air supplier with the needle, the needle radius and the needle length.

  14. Exercise and nitric oxide prevent bubble formation: a novel approach to the prevention of decompression sickness?

    PubMed

    Wisløff, Ulrik; Richardson, Russell S; Brubakk, Alf O

    2004-03-16

    Nitrogen dissolves in the blood during dives, but comes out of solution if divers return to normal pressure too rapidly. Nitrogen bubbles cause a range of effects from skin rashes to seizures, coma and death. It is believed that these bubbles form from bubble precursors (gas nuclei). Recently we have shown that a single bout of exercise 20 h, but not 48 h, before a simulated dive prevents bubble formation and protects rats from severe decompression sickness (DCS) and death. Furthermore, we demonstrated that administration of N(omega)-nitro-l-arginine methyl ester, a non-selective inhibitor of NO synthase (NOS), turns a dive from safe to unsafe in sedentary but not exercised rats. Therefore based upon previous data an attractive hypothesis is that it may be possible to use either exercise or NO-releasing agents before a dive to inhibit bubble formation and thus protect against DCS. Consequently, the aims of the present study were to determine whether protection against bubble formation in 'diving' rats was provided by (1) chronic and acute administration of a NO-releasing agent and (2) exercise less than 20 h prior to the dive. NO given for 5 days and then 20 h prior to a dive to 700 kPa lasting 45 min breathing air significantly reduced bubble formation and prevented death. The same effect was seen if NO was given only 30 min before the dive. Exercise 20 h before a dive suppressed bubble formation and prevented death, with no effect at any other time (48, 10, 5 and 0.5 h prior to the dive). Pre-dive activities have not been considered to influence the growth of bubbles and thus the risk of serious DCS. The present novel findings of a protective effect against bubble formation and death by appropriately timed exercise and an NO-releasing agent may form the basis of a new approach to preventing serious decompression sickness.

  15. Formation of bubbles in a multisection flow-focusing junction.

    PubMed

    Hashimoto, Michinao; Whitesides, George M

    2010-05-01

    The formation of bubbles in a flow-focusing (FF) junction comprising multiple rectangular sections is described. The simplest junctions comprise two sections (throat and orifice). Systematic investigation of the influence on the formation of bubbles of the flow of liquid and the geometry of the junction identifies regimes that generate monodisperse, bidisperse, and tridisperse trains of bubbles. The mechanisms by which these junctions form monodisperse and bidisperse bubbles are inferred from the shapes of the gas thread during breakup: these mechanisms differ primarily by the process in which the gas thread collapses in the throat and/or orifice. The dynamic self-assembly of bidisperse bubbles leads to unexpected groupings of bubbles during their flow along the outlet channel.

  16. Three-dimensionally ordered array of air bubbles in a polymer film

    NASA Technical Reports Server (NTRS)

    Srinivasarao, M.; Collings, D.; Philips, A.; Patel, S.; Brown, C. S. (Principal Investigator)

    2001-01-01

    We report the formation of a three-dimensionally ordered array of air bubbles of monodisperse pore size in a polymer film through a templating mechanism based on thermocapillary convection. Dilute solutions of a simple, coil-like polymer in a volatile solvent are cast on a glass slide in the presence of moist air flowing across the surface. Evaporative cooling and the generation of an ordered array of breath figures leads to the formation of multilayers of hexagonally packed water droplets that are preserved in the final, solid polymer film as spherical air bubbles. The dimensions of these bubbles can be controlled simply by changing the velocity of the airflow across the surface. When these three-dimensionally ordered macroporous materials have pore dimensions comparable to the wavelength of visible light, they are of interest as photonic band gaps and optical stop-bands.

  17. Featured Image: A Bubble Triggering Star Formation

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-05-01

    This remarkable false-color, mid-infrared image (click for the full view!) was produced by the Wide-field Infrared Survey Explorer (WISE). It captures a tantalizing view of Sh 2-207 and Sh 2-208, the latter of which is one of the lowest-metallicity star-forming regions in the Galaxy. In a recent study led by Chikako Yasui (University of Tokyo and the Koyama Astronomical Observatory), a team of scientists has examined this region to better understand how star formation in low-metallicity environments differs from that in the solar neighborhood. The authors analysis suggests that sequential star formation is taking place in these low-metallicity regions, triggered by an expanding bubble (the large dashed oval indicated in the image) with a ~30 pc radius. You can find out more about their study by checking out the paper below!CitationChikako Yasui et al 2016 AJ 151 115. doi:10.3847/0004-6256/151/5/115

  18. Light Scattering by Ice Crystals Containing Air Bubbles

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Panetta, R. L.; Yang, P.; Bi, L.

    2014-12-01

    The radiative effects of ice clouds are often difficult to estimate accurately, but are very important for interpretation of observations and for climate modeling. Our understanding of these effects is primarily based on scattering calculations, but due to the variability in ice habit it is computationally difficult to determine the required scattering and absorption properties, and the difficulties are only compounded by the need to include consideration of air and carbon inclusions of the sort frequently observed in collected samples. Much of the previous work on effects of inclusions in ice particles on scattering properties has been conducted with variants of geometric optics methods. We report on simulations of scattering by ice crystals with enclosed air bubbles using the pseudo-spectral time domain method (PSTD) and improved geometric optics method (IGOM). A Bouncing Ball Model (BBM) is proposed as a parametrization of air bubbles, and the results are compared with Monte Carlo radiative transfer calculations. Consistent with earlier studies, we find that air inclusions lead to a smoothing of variations in the phase function, weakening of halos, and a reduction of backscattering. We extend these studies by examining the effects of the particular arrangement of a fixed number of bubbles, as well as the effects of splitting a given number of bubbles into a greater number of smaller bubbles with the same total volume fraction. The result shows that the phase function will not change much for stochastic distributed air bubbles. It also shows that local maxima of phase functions are smoothed out for backward directions, when we break bubbles into small ones, single big bubble scatter favors more forward scattering than multi small internal scatters.

  19. Simple test to confirm cleavage with air between Descemet's membrane and stroma during big-bubble deep anterior lamellar keratoplasty.

    PubMed

    Fontana, Luigi; Parente, Gabriella; Tassinari, Giorgio

    2007-04-01

    We describe a simple test to confirm big-bubble formation in deep anterior lamellar keratoplasty by observing the position and movements of small air bubbles injected into the anterior chamber through a limbal paracentesis. The test also allows evaluation of the extension of Descemet's membrane cleavage from the posterior stroma relative to the margins of the corneal trephination.

  20. High-frequency sound field and bubble formation in a rat decompression model.

    PubMed

    Shupak, Avi; Arieli, Yehuda; Bitterman, Haim; Brod, Vera; Arieli, Ran; Rosenhause, Giora

    2002-05-01

    High-frequency sound might cause bubble enlargement by rectified diffusion. The purpose of the present study was to investigate gas bubble formation in the immersed diving animal during exposure to high-frequency sound. Anaesthetised rats were subjected to a simulated diving profile while immersed inside a hyperbaric chamber. An acoustic beacon (pinger) was placed ventral to the animal's abdomen, transmitting at an intensity of 208.9 dB re 1 micro Pa and a frequency of 37 kHz. Six groups of eight animals were included in the study as in Table 1, breathing air (n = 4) or Nitrox 72/28 (n = 2), at a depth of 0 m, 30 m or 40 m. Immediately after decompression, the intestinal mesenterium was imaged, and frames were acquired digitally. The number of bubbles and their radii were analysed and compared among the groups. The mean bubble density for group 1 was 1.35 +/- 0.18 bubbles/mm(2), significantly higher when compared with the other groups (p < 0.0001). The average bubble radius for groups 1 and 2 was similar (12.57 +/- 4.1 and 10.63 +/- 1.8 microm, respectively), but significantly larger than in the other groups (p < 0.0002). The percentage of bubbles with a radius greater than 50 microm was significantly higher in group 1 (p < 0.0001). The results suggest that commercially available underwater pingers might enhance bubble growth during deep air diving.

  1. Formation and ascent of nonisothermal ionospheric and chromospheric bubbles

    SciTech Connect

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

    1987-11-01

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

  2. Amateur scientists - producing light from a bubble of air

    SciTech Connect

    Hiller, R.A.; Barber, B.P.

    1995-02-01

    A glowing bubble of air cannot be bought anywhere at any price. But with an oscilloscope, a moderately precise sound generator, a home stereo amplifier and about $100, readers can turn sound into light through a process called sonoluminescence. The apparatus is relatively simple. A glass spherical flask filled with water serves as the resonator - the cavity in which sound is created to trap and drive the bubble. Small speakers, called piezoelectric transducers, are cemented to the flask and powered by an audo generator and amplifier. Bubbles introduced into the water coalesce at the center of the flask and produce a dim light visible to the unaided eye in a darkened room.

  3. Bubble Formation and Detachment in Reduced Gravity Under the Influence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, Cila; Iacona, Estelle; Chang, Shinan

    2002-01-01

    The objective of the study is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Both uniform and nonuniform electric field configurations were considered. Bubble formation and detachment were recorded and visualized in reduced gravity (corresponding to gravity levels on Mars, on the Moon as well as microgravity) using a high-speed video camera. Bubble volume, dimensions and contact angle at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. Measured data and model predictions show good agreement and indicate that the level of gravity and the electric field magnitude significantly affect bubble shape, volume and dimensions.

  4. Vapor bubble formation during erbium:YAG laser vitrectomy

    NASA Astrophysics Data System (ADS)

    Mrochen, Michael; Donitzky, Christof; Riedel, Peter; Wenig, Micaela; Reindl, Max; Seiler, Theo

    1999-06-01

    Background: The formation of evaporation bubbles and pressure waves during Erbium:YAG laser vitrectomy might cause intraocular damages. Methods: In water, the formation of the evaporation bubbles was observed by high-speed photography. The output energy of the quartz tip ranges from 5 to 50 mJ and the laser pulse duration from 50 μsec to 300 μsec. The dynamic of the evaporation bubbles were investigated for different diameters, various angles and radii of the quartz fiber tip. Furthermore, the spread out of the evaporation bubbles was observed for various geometries of the microsurgery probe. The induced stress waves were measured with a PVDF-hydrophone. Results: The evaporation bubble size increases semi-logarithmic with the pulse energy and reduces with the increase of the pulse duration. The diameter of the tip has no significant influence in the vapor bubble size. The expansion of the vapor bubble can be controlled by the geometry of the tip. The spread out of the vapor bubble can reduced by a slit geometry of the aspiration hole. The maximum pressure amplitude as found to be < 2 MPa. Conclusions: The evolution of evaporation bubbles and the induced pressure amplitudes from the microsurgery probe can be minimized for Erbium:YAG laser vitrectomy.

  5. Numerical Simulation of Bubble Formation in Co-Flowing Mercury

    SciTech Connect

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

    2008-01-01

    In this work, we present computational fluid dynamics (CFD) simulations of helium bubble formation and detachment at a submerged needle in stagnant and co-flowing mercury. Since mercury is opaque, visualization of internal gas bubbles was done with proton radiography (pRad) at the Los Alamos Neutron Science Center (LANSCE2). The acoustic waves emitted at the time of detachment and during subsequent oscillations of the bubble were recorded with a microphone. The Volume of Fluid (VOF) model was used to simulate the unsteady two-phase flow of gas injection in mercury. The VOF model is validated by comparing detailed bubble sizes and shapes at various stages of the bubble growth and detachment, with the experimental measurements at different gas flow rates and mercury velocities. The experimental and computational results show a two-stage bubble formation. The first stage involves growing bubble around the needle, and the second follows as the buoyancy overcomes wall adhesion. The comparison of predicted and measured bubble sizes and shapes at various stages of the bubble growth and detachment is in good agreement.

  6. The role of bubbles during air-sea gas exchange

    NASA Astrophysics Data System (ADS)

    Emerson, Steven; Bushinsky, Seth

    2016-06-01

    The potential for using the air-sea exchange rate of oxygen as a tracer for net community biological production in the ocean is greatly enhanced by recent accuracy improvements for in situ measurements of oxygen on unmanned platforms. A limiting factor for determining the exchange process is evaluating the air-sea flux contributed by bubble processes produced by breaking waves, particularly during winter months under high winds. Highly accurate measurements of noble gases (Ne, Ar & Kr) and nitrogen, N2, in seawater are tracers of the importance of bubble process in the surface mixed layer. We use measured distributions of these gases in the ventilated thermocline of the North Pacific and an annual time series of N2 in the surface ocean of the NE Subarctic Pacific to evaluate four different air-water exchange models chosen to represent the range of model interpretation of bubble processes. We find that models must have an explicit bubble mechanism to reproduce concentrations of insoluble atmospheric gases, but there are periods when they all depart from observations. The recent model of Liang et al. (2013) stems from a highly resolved model of bubble plumes and categorizes bubble mechanisms into those that are small enough to collapse and larger ones that exchange gases before they resurface, both of which are necessary to explain the data.

  7. Methods for advanced hepatocyte cell culture in microwells utilizing air bubbles.

    PubMed

    Goral, Vasiliy N; Au, Sam H; Faris, Ronald A; Yuen, Po Ki

    2015-02-21

    Flat, two-dimensional (2D) cell culture substrates are simple to use but offer little control over cell morphologies and behavior. In this article, we present a number of novel and unique methods for advanced cell culture in microwells utilizing air bubbles as a way to seed cells in order to provide substantial control over cellular microenvironments and organization to achieve specific cell-based applications. These cell culture methods enable controlled formation of stable air bubbles in the microwells that spontaneously formed when polar solvents such as cell culture media are loaded. The presence of air bubbles (air bubble masking) enables highly controllable cell patterning and organization of seeded cells as well as cell co-culture in microwells. In addition, these cell culture methods are simple to use and implement, yet versatile, and have the potential to provide a wide range of microenvironments to improve in vivo-like behavior for a number of cell types and applications. The air bubble masking technique can also be used to produce a micron thick layer of collagen film suspended on top of the microwells. These collagen film enclosed microwells could provide an easy way for high throughput drug screening and cytotoxicity assays as different drug compounds could be pre-loaded and dried in selected microwells and then released during cell culture.

  8. Effects of system parameters on the physical characteristics of bubbles produced through air sparging.

    PubMed

    Burns, S E; Zhang, M

    2001-01-01

    Air sparging is a relatively new, cost-effective technology for the remediation of soil and groundwater contaminated with volatile organic compounds (VOCs). While the method has met with reasonable success at a large number of field sites, implementation of the technique is restricted to relatively coarse-grained soils with large values of air permeability, which significantly limits its applicability. An understanding of the fundamental parameters that control the formation and distribution of air in the sparging process is useful for optimizing the system implementation and extending its range of applicability. This work presents the results of an experimental investigation into the effect of process control parameters on the size and size distribution of air bubbles produced in aqueous and idealized saturated porous media systems. The experiments used digital image analysis to image and quantify the physical characteristics of the bubbles generated in a bench scale test cell. Results demonstrated that the average bubble size and range of size distribution increased as the injection pressure and size of the injection orifice were increased. Larger diameter bubbles with wider size distributions were produced in the presence of particles when compared to aqueous systems. As the particle size was decreased, the size of bubbles produced increased. Finally, the presence of trace quantities of the surfactant Triton X100 led to uniformly small diameter bubbles under all experimental conditions. The presence of the surfactant coating produced bubbles with physical characteristics that are more suited to in situ stripping of VOCs than the bubbles produced in the absence of a surfactant. PMID:11352012

  9. Effects of system parameters on the physical characteristics of bubbles produced through air sparging.

    PubMed

    Burns, S E; Zhang, M

    2001-01-01

    Air sparging is a relatively new, cost-effective technology for the remediation of soil and groundwater contaminated with volatile organic compounds (VOCs). While the method has met with reasonable success at a large number of field sites, implementation of the technique is restricted to relatively coarse-grained soils with large values of air permeability, which significantly limits its applicability. An understanding of the fundamental parameters that control the formation and distribution of air in the sparging process is useful for optimizing the system implementation and extending its range of applicability. This work presents the results of an experimental investigation into the effect of process control parameters on the size and size distribution of air bubbles produced in aqueous and idealized saturated porous media systems. The experiments used digital image analysis to image and quantify the physical characteristics of the bubbles generated in a bench scale test cell. Results demonstrated that the average bubble size and range of size distribution increased as the injection pressure and size of the injection orifice were increased. Larger diameter bubbles with wider size distributions were produced in the presence of particles when compared to aqueous systems. As the particle size was decreased, the size of bubbles produced increased. Finally, the presence of trace quantities of the surfactant Triton X100 led to uniformly small diameter bubbles under all experimental conditions. The presence of the surfactant coating produced bubbles with physical characteristics that are more suited to in situ stripping of VOCs than the bubbles produced in the absence of a surfactant.

  10. Pre-dive normobaric oxygen reduces bubble formation in scuba divers.

    PubMed

    Castagna, Olivier; Gempp, Emmanuel; Blatteau, Jean-Eric

    2009-05-01

    Oxygen pre-breathing is routinely employed as a protective measure to reduce the incidence of altitude decompression sickness in aviators and astronauts, but the effectiveness of normobaric oxygen before hyperbaric exposure has not been well explored. The objective of this study was to evaluate the effect of 30-min normobaric oxygen (O(2)) breathing before diving upon bubble formation in recreational divers. Twenty-one subjects (13 men and 8 women, mean age (SD) 33 +/- 8 years) performed random repetitive open-sea dives (surface interval of 100 min) to 30 msw for 30 min with a 6-min stop at 3 msw under four experimental protocols: "air-air" (control), "O(2)-O(2)", "O(2)-air" and "air-O(2)" where "O(2)" corresponds to a dive with oxygen pre-breathing and "air" a dive without oxygen administration. Post-dive venous gas emboli were examined by means of a precordial Doppler ultrasound. The results showed decreased bubble scores in all dives where preoxygenation had taken place (p < 0.01). Oxygen pre-breathing before each dive ("O(2)-O(2)" condition) resulted in the highest reduction in bubble scores measured after the second dive compared to the control condition (-66%, p < 0.05). The "O(2)-air" and "air-O(2) "conditions produced fewer circulating bubbles after the second dive than "air-air" condition (-47.3% and -52.2%, respectively, p < 0.05) but less bubbles were detected in "air-O(2) "condition compared to "O(2)-air" (p < 0.05). Our findings provide evidence that normobaric oxygen pre-breathing decreases venous gas emboli formation with a prolonged protective effect over time. This procedure could therefore be beneficial for multi-day repetitive diving.

  11. Propagation of compression waves in bubbly liquid with hydrate formation

    NASA Astrophysics Data System (ADS)

    Shagapov, V. Sh.; Lepikhin, S. A.; Chiglintsev, I. A.

    2010-06-01

    The dynamics of planar one-dimensional shock waves applied to the available experimental data for the water-Freon system is studied on the basis of the theoretical model of the bubbly liquid refined with regard for a possible hydrate formation. A scheme is proposed for considering the fragmentation of bubbles in the shock wave, which is one of the main factors of the intensification of the hydrate formation process with the growth of the shock wave amplitude.

  12. Descemet membrane air-bubble separation in donor corneas.

    PubMed

    Venzano, Davide; Pagani, Paola; Randazzo, Nadia; Cabiddu, Francesco; Traverso, Carlo Enrico

    2010-12-01

    We describe a technique to obtain Descemet-endothelium disks from donors. To detach Descemet membrane, an air bubble was introduced in the deep stroma of human donor corneas mounted on an artificial chamber. In Group A (n = 5), the bubble was left inflated. In Group B (n = 4), the bubble was deflated immediately after the membrane was detached. In Group C (n = 7), the Descemet-endothelium disk was trephined and separated from the stroma after the bubble was deflated. All tissues were stored at 4°C. Descemet detachment was achieved in 89% of the tissues. After 48 hours, the mean endothelial loss was 83% ± 10% (SD), 15% ± 11%, and 3% ± 3% in the 3 groups, respectively. With this technique, Descemet-endothelium disks were obtained without significant alterations in the endothelial layer.

  13. 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

  14. Effects of Gravity on Bubble Formation in an Annular Jet

    NASA Technical Reports Server (NTRS)

    Koepp, R. A.; Parthasarathy, R. N.; Gollahalli, S. R.

    2004-01-01

    The effects of gravity on the bubble formation in an annular jet were studied. The experiments were conducted in the 2.2-second drop tower at the NASA Glenn Research Center. Terrestrial gravity experiments were conducted at the Fluid Dynamics Research Laboratory at the University of Oklahoma. Stainless steel tubing with inner diameters of 1/8" (gas inner annulus) and 5/16" (liquid outer annulus) served as the injector. A rectangular test section, 6" x 6" x 14" tall, made out of half-inch thick Lexan was used. Images of the annular jet were acquired using a high-speed camera. The effects of gravity and varying liquid and gas flow rates on bubble size, wavelength, and breakup length were documented. In general, the bubble diameter was found to be larger in terrestrial gravity than in microgravity for varying Weber numbers (0.05 - 0.16 and 5 - 11) and liquid flow rates (1.5 ft/s - 3.0 ft/s). The wavelength was found to be larger in terrestrial gravity than in microgravity, but remained constant for varying Weber numbers. For low Weber numbers (0.05 - 0.16), the breakup length in microgravity was significantly higher than in terrestrial gravity. Comparison with linear stability analysis showed estimated bubble sizes within 9% of experimental bubble sizes. Bubble size compared to other terrestrial gravity experiments with same flow conditions showed distinct differences in bubble size, which displayed the importance of injector geometry on bubble formation.

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

    PubMed

    Hyldegaard, O; Kerem, D; Melamed, Y

    2011-09-01

    Deep tissue isobaric counterdiffusion that may cause unwanted bubble formation or transient bubble growth has been referred to in theoretical models and demonstrated by intravascular gas formation in animals, when changing inert breathing gas from nitrogen to helium after hyperbaric air breathing. We visually followed the in vivo resolution of extravascular air bubbles injected at 101 kPa into nitrogen supersaturated rat tissues: adipose, spinal white matter, skeletal muscle or tail tendon. Bubbles were observed during isobaric breathing-gas shifts from air to normoxic (80:20) heliox mixture while at 285 kPa or following immediate recompression to either 285 or 405 kPa, breathing 80:20 and 50:50 heliox mixtures. During the isobaric shifts, some bubbles in adipose tissue grew marginally for 10-30 min, subsequently they shrank and disappeared at a rate similar to or faster than during air breathing. No such bubble growth was observed in spinal white matter, skeletal muscle or tendon. In spinal white matter, an immediate breathing gas shift after the hyperbaric air exposure from air to both (80:20) and (50:50) heliox, coincident with recompression to either 285 or 405 kPa, caused consistent shrinkage of all air bubbles, until they disappeared from view. Deep tissue isobaric counterdiffusion may cause some air bubbles to grow transiently in adipose tissue. The effect is marginal and of no clinical consequence. Bubble disappearance rate is faster with heliox breathing mixtures as compared to air. We see no reason for reservations in the use of heliox breathing during treatment of air-diving-induced decompression sickness.

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

    PubMed

    Hyldegaard, O; Kerem, D; Melamed, Y

    2011-09-01

    Deep tissue isobaric counterdiffusion that may cause unwanted bubble formation or transient bubble growth has been referred to in theoretical models and demonstrated by intravascular gas formation in animals, when changing inert breathing gas from nitrogen to helium after hyperbaric air breathing. We visually followed the in vivo resolution of extravascular air bubbles injected at 101 kPa into nitrogen supersaturated rat tissues: adipose, spinal white matter, skeletal muscle or tail tendon. Bubbles were observed during isobaric breathing-gas shifts from air to normoxic (80:20) heliox mixture while at 285 kPa or following immediate recompression to either 285 or 405 kPa, breathing 80:20 and 50:50 heliox mixtures. During the isobaric shifts, some bubbles in adipose tissue grew marginally for 10-30 min, subsequently they shrank and disappeared at a rate similar to or faster than during air breathing. No such bubble growth was observed in spinal white matter, skeletal muscle or tendon. In spinal white matter, an immediate breathing gas shift after the hyperbaric air exposure from air to both (80:20) and (50:50) heliox, coincident with recompression to either 285 or 405 kPa, caused consistent shrinkage of all air bubbles, until they disappeared from view. Deep tissue isobaric counterdiffusion may cause some air bubbles to grow transiently in adipose tissue. The effect is marginal and of no clinical consequence. Bubble disappearance rate is faster with heliox breathing mixtures as compared to air. We see no reason for reservations in the use of heliox breathing during treatment of air-diving-induced decompression sickness. PMID:21318313

  17. Motion of Air Bubbles in Water Subjected to Microgravity Accelerations

    NASA Technical Reports Server (NTRS)

    DeLombard, Richard; Kelly, Eric M.; Hrovat, Kenneth; Nelson, Emily S.; Pettit, Donald R.

    2006-01-01

    The International Space Station (ISS) serves as a platform for microgravity research for the foreseeable future. A microgravity environment is one in which the effects of gravity are drastically reduced which then allows physical experiments to be conducted without the over powering effects of gravity. During his 6-month stay on the ISS, astronaut Donald R. Pettit performed many informal/impromptu science experiments with available equipment. One such experiment focused on the motion of air bubbles in a rectangular container nearly filled with de-ionized water. Bubbles were introduced by shaking and then the container was secured in place for several hours while motion of the bubbles was recorded using time-lapse photography. This paper shows correlation between bubble motion and quasi-steady acceleration levels during one such experiment operation. The quasi-steady acceleration vectors were measured by the Microgravity Acceleration Measurement System (MAMS). Essentially linear motion was observed in the condition considered here. Dr. Pettit also created other conditions which produced linear and circulating motion, which are the subjects of further study. Initial observations of this bubble motion agree with calculations from many microgravity physical science experiments conducted on shuttle microgravity science missions. Many crystal-growth furnaces involve heavy metals and high temperatures in which undesired acceleration-driven convection during solidification can adversely affect the crystal. Presented in this paper will be results showing correlation between bubble motion and the quasi-steady acceleration vector.

  18. Motion of Air Bubbles in Water Subjected to Microgravity Accelerations

    NASA Technical Reports Server (NTRS)

    DeLombard, Richard; Kelly, Eric M.; Hrovar, Kenneth; Nelson, Emily S.; Pettit, Donald R.

    2004-01-01

    The International Space Station (ISS) serves as a platform for microgravity research for the foreseeable future. A microgravity environment is one in which the effects of gravity are drastically reduced which then allows physical experiments to be conducted without the overpowering effects of gravity. During his six month stay on the ISS, astronaut Donald R Pettit performed many informal/impromptu science experiments with available equipment. One such experiment focused on the motion of air bubbles in a rectangular container nearly filled with de-ionized water. Bubbles were introduced by shaking and the container was secured in place for several hours while motion of the bubbles were recorded using time-lapse photography. This paper shows correlation between bubble motion and quasi-steady acceleration levels during one such experiment operation. The quasi-steady acceleration vectors were measured by the Microgravity Acceleration Measurement System. Essentially linear motion was observed in the condition considered here. Dr. Pettit also created other conditions which produced linear and circulating motion, which are the subjects of further study. Initial observations of this bubble motion agree with calculations from many microgravity physical science experiments conducted on Shuttle microgravity science missions. Many crystal-growth furnaces involve heavy metals and high temperatures in which undesired acceleration-driven convection during solidification can adversely affect the crystal. Presented in this paper will be results showing correlation between bubble motion and the quasi-steady acceleration vector.

  19. Ocular bubble formation as a method of assessing decompression stress.

    PubMed

    Mekjavić, I B; Campbell, D G; Jaki, P; Dovsak, P A

    1998-01-01

    Tear film bubble formation and ultrasound reflectivity of the lens-vitreous humor compartments were monitored following simulated dives in a hyperbaric chamber. the sensitivity of these methods in determining decompression stress was compared with the results of precordial Doppler ultrasound. In addition, the utility of these diagnostic techniques in testing decompression dive profiles was evaluated. Eleven divers completed two series of chamber dives according to the decompression schedule of the Professional Association of Diving Instructors. The first dive series comprised dives to 70 feet of seawater (fsw) for 15, 29, and 40 min. The second series comprised maximum duration no-stop decompression dives to 40 fsw for 140 min, 70 fsw for 40 min, 90 fsw for 25 min, and 120 fsw for 13 min. Before and immediately after each dive, the following measurements were obtained from each subject: eye surface tear film bubble counts with a slit-lamp microscope, lens and vitreous humor reflectivity using A- and B-mode ophthalmic ultrasonic scan, and precordial Doppler ultrasonic detection of venous gas bubbles. Tear film bubble assessment and ocular scanning ultrasound were observed to be more sensitive in detecting decompression stress than the conventional Doppler ultrasonic surveillance of the precordial region. In contrast to precordial Doppler ultrasonic surveillance, which failed to detect any significant changes in circulating bubbles, tear film bubble formation displayed a dose-response relationship with increasing duration of the 70-fsw dives. Reflectivity changes of the lens-vitreous humor interface were not significant until the no-stop decompression limit was reached. In addition, for each of the no-stop decompression limit dives, increases in the average tear film bubble formation and lens-vitreous humor interface reflectivity were similar. Ocular bubble observations may provide a practical and objective ocular bubble index for analyzing existing decompression

  20. Contact lens wear at altitude: subcontact lens bubble formation.

    PubMed

    Flynn, W J; Miller, R E; Tredici, T J; Block, M G; Kirby, E E; Provines, W F

    1987-11-01

    A concern in the past regarding contact lens wear in aviation has been the fear of subcontact lens bubble formation. Previous reports have documented the occurrence of bubbles with hard (PMMA) lenses. Reported here are the results of contact lens bubble studies with soft hydrophilic and rigid gas-permeable lenses. Testing was accomplished in hypobaric chambers and onboard USAF transport aircraft. Hypobaric chamber flights were of three types: high-altitude flights up to 7,620 m (25,000 ft); explosive rapid decompressions from 2,438.4 m (8,000 ft) to 7,620 m (25,000 ft); and 4-h flights at 3,048 m (10,000 ft). Flights aboard transport aircraft typically had cabin pressures equivalent to 1,524-2,438.4 m (5,000-8,000 ft), and ranged in duration from 3 to 10 h. For subjects wearing rigid gas-permeable lenses, central bubbles were detected in 2 of 10 eyes and occurred at altitudes greater than 6,096 m (20,000 ft). With soft contact lenses, bubble formation was detected in approximately 24% (22 of 92 eyes) of the eyes tested, sometimes occurring at altitudes as low as 1,828.8 m (6,000 ft). Soft lens bubbles were always located at the limbus and were without sequela to vision or corneal epithelial integrity. Bubbles under the rigid lenses were primarily central, with potential adverse effects on vision and the corneal epithelium.

  1. Enriched Air Nitrox Breathing Reduces Venous Gas Bubbles after Simulated SCUBA Diving: A Double-Blind Cross-Over Randomized Trial

    PubMed Central

    Souday, Vincent; Koning, Nick J.; Perez, Bruno; Grelon, Fabien; Mercat, Alain; Boer, Christa; Seegers, Valérie; Radermacher, Peter; Asfar, Pierre

    2016-01-01

    Objective To test the hypothesis whether enriched air nitrox (EAN) breathing during simulated diving reduces decompression stress when compared to compressed air breathing as assessed by intravascular bubble formation after decompression. Methods Human volunteers underwent a first simulated dive breathing compressed air to include subjects prone to post-decompression venous gas bubbling. Twelve subjects prone to bubbling underwent a double-blind, randomized, cross-over trial including one simulated dive breathing compressed air, and one dive breathing EAN (36% O2) in a hyperbaric chamber, with identical diving profiles (28 msw for 55 minutes). Intravascular bubble formation was assessed after decompression using pulmonary artery pulsed Doppler. Results Twelve subjects showing high bubble production were included for the cross-over trial, and all completed the experimental protocol. In the randomized protocol, EAN significantly reduced the bubble score at all time points (cumulative bubble scores: 1 [0–3.5] vs. 8 [4.5–10]; P < 0.001). Three decompression incidents, all presenting as cutaneous itching, occurred in the air versus zero in the EAN group (P = 0.217). Weak correlations were observed between bubble scores and age or body mass index, respectively. Conclusion EAN breathing markedly reduces venous gas bubble emboli after decompression in volunteers selected for susceptibility for intravascular bubble formation. When using similar diving profiles and avoiding oxygen toxicity limits, EAN increases safety of diving as compared to compressed air breathing. Trial Registration ISRCTN 31681480 PMID:27163253

  2. Porosity/bubble formation mechanism in laser surface enamelling

    NASA Astrophysics Data System (ADS)

    Akhter, R.; Li, L.; Edwards, R. E.; Gale, A. W.

    2003-03-01

    The grouts between commercial tiles applied to walls and floors can be contaminated over time and normally have to be removed by manual or mechanical processes. To overcome the contamination problem, a specially developed tile grout was used to fill the voids between the tiles. The base filler was overlaid with an enamel surface that glazes after laser irradiation. One problem discovered in this work is that bubbles and porosities were formed after laser treatment. The use of water glass (sodium silicate) as a binder has been undertaken in this study. This paper investigates the mechanism of bubble formation and its effects on the enamel surface. It has been found that the CO 2 gas released during the reaction causes bubble formation. The results and the technique for the removal of bubbles/porosities are presented in the paper.

  3. The formation of soap bubbles created by blowing on soap films

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Using either circular bubble wands or long-lasting vertically falling soap films having an adjustable steady state thickness, we study the formation of soap bubbles created when air is blown through a nozzle onto a soap film. We vary nozzle radius, film size, space between the film and nozzle, and gas density, and we measure the gas velocity threshold above which bubbles are generated. The response is sensitive to confinement, that is, the ratio between film and jet sizes, and dissipation in the turbulent gas jet which is a function of the distance from the nozzle to the film. We observe four different regimes that we rationalize by comparing the dynamic pressure of a jet on the film and the Laplace pressure needed to create the curved surface of a bubble.

  4. Air bubble-shock wave interaction adjacent to gelantine surface

    NASA Astrophysics Data System (ADS)

    Lush, P. A.; Tomita, Y.; Onodera, O.; Takayama, K.; Sanada, N.; Kuwahara, M.; Ioritani, N.; Kitayama, O.

    1990-07-01

    The interaction between a shock wave and an air bubble-adjacent to a gelatine surface is investigated in order to simulate human tissue damage resulting from extracorporeal shock wave lithotripsy. Using high speed cine photography it is found that a shock wave of strength 11 MPa causes 1-3 mm diameter bubbles to produce high velocity microjets with penetration rates of approximately 110 m/s and penetration depths approximately equal to twice the initial bubble diameter. Theoretical considerations for liquid impact on soft solid of similar density indicate that microjet velocities will be twice the penetration rate, i.e. 220 m/s in the present case. Such events are the probable cause of observed renal tissue damage.

  5. Air-bubble entrapment due to a drop

    NASA Astrophysics Data System (ADS)

    Ootsuka, Nao; Etoh, Takeharu G.; Takehara, Kohsei; Oki, Sachio; Takano, Yasuhide; Hatsuki, Yuya; Thoroddsen, Sigurdur T.

    2005-03-01

    In 2001, an ultra-high-speed video camera of 1,000,000 frames per second was developed in Hydraulics Laboratory of Kinki University. The image sensor of the camera was the ISIS-V2, the In-situ Storage Image Sensor-Version 2. The camera has been applied to visualization of high-speed phenomena in various fields of science and engineering. We observed entrapment phenomena of bubbles resulting from thermal spraying of metals. Thermal spraying is used to improve solid surfaces by spraying melted metal or ceramic particles to the surfaces. One of the problems relating to the thermal spraying is entrapment of air bubbles under the metal or ceramic layers covering the solid surfaces. The bubbles decrease bonding strength of the layers made by the thermal spraying. The entrapment processes were successfully visualized by application of the ultra-high-speed video camera.

  6. [Emphysematous cystitis with air bubbles in the vena cava].

    PubMed

    Yokokawa, Ryusei; Tsuka, Harutoshi; Muranaka, Koji

    2014-01-01

    A 76-year-old diabetic woman was referred to our hospital with an episode of high fever and sub-abdominal pain. Computed tomography (CT) of the pelvis revealed gas accumulation within the lumen and wall of the bladder and CT of the abdomen demonstrated bubbles in the inferior vena cava. She recovered by urinary drainage and antibiotic therapy. Urinary culture revealed Escherichia coli. CT after the therapy didn't demonstrate gas accumulation of the bladder and bubbles in the inferior vena cava. Emphysematous urinary tract infections (UTIs) have the high fatality rate, it seems to be a possibility that venous bubbles with emphysematous UTIs contribute to the high fatality rate such as air embolisms. It was suspected that bacterial injury of the bladder wall and high vesical pressure caused by urinary outlet obstruction such as neurogenic bladder lead gas translocation into the venous system. Six previous cases of emphysematous UTIs (three emphysematous cystitis cases and three emphysematous pyelonephritis cases) with venous bubbles have been reported to this day. Our case is seems to be the fourth case report that venous bubbles with emphysematous cystitis was demonstrated.

  7. Bubble Formation at a Submerged Orifice in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Buyevich, Yu A.; Webbon, Bruce W.

    1994-01-01

    The dynamic regime of gas injection through a circular plate orifice into an ideally wetting liquid is considered, when successively detached bubbles may be regarded as separate identities. In normal gravity and at relatively low gas flow rates, a growing bubble is modeled as a spherical segment touching the orifice perimeter during the whole time of its evolution. If the flow rate exceeds a certain threshold value, another stage of the detachment process takes place in which an almost spherical gas envelope is connected with the orifice by a nearly cylindrical stem that lengthens as the bubble rises above the plate. The bubble shape resembles then that of a mushroom and the upper envelope continues to grow until the gas supply through the stem is completely cut off. Such a stage is always present under conditions of sufficiently low gravity, irrespective of the flow rate. Two major reasons make for bubble detachment: the buoyancy force and the force due to the momentum inflow into the bubble with the injected gas. The former force dominates the process at normal gravity whereas the second one plays a key role under negligible gravity conditions. It is precisely this fundamental factor that conditions the drastic influence on bubble growth and detachment that changes in gravity are able to cause. The frequency of bubble formation is proportional to and the volume of detached bubbles is independent of the gas flow rate in sufficiently low gravity, while at normal and moderately reduced gravity conditions the first variable slightly decreases and the second one almost linearly increases as the flow rate grows. Effects of other parameters, such as the orifice radius, gas and liquid densities, and surface tension are discussed.

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

    NASA Astrophysics Data System (ADS)

    Fsadni, Andrew M.; Ge, Yunting

    2012-04-01

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

  9. 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

  10. 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. PMID:26142694

  11. A Mathematical Modeling Study of Bubble Formations in a Molten Steel Bath

    NASA Astrophysics Data System (ADS)

    Xu, Yonggui; Ersson, Mikael; Jönsson, Pär Göran

    2015-12-01

    The bubble formation during gas injection into liquids was studied using a water model and a three-dimensional numerical model. In the experiment, a high-speed camera was used to record the bubble formation processes. Nozzle diameters of 0.5, 1, and 2 mm were investigated under both wetting and non-wetting conditions. The bubble sizes and formation frequencies as well as the bubbling regimes were identified for each nozzle size and for different wettabilities. The results show that the upper limits of the bubbling regime are 7.35, 12.05, and 15.22 L/h under wetting conditions for the 0.5, 1, and 2 mm nozzle diameters, respectively. Meanwhile, the limits are 12.66, 13.64, and 15.33 L/h for the non-wetting conditions. In the numerical model, the volume-of-fluid method was used to track the interface between the gas and liquid. The simulation results were compared with the experimental observations in the air-water system. The comparisons show a satisfactory good agreement between the two methods. The mathematical model was then applied to simulate the argon-steel system. Simulation results show that the effect of nozzle size is insignificant for the current studied metallurgical conditions. The upper limits of the bubbling regime are approximately 60 and 80 L/h for a 2-mm nozzle for the wetting and non-wetting conditions, respectively. In addition, a poor wettability leads to a bigger bubble and a lower frequency compared with a good wettability, for the same gas flow rate.

  12. Effect of compressibility on the rise velocity of an air bubble in porous media

    NASA Astrophysics Data System (ADS)

    Cihan, Abdullah; Corapcioglu, M. Yavuz

    2008-04-01

    The objective of this study is to develop a theoretical model to analyze the effect of air compressibility on air bubble migration in porous media. The model is obtained by combining the Newton's second law of motion and the ideal gas law assuming that the air phase in the bubble behaves as an ideal gas. Numerical and analytical solutions are presented for various cases of interest. The model results compare favorably with both experimental data and analytical solutions reported in the literature obtained for an incompressible air bubble migration. The results show that travel velocity of a compressible air bubble in porous media strongly depends on the depth of air phase injection. A bubble released from greater depths travels with a slower velocity than a bubble with an equal volume injected at shallower depths. As an air bubble rises up, it expands with decreasing bubble pressure with depth. The volume of a bubble injected at a 1-m depth increases 10% as the bubble reaches the water table. However, bubble volume increases almost twofold when it reaches to the surface from a depth of 10 m. The vertical rise velocity of a compressible bubble approaches that of an incompressible one regardless of the injection depth and volume as it reaches the water table. The compressible bubble velocity does not exceed 18.8 cm/s regardless of the injection depth and bubble volume. The results demonstrate that the effect of air compressibility on the motion of a bubble cannot be neglected except when the air is injected at very shallow depths.

  13. Kinetics of helium bubble formation in nuclear materials

    SciTech Connect

    Bonilla, L L; Carpio, A; Neu, J C; Wolfer, W G

    2005-10-13

    The formation and growth of helium bubbles due to self-irradiation in plutonium has been modeled by a discrete kinetic equations for the number densities of bubbles having k atoms. Analysis of these equations shows that the bubble size distribution function can be approximated by a composite of: (1) the solution of partial differential equations describing the continuum limit of the theory but corrected to take into account the effects of discreteness, and (2) a local expansion about the advancing leading edge of the distribution function in size space. Both approximations contribute to the memory term in a close integrodifferential equation for the monomer concentration of single helium atoms. The present theory is compared to the numerical solution of the full kinetic model and to previous approximation of Schaldach and Wolfer involving a truncated system of moment equations.

  14. Memory encoding vibrations in a disconnecting air bubble

    NASA Astrophysics Data System (ADS)

    Zhang, Wendy

    2009-03-01

    The implosion that disconnects a submerged air bubble into several bubbles provides a simple example of energy focusing. The most efficient disconnection is an entirely symmetric one terminating in a finite-time singularity. At the final moment, the potential energy at the start of the disconnection is entirely condensed into the kinetic energy of a vanishingly small amount of liquid rushing inwards to disconnect the bubble. In reality, however, the initial shape always possesses slight imperfections. We show that a memory of the imperfection remains and controls the final fate of the focusing. Linear stability reveals that even an infinitesimal perturbation is remembered. A slight initial asymmetry excites vibrations in the cross-section shape of the bubble neck. The vibrations persist over time. Near the singularity, their amplitudes freeze, locking onto constant values, while their frequencies chirp, increasing more and more rapidly. The net effect is that the singularity remembers exactly half of the information about the initial imperfection, the half encoded by the vibration amplitudes. We check this scenario in an experiment by releasing an air bubble from a nozzle with an oblong cross-section. This excites an elongation-compression vibrational mode. We measure the vibration excited and find quantitative agreement with linear stability. When the initial distortion has a small, but finite, size, the saturation of the vibration amplitude causes the symmetric singularity to be pre-empted by an asymmetric contact between two distant points on the interface. Numerics reveal that the contact is typically smooth, corresponding to two inward-curving portions of the bubble surface colliding at finite speed. Both the contact speed and curvature vary non-monotonically with the initial distortion size, with abrupt jumps at specific values. This is because the vibration causes contact to occur at different values of the phase. A contact produced when the shape distortion

  15. Critical concentration for hydrogen bubble formation in metals.

    PubMed

    Sun, Lu; Jin, Shuo; Zhou, Hong-Bo; Zhang, Ying; Zhang, Wenqing; Ueda, Y; Lee, H T; Lu, Guang-Hong

    2014-10-01

    Employing a thermodynamic model with previously calculated first-principle energetics as inputs, we determined the hydrogen (H) concentration at the interstitial and monovacancy as well as its dependence on temperature and pressure in tungsten and molybdenum. Based on this, we predicted the critical H concentration for H bubble formation at different temperatures. The critical concentration, defined as the value when the concentration of H at a certain mH-vacancy complex first became equal to that of H at the interstitial, was 24 ppm/7.3 GPa and 410 ppm/4.7 GPa at 600 K in tungsten and molybdenum in the case of a monovacancy. Beyond the critical H concentration, numerous H atoms accumulated in the monovacancy, leading to the formation and rapid growth of H-vacancy complexes, which was considered the preliminary stage of H bubble formation. We expect that the proposed approach will be generally used to determine the critical H concentration for H bubble formation in metals.

  16. NOS inhibition increases bubble formation and reduces survival in sedentary but not exercised rats.

    PubMed

    Wisløff, Ulrik; Richardson, Russell S; Brubakk, Alf O

    2003-01-15

    Previously we have shown that chronic as well as a single bout of exercise 20 h prior to a simulated dive protects rats from severe decompression illness (DCI) and death. However, the mechanism behind this protection is still not known. The present study determines the effect of inhibiting nitric oxide synthase (NOS) on bubble formation in acutely exercised and sedentary rats exposed to hyperbaric pressure. A total of 45 adult female Sprague-Dawley rats (270-320 g) were randomly assigned into exercise or sedentary control groups, with and without NOS inhibition, using L-NAME (0.05 or 1 mg ml(-1)) (a nonselective NOS inhibitor). Exercising rats ran intervals on a treadmill for 1.5 h, 20 h prior to the simulated dive. Intervals alternated between 8 min at 85-90 % of maximal oxygen uptake, and 2 min at 50-60 %. Rats were compressed (simulated dive) in a pressure chamber, at a rate of 200 kPa min(-1) to a pressure of 700 kPa, and maintained for 45 min breathing air. At the end of the exposure period, rats were decompressed linearly to the "surface" (100 kPa) at a rate of 50 kPa min(-1). Immediately after reaching the surface the animals were anaesthetised and the right ventricle was insonated using ultrasound. The study demonstrated that sedentary rats weighing more than 300 g produced a large amount of bubbles, while those weighing less than 300 g produced few bubbles and most survived the protocol. Prior exercise reduced bubble formation and increased survival in rats weighing more than 300 g, confirming the results from the previous study. During NOS inhibition, the simulated dive induced significantly more bubbles in all sedentary rats weighing less than 300 g. However, this effect could be attenuated by a single bout of exercise 20 h before exposure. The present study demonstrates two previously unreported findings: that administration of L-NAME allows substantial bubble formation and decreased survival in sedentary rats, and that a single bout of exercise

  17. A model of particle removal in a dissolved air flotation tank: importance of stratified flow and bubble size.

    PubMed

    Lakghomi, B; Lawryshyn, Y; Hofmann, R

    2015-01-01

    An analytical model and a computational fluid dynamic model of particle removal in dissolved air flotation were developed that included the effects of stratified flow and bubble-particle clustering. The models were applied to study the effect of operating conditions and formation of stratified flow on particle removal. Both modeling approaches demonstrated that the presence of stratified flow enhanced particle removal in the tank. A higher air fraction was shown to be needed at higher loading rates to achieve the same removal efficiency. The model predictions showed that an optimum bubble size was present that increased with an increase in particle size.

  18. Ceramic membrane defouling (cleaning) by air Nano Bubbles.

    PubMed

    Ghadimkhani, Aliasghar; Zhang, Wen; Marhaba, Taha

    2016-03-01

    Ceramic membranes are among the most promising technologies for membrane applications, owing to their excellent resistance to mechanical, chemical, and thermal stresses. However, membrane fouling is still an issue that hampers the applications at large scales. Air Nano Bubbles (NBs), due to high mass transfer efficiency, could potentially prevent fouling of ceramic membrane filtration processes. In this study, bench and pilot scale ceramic membrane filtration was performed with air NBs to resist fouling. To simulate fouling, humic acid, as an organic foulant, was applied to the membrane flat sheet surface. Complete membrane clogging was achieved in less than 6 h. Membrane defouling (cleaning) was performed by directly feeding of air NBs to the membrane cells. The surface of the ceramic membrane was superbly cleaned by air NBs, as revealed by atomic force microscope (AFM) images before and after the treatment. The permeate flux recovered to its initial level (e.g., 26.7 × 10(-9) m(3)/m(2)/s at applied pressure of 275.8 kPa), which indicated that NBs successfully unclogged the pores of the membrane. The integrated ceramic membrane and air NBs system holds potential as an innovative sustainable technology.

  19. Ceramic membrane defouling (cleaning) by air Nano Bubbles.

    PubMed

    Ghadimkhani, Aliasghar; Zhang, Wen; Marhaba, Taha

    2016-03-01

    Ceramic membranes are among the most promising technologies for membrane applications, owing to their excellent resistance to mechanical, chemical, and thermal stresses. However, membrane fouling is still an issue that hampers the applications at large scales. Air Nano Bubbles (NBs), due to high mass transfer efficiency, could potentially prevent fouling of ceramic membrane filtration processes. In this study, bench and pilot scale ceramic membrane filtration was performed with air NBs to resist fouling. To simulate fouling, humic acid, as an organic foulant, was applied to the membrane flat sheet surface. Complete membrane clogging was achieved in less than 6 h. Membrane defouling (cleaning) was performed by directly feeding of air NBs to the membrane cells. The surface of the ceramic membrane was superbly cleaned by air NBs, as revealed by atomic force microscope (AFM) images before and after the treatment. The permeate flux recovered to its initial level (e.g., 26.7 × 10(-9) m(3)/m(2)/s at applied pressure of 275.8 kPa), which indicated that NBs successfully unclogged the pores of the membrane. The integrated ceramic membrane and air NBs system holds potential as an innovative sustainable technology. PMID:26741542

  20. Size Distribution of Air Bubbles Entering the Brain during Cardiac Surgery

    PubMed Central

    Janus, Justyna; Marshall, David; Horsfield, Mark A.; Rousseau, Clément; Keelan, Jonathan; Evans, David H.; Hague, James P.

    2015-01-01

    Background Thousands of air bubbles enter the cerebral circulation during cardiac surgery, but whether high numbers of bubbles explain post-operative cognitive decline is currently controversial. This study estimates the size distribution of air bubbles and volume of air entering the cerebral arteries intra-operatively based on analysis of transcranial Doppler ultrasound data. Methods Transcranial Doppler ultrasound recordings from ten patients undergoing heart surgery were analysed for the presence of embolic signals. The backscattered intensity of each embolic signal was modelled based on ultrasound scattering theory to provide an estimate of bubble diameter. The impact of showers of bubbles on cerebral blood-flow was then investigated using patient-specific Monte-Carlo simulations to model the accumulation and clearance of bubbles within a model vasculature. Results Analysis of Doppler ultrasound recordings revealed a minimum of 371 and maximum of 6476 bubbles entering the middle cerebral artery territories during surgery. This was estimated to correspond to a total volume of air ranging between 0.003 and 0.12 mL. Based on analysis of a total of 18667 embolic signals, the median diameter of bubbles entering the cerebral arteries was 33 μm (IQR: 18 to 69 μm). Although bubble diameters ranged from ~5 μm to 3.5 mm, the majority (85%) were less than 100 μm. Numerous small bubbles detected during cardiopulmonary bypass were estimated by Monte-Carlo simulation to be benign. However, during weaning from bypass, showers containing large macro-bubbles were observed, which were estimated to transiently affect up to 2.2% of arterioles. Conclusions Detailed analysis of Doppler ultrasound data can be used to provide an estimate of bubble diameter, total volume of air, and the likely impact of embolic showers on cerebral blood flow. Although bubbles are alarmingly numerous during surgery, our simulations suggest that the majority of bubbles are too small to be harmful

  1. Role of metabolic gases in bubble formation during hypobaric exposures.

    PubMed

    Foster, P P; Conkin, J; Powell, M R; Waligora, J M; Chhikara, R S

    1998-03-01

    Our hypothesis is that metabolic gases play a role in the initial explosive growth phase of bubble formation during hypobaric exposures. Models that account for optimal internal tensions of dissolved gases to predict the probability of occurrence of venous gas emboli were statistically fitted to 426 hypobaric exposures from National Aeronautics and Space Administration tests. The presence of venous gas emboli in the pulmonary artery was detected with an ultrasound Doppler detector. The model fit and parameter estimation were done by using the statistical method of maximum likelihood. The analysis results were as follows. 1) For the model without an input of noninert dissolved gas tissue tension, the log likelihood (in absolute value) was 255.01. 2) When an additional parameter was added to the model to account for the dissolved noninert gas tissue tension, the log likelihood was 251.70. The significance of the additional parameter was established based on the likelihood ratio test (P < 0.012). 3) The parameter estimate for the dissolved noninert gas tissue tension participating in bubble formation was 19. 1 kPa (143 mmHg). 4) The additional gas tissue tension, supposedly due to noninert gases, did not show an exponential decay as a function of time during denitrogenation, but it remained constant. 5) The positive sign for this parameter term in the model is characteristic of an outward radial pressure of gases in the bubble. This analysis suggests that dissolved gases other than N2 in tissues may facilitate the initial explosive bubble-growth phase.

  2. Role of metabolic gases in bubble formation during hypobaric exposures

    NASA Technical Reports Server (NTRS)

    Foster, P. P.; Conkin, J.; Powell, M. R.; Waligora, J. M.; Chhikara, R. S.

    1998-01-01

    Our hypothesis is that metabolic gases play a role in the initial explosive growth phase of bubble formation during hypobaric exposures. Models that account for optimal internal tensions of dissolved gases to predict the probability of occurrence of venous gas emboli were statistically fitted to 426 hypobaric exposures from National Aeronautics and Space Administration tests. The presence of venous gas emboli in the pulmonary artery was detected with an ultrasound Doppler detector. The model fit and parameter estimation were done by using the statistical method of maximum likelihood. The analysis results were as follows. 1) For the model without an input of noninert dissolved gas tissue tension, the log likelihood (in absolute value) was 255.01. 2) When an additional parameter was added to the model to account for the dissolved noninert gas tissue tension, the log likelihood was 251.70. The significance of the additional parameter was established based on the likelihood ratio test (P < 0.012). 3) The parameter estimate for the dissolved noninert gas tissue tension participating in bubble formation was 19. 1 kPa (143 mmHg). 4) The additional gas tissue tension, supposedly due to noninert gases, did not show an exponential decay as a function of time during denitrogenation, but it remained constant. 5) The positive sign for this parameter term in the model is characteristic of an outward radial pressure of gases in the bubble. This analysis suggests that dissolved gases other than N2 in tissues may facilitate the initial explosive bubble-growth phase.

  3. 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.

  4. Effects of gravity level on bubble formation and rise in low-viscosity liquids

    NASA Astrophysics Data System (ADS)

    Suñol, Francesc; González-Cinca, Ricard

    2015-05-01

    We present an experimental analysis of the effects of gravity level on the formation and rise dynamics of bubbles. Experiments were carried out with millimeter-diameter bubbles in the hypergravity environment provided by the large-diameter centrifuge of the European Space Agency. Bubble detachment from a nozzle is determined by buoyancy and surface tension forces regardless of the gravity level. Immediately after detachment, bubble trajectory is deviated by the Coriolis force. Subsequent bubble rise is dominated by inertial forces and follows a zig-zag trajectory with amplitude and frequency dependent on the gravity level. Vorticity production is enhanced as gravity increases, which destabilizes the flow and therefore the bubble path.

  5. Effects of gravity level on bubble formation and rise in low-viscosity liquids.

    PubMed

    Suñol, Francesc; González-Cinca, Ricard

    2015-05-01

    We present an experimental analysis of the effects of gravity level on the formation and rise dynamics of bubbles. Experiments were carried out with millimeter-diameter bubbles in the hypergravity environment provided by the large-diameter centrifuge of the European Space Agency. Bubble detachment from a nozzle is determined by buoyancy and surface tension forces regardless of the gravity level. Immediately after detachment, bubble trajectory is deviated by the Coriolis force. Subsequent bubble rise is dominated by inertial forces and follows a zig-zag trajectory with amplitude and frequency dependent on the gravity level. Vorticity production is enhanced as gravity increases, which destabilizes the flow and therefore the bubble path.

  6. Hydrodynamic effects of air sparging on hollow fiber membranes in a bubble column reactor.

    PubMed

    Xia, Lijun; Law, Adrian Wing-Keung; Fane, Anthony G

    2013-07-01

    Air sparging is now a standard approach to reduce concentration polarization and fouling of membrane modules in membrane bioreactors (MBRs). The hydrodynamic shear stresses, bubble-induced turbulence and cross flows scour the membrane surfaces and help reduce the deposit of foulants onto the membrane surface. However, the detailed quantitative knowledge on the effect of air sparging remains lacking in the literature due to the complex hydrodynamics generated by the gas-liquid flows. To date, there is no valid model that describes the relationship between the membrane fouling performance and the flow hydrodynamics. The present study aims to examine the impact of hydrodynamics induced by air sparging on the membrane fouling mitigation in a quantitative manner. A modelled hollow fiber module was placed in a cylindrical bubble column reactor at different axial heights with the trans-membrane pressure (TMP) monitored under constant flux conditions. The configuration of bubble column without the membrane module immersed was identical to that studied by Gan et al. (2011) using Phase Doppler Anemometry (PDA), to ensure a good quantitative understanding of turbulent flow conditions along the column height. The experimental results showed that the meandering flow regime which exhibits high flow instability at the 0.3 m is more beneficial to fouling alleviation compared with the steady flow circulation regime at the 0.6 m. The filtration tests also confirmed the existence of an optimal superficial air velocity beyond which a further increase is of no significant benefit on the membrane fouling reduction. In addition, the alternate aeration provided by two air stones mounted at the opposite end of the diameter of the bubble column was also studied to investigate the associated flow dynamics and its influence on the membrane filtration performance. It was found that with a proper switching interval and membrane module orientation, the membrane fouling can be effectively

  7. Hydrodynamic effects of air sparging on hollow fiber membranes in a bubble column reactor.

    PubMed

    Xia, Lijun; Law, Adrian Wing-Keung; Fane, Anthony G

    2013-07-01

    Air sparging is now a standard approach to reduce concentration polarization and fouling of membrane modules in membrane bioreactors (MBRs). The hydrodynamic shear stresses, bubble-induced turbulence and cross flows scour the membrane surfaces and help reduce the deposit of foulants onto the membrane surface. However, the detailed quantitative knowledge on the effect of air sparging remains lacking in the literature due to the complex hydrodynamics generated by the gas-liquid flows. To date, there is no valid model that describes the relationship between the membrane fouling performance and the flow hydrodynamics. The present study aims to examine the impact of hydrodynamics induced by air sparging on the membrane fouling mitigation in a quantitative manner. A modelled hollow fiber module was placed in a cylindrical bubble column reactor at different axial heights with the trans-membrane pressure (TMP) monitored under constant flux conditions. The configuration of bubble column without the membrane module immersed was identical to that studied by Gan et al. (2011) using Phase Doppler Anemometry (PDA), to ensure a good quantitative understanding of turbulent flow conditions along the column height. The experimental results showed that the meandering flow regime which exhibits high flow instability at the 0.3 m is more beneficial to fouling alleviation compared with the steady flow circulation regime at the 0.6 m. The filtration tests also confirmed the existence of an optimal superficial air velocity beyond which a further increase is of no significant benefit on the membrane fouling reduction. In addition, the alternate aeration provided by two air stones mounted at the opposite end of the diameter of the bubble column was also studied to investigate the associated flow dynamics and its influence on the membrane filtration performance. It was found that with a proper switching interval and membrane module orientation, the membrane fouling can be effectively

  8. Probing the interaction between air bubble and sphalerite mineral surface using atomic force microscope.

    PubMed

    Xie, Lei; Shi, Chen; Wang, Jingyi; Huang, Jun; Lu, Qiuyi; Liu, Qingxia; Zeng, Hongbo

    2015-03-01

    The interaction between air bubbles and solid surfaces plays important roles in many engineering processes, such as mineral froth flotation. In this work, an atomic force microscope (AFM) bubble probe technique was employed, for the first time, to directly measure the interaction forces between an air bubble and sphalerite mineral surfaces of different hydrophobicity (i.e., sphalerite before/after conditioning treatment) under various hydrodynamic conditions. The direct force measurements demonstrate the critical role of the hydrodynamic force and surface forces in bubble-mineral interaction and attachment, which agree well with the theoretical calculations based on Reynolds lubrication theory and augmented Young-Laplace equation by including the effect of disjoining pressure. The hydrophobic disjoining pressure was found to be stronger for the bubble-water-conditioned sphalerite interaction with a larger hydrophobic decay length, which enables the bubble attachment on conditioned sphalerite at relatively higher bubble approaching velocities than that of unconditioned sphalerite. Increasing the salt concentration (i.e., NaCl, CaCl2) leads to weakened electrical double layer force and thereby facilitates the bubble-mineral attachment, which follows the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory by including the effects of hydrophobic interaction. The results provide insights into the basic understanding of the interaction mechanism between bubbles and minerals at nanoscale in froth flotation processes, and the methodology on probing the interaction forces of air bubble and sphalerite surfaces in this work can be extended to many other mineral and particle systems.

  9. A study of the accuracy of neutrally buoyant bubbles used as flow tracers in air

    NASA Technical Reports Server (NTRS)

    Kerho, Michael F.

    1993-01-01

    Research has been performed to determine the accuracy of neutrally buoyant and near neutrally buoyant bubbles used as flow tracers in air. Theoretical, computational, and experimental results are presented to evaluate the dynamics of bubble trajectories and factors affecting their ability to trace flow-field streamlines. The equation of motion for a single bubble was obtained and evaluated using a computational scheme to determine the factors which affect a bubble's trajectory. A two-dimensional experiment was also conducted to experimentally determine bubble trajectories in the stagnation region of NACA 0012 airfoil at 0 deg angle of attack using a commercially available helium bubble generation system. Physical properties of the experimental bubble trajectories were estimated using the computational scheme. These properties included the density ratio and diameter of the individual bubbles. the helium bubble system was then used to visualize and document the flow field about a 30 deg swept semispan wing with simulated glaze ice. Results were compared to Navier-Stokes calculations and surface oil flow visualization. The theoretical and computational analysis have shown that neutrally buoyant bubbles will trace even the most complex flow patterns. Experimental analysis revealed that the use of bubbles to trace flow patterns should be limited to qualitative measurements unless care is taken to ensure neutral buoyancy. This is due to the difficulty in the production of neutrally buoyant bubbles.

  10. The impact and bounce of air bubbles at a flat fluid interface.

    PubMed

    Manica, Rogerio; Klaseboer, Evert; Chan, Derek Y C

    2016-04-01

    The rise and impact of bubbles at an initially flat but deformable liquid-air interface in ultraclean liquid systems are modelled by taking into account the buoyancy force, hydrodynamic drag, inertial added mass effect and drainage of the thin film between the bubble and the interface. The bubble-surface interaction is analyzed using lubrication theory that allows for both bubble and surface deformation under a balance of normal stresses and surface tension as well as the long-range nature of deformation along the interface. The quantitative result for collision and bounce is sensitive to the impact velocity of the rising bubble. This velocity is controlled by the combined effects of interfacial tension via the Young-Laplace equation and hydrodynamic stress on the surface, which determine the deformation of the bubble. The drag force that arises from the hydrodynamic stress in turn depends on the hydrodynamic boundary conditions on the bubble surface and its shape. These interrelated factors are accounted for in a consistent manner. The model can predict the rise velocity and shape of millimeter-size bubbles in ultra-clean water, in two silicone oils of different densities and viscosities and in ethanol without any adjustable parameters. The collision and bounce of such bubbles with a flat water/air, silicone oil/air and ethanol/air interface can then be predicted with excellent agreement when compared to experimental observations. PMID:26924623

  11. Aerobic exercise before diving reduces venous gas bubble formation in humans

    PubMed Central

    Dujić, Željko; Duplančic, Darko; Marinovic-Terzić, Ivana; Baković, Darija; Ivančev, Vladimir; Valic, Zoran; Eterović, Davor; Petri, Nadan M; Wisløff, Ulrik; Brubakk, Alf O

    2004-01-01

    We have previously shown in a rat model that a single bout of high-intensity aerobic exercise 20h before a simulated dive reduces bubble formation and after the dive protects from lethal decompression sickness. The present study investigated the importance of these findings in man. Twelve healthy male divers were compressed in a hyperbaric chamber to 280kPa at a rate of 100kPamin−1 breathing air and remaining at pressure for 80min. The ascent rate was 9mmin−1 with a 7min stop at 130kPa. Each diver underwent two randomly assigned simulated dives, with or without preceding exercise. A single interval exercise performed 24h before the dive consisted of treadmill running at 90% of maximum heart rate for 3min, followed by exercise at 50% of maximum heart rate for 2min; this was repeated eight times for a total exercise period of 40min. Venous gas bubbles were monitored with an ultrasonic scanner every 20min for 80min after reaching surface pressure. The study demonstrated that a single bout of strenuous exercise 24h before a dive to 18 m of seawater significantly reduced the average number of bubbles in the pulmonary artery from 0.98 to 0.22 bubbles cm−2(P= 0.006) compared to dives without preceding exercise. The maximum bubble grade was decreased from 3 to 1.5 (P= 0.002) by pre-dive exercise, thereby increasing safety. This is the first report to indicate that pre-dive exercise may form the basis for a new way of preventing serious decompression sickness. PMID:14755001

  12. Solution-Processed Ultraelastic and Strong Air-Bubbled Graphene Foams.

    PubMed

    Lv, Lingxiao; Zhang, Panpan; Cheng, Huhu; Zhao, Yang; Zhang, Zhipan; Shi, Gaoquan; Qu, Liangti

    2016-06-01

    Solution-processed ultraelastic graphene foams are prepared via a convenient air-bubble-promoted synthesis. These foams can dissipate external compression through the ordered interconnecting graphene network between the bubbles without causing a local fracture and thus reliably show compressive stress of 5.4 MPa at a very high strain of 99%, setting a new benchmark for solution-processed graphene foams.

  13. Modeling biogenic gas bubbles formation and migration in coarse sand

    NASA Astrophysics Data System (ADS)

    Ye, S.

    2011-12-01

    Shujun Ye Department of Hydrosciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China; sjye@nju.edu.cn Brent E. Sleep Department of Civil Engineering, University of Toronto, Toronto, ON, M5S 1A4 CANADA; sleep@ecf.utoronto.ca Methane gas generation in porous media was investigated in an anaerobic two-dimensional sand-filled cell. Inoculation of the lower portion of the cell with a methanogenic culture and addition of methanol to the bottom of the cell led to biomass growth and formation of a gas phase. The formation, migration, distribution and saturation of gases in the cell were visualized by the charge-coupled device (CCD) camera. Gas generated at the bottom of the cell in the biologically active zone moved upwards in discrete fingers, so that gas phase saturations (gas-filled fraction of void space) in the biologically active zone at the bottom of the cell did not exceed 40-50%, while gas accumulation at the top of the cell produced gas phase saturations as high as 80%. Macroscopic invasion percolation (MIP) at near pore scale[Glass, et al., 2001; Kueper and McWhorter, 1992]was used to model gas bubbles growth in porous media. The nonwetting phase migration pathway can be yielded directly by MIP. MIP was adopted to simulate the expansion, fragmentation, and mobilization of gas clusters in the cell. The production of gas, and gas phash saturations were simulated by a continuum model - compositional simulator (COMPSIM) [Sleep and Sykes, 1993]. So a combination of a continuum model and a MIP model was used to simulate the formation, fragmentation and migration of biogenic gas bubbles. Key words: biogenic gas; two dimensional; porous media; MIP; COMPSIM

  14. Gas and liquid measurements in air-water bubbly flows

    SciTech Connect

    Zhou, X.; Doup, B.; Sun, X.

    2012-07-01

    Local measurements of gas- and liquid-phase flow parameters are conducted in an air-water two-phase flow loop. The test section is a vertical pipe with an inner diameter of 50 mm and a height of 3.2 m. The measurements are performed at z/D = 10. The gas-phase measurements are performed using a four-sensor conductivity probe. The data taken from this probe are processed using a signal processing program to yield radial profiles of the void fraction, bubble velocity, and interfacial area concentration. The velocity measurements of the liquid-phase are performed using a state-of-the-art Particle Image Velocimetry (PIV) system. The raw PIV images are acquired using fluorescent particles and an optical filtration device. Image processing is used to remove noise in the raw PIV images. The statistical cross correlation is introduced to determine the axial velocity field and turbulence intensity of the liquid-phase. Measurements are currently being performed at z/D = 32 to provide a more complete data set. These data can be used for computational fluid dynamic model development and validation. (authors)

  15. Role of air bubbles overlooked in the adsorption of perfluorooctanesulfonate on hydrophobic carbonaceous adsorbents.

    PubMed

    Meng, Pingping; Deng, Shubo; Lu, Xinyu; Du, Ziwen; Wang, Bin; Huang, Jun; Wang, Yujue; Yu, Gang; Xing, Baoshan

    2014-12-01

    Hydrophobic interaction has been considered to be responsible for adsorption of perfluorooctanesulfonate (PFOS) on the surface of hydrophobic adsorbents, but the long C-F chain in PFOS is not only hydrophobic but also oleophobic. In this study, for the first time we propose that air bubbles on the surface of hydrophobic carbonaceous adsorbents play an important role in the adsorption of PFOS. The level of adsorption of PFOS on carbon nanotubes (CNTs), graphite (GI), graphene (GE), and powdered activated carbon (PAC) decreases after vacuum degassing. Vacuum degassing time and pressure significantly affect the removal of PFOS by these adsorbents. After vacuum degassing at 0.01 atm for 36 h, the extent of removal of PFOS by the pristine CNTs and GI decreases 79% and 74%, respectively, indicating the main contribution of air bubbles to PFOS adsorption. When the degassed solution is recontacted with air during the adsorption process, the removal of PFOS recovers to the value obtained without vacuum degassing, further verifying the key role of air bubbles in PFOS adsorption. By theoretical calculation, the distribution of PFOS in air bubbles on the adsorbent surfaces is discussed, and a new schematic sorption model of PFOS on carbonaceous adsorbents in the presence of air bubbles is proposed. The accumulation of PFOS at the interface of air bubbles on the adsorbents is primarily responsible for its adsorption, providing a new mechanistic insight into the transport, fate, and removal of PFOS. PMID:25365738

  16. Role of air bubbles overlooked in the adsorption of perfluorooctanesulfonate on hydrophobic carbonaceous adsorbents.

    PubMed

    Meng, Pingping; Deng, Shubo; Lu, Xinyu; Du, Ziwen; Wang, Bin; Huang, Jun; Wang, Yujue; Yu, Gang; Xing, Baoshan

    2014-12-01

    Hydrophobic interaction has been considered to be responsible for adsorption of perfluorooctanesulfonate (PFOS) on the surface of hydrophobic adsorbents, but the long C-F chain in PFOS is not only hydrophobic but also oleophobic. In this study, for the first time we propose that air bubbles on the surface of hydrophobic carbonaceous adsorbents play an important role in the adsorption of PFOS. The level of adsorption of PFOS on carbon nanotubes (CNTs), graphite (GI), graphene (GE), and powdered activated carbon (PAC) decreases after vacuum degassing. Vacuum degassing time and pressure significantly affect the removal of PFOS by these adsorbents. After vacuum degassing at 0.01 atm for 36 h, the extent of removal of PFOS by the pristine CNTs and GI decreases 79% and 74%, respectively, indicating the main contribution of air bubbles to PFOS adsorption. When the degassed solution is recontacted with air during the adsorption process, the removal of PFOS recovers to the value obtained without vacuum degassing, further verifying the key role of air bubbles in PFOS adsorption. By theoretical calculation, the distribution of PFOS in air bubbles on the adsorbent surfaces is discussed, and a new schematic sorption model of PFOS on carbonaceous adsorbents in the presence of air bubbles is proposed. The accumulation of PFOS at the interface of air bubbles on the adsorbents is primarily responsible for its adsorption, providing a new mechanistic insight into the transport, fate, and removal of PFOS.

  17. Pachymetry-guided intrastromal air injection ("pachy-bubble") for deep anterior lamellar keratoplasty.

    PubMed

    Ghanem, Ramon C; Ghanem, Marcielle A

    2012-09-01

    To evaluate an innovative technique for intrastromal air injection to achieve deep anterior lamellar keratoplasty (DALK) with bare Descemet membrane (DM). Thirty-four eyes with anterior corneal pathology, including 27 with keratoconus, underwent DALK. After 400 μm trephination with a suction trephine, ultrasound pachymetry was performed 0.8 mm internally from the trephination groove in the 11 to 1 o'clock position. In this area, a 2-mm incision was created, parallel to the groove, with a micrometer diamond knife calibrated to 90% depth of the thinnest measurement. A cannula was inserted through the incision and 0.5 mL of air was injected to dissect the DM from the stroma. After peripheral paracentesis, anterior keratectomy was carried out to bare the DM. A 0.25-mm oversized graft was sutured in place. Overall, 94.1% of eyes achieved DALK. Bare DM was achieved in 30 eyes, and a pre-DM dissection was performed in 2 eyes. Air injection was successful in detaching the DM (achieving the big bubble) in 88.2% of the eyes. In keratoconus eyes, the rate was 88.9%. All cases but one required a single air injection to achieve DM detachment. Microperforations occurred in 5 cases: 3 during manual layer-by-layer dissection after air injection failed to detach the DM, 1 during removal of the residual stroma after big-bubble formation, and 1 during the diamond knife incision. Two cases (5.9%) were converted to penetrating keratoplasty because of macroperforations. The technique was reproducible, safe, and highly effective in promoting DALK with bare DM. PMID:22367050

  18. Elastic oscillations of bubbles separated from an air cavity in a magnetic fluid

    NASA Astrophysics Data System (ADS)

    Polunin, V. M.; Shabanova, I. A.; Karpova, G. V.; Kobelev, N. S.; Ryabtsev, K. S.; Platonov, V. B.; Aref'ev, I. M.

    2015-07-01

    The elastic oscillations of air bubbles separated from an air cavity compressed by the ponderomotive forces of a magnetic field in a magnetic fluid are accompanied by the appearance of an alternating magnetic field component. The frequency of the alternating component corresponds to the frequency of radial bubble oscillations, and this fact is used to determine the bubble size. A great body of experimental data has been obtained from six magnetic fluid samples with different viscosities. Based on these data, histograms illustrating the bubble radius distribution are plotted. The appearance of the alternating magnetic field component caused by bubble oscillations in a magnetized magnetic fluid can be used to develop a fundamentally new method for supplying small metered gas shots to a reactor, as well as to study the boiling process in a magnetic fluid.

  19. 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.

  20. A method for measurement of the bubble formation threshold in biological liquids.

    PubMed

    Bjorno, L; Kornum, L O; Krag, P; Nielsen, C H; Paulev, P E

    1977-06-01

    Liquid under pressure is saturated with a given gas, such as argon, nitrogen, or air, by circulation through a column of gas exchangers. A sample of the gas-saturated liquid is isolated in a test chamber, the volume of which can be increased by means of a moving piston. The piston motion is cyclical with a variable frequency. Pressure in the test chamber is measured by means of a capacitive pressure pick-up. When the volume increase of the gas-saturated liquid in the test chamber is compensated for by the development of gas phase bubbles, the pressure decrease will stop; the recording device will show a pressure plateau, or a dip in the pressure-time course, depending on the velocity of the growth of the bubbles. Bubble formation threshold was independent of the frequency of the piston movement within frequency limits from 1 Hz down to 10(-3) Hz. Most experiements were carried out at a single frequency of 0.5 Hz. This new method appears to have advantages over previous ones.

  1. THE MILKY WAY PROJECT: A STATISTICAL STUDY OF MASSIVE STAR FORMATION ASSOCIATED WITH INFRARED BUBBLES

    SciTech Connect

    Kendrew, S.; Robitaille, T. P.; Simpson, R.; Lintott, C. J.; Bressert, E.; Povich, M. S.; Sherman, R.; Schawinski, K.; Wolf-Chase, G.

    2012-08-10

    The Milky Way Project citizen science initiative recently increased the number of known infrared bubbles in the inner Galactic plane by an order of magnitude compared to previous studies. We present a detailed statistical analysis of this data set with the Red MSX Source (RMS) catalog of massive young stellar sources to investigate the association of these bubbles with massive star formation. We particularly address the question of massive triggered star formation near infrared bubbles. We find a strong positional correlation of massive young stellar objects (MYSOs) and H II regions with Milky Way Project bubbles at separations of <2 bubble radii. As bubble sizes increase, a statistically significant overdensity of massive young sources emerges in the region of the bubble rims, possibly indicating the occurrence of triggered star formation. Based on numbers of bubble-associated RMS sources, we find that 67% {+-} 3% of MYSOs and (ultra-)compact H II regions appear to be associated with a bubble. We estimate that approximately 22% {+-} 2% of massive young stars may have formed as a result of feedback from expanding H II regions. Using MYSO-bubble correlations, we serendipitously recovered the location of the recently discovered massive cluster Mercer 81, suggesting the potential of such analyses for discovery of heavily extincted distant clusters.

  2. Oxygenation of Stratified Reservoir Using Air Bubble Plume

    NASA Astrophysics Data System (ADS)

    Schladow, S. G.

    2006-12-01

    Excess nutrients loading from urban area and watershed into lakes and reservoirs increases the content of organic matter, which, through decomposition, needs increased dissolve oxygen (DO). Many eutrophic reservoirs and lakes cannot meet the DO requirement during stratified season and suffers from the hypolimnetic anoxia. As a result, benthic sediment produces anoxic products such as methane, hydrogen sulphide, ammonia, iron, manganese, and phosphorus. In order to address the hypolimnetic anoxia, oxygen is artificially supplied into reservoir using an aeration system (i.e., bubbler). The most common result of lake/reservoir aeration is to destratify the reservoir so that the water body may completely mix under natural phenomena and remain well oxygenated throughout. Other advantages of destratification are: (1) allows warm- water fish to inhabit the entire reservoir, (2) suppress the nutrient release from sediment, and (3) decreases the algal growth by sending them to the darker zone. A one-dimensional reservoir-bubbler model is developed and applied to examine the effects of an aeration system on mixing and dissolved oxygen dynamics in the Upper Peirce Reservoir, Singapore. After introduction of the aeration system in the reservoir, it was found that the hypolimnetic DO increased significantly, and the concentration of algae, soluble manganese and iron substantially reduced. It is found that the reservoir-bubbler model predicts the mixing (temperature as mixing parameter) and dissolved oxygen concentration in the reservoir with acceptable accuracy. It is shown in terms of bubbler mechanical efficiency (i.e., operating cost) and total DO contribution from the aeration system into the reservoir that the selections of airflow rate per diffuser, air bubble radius, and total number of diffusers are important design criteria of a bubbler system. However, the overall bubbler design also depends on the reservoir size and stratified area of interest, ambient climate, and

  3. Molecular dynamics simulation of helium cluster diffusion and bubble formation in bulk tungsten

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Chun; Shu, Xiaolin; Tao, Peng; Yu, Yi; Niu, Guo-Jiang; Xu, Yuping; Gao, Fei; Luo, Guang-Nan

    2014-12-01

    Molecular dynamics (MD) simulations have been performed to investigate the diffusion behavior of helium (He) clusters in tungsten (W), because their diffusion properties provide basic knowledge in understanding the He bubble formation. The binding energy between He and He cluster is shown to be positive, and thus, He is easy to form bubbles by self-trapping. The mean squared displacements (MSDs) were employed to determine the diffusivities of He clusters with different sizes at different temperatures. The He bubble formation at different temperatures with 1% He was also investigated. It is revealed that the formation of He bubbles is strongly associated with the temperature and the diffusivities of the He clusters in W. The results demonstrate the initial stage of the He bubble formation and growth in W.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  5. Impact of bubble size in a rat model of cerebral air microembolization

    PubMed Central

    2013-01-01

    Background Cerebral air microembolization (CAM) is a frequent side effect of diagnostic or therapeutic interventions. Besides reduction of the amount of bubbles, filter systems in the clinical setting may also lead to a dispersion of large gas bubbles and therefore to an increase of the gas–liquid-endothelium interface. We evaluated the production and application of different strictly defined bubble diameters in a rat model of CAM and assessed functional outcome and infarct volumes in relation to the bubble diameter. Methods Gas emboli of defined number and diameter were injected into the carotid artery of rats. Group I (n = 7) received 1800 air bubbles with a diameter of 45 μm, group II (n = 7) 40 bubbles of 160 μm, controls (n = 6) saline without gas bubbles; group I and II yielded the same total injection volume of air with 86 nl. Functional outcome was assessed at baseline, after 4 h and 24 h following cerebral MR imaging and infarct size calculation. Results Computer-aided evaluation of bubble diameters showed high constancy (group I: 45.83 μm ± 2.79; group II: 159 μm ± 1.26). Animals in group I and II suffered cerebral ischemia and clinical deterioration without significant difference. Infarct sizes did not differ significantly between the two groups (p = 0.931 u-test). Conclusions We present further development of a new method, which allows reliable and controlled CAM with different bubble diameters, producing neurological deficits due to unilateral cerebral damage. Our findings could not display a strong dependency of stroke frequency and severity on bubble diameter. PMID:24139539

  6. Bubble Formation from Wall Orifice in Liquid Cross-Flow Under Low Gravity

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.; Kamotani, Y.

    2000-01-01

    Two-phase flows present a wide variety of applications for spacecraft thermal control systems design. Bubble formation and detachment is an integral part of the two phase flow science. The objective of the present work is to experimentally investigate the effects of liquid cross-flow velocity, gas flow rate, and orifice diameter on bubble formation in a wall-bubble injection configuration. Data were taken mainly under reduced gravity conditions but some data were taken in normal gravity for comparison. The reduced gravity experiment was conducted aboard the NASA DC-9 Reduced Gravity Aircraft. The results show that the process of bubble formation and detachment depends on gravity, the orifice diameter, the gas flow rate, and the liquid cross-flow velocity. The data are analyzed based on a force balance, and two different detachment mechanisms are identified. When the gas momentum is large, the bubble detaches from the injection orifice as the gas momentum overcomes the attaching effects of liquid drag and inertia. The surface tension force is much reduced because a large part of the bubble pinning edge at the orifice is lost as the bubble axis is tilted by the liquid flow. When the gas momentum is small, the force balance in the liquid flow direction is important, and the bubble detaches when the bubble axis inclination exceeds a certain angle.

  7. Gas Bubble Formation in Stagnant and Flowing Mercury

    SciTech Connect

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

    2007-01-01

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

  8. Noise reduction by the application of an air-bubble curtain in offshore pile driving

    NASA Astrophysics Data System (ADS)

    Tsouvalas, A.; Metrikine, A. V.

    2016-06-01

    Underwater noise pollution is a by-product of marine industrial operations. In particular, the noise generated when a foundation pile is driven into the soil with an impact hammer is considered to be harmful for the aquatic species. In an attempt to reduce the ecological footprint, several noise mitigation techniques have been investigated. Among the various solutions proposed, the air-bubble curtain is often applied due to its efficacy in noise reduction. In this paper, a model is proposed for the investigation of the sound reduction during marine piling when an air-bubble curtain is placed around the pile. The model consists of the pile, the surrounding water and soil media, and the air-bubble curtain which is positioned at a certain distance from the pile surface. The solution approach is semi-analytical and is based on the dynamic sub-structuring technique and the modal decomposition method. Two main results of the paper can be distinguished. First, a new model is proposed that can be used for predictions of the noise levels in a computationally efficient manner. Second, an analysis is presented of the principal mechanisms that are responsible for the noise reduction due to the application of the air-bubble curtain in marine piling. The understanding of these mechanisms turns to be crucial for the exploitation of the maximum efficiency of the system. It is shown that the principal mechanism of noise reduction depends strongly on the frequency content of the radiated sound and the characteristics of the bubbly medium. For piles of large diameter which radiate most of the acoustic energy at relatively low frequencies, the noise reduction is mainly attributed to the mismatch of the acoustic impedances between the seawater and the bubbly layer. On the contrary, for smaller piles and when the radiated acoustic energy is concentrated at frequencies close to, or higher than, the resonance frequency of the air bubbles, the sound absorption within the bubbly layer

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  10. Laser induced fluorescence measurements of dissolved oxygen concentration fields near air bubble surfaces

    NASA Astrophysics Data System (ADS)

    Roy, Sabita; Duke, Steve R.

    2000-09-01

    This article describes a laser-induced fluorescence (LIF) technique for measuring dissolved oxygen concentration gradients in water near the surface of an air bubble. Air bubbles are created at the tip of a needle in a rectangular bubble column filled with water that contains pyrenebutyric acid (PBA). The fluorescence of the PBA is induced by a planar pulse of nitrogen laser light. Oxygen transferring from the air bubble to the deoxygenated water quenches the fluorescence of the PBA. Images of the instantaneous and two-dimensional fluorescence field are obtained by a UV-intensified charge-coupled device (CCD) camera. Quenching of fluorescence intensity is determined at each pixel in the CCD image to measure dissolved oxygen concentration. Two-dimensional concentration fields are presented for a series of measurements of oxygen transfer from 1.6 mm bubbles suspended on the tip of a needle in a quiescent fluid. The images show the spatially varying concentration profiles, gradients, and boundary layer thicknesses at positions around the bubble surfaces. These direct and local measurements of concentration behavior within the mass transfer boundary layer show the potential of this LIF technique for the development of general and mechanistic models for oxygen transport across the air-water interface.

  11. Acoustic wave propagation in air-bubble curtains in water. Part 2. Field experiment

    SciTech Connect

    Domenico, S.N.

    1982-03-01

    A field experiment consisted of hydrophone recordings in a pond, 25 ft deep, of signals transmitted through air-bubble curtains from a water gun source. The air curtains issued from one to 13 pipes (20 ft long and spaced at 1.67-ft intervals). Air pressures used in the pipes were 15, 25, and 50 psi. Length and complexity of the signals indicate that reverberations occurred to an increasing extent as the number of consecutive air curtains was increased. Analysis of the first pulse in the recorded signals, after approximate removal of hydrophone and recorder response, indicates that the reverberations occur principally in the bubble-free corridors between air curtains. This pulse broadens and its peak amplitude is delayed linearly as the number of successive air curtains is increased. The peak amplitude is decreased substantially by the first air curtain and thereafter remains between 0.1 and 0.2 of the amplitude without air curtains.

  12. In-situ observation of bubble formation at silicon melt-silica glass interface

    NASA Astrophysics Data System (ADS)

    Minami, Toshiro; Maeda, Susumu; Higasa, Mitsuo; Kashima, Kazuhiko

    2011-03-01

    The generation mechanism of pinhole defects in the Czochralski (CZ)-grown silicon (Si) single crystals was clarified by in-situ observations of bubble formation at the interface between Si melt and a silica glass crucible in a small experimental apparatus. The nucleation and growth of bubbles were facilitated by creating small cavities on the inner wall of the crucible. Si melting was conducted in an argon (Ar) atmosphere, and the pressure was maintained at either 100 Torr or close to a vacuum (no Ar-gas flow). It was found that in the presence of Ar, bubbles formed in the cavities immediately after the cavities came in contact with the melt. However, no bubbles formed in a vacuum in the experimental apparatus. These results indicate that the bubbles formed in the cavities are largely filled with Ar, and the initial bubble volumes are nearly comparable with those of the cavities. In an initial stage of expansion of a bubble, estimated volumes changed nearly in accordance with the Boyle-Charles law. Further, participation of SiO gas in bubble growth may explain the deviation of the bubble volume from the theoretical value anticipated if only Ar gas was involved in the bubble growth.

  13. Effect of a short-acting NO donor on bubble formation from a saturation dive in pigs.

    PubMed

    Møllerløkken, A; Berge, V J; Jørgensen, A; Wisløff, U; Brubakk, A O

    2006-12-01

    It has previously been reported that a nitric oxide (NO) donor reduces bubble formation from an air dive and that blocking NO production increases bubble formation. The present study was initiated to see whether a short-acting NO donor (glycerol trinitrate, 5 mg/ml; Nycomed Pharma) given immediately before start of decompression would affect the amount of vascular bubbles during and after decompression from a saturation dive in pigs. A total of 14 pigs (Sus scrofa domestica of the strain Norsk landsvin) were randomly divided into an experimental (n = 7) and a control group (n = 7). The pigs were anesthetized with ketamine and alpha-chloralose and compressed in a hyperbaric chamber to 500 kPa (40 m of seawater) in 2 min, and they had 3-h bottom time while breathing nitrox (35 kPa O(2)). The pigs were all decompressed to the surface (100 kPa) at a rate of 200 kPa/h. During decompression, the inspired Po(2) of the breathing gas was kept at 100 kPa. Thirty minutes before decompression, the experimental group received a short-acting NO donor intravenously, while the control group were given equal amounts of saline. The average number of bubbles seen during the observation period decreased from 0.2 to 0.02 bubbles/cm(2) (P < 0.0001) in the experimental group compared with the controls. The present study gives further support to the role of NO in preventing vascular bubble formation after decompression.

  14. Effects of gravity level on bubble formation and rise in low-viscosity liquids.

    PubMed

    Suñol, Francesc; González-Cinca, Ricard

    2015-05-01

    We present an experimental analysis of the effects of gravity level on the formation and rise dynamics of bubbles. Experiments were carried out with millimeter-diameter bubbles in the hypergravity environment provided by the large-diameter centrifuge of the European Space Agency. Bubble detachment from a nozzle is determined by buoyancy and surface tension forces regardless of the gravity level. Immediately after detachment, bubble trajectory is deviated by the Coriolis force. Subsequent bubble rise is dominated by inertial forces and follows a zig-zag trajectory with amplitude and frequency dependent on the gravity level. Vorticity production is enhanced as gravity increases, which destabilizes the flow and therefore the bubble path. PMID:26066251

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

    SciTech Connect

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

    2011-03-01

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

  16. Interaction between bubble and air-backed plate with circular hole

    NASA Astrophysics Data System (ADS)

    Liu, Y. L.; Wang, S. P.; Zhang, A. M.

    2016-06-01

    This paper investigates the nonlinear interaction between a violent bubble and an air-backed plate with a circular hole. A numerical model is established using the incompressible potential theory coupled with the boundary integral method. A double-node technique is used to solve the overdetermined problem caused by the intersection between the solid wall and the free surface. A spark-generated bubble near the air-backed plate with a circular hole is observed experimentally using a high-speed camera. Our numerical results agree well with the experimental results. Both experimental and numerical results show that a multilevel spike emerges during the bubble's expansion and contraction. Careful numerical simulation reveals that this special type of spike is caused by the discontinuity in the boundary condition. The influences of the hole size and depth on the bubble and spike dynamics are also analyzed.

  17. Bubble Formation at a Submerged Orifice in High-Speed Horizontal Oscillation

    NASA Astrophysics Data System (ADS)

    Wang, Ningzhen; Chen, Xiang; Yuan, Jianyu; Wang, Guiquan; Li, Yanxiang; Zhang, Huawei; Liu, Yuan

    2016-08-01

    Reducing the cell size of aluminum foams is always a hot and difficult topic in the fabrication of aluminum foams by gas injection route. There lacks theoretical guidance for the bubble size reduction when foaming by the dynamic gas injection method. For the convenience of observation, the aqueous bubbles from small-sized orifice in the high-speed horizontal oscillation were investigated in this paper. A bubble formation and detachment model in the high-speed horizontal oscillation system was proposed. The high-speed system with horizontal simple harmonic oscillation could reduce the average bubble size of aqueous foam effectively. The regularity of bubble formation and the influence of experimental parameters on average bubble size can be predicted by the theoretical model, and the experimental results agree well with the theoretical calculation. The results have shown that bubbles generally detach from the orifice at deceleration periods of the simple harmonic oscillation, and there exist several fixed sizes of bubbles with the fixed experimental parameters due to the effects of periodic forces. The average bubble size decreases with the increase of oscillation frequency and amplitude, and it roughly increases with the increase of gas flow rate. Using the high-speed horizontal oscillation method to prepare aluminum foams, the cell size can be reduced to about 1 mm. Moreover, the cell sizes of aluminum foam can be well predicted by this theoretical model.

  18. Formation and stability of oxygen-rich bubbles that shape photosynthetic mats.

    PubMed

    Bosak, T; Bush, J W M; Flynn, M R; Liang, B; Ono, S; Petroff, A P; Sim, M S

    2010-01-01

    Gas release in photic-zone microbialites can lead to preservable morphological biosignatures. Here, we investigate the formation and stability of oxygen-rich bubbles enmeshed by filamentous cyanobacteria. Sub-millimetric and millimetric bubbles can be stable for weeks and even months. During this time, lithifying organic-rich laminae surrounding the bubbles can preserve the shape of bubbles. Cm-scale unstable bubbles support the growth of centimetric tubular towers with distinctly laminated mineralized walls. In environments that enable high photosynthetic rates, only small stable bubbles will be enclosed by a dense microbial mesh, while in deep waters extensive microbial mesh will cover even larger photosynthetic bubbles, increasing their preservation potential. Stable photosynthetic bubbles may be preserved as sub-millimeter and millimeter-diameter features with nearly circular cross-sections in the crests of some Proterozoic conical stromatolites, while centrimetric tubes formed around unstable bubbles provide a model for the formation of tubular carbonate microbialites that are not markedly depleted in (13)C.

  19. [Air Bubble in the Left Ventricle due to Computed Tomography Guided Lung Needle Biopsy].

    PubMed

    Matsuda, Eisuke; Yoshida, Kumiko; Yoshiyama, Koichi; Hayashi, Tatsuro; Tanaka, Toshiki; Tao, Hiroyuki; Okabe, Kazunori

    2015-11-01

    Computed tomography (CT) guided lung biopsy is a useful examination in diagnosing pulmonary diseases, but the complications such as pneumothorax or pulmonary hemorrhage can not be ignored. Among them, air embolization is a severe complication, although it is infrequently encountered. Forty two-year-old man admitted to our department for the examination of left lung tumor. CT guided lung biopsy was performed. After examination, the patient showed disturbance in cardiac function, which recovered in several minutes. Chest CT revealed air bubble in the left ventricle. After 2-hours head down position followed by bed rest, air bubble is confirmed to be dissappeared by CT.

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

    NASA Technical Reports Server (NTRS)

    Darrozes, J. S.; Ligneul, P.

    1982-01-01

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

  1. Effect of air bubble on inflammation after cataract surgery in rabbit eyes

    PubMed Central

    Demirci, Goktug; Karabaş, Levent; Maral, Hale; Ozdek, Şengül; Gülkılık, Gökhan

    2013-01-01

    Purpose: Intense inflammation after cataract surgery can cause cystoid macular edema, posterior synechia and posterior capsule opacification. This experimental study was performed to investigate the effect of air bubble on inflammation when given to anterior chamber of rabbit eyes after cataract surgery. Materials and Methods: 30 eyes of 15 rabbits were enrolled in the study. One of the two eyes was in the study group and the other eye was in the control group. After surgery air bubble was given to the anterior chamber of the study group eye and balanced salt solution (BSS; Alcon) was left in the anterior chamber of control eye. Results: On the first, second, fourth and fifth days, anterior chamber inflammations of the eyes were examined by biomicroscopy. On the sixth day anterior chamber fluid samples were taken for evaluation of nitric oxide levels as an inflammation marker. When the two groups were compared, in the air bubble group there was statistically less inflammation was seen. (1, 2, 4. days P = 0,001, and 5. day P = 0,009). Conclusions: These results have shown that when air bubble is left in anterior chamber of rabbits’ eyes after cataract surgery, it reduced inflammation. We believe that, air bubble in the anterior chamber may be more beneficial in the cataract surgery of especially pediatric age group, uveitis patients and diabetics where we see higher inflammation. However, greater and long termed experimental and clinical studies are necessary for more accurate findings. PMID:23571264

  2. Aerobic endurance training reduces bubble formation and increases survival in rats exposed to hyperbaric pressure

    PubMed Central

    Wisløff, Ulrik; Brubakk, Alf O

    2001-01-01

    The formation of bubbles is the basis for injury to divers after decompression, a condition known as decompression illness. In the present study we investigated the effect of endurance training in the rat on decompression-induced bubble formation. A total of 52 adult female Sprague-Dawley rats (300-370 g) were randomly assigned to one of two experimental groups: training or sedentary control. Trained rats exercised on a treadmill for 1.5 h per day for 1 day, or for 2 or 6 weeks (5 days per week) at exercise intervals that alternated between 8 min at 85-90 % of maximal oxygen uptake (V̇O2,max) and 2 min at 50-60 % of V̇O2,max. Rats were compressed (simulated dive) in a decompression chamber in pairs, one sedentary and one trained, at a rate of 200 kPa min−1 to a pressure of 700 kPa, and maintained for 45 min breathing air. At the end of the exposure period, rats were decompressed linearly to the ‘surface’ (100 kPa) at a rate of 50 kPa min−1. Immediately after reaching the ‘surface’ (100 kPa) the animals were anaesthetized and the right ventricle was insonated using Doppler ultrasound. Intensity-controlled interval training significantly increased V̇O2,max by 12 and 60 % after 2 and 6 weeks, respectively. At 6 weeks, left and right ventricular weights were 14 and 17 % higher, respectively, in trained compared to control rats. No effect of training was observed on skeletal muscle weight. Bubble formation was significantly reduced in trained rats after both 2 and 6 weeks. However, the same effect was seen after a single bout of aerobic exercise lasting 1.5 h on the day prior to decompression. All of the rats that exercised for 1.5 h and 2 weeks, and most of those that trained for 6 weeks, survived the protocol, whereas most sedentary rats died within 60 min post-decompression. This study shows that aerobic exercise protects rats from severe decompression and death. This may be a result of less bubbling in the trained animals. The data showed that the

  3. Formation of micro/nano structures out of soap bubbles

    NASA Astrophysics Data System (ADS)

    Bai, Xiao-Dan; Liu, Jing

    2007-07-01

    We proposed to synthesize, etch and construct micro/nano structures through manipulating the large-scale bubbles composed of specific chemical compounds. The core of the method lies in the chemical reaction occurred at the interfaces between two or more soap bubbles. A unique virtue of the bubble is that it can have a rather large diameter however an extremely small membrane thickness, whose smallest size could reach nano scale. Therefore, the chemical reaction and synthesis occurred in the common interface of such contacting bubbles would lead to products with very small size. Several typical micro structures were fabricated to demonstrate the feasibility of the new method. Being flexible, easily controllable and environment friendly, the present concept may open a straightforward low-cost way for making micro/nano structures.

  4. Bubble Festival: Presenting Bubble Activities in a Learning Station Format. Teacher's Guide.

    ERIC Educational Resources Information Center

    Barber, Jacqueline; Willard, Carolyn

    This learning station guide adapts the Bubble Festival, an all-school event, for individual classrooms. It presents students with a variety of different challenges at learning stations set up around the classroom. The activities are student-centered and involve open-ended investigations. Also included are ways to extend students' experiences at…

  5. The air bubble entrapped under a drop impacting on a solid surface

    NASA Astrophysics Data System (ADS)

    Thoroddsen, S. T.; Etoh, T. G.; Takehara, K.; Ootsuka, N.; Hatsuki, Y.

    2005-12-01

    We present experimental observations of the disk of air caught under a drop impacting onto a solid surface. By imaging the impact through an acrylic plate with an ultra-high-speed video camera, we can follow the evolution of the air disk as it contracts into a bubble under the centre of the drop. The initial size and contraction speed of the disk were measured for a range of impact Weber and Reynolds numbers. The size of the initial disk is related to the bottom curvature of the drop at the initial contact, as measured in free-fall. The initial contact often leaves behind a ring of micro-bubbles, marking its location. The air disk contracts at a speed comparable to the corresponding air disks caught under a drop impacting onto a liquid surface. This speed also seems independent of the wettability of the liquid, which only affects the azimuthal shape of the contact line. For some impact conditions, the dynamics of the contraction leaves a small droplet at the centre of the bubble. This arises from a capillary wave propagating from the edges of the contracting disk towards the centre. As the wave converges its amplitude grows until it touches the solid substrate, thereby pinching off the micro-droplet at the plate, in the centre of the bubble. The effect of increasing liquid viscosity is to slow down the contraction speed and to produce a more irregular contact line leaving more micro-bubbles along the initial ring.

  6. Acoustic localization in weakly compressible elastic media containing random air bubbles.

    PubMed

    Liang, Bin; Cheng, Jian-chun

    2007-01-01

    We study theoretically the propagation of longitudinal wave in weakly compressible elastic media containing random air bubbles by using a self-consistent method. By inspecting the scattering cross section of an individual bubble and estimating the mean free paths of the elastic wave propagating in the bubbly weakly compressible media, the mode conversion is numerically proved negligible as the longitudinal wave is scattered by the bubbles. On the basis of the bubble dynamic equation, the wave propagation is solved rigorously with the multiple scattering effects incorporated. In a range of frequency slightly above the bubble resonance frequency, the acoustic localization in such a class of media is theoretically identified with even a very small volume fraction of bubbles. We present a method by analyzing the spatial correlation of wave field to identify the phenomenon of localization, which turns out to be effective. The sensibility of the features of localization to the structure parameters is numerically investigated. The spatial distribution of acoustic energy is also studied and the results show that the waves are trapped within a spatial domain adjacent to the source when localization occurs.

  7. Massively-multicellular alignment with the self-aggregate of air bubbles.

    PubMed

    Tanaka, Nobuyuki; Haraguchi, Yuji; Shimizu, Tatsuya; Yamato, Masayuki; Okano, Teruo; Miyake, Jun

    2015-08-01

    This study proposes a cell manipulation method with aggregated air bubbles on cell culture medium. This method requires no additional regents nor devices, except for normal cell-culture materials such as cell culture dishes and pipettes. Bubbles generated by pipetting were spontaneously aggregated with regularity on the whole surface and used as a mask for avoiding cell adhesion after cell-seeding. The diameter of bubbles was able to be controlled by the size of micro-pipette tips. Seeded cells spread to the whole area along the bubble gap. This technique is a surface-tension-driven self-assembly-based method. Using this technique, millions of living cells were successfully aligned into a hexagonal pattern within 300 μm in pattern width on the whole surface of dish for less than 2 h. PMID:26737056

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

    NASA Astrophysics Data System (ADS)

    Asakuma, Yusuke; Munenaga, Takuya; Nakata, Ryosuke

    2016-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Asakuma, Yusuke; Munenaga, Takuya; Nakata, Ryosuke

    2015-10-01

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

  10. Size distribution of oceanic air bubbles entrained in sea-water by wave-breaking

    NASA Technical Reports Server (NTRS)

    Resch, F.; Avellan, F.

    1982-01-01

    The size of oceanic air bubbles produced by whitecaps and wave-breaking is determined. The production of liquid aerosols at the sea surface is predicted. These liquid aerosols are at the origin of most of the particulate materials exchanged between the ocean and the atmosphere. A prototype was designed and built using an optical technique based on the principle of light scattering at an angle of ninety degrees from the incident light beam. The output voltage is a direct function of the bubble diameter. Calibration of the probe was carried out within a range of 300 microns to 1.2 mm. Bubbles produced by wave-breaking in a large air-sea interaction simulating facility. Experimental results are given in the form of size spectrum.

  11. A simple technique for evacuating air bubbles with scum from the bladder dome during transurethral resection of bladder tumor.

    PubMed

    Takeshita, Hideki; Moriyama, Shingo; Chiba, Koji; Noro, Akira

    2014-12-01

    Air bubbles floating in the bladder dome during transurethral resection of a bladder tumor can interfere with the resection, causing intravesical explosion and increasing the potential risk of tumor cell reimplantation. We describe a simple and effective technique for evacuating air bubbles from the bladder dome using routine resectoscopes. First, the beak of the resectoscope is positioned near the air bubble in the bladder dome. Second, the drainage channel of the resectoscope is closed. Third, the irrigation tube is detached from the irrigation channel, and then the channel is opened. Subsequently, the air bubble with entangled scum will be retrogradely aspirated from the beak of the resectoscope to the irrigation channel. Reversing the direction of the water stream enables evacuation of the air bubble with the scum under direct vision. This simple and effective technique may assist surgeons and ensure the safety of patients during a transurethral procedure. PMID:25562002

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    , the force balance in the liquid flow direction is important, and the bubble detaches when the bubble axis inclination exceeds a certain angle. With wall heating, liquid motion around an air bubble in cross-flowing 2cs silicone oil is experimentally investigated in 1-g. A spectral element based steady 2D numerical model is also developed. The traces of particles from experimental flow visualization and the corresponding computed streamlines are shown. At the upstream side of the bubble facing the cross-flow, thermocapillary and forced convection create liquid motion away from the wall, up along the surface. At the downstream side, a competing interaction between the two creates a recirculation cell, causing the bulk liquid to stagnate on the surface and separate thereafter. The important dimensionless parameters are - Surface tension and local cross-flow Reynolds numbers R(sub sigma)(U(sub ref)a/v) and Re(sub loc)(U(sub L)a/v), respectively based on reference thermocapillary U(sub ref)(sigma(sub T)Delta.T/mu, Delta T=T(sub wall)-T(sub liquid)) and local cross-flow velocity U(sub L), Prandtl number P(sub r) and Grashoff number Gr(rho.g.beta.DeltaTa(sup 3)/mu.v). Variation of the stagnation point with R(sub sigma) and Re(sub loc) is shown. Also shown are good agreement between experimental and numerical results in 1-g. The computational model is extended to mu-g condition to investigate temperature and velocity on the bubble surface, stagnation and reattachment points of the recirculation cell and wall heat transfer. It is observed that wall heating significantly alters the flow field around the bubble and thus the forces acting on the bubble, which control its detachment. Thus a combination of heating and liquid cross-flow can be utilized to precisely control bubble formation in a mu-g environment.

  13. Using strobe lights, air bubble curtains for cost-effective fish diversion

    SciTech Connect

    McCauley, D.J.; Navarro, J.E.; Mountouri, L.

    1996-04-01

    Faced with a high, and potentially costly, rate of fish turbine passage, a northern Michigan hydro project owner began investigating the use of behavioral barriers to divert fish away from turbines. Strobe lights, with and without air bubbles, proved to be highly effective, yielding dramatic reductions in the number of fish entrained.

  14. Hydrostatic pressure effect on micro air bubbles deposited on surfaces with a retreating tip.

    PubMed

    Huynh, So Hung; Wang, Jingming; Yu, Yang; Ng, Tuck Wah

    2014-06-01

    The effect of hydrostatic pressure on 6 μL air bubbles formed on micropillar structured PDMS and silicone surfaces using a 2 mm diameter stainless steel tip retreated at 1 mm/s was investigated. Dimensional analysis of the tip retraction process showed the experiments to be conducted in the condition where fluid inertial forces are comparable in magnitude with surface tension forces, while viscous forces were lower. Larger bubbles could be left behind on the structured PDMS surface. For hydrostatic pressures in excess of 20 mm H2O (196 Pa), the volume of bubble deposited was found to decrease progressively with pressure increase. The differences in width of the deposited bubbles (in contact with the substrate) were significant at any particular pressure but marginal in height. The attainable height before rupture reduced with pressure increase, thereby accounting for the reducing dispensed volume characteristic. On structured PDMS, the gaseous bridge width (in contact with the substrate) was invariant with tip retraction, while on silicone it was initially reducing before becoming invariant in the lead up to rupture. With silicone, hence, reductions in the contact width and height were both responsible for reduced volumes with pressure increase. Increased hydrostatic pressure was also found to restrict the growth in contact width on silicone during the stage when air was injected in through the tip. The ability to effect bubble size in such a simple manner may already be harnessed in nature and suggests possibilities in technological applications.

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

    PubMed

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

    2015-06-01

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

  16. 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

  17. Measurement of interfacial structures in horizontal air-water bubbly flows

    SciTech Connect

    Talley, J. D.; Worosz, T.; Dodds, M. R.; Kim, S.

    2012-07-01

    In order to predict multi-dimensional phenomena in nuclear reactor systems, methods relying on computational fluid dynamics (CFD) codes are essential. However, to be applicable in assessing thermal-hydraulic safety, these codes must be able to accurately predict the development of two-phase flows. Therefore, before practical application these codes must be assessed using experimental databases that capture multi-dimensional phenomena. While a large database exists that can be employed to assess predictions in vertical flows, the available database for horizontal flows is significantly lacking. Therefore, the current work seeks to develop an additional database in air-water horizontal bubbly flow through a 38.1 mm ID test section with a total development length of approximately 250 diameters. The experimental conditions are chosen to cover a wide range of the bubbly flow regime based upon flow visualization using a high-speed video camera. A database of local time-averaged void fraction, bubble velocity, interfacial area concentration, and bubble Sauter mean diameter are acquired throughout the pipe cross-section using a four-sensor conductivity probe. To investigate the evolution of the flow, measurements are made at axial locations of 44, 116, and 244 diameters downstream of the inlet. In the current work, only measurements obtained at L/D = 244 are presented. It is found that increasing the liquid superficial velocity tends to reduce both the bubble size and the degree of bubble packing near the upper wall. However, it is observed that the position of the maximum void fraction value remains nearly constant and is located approximately one bubble diameter away from the upper wall. It is also found that the bubble velocity exhibits a power law behavior resembling a single phase liquid turbulent velocity profile. Moreover, the local bubble velocity tends to decrease as the local void fraction increases. Conversely, increasing the gas superficial velocity is found to

  18. Hydrogen Bubbles and Formation of Nanoporous Silicon during Electrochemical Etching

    SciTech Connect

    Saraf, Laxmikant V.; Baer, Donald R.; Wang, Zheming; Young, James S.; Engelhard, Mark H.; Thevuthasan, Suntharampillai

    2005-06-01

    Many nanoporous Si structures, including those formed by common electrochemical etching procedures, produce a uniformly etch nanoporous surface. If the electrochemical etch rate is slowed down, details of the etch process can be explored and process parameters may be varied to test hypotheses and obtain controlled nanoporous and defect structures. For example, after electrochemical etching of a heavily n-doped (R = 0.05-0.5 ? -cm) <100> silicon at a current density of 10 mA/cm? in buffer oxide etch (BOE) electrolyte solution defect craters, containing textured nanopores, were observed to occur in ring shaped patterns of rings. The defect craters apparently originate at the hydrogen-BOE bubble interface, which forms during hydrogen evolution in the reaction. The slower hydrogen evolution due to low current density allows sufficient bubble residence time so that a high defect density appears at the bubble edges where local reaction rates are highest. Current carrying Si-OH species are most likely responsible for the widening in the craters. Reducing the defect/doping density in silicon lowers the defect concentration and thereby the density of nanopores. Measurements of photoluminescence lifetime and intensity show a distinct feature when the low density of nanopores formed at ring edges are isolated from each other. Overall features observed in photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) intensity strongly emphasize the role of surface oxide that influences these properties.

  19. Air entrainment and bubble statistics in three-dimensional breaking waves

    NASA Astrophysics Data System (ADS)

    Deike, Luc; Melville, W. K.; Popinet, Stephane

    2015-11-01

    Wave breaking in the ocean is of fundamental importance in order to quantify wave dissipation and air-sea interaction, including gas and momentum exchange, and to improve parametrizationsfor weather and climate models. Here, we investigate air entrainment and bubble statistics in three-dimensional breaking waves through direct numerical simulations of the two-phase air-water flow using the Open Source solver Gerris. As in previous 2D simulations, the dissipation due to breaking is found to be in good agreement with previous experimental observations and inertial-scaling arguments. For radii larger than the Hinze scale, the bubble size distribution, is found to follow a power law of the radius, r-3and to scale linearly with the time dependent turbulent dissipation rate during the active breaking stages. The time-averaged bubble size distribution is found to follow the same power law of the radius and to scale linearly with the wave dissipation rate per unit length of breaking crest. We propose a phenomenological turbulent bubble break-up model that describes the numerical results and existing experimental results.

  20. A novel technique to control the bubble formation process in a co-flow configuration with planar geometry

    NASA Astrophysics Data System (ADS)

    Ruiz-Rus, Javier; Bolaños-Jiménez, Rocío; Gutiérrez-Montes, Cándido; Martínez-Bazán, Carlos; Sevilla, Alejandro

    2015-11-01

    We present a novel technique to properly control the bubble formation frequency and size by forcing the water stream in a co-flow configuration with planar geometry through the modulation of the water velocity at the nozzle exit. The main goal of this work is to experimentally explore whether the bubbling regime, which is naturally established for certain values of the water-to-air velocity ratio, Λ =uw /ua , and the Weber number, We =ρwuw2Ho / σ , can be controlled by the imposed disturbances. A detailed experimental characterization of the forcing effect has been performed by measuring the pressure fluctuations in both the water and the air streams. In addition, the velocity amplitude, which characterizes the process, is obtained. The results show that a minimum disturbance amplitude is needed for an effective control of the bubbling process. Moreover, the process is governed by kinematic non-linear effects, and the position of the maximum deformation is shown to be described through a one-dimensional flow model for the water sheet, based on the exact solution of the Euler equation. Supported by the Spanish MINECO, Junta de Andalucía and EU Funds under projects DPI2014-59292-C3-3-P, P11-TEP7495 and UJA2013/08/05.

  1. Effect of in-water oxygen prebreathing at different depths on decompression-induced bubble formation and platelet activation.

    PubMed

    Bosco, Gerardo; Yang, Zhong-jin; Di Tano, Guglielmo; Camporesi, Enrico M; Faralli, Fabio; Savini, Fabio; Landolfi, Angelo; Doria, Christian; Fanò, Giorgio

    2010-05-01

    Effect of in-water oxygen prebreathing at different depths on decompression-induced bubble formation and platelet activation in scuba divers was evaluated. Six volunteers participated in four diving protocols, with 2 wk of recovery between dives. On dive 1, before diving, all divers breathed normally for 20 min at the surface of the sea (Air). On dive 2, before diving, all divers breathed 100% oxygen for 20 min at the surface of the sea [normobaric oxygenation (NBO)]. On dive 3, before diving, all divers breathed 100% O2 for 20 min at 6 m of seawater [msw; hyperbaric oxygenation (HBO) 1.6 atmospheres absolute (ATA)]. On dive 4, before diving, all divers breathed 100% O2 for 20 min at 12 msw (HBO 2.2 ATA). Then they dove to 30 msw (4 ATA) for 20 min breathing air from scuba. After each dive, blood samples were collected as soon as the divers surfaced. Bubbles were measured at 20 and 50 min after decompression and converted to bubble count estimate (BCE) and numeric bubble grade (NBG). BCE and NBG were significantly lower in NBO than in Air [0.142+/-0.034 vs. 0.191+/-0.066 (P<0.05) and 1.61+/-0.25 vs. 1.89+/-0.31 (P<0.05), respectively] at 20 min, but not at 50 min. HBO at 1.6 ATA and 2.2 ATA has a similar significant effect of reducing BCE and NBG. BCE was 0.067+/-0.026 and 0.040+/-0.018 at 20 min and 0.030+/-0.022 and 0.020+/-0.020 at 50 min. NBG was 1.11+/-0.17 and 0.92+/-0.16 at 20 min and 0.83+/-0.18 and 0.75+/-0.16 at 50 min. Prebreathing NBO and HBO significantly alleviated decompression-induced platelet activation. Activation of CD62p was 3.0+/-0.4, 13.5+/-1.3, 10.7+/-0.9, 4.5+/-0.7, and 7.6+/-0.8% for baseline, Air, NBO, HBO at 1.6 ATA, and HBO at 2.2 ATA, respectively. The data show that prebreathing oxygen, more effective with HBO than NBO, decreases air bubbles and platelet activation and, therefore, may be beneficial in reducing the development of decompression sickness.

  2. High-sensitivity strain sensor based on in-fiber rectangular air bubble.

    PubMed

    Liu, Shen; Yang, Kaiming; Wang, Yiping; Qu, Junle; Liao, Changrui; He, Jun; Li, Zhengyong; Yin, Guolu; Sun, Bing; Zhou, Jiangtao; Wang, Guanjun; Tang, Jian; Zhao, Jing

    2015-01-01

    We demonstrated a unique rectangular air bubble by means of splicing two sections of standard single mode fibers together and tapering the splicing joint. Such an air bubble can be used to develop a promising high-sensitivity strain sensor based on Fabry-Perot interference. The sensitivity of the strain sensor with a cavity length of about 61 μm and a wall thickness of about 1 μm was measured to be up to 43.0 pm/με and is the highest strain sensitivity among the in-fiber FPI-based strain sensors with air cavities reported so far. Moreover, our strain sensor has a very low temperature sensitivity of about 2.0 pm/°C. Thus, the temperature-induced strain measurement error is less than 0.046 με/°C. PMID:25557614

  3. Bubble formation and Kr distribution in Kr-irradiated UO2

    SciTech Connect

    He, L. F.; Valderrama, B.; Hassan, A. -R.; Yu, J.; Gupta, M.; Pakarinen, J.; Henderson, H. B.; Gan, J.; Kirk, M. A.; Nelson, A. T.; Manuel, M. V.; El-Azab, A.; Allen, T. R.

    2015-01-01

    In situ and ex situ transmission electron microscopy observation of small Kr bubbles in both single-crystal and polycrystalline UO2 were conducted to understand the inert gas bubble behavior in oxide nuclear fuel. The bubble size and volume swelling are shown as a weak function of ion dose but strongly depend on the temperature. The Kr bubble formation at room temperature was observed for the first time. The depth profiles of implanted Kr determined by atom probe tomography are in good agreement with the calculated profiles by SRIM, but the measured concentration of Kr is about 1/3 of calculated one. This difference is mainly due to low solubility of Kr in UO2 matrix, which has been confirmed by both density-functional theory calculations and chemical equilibrium analysis.

  4. Effective medium method for sound propagation in a soft medium containing air bubbles.

    PubMed

    Liang, Bin; Zou, Xinye; Cheng, Jianchun

    2008-09-01

    An effective medium method (EMM) is developed to investigate the nonlinear propagation of acoustic waves for soft media containing air bubbles, which accounts for the effects of weak compressibility, viscosity, surrounding pressure, surface tension, and encapsulating shells. Based on the dynamics model of an individual bubble that has included these effects, the EMM is presented by employing a simple perturbation approach to "homogenize" the bubbly soft media. The equations describing the fundamental and the second harmonic waves are derived that applies to three-dimensional cases, and then solved in a one-dimensional case to obtain the effective acoustical parameters of a longitudinal wave. The EMM is compared with the previous theories in three representative cases regarded as simple models of significant practical applications. The results show that the EMM agrees well with the previous theories and can incorporate the additional effects, which may notably affect the accuracy of the results. The limitations of the EMM are also identified and stated.

  5. Study of interfacial area transport and sensitivity analysis for air-water bubbly flow

    SciTech Connect

    Kim, S.; Sun, X.; Ishii, M.; Beus, S.G.

    2000-09-01

    The interfacial area transport equation applicable to the bubbly flow is presented. The model is evaluated against the data acquired by the state-of-the-art miniaturized double-sensor conductivity probe in an adiabatic air-water co-current vertical test loop under atmospheric pressure condition. In general, a good agreement, within the measurement error of plus/minus 10%, is observed for a wide range in the bubbly flow regime. The sensitivity analysis on the individual particle interaction mechanisms demonstrates the active interactions between the bubbles and highlights the mechanisms playing the dominant role in interfacial area transport. The analysis employing the drift flux model is also performed for the data acquired. Under the given flow conditions, the distribution parameter of 1.076 yields the best fit to the data.

  6. Tunneling effects in resonant acoustic scattering of an air bubble in unbounded water.

    PubMed

    Simão, André G; Guimarães, Luiz G

    2016-01-01

    The problem of acoustic scattering of a gaseous spherical bubble immersed within unbounded liquid surrounding is considered in this work. The theory of partial wave expansion related to this problem is revisited. A physical model based on the analogy between acoustic scattering and potential scattering in quantum mechanics is proposed to describe and interpret the acoustical natural oscillation modes of the bubble, namely, the resonances. In this context, a physical model is devised in order to describe the air water interface and the implications of the high density contrast on the various regimes of the scattering resonances. The main results are presented in terms of resonance lifetime periods and quality factors. The explicit numerical calculations are undertaken through an asymptotic analysis considering typical bubble dimensions and underwater sound wavelengths. It is shown that the resonance periods are scaled according to the Minnaert's period, which is the short lived resonance mode, called breathing mode of the bubble. As expected, resonances with longer lifetimes lead to impressive cavity quality Q-factor ranging from 1010 to 105. The present theoretical findings lead to a better understanding of the energy storage mechanism in a bubbly medium. PMID:27331803

  7. Influence of surface active solute on ultrasonic waveform distortion in liquid containing air bubbles.

    PubMed

    Tuziuti, Toru; Yasui, Kyuichi; Lee, Judy; Kozuka, Teruyuki; Towata, Atsuya; Iida, Yasuo

    2009-08-01

    The influence of sodium dodecyl sulfate (SDS) on waveform distortion of 141 kHz ultrasonic standing waves in liquids containing air bubbles was investigated for various transducer powers. Fast Fourier transform (FFT) operations were performed on the pressure waveform to obtain the harmonic components. In addition, the intensity of sonoluminescence (SL) was measured as a function of the power. Waveform distortion was observed for water at high applied power, with the curve exhibiting a steeper gradient for positive pressures and a broadened minimum for negative pressures. This was in reasonable agreement with theoretical studies reported in the literature. Much less distortion was found for a 1 mM SDS solution as the applied power was increased than for water or a 10 mM SDS solution. This may be attributed to a lower population of large coalesced bubbles in the 1 mM solution due to electrostatic repulsion, leading to damping of the sound energy and little cavitation noise because of viscous resistance to bubble radial motion in addition to adsorption and desorption of surfactant molecules at the bubble-liquid interface. For 10 mM SDS, the power threshold for the harmonic components was lower than that for the SL. In this case, it appears that there is a range of applied powers where most bubbles are stable and cannot collapse. The influence of the addition of an electrolyte and a nonionic surfactant was also investigated.

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

    PubMed

    Randsoe, T; Hyldegaard, O

    2009-12-01

    Decompression sickness (DCS) after air diving has been treated with success by means of combined normobaric oxygen breathing and intravascular perfluorocarbon (PFC) emulsions causing increased survival rate and faster bubble clearance from the intravascular compartment. The beneficial PFC effect has been explained by the increased transport capacity of oxygen and inert gases in blood. However, previous reports have shown that extravascular bubbles in lipid tissue of rats suffering from DCS will initially grow during oxygen breathing at normobaric conditions. We hypothesize that the combined effect of normobaric oxygen breathing and intravascular PFC infusion could lead to either enhanced extravascular bubble growth on decompression due to the increased oxygen supply, or that PFC infusion could lead to faster bubble elimination due to the increased solubility and transport capacity in blood for nitrogen causing faster nitrogen tissue desaturation. In anesthetized rats decompressed from a 60-min hyperbaric exposure breathing air at 385 kPa, we visually followed the resolution of micro-air bubbles injected into abdominal adipose tissue while the rats breathed either air, oxygen, or oxygen breathing combined with PFC infusion. All bubble observations were done at 101.3 kPa pressure. During oxygen breathing with or without combined PFC infusion, bubbles disappeared faster compared with air breathing. Combined oxygen breathing and PFC infusion caused faster bubble disappearance compared with oxygen breathing. The combined effect of oxygen breathing and PFC infusion neither prevented nor increased transient bubble growth time, rate, or growth ratio compared with oxygen breathing alone. We conclude that oxygen breathing in combination with PFC infusion causes faster bubble disappearance and does not exacerbate transient bubble growth. PFC infusion may be a valuable adjunct therapy during the first-aid treatment of DCS at normobaric conditions.

  9. Endurance exercise immediately before sea diving reduces bubble formation in scuba divers.

    PubMed

    Castagna, Olivier; Brisswalter, Jeanick; Vallee, Nicolas; Blatteau, Jean-Eric

    2011-06-01

    Previous studies have observed that a single bout of exercise can reduce the formation of circulating bubbles on decompression but, according to different authors, several hours delay were considered necessary between the end of exercise and the beginning of the dive. The objective of this study was to evaluate the effect of a single bout of exercise taken immediately before a dive on bubble formation. 24 trained divers performed open-sea dives to 30 msw depth for 30 min followed by a 3 min stop at 3 msw, under two conditions: (1) a control dive without exercise before (No-Ex), (2) an experimental condition in which subjects performed an exercise before diving (Ex). In the Ex condition, divers began running on a treadmill for 45 min at a speed corresponding to their own ventilatory threshold 1 h before immersion. Body weight, total body fluid volume, core temperature, and volume of consumed water were measured. Circulating bubbles were graded according to the Spencer scale using a precordial Doppler every 30 min for 90 min after surfacing. A single sub-maximal exercise performed immediately before immersion significantly reduces bubble grades (p < 0.001). This reduction was correlated not only to sweat dehydration, but also to the volume of water drunk at the end of the exercise. Moderate dehydration seems to be beneficial at the start of the dive whereas restoring the hydration balance should be given priority during decompression. This suggests a biphasic effect of the hydration status on bubble formation.

  10. Helium bubble formation in ultrafine and nanocrystalline tungsten under different extreme conditions

    SciTech Connect

    El-atwani, O.; Hattar, Khalid Mikhiel; Hinks, J. A.; Greaves, G.; Harilal, S. S.; Hassanein, A.

    2014-12-25

    We investigated the effects of helium ion irradiation energy and sample temperature on the performance of grain boundaries as helium sinks in ultrafine grained and nanocrystalline tungsten. Irradiations were performed at displacement and non-displacement energies and at temperatures above and below that required for vacancy migration. Microstructural investigations were performed using Transmission Electron Microscopy (TEM) combined with either in-situ or ex-situ ion irradiation. Under helium irradiation at an energy which does not cause atomic displacements in tungsten (70 eV), regardless of temperature and thus vacancy migration conditions, bubbles were uniformly distributed with no preferential bubble formation on grain boundaries. Moreover, at energies that can cause displacements, bubbles were observed to be preferentially formed on the grain boundaries only at high temperatures where vacancy migration occurs. Under these conditions, the decoration of grain boundaries with large facetted bubbles occurred on nanocrystalline grains with dimensions less than 60 nm. Finally, we discuss the importance of vacancy supply and the formation and migration of radiation-induced defects on the performance of grain boundaries as helium sinks and the resulting irradiation tolerance of ultrafine grained and nanocrystalline tungsten to bubble formation.

  11. Helium bubble formation in ultrafine and nanocrystalline tungsten under different extreme conditions

    DOE PAGES

    El-atwani, O.; Hattar, Khalid Mikhiel; Hinks, J. A.; Greaves, G.; Harilal, S. S.; Hassanein, A.

    2014-12-25

    We investigated the effects of helium ion irradiation energy and sample temperature on the performance of grain boundaries as helium sinks in ultrafine grained and nanocrystalline tungsten. Irradiations were performed at displacement and non-displacement energies and at temperatures above and below that required for vacancy migration. Microstructural investigations were performed using Transmission Electron Microscopy (TEM) combined with either in-situ or ex-situ ion irradiation. Under helium irradiation at an energy which does not cause atomic displacements in tungsten (70 eV), regardless of temperature and thus vacancy migration conditions, bubbles were uniformly distributed with no preferential bubble formation on grain boundaries. Moreover,more » at energies that can cause displacements, bubbles were observed to be preferentially formed on the grain boundaries only at high temperatures where vacancy migration occurs. Under these conditions, the decoration of grain boundaries with large facetted bubbles occurred on nanocrystalline grains with dimensions less than 60 nm. Finally, we discuss the importance of vacancy supply and the formation and migration of radiation-induced defects on the performance of grain boundaries as helium sinks and the resulting irradiation tolerance of ultrafine grained and nanocrystalline tungsten to bubble formation.« less

  12. Formation and X-ray Emission from Hot bubbles in Planetary Nebulae II. Hot bubble X-ray emission

    NASA Astrophysics Data System (ADS)

    Toalá, J. A.; Arthur, S. J.

    2016-09-01

    We present a study of the X-ray emission from numerical simulations of hot bubbles in planetary nebulae (PNe). High-resolution, two-dimensional, radiation-hydrodynamical simulations of the formation and evolution of hot bubbles in PNe, with and without thermal conduction, are used to calculate the X-ray emission and study its time-dependence and relationship to the changing stellar parameters. Instabilities in the wind-wind interaction zone produce clumps and filaments in the swept-up shell of nebular material. Turbulent mixing and thermal conduction at the corrugated interface can produce quantities of intermediate temperature and density gas between the hot, shocked wind bubble and the swept-up photoionized nebular material, which can emit in soft, diffuse X-rays. We use the CHIANTI software to compute synthetic spectra for the models and calculate their luminosities. We find that models both with conduction and those without can produce the X-ray temperatures and luminosities that are in the ranges reported in observations, although the models including thermal conduction are an order of magnitude more luminous than those without. Our results show that at early times the diffuse X-ray emission should be dominated by the contribution from the hot, shocked stellar wind, whereas at later times the nebular gas will dominate the spectrum. We analyse the effect of sampling on the resultant spectra and conclude that a minimum of 200 counts is required to reliably reproduce the spectral shape. Likewise, heavily smoothed surface-brightness profiles obtained from low-count detections of PNe do not provide a reliable description of the spatial distribution of the X-ray emitting gas.

  13. Importance of flow stratification and bubble aggregation in the separation zone of a dissolved air flotation tank.

    PubMed

    Lakghomi, B; Lawryshyn, Y; Hofmann, R

    2012-09-15

    The importance of horizontal flow patterns and bubble aggregation on the ability of dissolved air flotation (DAF) systems to improve bubble removal during drinking water treatment were explored using computational fluid dynamics (CFD) modeling. Both analytical and CFD analyses demonstrated benefits to horizontal flow. Two dimensional CFD modeling of a DAF system showed that increasing the amount of air in the system improved the bubble removal and generated a beneficial stratified horizontal flow pattern. Loading rates beyond a critical level disrupted the horizontal flow pattern, leading to significantly lower bubble removal. The results also demonstrated that including the effects of bubble aggregation in CFD modeling of DAF systems is an essential component toward achieving realistic modeling results.

  14. Direct AFM force measurements between air bubbles in aqueous monodisperse sodium poly(styrene sulfonate) solutions.

    PubMed

    Browne, Christine; Tabor, Rico F; Grieser, Franz; Dagastine, Raymond R

    2015-08-01

    Structural forces play an important role in the rheology, processing and stability of colloidal systems and complex fluids, with polyelectrolytes representing a key class of structuring colloids. Here, we explore the interactions between soft colloids, in the form of air bubbles, in solutions of monodisperse sodium poly(styrene sulfonate) as a model polyelectrolyte. It is found that by self-consistently modelling the force oscillations due to structuring of the polymer chains along with deformation of the bubbles, it is possible to precisely predict the interaction potential between approaching bubbles. In line with polyelectrolyte scaling theory, two distinct regimes of behaviour are seen, corresponding to dilute and semi-dilute polymer solutions. It is also seen that by blending monodisperse systems to give a bidisperse sample, the interaction forces between soft colloids can be controlled with a high degree of precision. At increasing bubble collision velocity, it is revealed that hydrodynamic flow overwhelms oscillatory structural interactions, showing the important disparity between equilibrium behaviour and dynamic interactions.

  15. Visual observation of the effect of magnetic field on moving air and vapor bubbles in a magnetic fluid

    NASA Astrophysics Data System (ADS)

    Nakatsuka, K.; Jeyadevan, B.; Akagami, Y.; Torigoe, T.; Asari, S.

    1999-07-01

    Theoretical prediction suggests that magnetic fluid (MF) as working liquid in heat pipe could enhance and control the heat transfer under the application of magnetic field. However, heat pipe experiments using ionic MF showed only marginal gain and demands investigation. As an initial step, visualization of air and vapor bubbles behavior under zero and applied magnetic field has been carried out using X-ray. The observations can be summarized as follows; applied magnetic field (a) reduces the size and deforms the shape of the bubble that secede from the heating surface or air supply tube, and (b) accelerates the movement of the bubble in the liquid.

  16. Air at hydrophobic surfaces and kinetics of three phase contact formation.

    PubMed

    Krasowska, M; Zawala, J; Malysa, K

    2009-01-01

    This review focuses on the importance of air presence at hydrophobic solid surfaces for wetting film rupture and kinetics of three phase contact formation. Affinity to air is a typical feature of hydrophobic surfaces, but it has been often either overlooked or not taken into consideration. When the hydrophobic surface, contacted earlier with air, is immersed into water then air can stay attached to the surface. The origin of long range hydrophobic forces and data showing that these interactions were due to the bridging of nanobubbles attached to the hydrophobic surfaces are discussed. A major part of the review is devoted to the description and analysis of data showing that air (nano-, micro-bubbles and/or air film) present at a hydrophobic surface facilitated rupture of the liquid film and three phase contact formation during bubble collisions with flat Teflon plates of different surface roughness. Although all Teflon plates were highly hydrophobic (contact angles ca. 100 degrees -130 degrees ) the time of the three phase contact (TPC) formation and attachment of the colliding bubble was strongly affected by the plate surface roughness. The time of the TPC formation was shortened from over 80 down to 2-3 ms when the roughness was increased from below 1 microm to over 50 microm. Higher surface roughness means that larger amounts of air was entrapped during the Teflon plates' immersion in water. Additional experimental evidence is given, showing that facilitation of the TPC formation and the bubble attachment was due to air presence and re-distribution over the Teflon surfaces: i) prolonging the plate immersion time resulted in quicker attachment; ii) irregular and disappearing air pockets were recorded at a Teflon surface; iii) a satellite bubble left at a Teflon surface during the first collision facilitated the attachment; iv) attachment always occurred during the first collision in the case of a very rough "Teflon V" surface, but in highly concentrated n

  17. Bubble formation of aqueous humor and lens opacity during chamber flight.

    PubMed

    Fang, H S; Chen, H M

    1984-10-01

    A transparent miniature decompression chamber was placed on the stage of a large-working zoom-stereo microscope so that the effect of decompression on the frog eye could be microscopically observed and photographed. It was found that chamber flight at a simulated altitude of 66,000 ft (20,117 m) or more caused bubble formation in aqueous humor and lens opacities in some of the experimental animals. On return to ground level, the bubbles either decreased in size or completely disappeared. The cataract could also regress after recompression to 1 atm. Such lens opacities may be termed altitude cataract, instead of asphyxial or anoxic cataract.

  18. Lack of intracellular bubble formation in microorganisms at very high gas supersaturations.

    PubMed

    Hemmingsen, E A; Hemmingsen, B B

    1979-12-01

    Eucaryotic unicellular (a yeast, a cellular slime mold, and various protozoans) and two multicellular (aschelminths) microorganisms were saturated with gas at high pressures and rapidly decompressed. No effect was observed with pressures of argon up to 125 atm, nitrogen up to 175 atm, and helium up to 350 atm, showing that the induced gas supersaturations did not cause intracellular bubbles to form. With 25--50 atm higher gas pressures, the decompression usually produced killing and cell rupture, although differences in tolerances existed among the various organisms. Substantial fractions of the populations survived gas supersaturations well above the threshold values for massive spontaneous nucleation of bubbles in the water. When killing occurred, external rather than internal bubbles appeared to be the cause. Even with the 300 atm argon or nitrogen pressures, yeast cells were unaffected, apparently because of the external protection provided by their cell wall. It is concluded that the gas supersaturations required for intracellular formation of bubbles generally are at least equal to and probably higher than the bubble nucleation thresholds for water or aqueous solutions. PMID:395143

  19. Bubble Formation and Detachment in Liquid Flow Under Normal and Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.; Kamotani, Y.

    1998-01-01

    Two-phase flows are present in a wide variety of applications for spacecraft thermal control systems design. Bubble formation and detachment is an integral part of the two-phase flow science. The authors objective is to experimentally investigate the effects of liquid cross velocity, gas velocity, and nozzle diameter on the bubble diameter at detachment under reduced and normal gravity and under relatively low gas flow rates. Results from ground (1 g) and reduced gravity experiments will be presented in this paper. For the 1 g experiment, a flow loop was designed and built to accommodate a range of liquid and gas flow rates. The reduced gravity experiment was conducted on the NASA DC-9 reduced gravity platform using the two-phase flow loop qualified for operation on the low-gravity platform. Flow visualization is accomplished using a high speed 500 frames/s camera. The results suggest that the existence of buoyancy force contributes to the faster detachment of bubbles. Buoyancy helps the detachment process which results in smaller bubbles being formed. In reduced gravity, although drag force is present, the virtual non-existence of buoyant force results in larger bubbles and longer times for detachment. Theoretical predictions are also presented in this paper and seem to agree with the experimental results.

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

    PubMed

    Amos, Richard T; Ulrich Mayer, K

    2006-09-10

    In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O(2) to waters otherwise depleted in O(2). Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given

  1. An experimental study on resonance of oscillating air/vapor bubbles in water using a two-frequency acoustic apparatus

    NASA Astrophysics Data System (ADS)

    Ohsaka, K.

    2003-05-01

    A two-frequency acoustic apparatus is employed to study the growth behavior of vapor-saturated bubbles driven in a volumetric mode. A unique feature of the apparatus is its capability of trapping a bubble by an ultrasonic standing wave while independently driving it into oscillations by a second lower-frequency acoustic wave. It is observed that the growing vapor bubbles exhibit a periodic shape transition between the volumetric and shape modes due to resonant coupling. In order to explain this observation, we performed an experimental investigation on resonant coupling of air bubbles and obtained the following results: First, the induced shape oscillations are actually a mixed mode that contains the volume component, thus, vapor bubbles can grow while they exhibit shape oscillations. Second, the acoustically levitated bubbles are deformed and therefore, degeneracy in resonant frequency is partially removed. As a result, the vapor bubbles exhibit the shape oscillations in both the axisymmetric mode and asymmetric (three-dimensional) modes. Nonlinear effects in addition to the frequency shift and split due to deformation creates overlapping of the coupling ranges for different modes, which leads to the continuous shape oscillations above a certain bubble radius as the bubble grows.

  2. Interfacial structures of confined air-water two-phase bubbly flow

    SciTech Connect

    Kim, S.; Ishii, M.; Wu, Q.; McCreary, D.; Beus, S.G.

    2000-08-01

    The interfacial structure of the two-phase flows is of great importance in view of theoretical modeling and practical applications. In the present study, the focus is made on obtaining detailed local two-phase parameters in the air-water bubbly flow in a rectangular vertical duct using the double-sensor conductivity probe. The characteristic wall-peak is observed in the profiles of the interracial area concentration and the void fraction. The development of the interfacial area concentration along the axial direction of the flow is studied in view of the interfacial area transport and bubble interactions. The experimental data is compared with the drift flux model with C{sub 0} = 1.35.

  3. Trapping of Sodium Dodecyl Sulfate at the Air-Water Interface of Oscillating Bubbles.

    PubMed

    Corti, Mario; Pannuzzo, Martina; Raudino, Antonio

    2015-06-16

    We report that at very low initial bulk concentrations, a couple of hundred times below the critical micellar concentration (CMC), anionic surfactant sodium dodecyl sulfate (SDS) adsorbed at the air-water interface of a gas bubble cannot be removed, on the time scale of the experiment (hours), when the surrounding solution is gently replaced by pure water. Extremely sensitive interferometric measurements of the resonance frequency of the bubble-forced oscillations give precise access to the concentration of the surfactant monolayer. The bulk-interface dynamic exchange of SDS molecules is shown to be inhibited below a concentration which we believe refers to a kind of gas-liquid phase transition of the surface monolayer. Above this threshold we recover the expected concentration-dependent desorption. The experimental observations are interpreted within simple energetic considerations supported by molecular dynamics (MD) calculations. PMID:26039913

  4. Protective effects of Healon and Occucoat against air bubble endothelial damage during ultrasonic agitation of the anterior chamber.

    PubMed

    Monson, M C; Tamura, M; Mamalis, N; Olson, R J; Olson, R J

    1991-09-01

    An important aspect of any new viscoelastic substance is the corneal endothelial protection. We compared the protective effects of sodium hyaluronate (Healon) and hydroxypropylmethylcellulose (Occucoat) by introducing a controlled volume of air bubbles into the anterior chamber of human eye bank eyes during ultrasonic agitation of the anterior chamber. Eight eyes received Healon and 11 eyes received Occucoat. Damage to endothelial cells in the central cornea was quantified by vital staining. Endothelial damage averaged 4.5% in eyes in which no viscoelastic was used (positive control); damage was 0.4% in eyes in which a viscoelastic was injected but no air bubbles were introduced (negative control). We found that endothelial damage averaged 4.25% in specimens that received air plus Healon and 1.4% in specimens that received air plus Occucoat. Occucoat appeared to have somewhat better protective effects than Healon against air bubble damage to the corneal endothelium during ultrasonic agitation of the anterior chamber.

  5. Asymmetric Brownian motor driven by bubble formation in a hydrophobic channel.

    PubMed

    Arai, Noriyoshi; Yasuoka, Kenji; Koishi, Takahiro; Ebisuzaki, Toshikazu

    2010-10-26

    The "asymmetric brownian ratchet model" is a variation of Feynman's ratchet and pawl system proposed. In this model, a system consisting of a motor and a rail has two binding states. One is the random brownian state, and the other is the asymmetric potential state. When the system is alternatively switched between these states, the motor can be driven in one direction. This model is believed to explain nanomotor behavior in biological systems. The feasibility of the model has been demonstrated using electrical and magnetic forces; however, switching of these forces is unlikely to be found in biological systems. In this paper, we propose an original mechanism of transition between states by bubble formation in a nanosized channel surrounded by hydrophobic atoms. This amounts to a nanoscale motor system using bubble propulsion. The motor system consists of a hydrophobic motor and a rail on which hydrophobic patterns are printed. Potential asymmetry can be produced by using a left-right asymmetric pattern shape. Hydrophobic interactions are believed to play an important role in the binding of biomolecules and molecular recognition. The bubble formation is controlled by changing the width of the channel by an atomic distance (∼0.1 nm). Therefore, the motor is potentially more efficient than systems controlled by other forces, in which a much larger change in the motor position is necessary. We have simulated the bubble-powered motor using dissipative particle dynamics and found behavior in good agreement with that of motor proteins. Energy efficiency is as high as 60%.

  6. Experiments of air bubbles impacting a rigid wall in tap water

    NASA Astrophysics Data System (ADS)

    Pelletier, Etienne; Béguin, Cédric; Étienne, Stéphane

    2015-12-01

    Trajectory and impact dynamics of bubbles in tap water were studied. Results confirm that bubbles with identical radii can be classified in two categories: fast bubbles and slow bubbles. Each category of bubble can describe zig-zag or helical motion. The aspect ratio and terminal velocity of a bubble depend on its radius and category. Restitution relations are also presented for the two categories of bubble after impact with an horizontal wall. With these relations, the state of a bubble after rebound can be predicted from its state before rebound. The aspect ratio before rebound of the bubble is found to play a key role in the dynamics of the impacts.

  7. Preliminary formation analysis for compressed air energy storage in depleted natural gas reservoirs :

    SciTech Connect

    Gardner, William Payton

    2013-06-01

    The purpose of this study is to develop an engineering and operational understanding of CAES performance for a depleted natural gas reservoir by evaluation of relative permeability effects of air, water and natural gas in depleted natural gas reservoirs as a reservoir is initially depleted, an air bubble is created, and as air is initially cycled. The composition of produced gases will be evaluated as the three phase flow of methane, nitrogen and brine are modeled. The effects of a methane gas phase on the relative permeability of air in a formation are investigated and the composition of the produced fluid, which consists primarily of the amount of natural gas in the produced air are determined. Simulations of compressed air energy storage (CAES) in depleted natural gas reservoirs were carried out to assess the effect of formation permeability on the design of a simple CAES system. The injection of N2 (as a proxy to air), and the extraction of the resulting gas mixture in a depleted natural gas reservoir were modeled using the TOUGH2 reservoir simulator with the EOS7c equation of state. The optimal borehole spacing was determined as a function of the formation scale intrinsic permeability. Natural gas reservoir results are similar to those for an aquifer. Borehole spacing is dependent upon the intrinsic permeability of the formation. Higher permeability allows increased injection and extraction rates which is equivalent to more power per borehole for a given screen length. The number of boreholes per 100 MW for a given intrinsic permeability in a depleted natural gas reservoir is essentially identical to that determined for a simple aquifer of identical properties. During bubble formation methane is displaced and a sharp N2methane boundary is formed with an almost pure N2 gas phase in the bubble near the borehole. During cycling mixing of methane and air occurs along the boundary as the air bubble boundary moves. The extracted gas mixture changes as a

  8. Observations of internal flow inside an evaporating nanofluid sessile droplet in the presence of an entrapped air bubble

    NASA Astrophysics Data System (ADS)

    Shin, Dong Hwan; Allen, Jeffrey S.; Lee, Seong Hyuk; Choi, Chang Kyoung

    2016-09-01

    Using a unique, near-field microscopy technique, fringe patterns and nanoparticle motions are visualized immediately following a nanofluid droplet deposition on a glass substrate in which an air bubble is entrapped. The nanofluid consists of DI-water, 0.10% Aluminum Oxide nanoparticles with an average diameter of 50 nm, and 0.0005% yellow-green polystyrene fluorescent particles of 1 μm diameter. High-speed, fluorescent-mode confocal imaging enables investigation of depth-wise sectioned particle movements in the nanofluid droplet inside which a bubble is entrapped. The static contact angle is increased when a bubble is applied. In the presence of the bubble in the droplet, the observed flow toward the center of the droplet is opposite to the flow observed in a droplet without the bubble. When the bubble is present, the evaporation process is retarded. Also, random motion is observed in the contact line region instead of the typical evaporation-driven flow toward the droplet edge. Once the bubble bursts, however, the total evaporation time decreases due to the change in the contact line characteristics. Moreover, the area of fringe patterns beneath the bubble increases with time. Discussed herein is a unique internal flow that has not been observed in nanofluid droplet evaporation.

  9. Observations of internal flow inside an evaporating nanofluid sessile droplet in the presence of an entrapped air bubble.

    PubMed

    Shin, Dong Hwan; Allen, Jeffrey S; Lee, Seong Hyuk; Choi, Chang Kyoung

    2016-01-01

    Using a unique, near-field microscopy technique, fringe patterns and nanoparticle motions are visualized immediately following a nanofluid droplet deposition on a glass substrate in which an air bubble is entrapped. The nanofluid consists of DI-water, 0.10% Aluminum Oxide nanoparticles with an average diameter of 50 nm, and 0.0005% yellow-green polystyrene fluorescent particles of 1 μm diameter. High-speed, fluorescent-mode confocal imaging enables investigation of depth-wise sectioned particle movements in the nanofluid droplet inside which a bubble is entrapped. The static contact angle is increased when a bubble is applied. In the presence of the bubble in the droplet, the observed flow toward the center of the droplet is opposite to the flow observed in a droplet without the bubble. When the bubble is present, the evaporation process is retarded. Also, random motion is observed in the contact line region instead of the typical evaporation-driven flow toward the droplet edge. Once the bubble bursts, however, the total evaporation time decreases due to the change in the contact line characteristics. Moreover, the area of fringe patterns beneath the bubble increases with time. Discussed herein is a unique internal flow that has not been observed in nanofluid droplet evaporation. PMID:27615999

  10. Observations of internal flow inside an evaporating nanofluid sessile droplet in the presence of an entrapped air bubble

    PubMed Central

    Shin, Dong Hwan; Allen, Jeffrey S.; Lee, Seong Hyuk; Choi, Chang Kyoung

    2016-01-01

    Using a unique, near-field microscopy technique, fringe patterns and nanoparticle motions are visualized immediately following a nanofluid droplet deposition on a glass substrate in which an air bubble is entrapped. The nanofluid consists of DI-water, 0.10% Aluminum Oxide nanoparticles with an average diameter of 50 nm, and 0.0005% yellow-green polystyrene fluorescent particles of 1 μm diameter. High-speed, fluorescent-mode confocal imaging enables investigation of depth-wise sectioned particle movements in the nanofluid droplet inside which a bubble is entrapped. The static contact angle is increased when a bubble is applied. In the presence of the bubble in the droplet, the observed flow toward the center of the droplet is opposite to the flow observed in a droplet without the bubble. When the bubble is present, the evaporation process is retarded. Also, random motion is observed in the contact line region instead of the typical evaporation-driven flow toward the droplet edge. Once the bubble bursts, however, the total evaporation time decreases due to the change in the contact line characteristics. Moreover, the area of fringe patterns beneath the bubble increases with time. Discussed herein is a unique internal flow that has not been observed in nanofluid droplet evaporation. PMID:27615999

  11. Bubble Formation and Transport during Microgravity Materials Processing: Model Experiments on the International Space Station

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Anilkumar, A. V.; Lee, C. P.

    2003-01-01

    Flow Visualization experiments on the controlled melting and solidification of succinonitrile were conducted in the glovebox facility of the International Space Station (ISS). The experimental samples were prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with pure succinonitrile (SCN) under 450 millibar of nitrogen. Porosity in the samples arose from natural shrinkage, and in some cases by direct insertion of nitrogen bubbles, during solidification of the liquid SCN. The samples were processed in the Pore Formation and Mobility Investigation (PFMI) apparatus that is placed in the glovebox facility (GBX) aboard the ISS. Experimental processing parameters of temperature gradient and translation speed, as well as camera settings, were remotely monitored and manipulated from the ground Telescience Center (TSC) at the Marshall Space Flight Center. During the experiments, the sample is first subjected to a unidirectional melt back, generally at 10 microns per second, with a constant temperature gradient ahead of the melting interface. The temperatures in the sample are monitored by six in situ thermocouples. Real time visualization of the controlled directional melt back shows bubbles of different sizes initiating at the melt interface and, upon dislodging from the melting solid, migrating at different speeds into the temperature field ahead of them, before coming to rest. The thermocapillary flow field set up in the melt, ahead of the interface, is dramatic in the context of the large bubbles, and plays a major role in dislodging the bubble. A preliminary analysis of the observed bubble formation and mobility during melt back and its implication to future microgravity experiments is presented and discussed.

  12. Bubble Formation and Transport during Microgravity Materials Processing: Model Experiments on the Space Station

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Anilkumar, A. V.; Lee, C. P.

    2003-01-01

    Flow Visualization experiments on the controlled melting and solidification of succinonitrile were conducted in the glovebox facility of the International Space Station (ISS). The experimental samples were prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with pure succinonitrile (SCN) under 450 millibar of nitrogen. Porosity in the samples arose from natural shrinkage, and in some cases by direct insertion of nitrogen bubbles, during solidification of the liquid SCN. The samples were processed in the Pore Formation and Mobility Investigation (PFMI) apparatus that is placed in the glovebox facility (GBX) aboard the ISS. Experimental processing parameters of temperature gradient and translation speed, as well as camera settings, were remotely monitored and manipulated from the ground Telescience Center (TSC) at the Marshall Space Flight Center. During the experiments, the sample is first subjected to a unidirectional melt back, generally at 10 microns per second, with a constant temperature gradient ahead of the melting interface. The temperatures in the sample are monitored by six in situ thermocouples. Real time visualization of the controlled directional melt back shows bubbles of different sizes initiating at the melt interface and, upon dislodging from the melting solid, migrating at different speeds into the temperature field ahead of them, before coming to rest. The thermocapillary flow field set up in the melt, ahead of the interface, is dramatic in the context of the large bubbles, and plays a major role in dislodging the bubble. A preliminary analysis of the observed bubble formation and mobility during melt back and its implication to future microgravity experiments is presented and discussed.

  13. Lattice Boltzmann simulations of bubble formation in a microfluidic T-junction.

    PubMed

    Amaya-Bower, Luz; Lee, Taehun

    2011-06-28

    A lattice Boltzmann equation method based on the Cahn-Hilliard diffuse interface theory is developed to investigate the bubble formation process in a microchannel with T-junction mixing geometry. The bubble formation process has different regimes, namely, squeezing, dripping and jetting regimes, which correspond to the primary forces acting on the system. Transition from regime to regime is generally dictated by the capillary number Ca, volumetric flow ratio Q and viscosity ratio λ. A systematic analysis is performed to evaluate these effects. The computations are performed in the range of 10(-4)

  14. Molecular dynamics simulations of bubble formation and cavitation in liquid metals.

    SciTech Connect

    Insepov, Z.; Hassanein, A.; Bazhirov, T. T.; Norman, G. E.; Stegailov, V. V.; Mathematics and Computer Science; Inst. for High Energy Densities of Joint Inst. for High Temperatures of RAS

    2007-11-01

    Thermodynamics and kinetics of nano-scale bubble formation in liquid metals such as Li and Pb were studied by molecular dynamics (MD) simulations at pressures typical for magnetic and inertial fusion. Two different approaches to bubble formation were developed. In one method, radial densities, pressures, surface tensions, and work functions of the cavities in supercooled liquid lithium were calculated and compared with the surface tension experimental data. The critical radius of a stable cavity in liquid lithium was found for the first time. In the second method, the cavities were created in the highly stretched region of the liquid phase diagram; and then the stability boundary and the cavitation rates were calculated in liquid lead. The pressure dependences of cavitation frequencies were obtained over the temperature range 700-2700 K in liquid Pb. The results of MD calculations for cavitation rate were compared with estimates of classical nucleation theory (CNT).

  15. THE RELATION OF EXERCISE TO BUBBLE FORMATION IN ANIMALS DECOMPRESSED TO SEA LEVEL FROM HIGH BAROMETRIC PRESSURES.

    PubMed

    Harris, M; Berg, W E; Whitaker, D M; Twitty, V C

    1945-01-20

    1. Bullfrogs (Rana catesbiana) and rats have been subjected to high barometric pressures and studied for bubble formation on subsequent decompression to sea level. Pressures varying from 3 to 60 pounds per square inch, in excess of atmospheric pressure, were used. 2. Muscular activity after decompression is necessary for bubble formation in bullfrogs after pressure treatment throughout the above range. Anesthetized frogs remained bubble-free following decompression. Rats compressed at 15 to 45 pounds per square inch likewise did not contain bubbles unless exercised on return to sea level. 3. Bubbles form without voluntary muscular activity in anesthetized rats previously subjected to pressure of 60 pounds per square inch. Small movements involved in breathing and other vital activities are believed sufficient to initiate bubbles in the presence of very high supersaturations of N(2). 4. Bubbles appear (with exercise) in rats previously compressed at 15 pounds per square inch, and in bullfrogs subjected to pressure at levels as low as 3 pounds per square inch above atmospheric pressure. The percentage drop in pressure necessary for bubble formation is less in compressed animals than in those decompressed from sea level to simulated altitudes. 5. The action of exercise on bubble formation in compressed frogs and rats is attributed to mechanical factors associated with muscular activity, combined with the high supersaturation of N(2). CO(2) probably is not greatly involved, since its concentration does not reach supersatuation, as it does at high altitude. 6. Anoxia following decompression from high barometric pressures has no observable facilitating effect on bubble formation.

  16. Influence of water depth on the sound generated by air-bubble vibration in the water musical instrument

    NASA Astrophysics Data System (ADS)

    Ohuchi, Yoshito; Nakazono, Yoichi

    2014-06-01

    We have developed a water musical instrument that generates sound by the falling of water drops within resonance tubes. The instrument can give people who hear it the healing effect inherent in the sound of water. The sound produced by falling water drops arises from air- bubble vibrations. To investigate the impact of water depth on the air-bubble vibrations, we conducted experiments at varying values of water pressure and nozzle shape. We found that air-bubble vibration frequency does not change at a water depth of 50 mm or greater. Between 35 and 40 mm, however, the frequency decreases. At water depths of 30 mm or below, the air-bubble vibration frequency increases. In our tests, we varied the nozzle diameter from 2 to 4 mm. In addition, we discovered that the time taken for air-bubble vibration to start after the water drops start falling is constant at water depths of 40 mm or greater, but slower at depths below 40 mm.

  17. Measuring forces and spatiotemporal evolution of thin water films between an air bubble and solid surfaces of different hydrophobicity.

    PubMed

    Shi, Chen; Cui, Xin; Xie, Lei; Liu, Qingxia; Chan, Derek Y C; Israelachvili, Jacob N; Zeng, Hongbo

    2015-01-27

    A combination of atomic force microscopy (AFM) and reflection interference contrast microscopy (RICM) was used to measure simultaneously the interaction force and the spatiotemporal evolution of the thin water film between a bubble in water and mica surfaces with varying degrees of hydrophobicity. Stable films, supported by the repulsive van der Waals-Casimir-Lifshitz force were always observed between air bubble and hydrophilic mica surfaces (water contact angle, θ(w) < 5°) whereas bubble attachment occurred on hydrophobized mica surfaces. A theoretical model, based on the Reynolds lubrication theory and the augmented Young-Laplace equation including the effects of disjoining pressure, provided excellent agreement with experiment results, indicating the essential physics involved in the interaction between air bubble and solid surfaces can be elucidated. A hydrophobic interaction free energy per unit area of the form: WH(h) = -γ(1 - cos θ(w))exp(-h/D(H)) can be used to quantify the attraction between bubble and hydrophobized solid substrate at separation, h, with γ being the surface tension of water. For surfaces with water contact angle in the range 45° < θ(w) < 90°, the decay length DH varied between 0.8 and 1.0 nm. This study quantified the hydrophobic interaction in asymmetric system between air bubble and hydrophobic surfaces, and provided a feasible method for synchronous measurements of the interaction forces with sub-nN resolution and the drainage dynamics of thin films down to nm thickness.

  18. Measuring forces and spatiotemporal evolution of thin water films between an air bubble and solid surfaces of different hydrophobicity.

    PubMed

    Shi, Chen; Cui, Xin; Xie, Lei; Liu, Qingxia; Chan, Derek Y C; Israelachvili, Jacob N; Zeng, Hongbo

    2015-01-27

    A combination of atomic force microscopy (AFM) and reflection interference contrast microscopy (RICM) was used to measure simultaneously the interaction force and the spatiotemporal evolution of the thin water film between a bubble in water and mica surfaces with varying degrees of hydrophobicity. Stable films, supported by the repulsive van der Waals-Casimir-Lifshitz force were always observed between air bubble and hydrophilic mica surfaces (water contact angle, θ(w) < 5°) whereas bubble attachment occurred on hydrophobized mica surfaces. A theoretical model, based on the Reynolds lubrication theory and the augmented Young-Laplace equation including the effects of disjoining pressure, provided excellent agreement with experiment results, indicating the essential physics involved in the interaction between air bubble and solid surfaces can be elucidated. A hydrophobic interaction free energy per unit area of the form: WH(h) = -γ(1 - cos θ(w))exp(-h/D(H)) can be used to quantify the attraction between bubble and hydrophobized solid substrate at separation, h, with γ being the surface tension of water. For surfaces with water contact angle in the range 45° < θ(w) < 90°, the decay length DH varied between 0.8 and 1.0 nm. This study quantified the hydrophobic interaction in asymmetric system between air bubble and hydrophobic surfaces, and provided a feasible method for synchronous measurements of the interaction forces with sub-nN resolution and the drainage dynamics of thin films down to nm thickness. PMID:25514470

  19. Importance of air bubbles in the core of coated pellets: Synchrotron X-ray microtomography allows for new insights.

    PubMed

    Fahier, J; Muschert, S; Fayard, B; Velghe, C; Byrne, G; Doucet, J; Siepmann, F; Siepmann, J

    2016-09-10

    High-resolution X-ray microtomography was used to get deeper insight into the underlying mass transport mechanisms controlling drug release from coated pellets. Sugar starter cores were layered with propranolol HCl and subsequently coated with Kollicoat SR, plasticized with 10% TEC. Importantly, synchrotron X-ray computed microtomography (SR-μCT) allowed direct, non-invasive monitoring of crack formation in the film coatings upon exposure to the release medium. Propranolol HCl, as well as very small sugar particles from the pellets' core, were expulsed through these cracks into the surrounding bulk fluid. Interestingly, SR-μCT also revealed the existence of numerous tiny, air-filled pores (varying in size and shape) in the pellet cores before exposure to the release medium. Upon water penetration into the system, the contents of the pellet cores became semi-solid/liquid. Consequently, the air-pockets became mobile and fused together. They steadily increased in size (and decreased in number). Importantly, "big" air bubbles were often located in close vicinity of a crack within the film coating. Thus, they play a potentially crucial role for the control of drug release from coated pellets. PMID:27374626

  20. Variation of Local Surface Properties of an Air Bubble in Water Caused by Its Interaction with Another Surface.

    PubMed

    Del Castillo, Lorena A; Ohnishi, Satomi; Carnie, Steven L; Horn, Roger G

    2016-08-01

    Surface and hydrodynamic forces acting between an air bubble and a flat mica surface in surfactant-free water and in 1 mM KCl solution have been investigated by observing film drainage using a modified surface force apparatus (SFA). The bubble shapes observed with the SFA are compared to theoretical profiles computed from a model that considers hydrodynamic interactions, surface curvature, and disjoining pressure arising from electrical double layer and van der Waals interactions. It is shown that the bubble experiences double-layer forces, and a final equilibrium wetting film between the bubble and mica surfaces is formed by van der Waals repulsion. However, comparison with the theoretical model reveals that the double-layer forces are not simply a function of surface separation. Rather, they appear to be changed by one of more of the following: the bubble's dynamic deformation, its proximity to another surface, and/or hydrodynamic flow in the aqueous film that separate them. The same comments apply to the hydrodynamic mobility or immobility of the air-water interface. Together the results show that the bubble's surface is "soft" in two senses: in addition to its well-known deformability, its local properties are affected by weak external forces, in this case the electrical double-layer interactions with a nearby surface and hydrodynamic flow in the neighboring aqueous phase. PMID:27391417

  1. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  2. Bubble size measurements in a bubbly wake

    NASA Astrophysics Data System (ADS)

    Karn, Ashish; Hong, Jiarong; Ellis, Christopher; Arndt, Roger

    2014-11-01

    Measurements of bubble size distribution are ubiquitous in many industrial applications. Conventional methods using image analysis to measure bubble size are limited in their robustness and applicability in highly turbulent bubbly flows. These flows usually impose significant challenges for image processing such as a wide range of bubble size distribution, spatial and temporal inhomogeneity of image background including in-focus and out-of-focus bubbles, as well as the excessive presence of bubble clusters. This talk introduces a multi-level image analysis approach to detect a wide size range of bubbles and resolve bubble clusters from images obtained in a turbulent bubbly wake of a ventilated hydrofoil. The proposed approach was implemented to derive bubble size and air ventilation rate from the synthetic images and the experiments, respectively. The results show a great promise in its applicability for online monitoring of bubbly flows in a number of industrial applications. Sponsored by Office of Naval Research and the Department of Energy.

  3. CO Observations and Investigation of Triggered Star Formation toward the N10 Infrared Bubble and Surroundings

    NASA Astrophysics Data System (ADS)

    Gama, D. R. G.; Lepine, J. R. D.; Mendoza, E.; Wu, Y.; Yuan, J.

    2016-10-01

    We studied the environment of the dust bubble N10 in molecular emission. Infrared bubbles, first detected by the GLIMPSE survey at 8.0 μm, are ideal regions to investigate the effect of the expansion of the H ii region on its surroundings and the eventual triggering of star formation at its borders. In this work, we present a multi-wavelength study of N10. This bubble is especially interesting because infrared studies of the young stellar content suggest a scenario of ongoing star formation, possibly triggered on the edge of the H ii region. We carried out observations of 12CO(1-0) and 13CO(1-0) emission at PMO 13.7 m toward N10. We also analyzed the IR and sub-millimeter emission on this region and compare those different tracers to obtain a detailed view of the interaction between the expanding H ii region and the molecular gas. We also estimated the parameters of the denser cold dust condensation and the ionized gas inside the shell. Bright CO emission was detected and two molecular clumps were identified from which we have derived physical parameters. We also estimate the parameters for the densest cold dust condensation and for the ionized gas inside the shell. The comparison between the dynamical age of this region and the fragmentation timescale favors the “Radiation-Driven Implosion” mechanism of star formation. N10 is a case of particular interest with gas structures in a narrow frontier between the H ii region and surrounding molecular material, and with a range of ages of YSOs situated in the region, indicating triggered star formation.

  4. Bubble and pattern formation in liquid induced by an electron beam.

    PubMed

    Grogan, Joseph M; Schneider, Nicholas M; Ross, Frances M; Bau, Haim H

    2014-01-01

    Liquid cell electron microscopy has emerged as a powerful technique for in situ studies of nanoscale processes in liquids. An accurate understanding of the interactions between the electron beam and the liquid medium is essential to account for, suppress, and exploit beam effects. We quantify the interactions of high energy electrons with water, finding that radiolysis plays an important role, while heating is typically insignificant. For typical imaging conditions, we find that radiolysis products such as hydrogen and hydrated electrons achieve equilibrium concentrations within seconds. At sufficiently high dose-rate, the gaseous products form bubbles. We image bubble nucleation, growth, and migration. We develop a simplified reaction-diffusion model for the temporally and spatially varying concentrations of radiolysis species and predict the conditions for bubble formation by H2. We discuss the conditions under which hydrated electrons cause precipitation of cations from solution and show that the electron beam can be used to "write" structures directly, such as nanowires and other complex patterns, without the need for a mask.

  5. Is mudflow in Sidoarjo, East Java due to the pumping mechanism of hot air bubbles? : Laboratory simulations and field observations

    NASA Astrophysics Data System (ADS)

    Nurhandoko, Bagus Endar B.

    2015-09-01

    Extraordinary mudflow has happened in Sidoarjo, East Java, Indonesia since 2006. This mud comes from the giant crater that is located close to the BJP - 01. Thousands of homes have been submerged due to mudflow. Till today this giant mud crater is still has great strength despite the mud flowing over 8 years. This is a very rare phenomenon in the world. This mud flow mechanism raises big questions, because it has been going on for years, naturally the mudflow will stop by itself because the pressure should be reduced. This research evaluates all aspects of integrated observations, laboratory tests and field observations since the beginning of this ongoing mudflow. Laboratory tests were done by providing hot air bubbles into the fluid inside the inverted funnel showed that the fluid can flow with a high altitude. It is due to the mechanism of buoyant force from air bubbles to the water where the contrast density of the water and the air is quite large. Quantity of air bubbles provides direct effect to the debit of fluid flow. Direct observation in the field, in 2006 and 2007, with TIMNAS and LPPM ITB showed the large number of air bubbles on the surface of the mud craters. Temperature observation on the surface of mud crater is around 98 degree C whereas at greater depth shows the temperature is increasingly rising. This strengthens the hypothesis or proves that the mud pumping mechanism comes from buoyant force of hot air bubbles. Inversion gravity images show that the deep subsurface of main crater is close to volcanic layers or root of Arjuna mountain. Based on the simulation laboratory and field observation data, it can be concluded that the geothermal factor plays a key role in the mudflow mechanism.

  6. Period-adding bifurcations and chaos in a bubble column.

    PubMed

    Piassi, Viviane S M; Tufaile, Alberto; Sartorelli, Jose Carlos

    2004-06-01

    We obtained period-adding bifurcations in a bubble formation experiment. Using the air flow rate as the control parameter in this experiment, the bubble emission from the nozzle in a viscous fluid undergoes from single bubbling to a sequence of periodic bifurcations of k to k+1 periods, occasionally interspersed with some chaotic regions. Our main assumption is that this period-adding bifurcation in bubble formation depends on flow rate variations in the chamber under the nozzle. This assumption was experimentally tested by placing a tube between the air reservoir and the chamber under the nozzle in the bubble column experiment. By increasing the tube length, more period-adding bifurcations were observed. We associated two main types of bubble growth to the flow rate fluctuations inside the chamber for different bubbling regimes. We also studied the properties of piecewise nonlinear maps obtained from the experimental reconstructed attractors, and we concluded that this experiment is a spatially extended system.

  7. TRIGGERED STAR FORMATION AROUND MID-INFRARED BUBBLES IN THE G8.14+0.23 H II REGION

    SciTech Connect

    Dewangan, L. K.; Ojha, D. K.; Chakraborti, S.; Anandarao, B. G.; Ghosh, S. K.

    2012-09-10

    Mid-infrared shells or bubbles around expanding H II regions have received much attention due to their ability to initiate a new generation of star formation. We present multi-wavelength observations around two bubbles associated with a southern massive star-forming region G8.14+0.23, to investigate the triggered star formation signature on the edges of the bubbles by the expansion of the H II region. We have found observational signatures of the collected molecular and cold dust material along the bubbles and the {sup 12}CO(J = 3-2) velocity map reveals that the molecular gas in the bubbles is physically associated around the G8.14+0.23 region. We have detected 244 young stellar objects (YSOs) in the region and about 37% of these YSOs occur in clusters. Interestingly, these YSO clusters are associated with the collected material on the edges of the bubbles. We have found good agreement between the dynamical age of the H II region and the kinematical timescale of bubbles (from the {sup 12}CO(J = 3-2) line data) with the fragmentation time of the accumulated molecular materials to explain possible 'collect and collapse' process around the G8.14+0.23 region. However, one cannot entirely rule out the possibility of triggered star formation by compression of the pre-existing dense clumps by the shock wave. We have also found two massive embedded YSOs (about 10 and 22 M{sub Sun }) which are associated with the dense fragmented clump at the interface of the bubbles. We conclude that the expansion of the H II region is also leading to the formation of these two young massive embedded YSOs in the G8.14+0.23 region.

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

    NASA Astrophysics Data System (ADS)

    Liu, Shengguang; Dai, Shuyu; Sang, Chaofeng; Sun, Jizhong; Stirner, Thomas; Wang, Dezhen

    2015-08-01

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

  9. Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation.

    PubMed

    Yap, R K L; Whittaker, M; Diao, M; Stuetz, R M; Jefferson, B; Bulmus, V; Peirson, W L; Nguyen, A V; Henderson, R K

    2014-09-15

    Dissolved air flotation (DAF), an effective treatment method for clarifying algae/cyanobacteria-laden water, is highly dependent on coagulation-flocculation. Treatment of algae can be problematic due to unpredictable coagulant demand during blooms. To eliminate the need for coagulation-flocculation, the use of commercial polymers or surfactants to alter bubble charge in DAF has shown potential, termed the PosiDAF process. When using surfactants, poor removal was obtained but good bubble adherence was observed. Conversely, when using polymers, effective cell removal was obtained, attributed to polymer bridging, but polymers did not adhere well to the bubble surface, resulting in a cationic clarified effluent that was indicative of high polymer concentrations. In order to combine the attributes of both polymers (bridging ability) and surfactants (hydrophobicity), in this study, a commercially-available cationic polymer, poly(dimethylaminoethyl methacrylate) (polyDMAEMA), was functionalised with hydrophobic pendant groups of various carbon chain lengths to improve adherence of polymer to a bubble surface. Its performance in PosiDAF was contrasted against commercially-available poly(diallyl dimethyl ammonium chloride) (polyDADMAC). All synthesised polymers used for bubble surface modification were found to produce positively charged bubbles. When applying these cationic micro-bubbles in PosiDAF, in the absence of coagulation-flocculation, cell removals in excess of 90% were obtained, reaching a maximum of 99% cell removal and thus demonstrating process viability. Of the synthesised polymers, the polymer containing the largest hydrophobic functionality resulted in highly anionic treated effluent, suggesting stronger adherence of polymers to bubble surfaces and reduced residual polymer concentrations.

  10. Surfactant effects on cumulative drop size distributions produced by air bubbles bursting on a non-quiescent free surface

    NASA Astrophysics Data System (ADS)

    Parmar, K.; Liu, X.; Duncan, J. H.

    2013-11-01

    The generation of droplets when air bubbles travel upwards from within a liquid and burst at a free surface is studied experimentally. The bubbles are generated in a glass water tank that is 0.91 m long and 0.46 m wide with a water depth of 0.5 m. The tank is equipped with an acrylic box at its bottom that creates the bubble field using filtered air injected through an array of 180 hypodermic needles (0.33 mm ID). Two different surface conditions are created by using clean water and a 0.4% aqueous solution of Triton X-100 surfactant. Measurements of the bubble diameters as they approach the free surface are obtained with diffuse light shadowgraph images. The range of bubble diameters studied is 2.885 mm to 3.301 mm for clean water and 2.369 mm to 3.014 mm for the surfactant solution. A laser-light high-speed cinematic shadowgraph system is employed to record and measure the diameters and motions of the droplets at the free surface. This system can measure droplets with diameters <= 50 μm. The results show a clear distinction between the droplet distributions obtained in clean water and the surfactant solution. A bimodal droplet distribution is observed for clean water with at least two dominating peaks. For the surfactant solution, a single distribution peak is seen. This work is supported by the National Science Foundation, Division of Ocean Sciences.

  11. Formation and dynamics of a toroidal bubble during laser propelling a cavity object in water.

    PubMed

    Chen, Jun; Zhang, Hong-Chao; Shen, Zhong-Hua; Lu, Jian; Ni, Xiao-Wu

    2013-10-01

    We captured stable self-oscillations of a toroidal bubble moving away from a laser propelled cavity object in water using a high-speed imaging system. The entire laser propelling process generates a hemispherical bubble, two toroidal bubbles, and a microbubble cluster. The hemispherical bubble is formed by laser breakdown in water. The toroidal bubbles are formed by the variation of the pressure field as a result of the propagation, reflection, and convergence of the laser plasma shockwave in the cavity.

  12. Bubble Drag Reduction Requires Large Bubbles

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  13. Bubble Drag Reduction Requires Large Bubbles.

    PubMed

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

    2016-09-01

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

  14. Bubble Drag Reduction Requires Large Bubbles.

    PubMed

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

    2016-09-01

    In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag reduction in turbulent flow dramatically depends on the bubble size. By adding minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise completely unchanged strongly turbulent Taylor-Couette flow containing bubbles, we dramatically reduce the drag reduction from more than 40% to about 4%, corresponding to the trivial effect of the bubbles on the density and viscosity of the liquid. The reason for this striking behavior is that the addition of surfactants prevents bubble coalescence, leading to much smaller bubbles. Our result demonstrates that bubble deformability is crucial for bubble drag reduction in turbulent flow and opens the door for an optimization of the process. PMID:27636479

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    DOE PAGES

    Chen, Chien -Hung; Zhang, Yanwen; Wang, Yongqiang; Crespillo, Miguel L.; Fontana, Cristiano L.; Graham, Joseph T.; Duscher, Gerd; Shannon, Steven C.; Weber, William J.

    2016-02-03

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

  17. Numerical simulations of bubble-induced star formation in dwarf irregular galaxies with a novel stellar feedback scheme

    NASA Astrophysics Data System (ADS)

    Kawata, Daisuke; Gibson, Brad K.; Barnes, David J.; Grand, Robert J. J.; Rahimi, Awat

    2014-02-01

    To study the star formation and feedback mechanism, we simulate the evolution of an isolated dwarf irregular galaxy (dIrr) in a fixed dark matter halo, similar in size to Wolf-Lundmark-Melotte, using a new stellar feedback scheme. We use the new version of our original N-body/smoothed particle chemodynamics code, GCD+, which adopts improved hydrodynamics, metal diffusion between the gas particles and new modelling of star formation and stellar wind and supernovae feedback. Comparing the simulations with and without stellar feedback effects, we demonstrate that the collisions of bubbles produced by strong feedback can induce star formation in a more widely spread area. We also demonstrate that the metallicity in star-forming regions is kept low due to the mixing of the metal-rich bubbles and the metal-poor interstellar medium. Our simulations also suggest that the bubble-induced star formation leads to many counter-rotating stars. The bubble-induced star formation could be a dominant mechanism to maintain star formation in dIrrs, which is different from larger spiral galaxies where the non-axisymmetric structures, such as spiral arms, are a main driver of star formation.

  18. Gas bubble dimensions in Archean lava flows indicate low air pressure at 2.7 Ga

    NASA Astrophysics Data System (ADS)

    Som, S. M.; Buick, R.; Hagadorn, J.; Blake, T.; Perreault, J.; Harnmeijer, J.; Catling, D. C.

    2014-12-01

    Air pressure constrains atmospheric composition, which, in turn, is linked to the Earth system through biogeochemical cycles and fluxes of volatiles from and to the Earth's interior. Previous studies have only placed maximum levels on surface air pressure for the early Earth [1]. Here, we calculate an absolute value for Archean barometric pressure using gas bubble size (vesicle) distributions in uninflated basaltic lava flows that solidified at sea level 2.7 billion years ago in the Pilbara Craton, Western Australia. These vesicles have been filled in by secondary minerals deposited during metasomatism and so are now amydules, but thin sections show that infilling did not change vesicle dimensions. Amygdule dimensions are measured using high-resolution X-ray tomography from core samples obtained from the top and bottom of the lava flows. The modal size expressed at the top and at the bottom of an uninflated flow can be linked to atmospheric pressure using the ideal gas law. Such a technique has been verified as a paleoaltimeter using Hawaiian Quaternary lava flows [2]. We use statistical methods to estimate the mean and standard deviation of the volumetric size of the amygdules by applying 'bootstrap'resampling and the Central Limit Theorem. Our data indicate a surprisingly low atmospheric pressure. Greater nitrogen burial under anaerobic conditions likely explains lower pressure. Refs: [1] Som et al. (2012) Nature 484, 359-262. D. L. Sahagian et al. (2002) J. Geol., 110, 671-685.

  19. Field-scale tests for determining mixing patterns associated with coarse-bubble air diffuser configurations, Egan Quarry, Illinois

    USGS Publications Warehouse

    Hornewer, N.J.; Johnson, G.P.; Robertson, D.M.; Hondzo, Miki

    1997-01-01

    The U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers, Chicago District did field-scale tests in August-September 1996 to determine mixing patterns associated with different configurations of coarse-bubble air diffusers. The tests were done in an approximately 13-meter deep quarry near Chicago, Ill. Three-dimensional velocity, water-temperature, dissolved oxygen concentration, and specific-conductivity profiles were collected from locations between approximately 2 to 30 meters from the diffusers for two sets of five test configurations; one set for stratified and one set for destratified conditions in the quarry. The data-collection methods and instrumentation used to characterize mixing patterns and interactions of coarse-bubble diffusers were successful. An extensive data set was collected and is available to calibrate and verify aeration and stratification models, and to characterize basic features of bubble-plume interaction.

  20. Scale dependence of bubble creation mechanisms in breaking waves.

    PubMed

    Deane, Grant B; Stokes, M Dale

    2002-08-22

    Breaking ocean waves entrain air bubbles that enhance air-sea gas flux, produce aerosols, generate ambient noise and scavenge biological surfactants. The size distribution of the entrained bubbles is the most important factor in controlling these processes, but little is known about bubble properties and formation mechanisms inside whitecaps. We have measured bubble size distributions inside breaking waves in the laboratory and in the open ocean, and provide a quantitative description of bubble formation mechanisms in the laboratory. We find two distinct mechanisms controlling the size distribution, depending on bubble size. For bubbles larger than about 1 mm, turbulent fragmentation determines bubble size distribution, resulting in a bubble density proportional to the bubble radius to the power of -10/3. Smaller bubbles are created by jet and drop impact on the wave face, with a -3/2 power-law scaling. The length scale separating these processes is the scale where turbulent fragmentation ceases, also known as the Hinze scale. Our results will have important implications for the study of air-sea gas transfer.

  1. Quantitative measurement of size and three-dimensional position of fast-moving bubbles in air-water mixture flows using digital holography.

    PubMed

    Tian, Lei; Loomis, Nick; Domínguez-Caballero, José A; Barbastathis, George

    2010-03-20

    We present a digital in-line holographic imaging system for measuring the size and three-dimensional position of fast-moving bubbles in air-water mixture flows. The captured holograms are numerically processed by performing a two-dimensional projection followed by local depth estimation to quickly and efficiently obtain the size and position information of multiple bubbles simultaneously. Statistical analysis on measured bubble size distributions shows that they follow lognormal or gamma distributions.

  2. Preliminary investigation of air bubbling and dietary sulfur reduction to mitigate hydrogen sulfide and odor from swine waste.

    PubMed

    Clark, O Grant; Morin, Brent; Zhang, Yongcheng; Sauer, Willem C; Feddes, John J R

    2005-01-01

    When livestock manure slurry is agitated, the sudden release of hydrogen sulfide (H(2)S) can raise concentrations to dangerous levels. Low-level air bubbling and dietary S reduction were evaluated as methods for reducing peak H(2)S emissions from swine (Sus scrofa) manure slurry samples. In a first experiment, 15-L slurry samples were stored in bench-scale digesters and continuously bubbled with air at 0 (control), 5, or 10 mL min(-1) for 28 d. The 5-L headspace of each digester was also continuously ventilated at 40 mL min(-1) and the mean H(2)S concentration in the outlet air was <10 microL L(-1). On Day 28, the slurry was agitated suddenly. The peak H(2)S concentration exceeded instrument range (>120 microL L(-1)) from the control treatment, and was 47 and 3.4 microL L(-1) for the 5 and 10 mL min(-1) treatments, respectively. In a second experiment, individually penned barrows were fed rations with dietary S concentrations of 0.34, 0.24, and 0.15% (w/w). Slurry derived from each diet was bubbled with air in bench-scale digesters, as before, at 10 mL min(-1) for 12 d and the mean H(2)S concentration in the digester outlet air was 11 microL L(-1). On Day 12, the slurry was agitated but the H(2)S emissions did not change significantly. Both low-level bubbling of air through slurry and dietary S reduction appear to be viable methods for reducing peak H(2)S emissions from swine manure slurry at a bench scale, but these approaches must be validated at larger scales. PMID:16221821

  3. Cavitation bubble behavior and bubble-shock wave interaction near a gelatin surface as a study of in vivo bubble dynamics

    NASA Astrophysics Data System (ADS)

    Kodama, T.; Tomita, Y.

    The collapse of a single cavitation bubble near a gelatin surface, and the interaction of an air bubble attached to a gelatin surface with a shock wave, were investigated. These events permitted the study of the behavior of in vivo cavitation bubbles and the subsequent tissue damage mechanism during intraocular surgery, intracorporeal and extracorporeal shock wave lithotripsy. Results were obtained with high-speed framing photography. The cavitation bubbles near the gelatin surface did not produce significant liquid jets directed at the surface, and tended to migrate away from it. The period of the motion of a cavitation bubble near the gelatin surface was longer than that of twice the Rayleigh's collapse time for a wide range of relative distance, L/Rmax, excepting for very small L/Rmax values (L was the stand-off distance between the gelatin surface and the laser focus position, and Rmax was the maximum bubble radius). The interaction of an air bubble with a shock wave yielded a liquid jet inside the bubble, penetrating into the gelatin surface. The liquid jet had the potential to damage the gelatin. The results predicted that cavitation-bubble-induced tissue damage was closely related to the oscillatory bubble motion, the subsequent mechanical tissue displacement, and the liquid jet penetration generated by the interaction of the remaining gas bubbles with subsequent shock waves. The characteristic bubble motion and liquid jet formation depended on the tissue's mechanical properties, resulting in different damage mechanisms from those observed on hard materials.

  4. Effects of mixing technique on bubble formation in alginate impression material.

    PubMed

    McDaniel, Thomas F; Kramer, Robert T; Im, Francis; Snow, Dallin

    2013-01-01

    Previous studies have found that variations in mixing technique can influence the porosity content of alginate impression material. The aim of this study was twofold: determine whether bubble formation in alginate is influenced by the sequence of water/powder addition prior to mixing, and to compare 4 different mixing techniques. Manual spatulation, an automated spinning bowl, a centrifugal mixer and a vacuum mixer were evaluated for the resulting porosity in the set alginate. It was found that adding powder first, versus water first, made no difference in the bubble content using the 3 automated mixing techniques (P = 0.714). However, porosity was significantly less for powder-first trials using manual spatulation (P < 0.05). It was also found that surface porosity in the resulting impressions was significantly less for centrifugal and vacuum mixing when compared to manual spatulation, while internal porosity was significantly less for centrifugal mixing compared to all other mixing techniques (P < 0.05). The centrifugal mixing and vacuum mixing techniques required the least amount of mixing time.

  5. Effects of mixing technique on bubble formation in alginate impression material.

    PubMed

    McDaniel, Thomas F; Kramer, Robert T; Im, Francis; Snow, Dallin

    2013-01-01

    Previous studies have found that variations in mixing technique can influence the porosity content of alginate impression material. The aim of this study was twofold: determine whether bubble formation in alginate is influenced by the sequence of water/powder addition prior to mixing, and to compare 4 different mixing techniques. Manual spatulation, an automated spinning bowl, a centrifugal mixer and a vacuum mixer were evaluated for the resulting porosity in the set alginate. It was found that adding powder first, versus water first, made no difference in the bubble content using the 3 automated mixing techniques (P = 0.714). However, porosity was significantly less for powder-first trials using manual spatulation (P < 0.05). It was also found that surface porosity in the resulting impressions was significantly less for centrifugal and vacuum mixing when compared to manual spatulation, while internal porosity was significantly less for centrifugal mixing compared to all other mixing techniques (P < 0.05). The centrifugal mixing and vacuum mixing techniques required the least amount of mixing time. PMID:24064161

  6. Cold Heat Release Characteristics of Solidified Oil Droplet-Water Solution Latent Heat Emulsion by Air Bubbles

    NASA Astrophysics Data System (ADS)

    Inaba, Hideo; Morita, Shin-Ichi

    The present work investigates the cold heat-release characteristics of the solidified oil droplets (tetradecane, C14H30, freezing point 278.9 K)/water solution emulsion as a latent heat-storage material having a low melting point. An air bubbles-emulsion direct-contact heat exchange method is selected for the cold heat-results from the solidified oil droplet-emulsion layer. This type of direct-contact method results in the high thermal efficiency. The diameter of air bubbles in the emulsion increases as compared with that in the pure water. The air bubbles blown from a nozzle show a strong mixing behavior during rising in the emulsion. The temperature effectiveness, the sensible heat release time and the latent heat release time have been measured as experimental parameters. The useful nondimensional emulsion level equations for these parameters have been derived in terms of the nondimensional emalsion level expressed the emulsion layer dimensions, Reynolds number for air flow, Stefan number and heat capacity ratio.

  7. Formation of bubbly horizon in liquid-saturated porous medium by surface temperature oscillation.

    PubMed

    Goldobin, Denis S; Krauzin, Pavel V

    2015-12-01

    We study nonisothermal diffusion transport of a weakly soluble substance in a liquid-saturated porous medium in contact with a reservoir of this substance. The surface temperature of the porous medium half-space oscillates in time, which results in a decaying solubility wave propagating deep into the porous medium. In this system, zones of saturated solution and nondissolved phase coexist with ones of undersaturated solution. The effect is first considered for the case of annual oscillation of the surface temperature of water-saturated ground in contact with the atmosphere. We reveal the phenomenon of formation of a near-surface bubbly horizon due to temperature oscillation. An analytical theory of the phenomenon is developed. Further, the treatment is extended to the case of higher frequency oscillations and the case of weakly soluble solids and liquids. PMID:26764828

  8. Expanding shell and star formation in the infrared dust bubble N6

    SciTech Connect

    Yuan, Jing-Hua; Li, Jin Zeng; Liu, Hongli; Wu, Yuefang E-mail: ywu@pku.edu.cn

    2014-12-10

    We have carried out a multiwavelength study of the infrared dust bubble N6 to extensively investigate the molecular environs and star-forming activities therein. Mapping observations in {sup 12}CO J = 1-0 and {sup 13}CO J = 1-0 performed with the Purple Mountain Observatory 13.7 m telescope have revealed four velocity components. Comparison between distributions of each component and the infrared emission suggests that three components are correlated with N6. There are 10 molecular clumps detected. Among them, five have reliable detections in both {sup 12}CO and {sup 13}CO and have similar LTE and non-LTE masses ranging from 200 to higher than 5000 M {sub ☉}. With larger gas masses than virial masses, these five clumps are gravitationally unstable and have the potential to collapse to form new stars. The other five clumps are only reliably detected in {sup 12}CO and have relatively small masses. Five clumps are located on the border of the ring structure, and four of them are elongated along the shell. This is well in agreement with the collect-and-collapse scenario. The detected velocity gradient reveals that the ring structure is still under expansion owing to stellar winds from the exciting star(s). Furthermore, 99 young stellar objects (YSOs) have been identified based on their infrared colors. A group of YSOs reside inside the ring, indicating active star formation in N6. Although no confirmative features of triggered star formation are detected, the bubble and the enclosed H II region have profoundly reconstructed the natal cloud and altered the dynamics therein.

  9. Gas bubbles in fossil amber as possible indicators of the major gas composition of ancient air

    USGS Publications Warehouse

    Berner, R.A.; Landis, G.P.

    1988-01-01

    Gases trapped in Miocene to Upper Cretaceous amber were released by gently crushing the amber under vacuum and were analyzed by quadrupole mass spectrometry. After discounting the possibility that the major gases N2, O2, and CO2 underwent appreciable diffusion and diagenetic exchange with their surroundings or reaction with the amber, it has been concluded that in primary bubbles (gas released during initial breakage) these gases represent mainly original ancient air modified by the aerobic respiration of microorganisms. Values of N2/(CO2+O2) for each time period give consistent results despite varying O2/CO2 ratios that presumably were due to varying degrees of respiration. This allows calculation of original oxygen concentrations, which, on the basis of these preliminary results, appear to have changed from greater than 30 percent O2 during one part ofthe Late Cretaceous (between 75 and 95 million years ago) to 21 percent during the Eocene-Oligocene and for present-day samples, with possibly lower values during the Oligocene-Early Miocene. Variable O2 levels over time in general confirm theoretical isotope-mass balance calculations and suggest that the atmosphere has evolved over Phanerozoic time.

  10. Polymer Brush Surfaces Showing Superhydrophobicity and Air-Bubble Repellency in a Variety of Organic Liquids.

    PubMed

    Dunderdale, Gary J; England, Matt W; Urata, Chihiro; Hozumi, Atsushi

    2015-06-10

    Silicon (Si) substrates were modified with polyalkyl methacrylate brushes having different alkyl chain lengths (C(n), where n = 1, 4, 8, and 18) using ARGET-ATRP at ambient temperature without purging the reaction solution of oxygen. The dynamic hydrophobicity of these polymer brush-covered Si surfaces when submerged in a variety of organic solvents (1-butanol, dichloromethane, toluene, n-hexane) depended markedly on the alkyl chain length and to a lesser extent polymer solubility. Long-chain poly(stearyl methacrylate) brushes (C(n) = 18) submerged in toluene showed excellent water-repellant properties, having large advancing/receding contact angles (CAs) of 169°/168° with negligible CA hysteresis (1°). Whereas polymer brushes with short alkyl-chain (C(n) ≤ 4) had significantly worse water drop mobility because of small CAs (as low as 125°/55°) and large CA hysteresis (up to 70°). However, such poor dynamic dewetting behavior of these surfaces was found to significantly improve when water drops impacted onto the surfaces at moderate velocities. Under these conditions, all brush surfaces were able to expel water drops from their surface. In addition, our brush surfaces were also highly repellant toward air bubbles under all conditions, irrespective of C(n) or polymer solubility. These excellent surface properties were found to be vastly superior to the performance of conventional perfluoroalkylsilane-derived surfaces. PMID:25988214

  11. Gasification of torrefied Miscanthus × giganteus in an air-blown bubbling fluidized bed gasifier.

    PubMed

    Xue, G; Kwapinska, M; Horvat, A; Kwapinski, W; Rabou, L P L M; Dooley, S; Czajka, K M; Leahy, J J

    2014-05-01

    Torrefaction is suggested to be an effective method to improve the fuel properties of biomass and gasification of torrefied biomass should provide a higher quality product gas than that from unprocessed biomass. In this study, both raw and torrefied Miscanthus × giganteus (M×G) were gasified in an air-blown bubbling fluidized bed (BFB) gasifier using olivine as the bed material. The effects of equivalence ratio (ER) (0.18-0.32) and bed temperature (660-850°C) on the gasification performance were investigated. The results obtained suggest the optimum gasification conditions for the torrefied M × G are ER 0.21 and 800°C. The product gas from these process conditions had a higher heating value (HHV) of 6.70 MJ/m(3), gas yield 2m(3)/kg biomass (H2 8.6%, CO 16.4% and CH4 4.4%) and cold gas efficiency 62.7%. The comparison between raw and torrefied M × G indicates that the torrefied M × G is more suitable BFB gasification.

  12. The Dueling Bubble Experiment

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

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

  13. The use of an air bubble curtain to reduce the received sound levels for harbor porpoises (Phocoena phocoena).

    PubMed

    Lucke, Klaus; Lepper, Paul A; Blanchet, Marie-Anne; Siebert, Ursula

    2011-11-01

    In December 2005 construction work was started to replace a harbor wall in Kerteminde harbor, Denmark. A total of 175 wooden piles were piled into the ground at the waters edge over a period of 3 months. During the same period three harbor porpoises were housed in a marine mammal facility on the opposite side of the harbor. All animals showed strong avoidance reactions after the start of the piling activities. As a measure to reduce the sound exposure for the animals an air bubble curtain was constructed and operated in a direct path between the piling site and the opening of the animals' semi-natural pool. The sound attenuation effect achieved with this system was determined by quantitative comparison of pile driving impulses simultaneously measured in front of and behind the active air bubble curtain. Mean levels of sound attenuation over a sequence of 95 consecutive pile strikes were 14 dB (standard deviation (s.d.) 3.4 dB) for peak to peak values and 13 dB (s.d. 2.5 dB) for SEL values. As soon as the air bubble curtain was installed and operated, no further avoidance reactions of the animals to the piling activities were apparent.

  14. Electrical breakdown of a bubble in a water-filled capillary

    SciTech Connect

    Bruggeman, P.J.; Leys, C.A.; Vierendeels, J. A.

    2006-06-01

    In this Communication, the electrical breakdown of a static bubble in a water-filled capillary generated in a dc electrical field is studied. We present experimental results which indicate that the liquid layer between capillary and bubble wall can have an important influence on the breakdown mechanism of the bubble. The breakdown electrical field (atmospheric pressure) without a liquid layer in a (vapor) bubble is 18 kV/cm. When a liquid layer is present, the electrical breakdown of an air bubble is observed at electrical fields typically two times smaller. Local plasma formation is observed in this case possibly due to bubble deformation.

  15. Formation of droplets and bubbles in a microfluidic T-junction-scaling and mechanism of break-up.

    PubMed

    Garstecki, Piotr; Fuerstman, Michael J; Stone, Howard A; Whitesides, George M

    2006-03-01

    This article describes the process of formation of droplets and bubbles in microfluidic T-junction geometries. At low capillary numbers break-up is not dominated by shear stresses: experimental results support the assertion that the dominant contribution to the dynamics of break-up arises from the pressure drop across the emerging droplet or bubble. This pressure drop results from the high resistance to flow of the continuous (carrier) fluid in the thin films that separate the droplet from the walls of the microchannel when the droplet fills almost the entire cross-section of the channel. A simple scaling relation, based on this assertion, predicts the size of droplets and bubbles produced in the T-junctions over a range of rates of flow of the two immiscible phases, the viscosity of the continuous phase, the interfacial tension, and the geometrical dimensions of the device. PMID:16511628

  16. Experimental formation of massive hydrate deposits from accumulation of CH4 gas bubbles within synthetic and natural sediments

    SciTech Connect

    Madden, Megan Elwood; Szymcek, Phillip; Ulrich, Shannon M; McCallum, Scott D; Phelps, Tommy Joe

    2009-01-01

    In order for methane to be economically produced from the seafloor, prediction and detection of massive hydrate deposits will be necessary. In many cases, hydrate samples recovered from seafloor sediments appear as veins or nodules, suggesting that there are strong geologic controls on where hydrate is likely to accumulate. Experiments have been conducted examining massive hydrate accumulation from methane gas bubbles within natural and synthetic sediments in a large volume pressure vessels through temperature and pressure data, as well as visual observations. Observations of hydrate growth suggest that accumulation of gas bubbles within void spaces and at sediment interfaces likely results in the formation of massive hydrate deposits. Methane hydrate was first observed as a thin film forming at the gas/water interface of methane bubbles trapped within sediment void spaces. As bubbles accumulated, massive hydrate growth occurred. These experiments suggest that in systems containing free methane gas, bubble pathways and accumulation points likely control the location and habit of massive hydrate deposits.

  17. Nanostructure of aluminum oxide inclusion and formation of hydrogen bubbles in molten aluminum.

    PubMed

    Zeng, Jianmin; Li, Dezhi; Kang, Minglong; He, Huan; Hu, Zhiliu

    2013-10-01

    Hydrogen in molten aluminum is one of the major factors that lead to pore formation in the solidification process of aluminum castings. Previous research showed that aluminum oxide inclusion had a close correlation with the hydrogen content in molten aluminum. Though some researchers thought there must have been a relationship between surface morphology of the inclusion and hydrogen concentration in molten aluminum, very few documents have reported on the surface property of aluminum oxide inclusion. In the present work, AFM (Atomic Force Microscope) was first used to investigate surface morphology of aluminum oxide inclusion in molten aluminum. It was found that there were a large number of nanoscale micropores on the surface of aluminum oxide inclusion. The interior of the micropores was approximated as a tapered shape. These micropores were thought to be helpful to heterogeneous nucleation for hydrogen atoms aggregation because they provided necessary concentration fluctuation and energy undulation for the growth of hydrogen bubbles. Based on the nanostructure observed on the surface of aluminum oxide inclusion, a theoretical model was developed to describe the hydrogen pore formation in aluminum casting under the condition of heterogeneous nucleation.

  18. Direct Observation of Pore Formation and Bubble Mobility during Controlled Melting and Resolidification in Microgravity

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Anilkumar, A. V.; Lee, C. P.

    2004-01-01

    Detailed studies on the controlled melting and subsequent re-solidification of succinonitrile were conducted in the microgravity environment aboard the International Space Station (ISS) using the PFMI apparatus (Pore Formation and Mobility Investigation) located in the ISS glovebox facility (GBX). Samples were initially prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with pure succinonitrile (SCN) under 450 millibar of nitrogen. During Space processing, experimental parameters like temperature gradient and translation speed, for melting and solidification, were remotely monitored and controlled from the ground Telescience Center (TSC) at the Marshall Space Flight Center. Real time visualization during controlled melting revealed bubbles of different sizes initiating at the solid/liquid interface, and traveling up the temperature gradient ahead of them. Subsequent controlled re-solidification of the SCN revealed the details of porosity formation and evolution. A preliminary analysis of the melt back and re- solidification and its implications to future microgravity materials processing is presented and discussed.

  19. 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.

  20. Development of an air bubble curtain to reduce underwater noise of percussive piling.

    PubMed

    Würsig, B; Greene, C R; Jefferson, T A

    2000-02-01

    Underwater bubbles can inhibit sound transmission through water due to density mismatch and concomitant reflection and absorption of sound waves. For the present study, a perforated rubber hose was used to produce a bubble curtain, or screen, around pile-driving activity in 6-8-m depth waters of western Hong Kong. The percussive hammer blow sounds of the pile driver were measured on 2 days at distances of 250, 500, and 1000 m; broadband pulse levels were reduced by 3-5 dB by the bubble curtain. Sound intensities were measured from 100 Hz to 25.6 kHz, and greatest sound reduction by the bubble curtain was evident from 400 to 6400 Hz. Indo-Pacific hump-backed dolphins (Sousa chinensis) occurred in the immediate area of the industrial activity before and during pile driving, but with a lower abundance immediately after it. While hump-backed dolphins generally showed no overt behavioral changes with and without pile driving, their speeds of travel increased during pile driving, indicating that bubble screening did not eliminate all behavioral responses to the loud noise. Because the bubble curtain effectively lowered sound levels within 1 km of the activity, the experiment and its application during construction represented a success, and this measure should be considered for other appropriate areas with high industrial noises and resident or migrating sound-sensitive animals.

  1. A technique for automatic tubing occlusion in response to air bubble detection when using a centrifugal pump.

    PubMed

    Paulsen, A W; Hargadine, W L; Lambert, G S; Long, A C

    1990-01-01

    A double acting pneumatically powered cylinder, energized by an electrically activated solenoid valve, is used to occlude the outflow line from a Bio-Medicus (a) constrained vortex pump. The cylinder is mounted on a tubing guide that is fastened to a pole clamp. A Sarns (b) air bubble detector, placed on the pump inflow line is used to provide the signal to activate the solenoid valve. The outflow occluder is capable of 100% occlusion of 3/8 x 3/32 inch Tygon tubing up to pressures of 2586 mmHg. The occluder system is able to work with many types of bubble detectors and is applicable to any form of non-occlusive pump.

  2. 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.

  3. Bubble pinch-off and scaling during liquid drop impact on liquid pool

    NASA Astrophysics Data System (ADS)

    Ray, Bahni; Biswas, Gautam; Sharma, Ashutosh

    2012-08-01

    Simulations are performed to show entrapment of air bubble accompanied by high speed upward and downward water jets when a water drop impacts a pool of water surface. A new bubble entrapment zone characterised by small bubble pinch-off and long thick jet is found. Depending on the bubble and jet behaviour, the bubble entrapment zone is subdivided into three sub-regimes. The entrapped bubble size and jet height depends on the crater shape and its maximum depth. During the bubble formation, bubble neck develops an almost singular shape as it pinches off. The final pinch-off shape and the power law governing the pinching, rneck ∝ A(t0 - t)αvaries with the Weber number. Weber dependence of the function describing the radius of the bubble during the pinch-off only affects the coefficient A and not the power exponent α.

  4. Calibration of a bubble evolution model to observed bubble incidence in divers.

    PubMed

    Gault, K A; Tikuisis, P; Nishi, R Y

    1995-09-01

    The method of maximum likelihood was used to calibrate a probabilistic bubble evolution model against data of bubbles detected in divers. These data were obtained from a diverse set of 2,064 chamber man-dives involving air and heliox with and without oxygen decompression. Bubbles were measured with Doppler ultrasound and graded according to the Kisman-Masurel code from which a single maximum bubble grade (BG) per diver was compared to the maximum bubble radius (Rmax) predicted by the model. This comparison was accomplished using multinomial statistics by relating BG to Rmax through a series of probability functions. The model predicted the formation of the bubble according to the critical radius concept and its evolution was predicted by assuming a linear rate of inert gas exchange across the bubble boundary. Gas exchange between the model compartment and blood was assumed to be perfusion-limited. The most successful calibration of the model was found using a trinomial grouping of BG according to no bubbles, low, and high bubble activity, and by assuming a single tissue compartment. Parameter estimations converge to a tissue volume of 0.00036 cm3, a surface tension of 5.0 dyne.cm-1, respective time constants of 27.9 and 9.3 min for nitrogen and helium, and respective Ostwald tissue solubilities of 0.0438 and 0.0096. Although not part of the calibration algorithm, the predicted evolution of bubble size compares reasonably well with the temporal recordings of BGs.

  5. A numerical model of rupture formation in a bubbly liquid under pulsed loading

    NASA Astrophysics Data System (ADS)

    Vshivkov, V. A.; Kedrinskii, V. K.; Dudnikov, G. I.; Shokin, Yu. I.

    2015-09-01

    In this study, a new numerical model based on the method of particles in cells, which differs in principle from the schematic of particles in Harlow cells by the fact that the particles have their own velocity and, therefore, boundaries with a vacuum are not spread, is proposed for the first time. The model makes it possible to pass the stage of the "continuous" transition to rupture development and description of the dynamics of the further state of its "banks." Based on the Iordansky-Kogarko-van Wijngaarden mathematical model (IKW model), the formation of rupture and its further dynamics in the bubble fluid layer in the jump region of the mass velocity is numerically investigated using the proposed method. The dynamics of the state of the medium on both rupture "banks" is calculated including the structure of the rarefaction waves, fields of mass velocity and density, and cavitation development in the time range up to 2 μs when the subsequent dynamics of the layer succumbs to the prognosis.

  6. Heat Storage Characteristics of Latent-Heat Microcapsule Slurry Using Hot Air Bubbles by Direct-Contact Heat Exchange

    NASA Astrophysics Data System (ADS)

    Inaba, Hideo; Horibe, Akihiko; Kim, Myoung-Jun; Tsukamoto, Hirofumi

    This study deals with the heat storage characteristics of latent-heat microcapsule slurry consisting of a mixture of fine microcapsules packed with latent-heat storage material and water. The heat storage operation for the latent-heat microcapsules was carried out by the direct-contact heat exchange method using hot air bubbles. The latent-heat microcapsule consisted of n-paraffin as a core latent-heat storage material and melamine resin as a coating substance. The relationship between the completion time of latent-heat storage and some parameters was examined experimentally. The nondimensional correlation equations for temperature efficiency, the completion time period of the latent-heat storage process and variation in the enthalpy of air through the microcapsule slurry layer were derived in terms of the ratio of microcapsule slurry layer height to microcapsule diameter, Reynolds number for airflow, Stefan number and modified Stefan number for absolute humidity of flowing air.

  7. Initiation of breakdown in strings of bubbles immersed in transformer oil and water: string orientation and proximity of bubbles

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia Yu; Tereshonok, Dmitry V.; Naidis, George V.; Smirnov, Boris M.

    2016-01-01

    We computationally investigated the properties of positive streamers propagating inside strings of bubbles filled with humid air at atmospheric pressure, immersed in liquids and aligned along the electric field or transversal to it. We show that orientation of the string and proximity of bubbles are crucial for the streamer formation and re-initiation in the neighboring bubbles. For the vertical string (aligned along the electric field) there is a small field depletion inside the bubbles due to mutual polarization compared to the field in an isolated bubble. As a result, in a vertical string the ‘streamer hopping’ is more sensitive to the bubble separation. The streamer hopping is observed only when the separation is smaller than 300 μm. Polarization of the horizontal string of bubbles results in higher electric field inside the bubbles as compared to that in an isolated bubble. In this case, ‘streamer hopping’ is observed for the bubble separation 500 μm or larger. We also investigated the arrays of five and nine bubbles and showed that the enhancement of the electric field and streamer development depend on how many field depleting poles or field enhancing equators are in close proximity to the particular bubble.

  8. Investigation of helium interstitials aggregation in silicon: Why bubbles formation by a self-trapping mechanism does not work

    NASA Astrophysics Data System (ADS)

    Pizzagalli, L.; David, M.-L.; Charaf-Eddin, A.

    2015-06-01

    First-principles calculations of the aggregation of helium interstitials in silicon have been performed to determine whether the first steps of helium-filled bubbles formation could occur by a self-trapping mechanism. These simulations show that the interaction between helium interstitials is repulsive, of low magnitude, and that this effect will saturate for a large number of interstitials. Considering the relaxation of the computational cell only leads to a small reduction of the binding energy. These results imply that the aggregation of interstitial helium atoms is highly unlikely in silicon, which allowed us to conclude that a self-trapping mechanism can not occur, and that an initial amount of vacancies is required for helium-filled bubbles formation.

  9. What is the Shape of an Air Bubble on a Liquid Surface?

    PubMed

    Teixeira, Miguel A C; Arscott, Steve; Cox, Simon J; Teixeira, Paulo I C

    2015-12-29

    We have calculated the equilibrium shape of the axially symmetric meniscus along which a spherical bubble contacts a flat liquid surface by analytically integrating the Young-Laplace equation in the presence of gravity, in the limit of large Bond numbers. This method has the advantage that it provides semianalytical expressions for key geometrical properties of the bubble in terms of the Bond number. Results are in good overall agreement with experimental data and are consistent with fully numerical (Surface Evolver) calculations. In particular, we are able to describe how the bubble shape changes from hemispherical, with a flat, shallow bottom, to lenticular, with a deeper, curved bottom, as the Bond number is decreased.

  10. Buoyancy effects in steeply inclined air-water bubbly shear flow in a rectangular channel

    NASA Astrophysics Data System (ADS)

    Sanaullah, K.; Arshad, M.; Khan, A.; Chughtai, I. R.

    2015-07-01

    We report measurements of two-dimensional ( B/ D = 5) fully turbulent and developed duct flows (overall length/depth, L/ D = 60; D-based Reynolds number Re > 104) for inclinations to 30° from vertical at low voidages (< 5 % sectional average) representative of disperse regime using tap water bubbles (4-6 mm) and smaller bubbles (2 mm) stabilised in ionic solution. Pitot and static probe instrumentation, primitive but validated, provided adequate (10 % local value) discrimination of main aspects of the mean velocity and voidage profiles at representative streamwise station i.e L/ D = 40. Our results can be divided into three categories of behaviour. For vertical flow (0°) the evidence is inconclusive as to whether bubbles are preferentially trapped within the wall-layer as found in some, may be most earlier experimental works. Thus, the 4-mm bubbles showed indication of voidage retention but the 2-mm bubbles did not. For nearly vertical flow (5°) there was pronounced profiling of voidage especially with 4-mm bubbles but the transverse transport was not suppressed sufficiently to induce any obvious layering. In this context, we also refer to similarities with previous work on one-phase vertical and nearly vertical mixed convection flows displaying buoyancy inhibited mean shear turbulence. However, with inclined flow (10+ degrees) a distinctively layered pattern was invariably manifested in which voidage confinement increased with increasing inclination. In this paper we address flow behavior at near vertical conditions. Eulerian, mixed and VOF models were used to compute voidage and mean velocity profiles.

  11. Air bubble in anterior chamber as indicator of full-thickness incisions in femtosecond-assisted astigmatic keratotomy.

    PubMed

    Vaddavalli, Pravin K; Hurmeric, Volkan; Yoo, Sonia H

    2011-09-01

    Femtosecond-assisted astigmatic keratotomy is predictable and precise but may occasionally lead to a full-thickness incision on the cornea and the attendant complications. The presence of an air bubble in the anterior chamber soon after creation of the keratotomy by the femtosecond laser may indicate a full-thickness incision. We present a case in which recognition of this clinical finding early in the procedure might have prevented undesirable complications, such as leakage of aqueous and the potential for intraocular infection.

  12. Effect of decompression-induced bubble formation on highly trained divers microvascular function.

    PubMed

    Lambrechts, Kate; Pontier, Jean-Michel; Mazur, Aleksandra; Buzzacott, Peter; Morin, Jean; Wang, Qiong; Theron, Michael; Guerrero, Francois

    2013-11-01

    We previously showed microvascular alteration of both endothelium-dependent and -independent reactivity after a single SCUBA dive. We aimed to study mechanisms involved in this postdive vascular dysfunction. Ten divers each completed three protocols: (1) a SCUBA dive at 400 kPa for 30 min; (2) a 41-min duration of seawater surface head immersed finning exercise to determine the effect of immersion and moderate physical activity; and (3) a simulated 41-min dive breathing 100% oxygen (hyperbaric oxygen [HBO]) at 170 kPa in order to analyze the effect of diving-induced hyperoxia. Bubble grades were monitored with Doppler. Cutaneous microvascular function was assessed by laser Doppler. Endothelium-dependent (acetylcholine, ACh) and -independent (sodium nitroprusside, SNP) reactivity was tested by iontophoresis. Endothelial cell activation was quantified by plasma Von Willebrand factor and nitric oxide (NO). Inactivation of NO by oxidative stress was assessed by plasma nitrotyrosine. Platelet factor 4 (PF4) was assessed in order to determine platelet aggregation. Blood was also analyzed for measurement of platelet count. Cutaneous vascular conductance (CVC) response to ACh delivery was not significantly decreased by the SCUBA protocol (23 ± 9% before vs. 17 ± 7% after; P = 0.122), whereas CVC response to SNP stimulation decreased significantly (23 ± 6% before vs. 10 ± 1% after; P = 0.039). The HBO and immersion protocols did not affect either endothelial-dependent or -independent function. The immersion protocol induced a significant increase in NO (0.07 ± 0.01 vs. 0.12 ± 0.02 μg/mL; P = 0.035). This study highlighted change in microvascular endothelial-independent but not -dependent function in highly trained divers after a single air dive. The results suggest that the effects of decompression on microvascular function may be modified by diving acclimatization. PMID:24400144

  13. Effect of decompression-induced bubble formation on highly trained divers microvascular function.

    PubMed

    Lambrechts, Kate; Pontier, Jean-Michel; Mazur, Aleksandra; Buzzacott, Peter; Morin, Jean; Wang, Qiong; Theron, Michael; Guerrero, Francois

    2013-11-01

    We previously showed microvascular alteration of both endothelium-dependent and -independent reactivity after a single SCUBA dive. We aimed to study mechanisms involved in this postdive vascular dysfunction. Ten divers each completed three protocols: (1) a SCUBA dive at 400 kPa for 30 min; (2) a 41-min duration of seawater surface head immersed finning exercise to determine the effect of immersion and moderate physical activity; and (3) a simulated 41-min dive breathing 100% oxygen (hyperbaric oxygen [HBO]) at 170 kPa in order to analyze the effect of diving-induced hyperoxia. Bubble grades were monitored with Doppler. Cutaneous microvascular function was assessed by laser Doppler. Endothelium-dependent (acetylcholine, ACh) and -independent (sodium nitroprusside, SNP) reactivity was tested by iontophoresis. Endothelial cell activation was quantified by plasma Von Willebrand factor and nitric oxide (NO). Inactivation of NO by oxidative stress was assessed by plasma nitrotyrosine. Platelet factor 4 (PF4) was assessed in order to determine platelet aggregation. Blood was also analyzed for measurement of platelet count. Cutaneous vascular conductance (CVC) response to ACh delivery was not significantly decreased by the SCUBA protocol (23 ± 9% before vs. 17 ± 7% after; P = 0.122), whereas CVC response to SNP stimulation decreased significantly (23 ± 6% before vs. 10 ± 1% after; P = 0.039). The HBO and immersion protocols did not affect either endothelial-dependent or -independent function. The immersion protocol induced a significant increase in NO (0.07 ± 0.01 vs. 0.12 ± 0.02 μg/mL; P = 0.035). This study highlighted change in microvascular endothelial-independent but not -dependent function in highly trained divers after a single air dive. The results suggest that the effects of decompression on microvascular function may be modified by diving acclimatization.

  14. Soap Films and Bubbles.

    ERIC Educational Resources Information Center

    Rice, Karen

    1986-01-01

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

  15. Post-Formation Shrinkage and Stabilization of Microfluidic Bubbles in Lipid Solution.

    PubMed

    Shih, Roger; Lee, Abraham P

    2016-03-01

    Medical ultrasound imaging often employs ultrasound contrast agents (UCAs), injectable microbubbles stabilized by shells or membranes. In tissue, the compressible gas cores can strongly scatter acoustic signals, resonate, and emit harmonics. However, bubbles generated by conventional methods have nonuniform sizes, reducing the fraction that resonates with a given transducer. Microfluidic flow-focusing is an alternative production method which generates highly monodisperse bubbles with uniform constituents, enabling more-efficient contrast enhancement than current UCAs. Production size is tunable by adjusting gas pressure and solution flow rate, but solution effects on downstream stable size and lifetime have not been closely examined. This study therefore investigated several solution parameters, including the DSPC/DSPE-PEG2000 lipid ratio, concentration, viscosity, and preparation temperature to determine their effects on stabilization. It was found that bubble lifetime roughly correlated with stable size, which in turn was strongly influenced by primary-lipid-to-emulsifier ratio, analogous to its effects on conventional bubble yield and Langmuir-trough compressibility in existing studies. Raising DSPE-PEG2000 fraction in solution reduced bubble surface area in proportion to its reduction of lipid packing density at low compression in literature. In addition, the surface area was found to increase proportionately with lipid concentration above 2.1 mM. However, viscosities above or below 2.3-3.3 mPa·s seemed to reduce bubble size. Finally, lipid preparation at room temperature led to smaller bubbles compared to preparation near or above the primary lipid's phase transition point. Understanding these effects will further improve on postformation control over microfluidic bubble production, and facilitate size-tuning for optimal contrast enhancement. PMID:26820229

  16. Stationary bubble formation and cavity collapse in wedge-shaped hoppers

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  17. 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

  18. The Making of an Air-Supported Campus. Antioch's Bubble. Final Report.

    ERIC Educational Resources Information Center

    Brann, James

    The inflation of the vinyl bubble by Antioch students and faculty climaxed more than a year of study, planning, dealing with contractors, county officials, manufacturers of equipment and materials--and maturing the technology of pneumatic buildings. These activities were combined into what Antioch calls a "process-oriented curriculum." This…

  19. Air bubbles in water: a strongly multiple scattering medium for acoustic waves.

    PubMed

    Kafesaki, M; Penciu, R S; Economou, E N

    2000-06-26

    Using a newly developed multiple scattering scheme, we calculate band structure and transmission properties for acoustic waves propagating in bubbly water. We prove that the multiple scattering effects are responsible for the creation of wide gaps in the transmission even in the presence of strong positional and size disorder.

  20. A FEEDBACK-DRIVEN BUBBLE G24.136+00.436: A POSSIBLE SITE OF TRIGGERED STAR FORMATION

    SciTech Connect

    Liu, Hong-Li; Li, JinZeng; Yuan, Jing-Hua; Wu, Yuefang; Dong, Xiaoyi; Liu, Tie E-mail: yfwu.pku@gmail.com

    2015-01-01

    We present a multi-wavelength study of the IR bubble G24.136+00.436. The J = 1-0 observations of {sup 12}CO, {sup 13}CO, and C{sup 18}O were carried out with the Purple Mountain Observatory 13.7 m telescope. Molecular gas with a velocity of 94.8 km s{sup –1} is found prominently in the southeast of the bubble, shaped as a shell with a total mass of ∼2 × 10{sup 4} M {sub ☉}. It was likely assembled during the expansion of the bubble. The expanding shell consists of six dense cores, whose dense (a few of 10{sup 3} cm{sup –3}) and massive (a few of 10{sup 3} M {sub ☉}) characteristics coupled with the broad linewidths (>2.5 km s{sup –1}) suggest that they are promising sites for forming high-mass stars or clusters. This could be further consolidated by the detection of compact H II regions in Cores A and E. We tentatively identified and classified 63 candidate young stellar objects (YSOs) based on the Spitzer and UKIDSS data. They are found to be dominantly distributed in regions with strong molecular gas emission, indicative of active star formation, especially in the shell. The H II region inside the bubble is mainly ionized by a ∼O8V star(s), of the dynamical age of ∼1.6 Myr. The enhanced number of candidate YSOs and secondary star formation in the shell as well as the timescales involved, indicate a possible scenario for triggering star formation, signified by the ''collect and collapse'' process.

  1. Air tube formation at the freezing transition in nematic liquid crystals.

    PubMed

    Völtz, C; Maeda, Y; Tabe, Y; Yokoyama, H

    2007-03-01

    A phenomenon is presented, which changes the shape of gas bubbles in liquid crystals and also creates long gas tubes. The system consists of air bubbles which are injected into a nematic liquid crystal host. The shape of these air bubbles changes from spherical to ellipsoidal by initiating freezing of the sample. Furthermore, long gas tubes are formed from the air which was formerly dissolved in the liquid crystal. The gas tubes are created by the progression of the crystalline-liquid interface. Their length can reach up to 40 times their diameter. The diameter of the tubes depends on the pressure applied to the system, as well as on the interface velocity.

  2. The Influence of Bubbles on the Perception Carbonation Bite

    PubMed Central

    Wise, Paul M.; Wolf, Madeline; Thom, Stephen R.; Bryant, Bruce

    2013-01-01

    Although many people naively assume that the bite of carbonation is due to tactile stimulation of the oral cavity by bubbles, it has become increasingly clear that carbonation bite comes mainly from formation of carbonic acid in the oral mucosa. In Experiment 1, we asked whether bubbles were in fact required to perceive carbonation bite. Subjects rated oral pungency from several concentrations of carbonated water both at normal atmospheric pressure (at which bubbles could form) and at 2.0 atmospheres pressure (at which bubbles did not form). Ratings of carbonation bite under the two pressure conditions were essentially identical, indicating that bubbles are not required for pungency. In Experiment 2, we created controlled streams of air bubbles around the tongue in mildly pungent CO2 solutions to determine how tactile stimulation from bubbles affects carbonation bite. Since innocuous sensations like light touch and cooling often suppress pain, we predicted that bubbles might reduce rated bite. Contrary to prediction, air bubbles flowing around the tongue significantly enhanced rated bite, without inducing perceived bite in blank (un-carbonated) solutions. Accordingly, though bubbles are clearly not required for carbonation bite, they may well modulate perceived bite. More generally, the results show that innocuous tactile stimulation can enhance chemogenic pain. Possible physiological mechanisms are discussed. PMID:23990956

  3. The influence of bubbles on the perception carbonation bite.

    PubMed

    Wise, Paul M; Wolf, Madeline; Thom, Stephen R; Bryant, Bruce

    2013-01-01

    Although many people naively assume that the bite of carbonation is due to tactile stimulation of the oral cavity by bubbles, it has become increasingly clear that carbonation bite comes mainly from formation of carbonic acid in the oral mucosa. In Experiment 1, we asked whether bubbles were in fact required to perceive carbonation bite. Subjects rated oral pungency from several concentrations of carbonated water both at normal atmospheric pressure (at which bubbles could form) and at 2.0 atmospheres pressure (at which bubbles did not form). Ratings of carbonation bite under the two pressure conditions were essentially identical, indicating that bubbles are not required for pungency. In Experiment 2, we created controlled streams of air bubbles around the tongue in mildly pungent CO2 solutions to determine how tactile stimulation from bubbles affects carbonation bite. Since innocuous sensations like light touch and cooling often suppress pain, we predicted that bubbles might reduce rated bite. Contrary to prediction, air bubbles flowing around the tongue significantly enhanced rated bite, without inducing perceived bite in blank (un-carbonated) solutions. Accordingly, though bubbles are clearly not required for carbonation bite, they may well modulate perceived bite. More generally, the results show that innocuous tactile stimulation can enhance chemogenic pain. Possible physiological mechanisms are discussed.

  4. The injection of air/oxygen bubble into the anterior chamber of rabbits as a treatment for hyphema in patients with sickle cell disease.

    PubMed

    Ayintap, Emre; Keskin, Uğurcan; Sadigov, Fariz; Coskun, Mesut; Ilhan, Nilufer; Motor, Sedat; Semiz, Hilal; Parlakfikirer, Nihan

    2014-01-01

    Purpose. To investigate the changes of partial oxygen pressure (PaO2) in aqueous humour after injecting air or oxygen bubble into the anterior chamber in sickle cell hyphema. Methods. Blood samples were taken from the same patient with sickle cell disease. Thirty-two rabbits were divided into 4 groups. In group 1 (n = 8), there was no injection. Only blood injection constituted group 2 (n = 8), both blood and air bubble injection constituted group 3 (n = 8), and both blood and oxygen bubble injection constituted group 4 (n = 8). Results. The PaO2 in the aqueous humour after 10 hours from the injections was 78.45 ± 9.9 mmHg (Mean ± SD) for group 1, 73.97 ± 8.86 mmHg for group 2, 123.35 ± 13.6 mmHg for group 3, and 306.47 ± 16.5 mmHg for group 4. There was statistically significant difference between group 1 and group 2, when compared with group 3 and group 4. Conclusions. PaO2 in aqueous humour was increased after injecting air or oxygen bubble into the anterior chamber. We offer to leave an air bubble in the anterior chamber of patients with sickle cell hemoglobinopathies and hyphema undergoing an anterior chamber washout. PMID:24808955

  5. The injection of air/oxygen bubble into the anterior chamber of rabbits as a treatment for hyphema in patients with sickle cell disease.

    PubMed

    Ayintap, Emre; Keskin, Uğurcan; Sadigov, Fariz; Coskun, Mesut; Ilhan, Nilufer; Motor, Sedat; Semiz, Hilal; Parlakfikirer, Nihan

    2014-01-01

    Purpose. To investigate the changes of partial oxygen pressure (PaO2) in aqueous humour after injecting air or oxygen bubble into the anterior chamber in sickle cell hyphema. Methods. Blood samples were taken from the same patient with sickle cell disease. Thirty-two rabbits were divided into 4 groups. In group 1 (n = 8), there was no injection. Only blood injection constituted group 2 (n = 8), both blood and air bubble injection constituted group 3 (n = 8), and both blood and oxygen bubble injection constituted group 4 (n = 8). Results. The PaO2 in the aqueous humour after 10 hours from the injections was 78.45 ± 9.9 mmHg (Mean ± SD) for group 1, 73.97 ± 8.86 mmHg for group 2, 123.35 ± 13.6 mmHg for group 3, and 306.47 ± 16.5 mmHg for group 4. There was statistically significant difference between group 1 and group 2, when compared with group 3 and group 4. Conclusions. PaO2 in aqueous humour was increased after injecting air or oxygen bubble into the anterior chamber. We offer to leave an air bubble in the anterior chamber of patients with sickle cell hemoglobinopathies and hyphema undergoing an anterior chamber washout.

  6. Direct AFM force measurements between air bubbles in aqueous polydisperse sodium poly(styrene sulfonate) solutions: effect of collision speed, polyelectrolyte concentration and molar mass.

    PubMed

    Browne, Christine; Tabor, Rico F; Grieser, Franz; Dagastine, Raymond R

    2015-07-01

    Interactions between colliding air bubbles in aqueous solutions of polydisperse sodium poly(styrene sulfonate) (NaPSS) using direct force measurements were studied. The forces measured with deformable interfaces were shown to be more sensitive to the presence of the polyelectrolytes when compared to similar measurements using rigid interfaces. The experimental factors that were examined were NaPSS concentration, bubble collision velocity and polyelectrolyte molar mass. These measurements were then compared with an analytical model based on polyelectrolyte scaling theory in order to explain the effects of concentration and bubble deformation on the interaction between bubbles. Typically structural forces from the presence of monodisperse polyelectrolyte between interacting surfaces may be expected, however, it was found that the polydispersity in molar mass resulted in the structural forces to be smoothed and only a depletion interaction was able to be measured between interacting bubbles. It was found that an increase in number density of NaPSS molecules resulted in an increase in the magnitude of the depletion interaction. Conversely this interaction was overwhelmed by an increase in the fluid flow in the system at higher bubble collision velocities. Polymer molar mass dispersity plays a significant role in the interactions present between the bubbles and has implications that also affect the polyelectrolyte overlap concentration of the solution. Further understanding of these implications can be expected to play a role in the improvement in operations in such fields as water treatment and mineral processing where polyelectrolytes are used extensively.

  7. Design and Construction of Experiment for Direct Electron Irradiation of Uranyl Sulfate Solution: Bubble Formation and Thermal Hydraulics Studies

    SciTech Connect

    Chemerisov, Sergey; Gromov, Roman; Makarashvili, Vakho; Heltemes, Thad; Sun, Zaijing; Wardle, Kent E.; Bailey, James; Quigley, Kevin; Stepinski, Dominique; Vandegrift, George

    2014-10-01

    Argonne is assisting SHINE Medical Technologies in developing SHINE, a system for producing fission-product 99Mo using a D/T-accelerator to produce fission in a non-critical target solution of aqueous uranyl sulfate. We have developed an experimental setup for studying thermal-hydraulics and bubble formation in the uranyl sulfate solution to simulate conditions expected in the SHINE target solution during irradiation. A direct electron beam from the linac accelerator will be used to irradiate a 20 L solution (sector of the solution vessel). Because the solution will undergo radiolytic decomposition, we will be able to study bubble formation and dynamics and effects of convection and temperature on bubble behavior. These experiments will serve as a verification/ validation tool for the thermal-hydraulic model. Utilization of the direct electron beam for irradiation allows homogeneous heating of a large solution volume and simplifies observation of the bubble dynamics simultaneously with thermal-hydraulic data collection, which will complement data collected during operation of the miniSHINE experiment. Irradiation will be conducted using a 30-40 MeV electron beam from the high-power linac accelerator. The total electron-beam power will be 20 kW, which will yield a power density on the order of 1 kW/L. The solution volume will be cooled on the front and back surfaces and central tube to mimic the geometry of the proposed SHINE solution vessel. Also, multiple thermocouples will be inserted into the solution vessel to map thermal profiles. The experimental design is now complete, and installation and testing are in progress.

  8. Exercise-induced myofibrillar disruption with sarcolemmal integrity prior to simulated diving has no effect on vascular bubble formation in rats.

    PubMed

    Jørgensen, Arve; Foster, Philip P; Eftedal, Ingrid; Wisløff, Ulrik; Paulsen, Gøran; Havnes, Marianne B; Brubakk, Alf O

    2013-05-01

    Decompression sickness is initiated by gas bubbles formed during decompression, and it has been generally accepted that exercise before decompression causes increased bubble formation. There are indications that exercise-induced muscle injury seems to be involved. Trauma-induced skeletal muscle injury and vigorous exercise that could theoretically injure muscle tissues before decompression have each been shown to result in profuse bubble formation. Based on these findings, we hypothesized that exercise-induced skeletal muscle injury prior to decompression from diving would cause increase of vascular bubbles and lower survival rates after decompression. In this study, we examined muscle injury caused by eccentric exercise in rats prior to simulated diving and we observed the resulting bubble formation. Female Sprague-Dawley rats (n = 42) ran downhill (-16º) for 100 min on a treadmill followed by 90 min rest before a 50-min simulated saturation dive (709 kPa) in a pressure chamber. Muscle injury was evaluated by immunohistochemistry and qPCR, and vascular bubbles after diving were detected by ultrasonic imaging. The exercise protocol resulted in increased mRNA expression of markers of muscle injury; αB-crystallin, NF-κB, and TNF-α, and myofibrillar disruption with preserved sarcolemmal integrity. Despite evident myofibrillar disruption after eccentric exercise, no differences in bubble amounts or survival rates were observed in the exercised animals as compared to non-exercised animals after diving, a novel finding that may be applicable to humans.

  9. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  10. Assessment of secondary bubble formation on a backward-facing step geometry

    NASA Astrophysics Data System (ADS)

    Juste, G. L.; Fajardo, P.; Guijarro, A.

    2016-07-01

    Flow visualization experiments and numerical simulations were performed on a narrow three-dimensional backward-facing step (BFS) flow with the main objective of characterizing the secondary bubble appearing at the top wall. The BFS has been widely studied because of its geometrical simplicity as well as its ability to reproduce most of the flow features appearing in many applications in which separation occurs. A BFS test rig with an expansion ratio of 2 and two aspect ratios (AR = 4 and AR = 8) was developed. Tests were performed at range of Reynolds numbers ranging from 50 to 1000; visualization experiments provided a qualitative description of secondary bubble and wall-jet flows. Large eddy simulations were carried out with two different codes for validation. Numerical solutions, once validated with experimental data from the literature, were used to acquire a deeper understanding of the experimental visualizations, to characterize the secondary bubble as a function of the flow variables (Reynolds and AR) and to analyze the effect of the secondary bubble on primary reattachment length. Finally, to decouple the sidewall effects due to the non-slip condition and the intrinsic flow three-dimensionality, numerical experiments with free-slip conditions over the sidewalls were computed. The main differences were as follows: When the non-slip condition is used, the secondary bubble appears at a Reynolds number of approximately 200, increases with the Reynolds number, and is limited to a small part of the span. This recirculation zone interacts with the wall-jets and causes the maximum and minimum lengths in the reattachment line of the primary recirculation. Under free slip conditions, the recirculation bubble appears at a higher Reynolds number and covers the entire channel span.

  11. Time-resolved imaging of electrical discharge development in underwater bubbles

    NASA Astrophysics Data System (ADS)

    Tu, Yalong; Xia, Hualei; Yang, Yong; Lu, Xinpei

    2016-01-01

    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 ground 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.

  12. In Search of the Big Bubble

    ERIC Educational Resources Information Center

    Simoson, Andrew; Wentzky, Bethany

    2011-01-01

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

  13. The Interstellar Bubbles of G38.9-0.4 and the Impact of Stellar Feedback on Star Formation

    NASA Astrophysics Data System (ADS)

    Alexander, Michael J.; Kobulnicky, Henry A.; Kerton, Charles R.; Arvidsson, Kim

    2013-06-01

    We present a study of the star formation (SF) region G38.9-0.4 using publicly available multiwavelength Galactic plane surveys from ground- and space-based observatories. This region is composed of four bright mid-IR bubbles and numerous infrared dark clouds. Two bubbles, N 74 and N 75, each host a star cluster anchored by a single O9.5V star. We identified 162 young stellar objects (YSOs) and classify 54 as stage I, 7 as stage II, 6 as stage III, and 32 as ambiguous. We do not detect the classical signposts of triggered SF, i.e., star-forming pillars or YSOs embedded within bubble rims. We conclude that feedback-triggered SF has not occurred in G38.9-0.4. The YSOs are preferentially coincident with infrared dark clouds. This leads to a strong correlation between areal YSO mass surface density and gas mass surface density with a power law slope near 1.3, which closely matches the Schmidt-Kennicutt Law. The correlation is similar inside and outside the bubbles and may mean that the SF efficiency is neither enhanced nor suppressed in regions potentially influenced by stellar feedback. This suggests that gas density, regardless of how it is collected, is a more important driver of SF than stellar feedback. Larger studies should be able to quantify the fraction of all SF that is feedback-triggered by determining the fraction SF, feedback-compressed gas surrounding H II regions relative to that already present in molecular clouds.

  14. THE INTERSTELLAR BUBBLES OF G38.9-0.4 AND THE IMPACT OF STELLAR FEEDBACK ON STAR FORMATION

    SciTech Connect

    Alexander, Michael J.; Kobulnicky, Henry A.; Kerton, Charles R.; Arvidsson, Kim E-mail: chipk@uwyo.edu E-mail: karvidsson@adlerplanetarium.org

    2013-06-10

    We present a study of the star formation (SF) region G38.9-0.4 using publicly available multiwavelength Galactic plane surveys from ground- and space-based observatories. This region is composed of four bright mid-IR bubbles and numerous infrared dark clouds. Two bubbles, N 74 and N 75, each host a star cluster anchored by a single O9.5V star. We identified 162 young stellar objects (YSOs) and classify 54 as stage I, 7 as stage II, 6 as stage III, and 32 as ambiguous. We do not detect the classical signposts of triggered SF, i.e., star-forming pillars or YSOs embedded within bubble rims. We conclude that feedback-triggered SF has not occurred in G38.9-0.4. The YSOs are preferentially coincident with infrared dark clouds. This leads to a strong correlation between areal YSO mass surface density and gas mass surface density with a power law slope near 1.3, which closely matches the Schmidt-Kennicutt Law. The correlation is similar inside and outside the bubbles and may mean that the SF efficiency is neither enhanced nor suppressed in regions potentially influenced by stellar feedback. This suggests that gas density, regardless of how it is collected, is a more important driver of SF than stellar feedback. Larger studies should be able to quantify the fraction of all SF that is feedback-triggered by determining the fraction SF, feedback-compressed gas surrounding H II regions relative to that already present in molecular clouds.

  15. Periodical bubble formation and the oscillatory change in dissolved oxygen concentration in a catalase-hydrogen peroxide system.

    PubMed

    Sasaki, Satoshi

    2006-06-01

    The relationship between the periodical bubble forming and the oscillatory change in the dissolved oxygen (DO) concentration in a catalase-hydrogen peroxide system was studied. Photographs of the bubbles and the responses from the DO electrode indicated that large bubbles were generated periodically, and that the DO profile depended on the geometrical relationship between the electrode and the bubbles. PMID:16772694

  16. Carbon dioxide induced bubble formation in a CH4-CO2-H2O ternary system: a molecular dynamics simulation study.

    PubMed

    Sujith, K S; Ramachandran, C N

    2016-02-01

    The extraction of methane from its hydrates using carbon dioxide involves the decomposition of the hydrate resulting in a CH4-CO2-H2O ternary solution. Using classical molecular dynamics simulations, we investigate the evolution of dissolved gas molecules in the ternary system at different concentrations of CO2. Various compositions considered in the present study resemble the solution formed during the decomposition of methane hydrates at the initial stages of the extraction process. We find that the presence of CO2 aids the formation of CH4 bubbles by causing its early nucleation. Elucidation of the composition of the bubble revealed that in ternary solutions with high concentration of CO2, mixed gas bubbles composed of CO2 and CH4 are formed. To understand the role of CO2 in the nucleation of CH4 bubbles, the structure of the bubble formed was analyzed, which revealed that there is an accumulation of CO2 at the interface of the bubble and the surrounding water. The aggregation of CO2 at the bubble-water interface occurs predominantly when the concentration of CO2 is high. Radial distribution function for the CH4-CO2 pair indicates that there is an increasingly favorable direct contact between dissolved CH4 and CO2 molecules in the bubble-water interface. It is also observed that the presence of CO2 at the interface results in the decrease in surface tension. Thus, CO2 leads to greater stability of the bubble-water interface thereby bringing down the critical size of the bubble nuclei. The results suggest that a rise in concentration of CO2 helps in the removal of dissolved CH4 thereby preventing the accumulation of methane in the liquid phase. Thus, the presence of CO2 is predicted to assist the decomposition of methane hydrates in the initial stages of the replacement process.

  17. Carbon dioxide induced bubble formation in a CH4-CO2-H2O ternary system: a molecular dynamics simulation study.

    PubMed

    Sujith, K S; Ramachandran, C N

    2016-02-01

    The extraction of methane from its hydrates using carbon dioxide involves the decomposition of the hydrate resulting in a CH4-CO2-H2O ternary solution. Using classical molecular dynamics simulations, we investigate the evolution of dissolved gas molecules in the ternary system at different concentrations of CO2. Various compositions considered in the present study resemble the solution formed during the decomposition of methane hydrates at the initial stages of the extraction process. We find that the presence of CO2 aids the formation of CH4 bubbles by causing its early nucleation. Elucidation of the composition of the bubble revealed that in ternary solutions with high concentration of CO2, mixed gas bubbles composed of CO2 and CH4 are formed. To understand the role of CO2 in the nucleation of CH4 bubbles, the structure of the bubble formed was analyzed, which revealed that there is an accumulation of CO2 at the interface of the bubble and the surrounding water. The aggregation of CO2 at the bubble-water interface occurs predominantly when the concentration of CO2 is high. Radial distribution function for the CH4-CO2 pair indicates that there is an increasingly favorable direct contact between dissolved CH4 and CO2 molecules in the bubble-water interface. It is also observed that the presence of CO2 at the interface results in the decrease in surface tension. Thus, CO2 leads to greater stability of the bubble-water interface thereby bringing down the critical size of the bubble nuclei. The results suggest that a rise in concentration of CO2 helps in the removal of dissolved CH4 thereby preventing the accumulation of methane in the liquid phase. Thus, the presence of CO2 is predicted to assist the decomposition of methane hydrates in the initial stages of the replacement process. PMID:26762545

  18. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

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

  19. Structure of Air-Water Bubbly Flow in a Vertical Annulus

    SciTech Connect

    Rong Situ; Takashi Hibiki; Ye Mi; Mamoru Ishii; Michitsugu Mori

    2002-07-01

    Local measurements of flow parameters were performed for vertical upward bubbly flows in an annulus. The annulus channel consisted of an inner rod with a diameter of 19.1 mm and an outer round tube with an inner diameter of 38.1 mm, and the hydraulic equivalent diameter was 19.1 mm. Double-sensor conductivity probe was used for measuring void fraction, interfacial area concentration, and interfacial velocity, and Laser Doppler anemometer was utilized for measuring liquid velocity and turbulence intensity. The mechanisms to form the radial profiles of local flow parameters were discussed in detail. The constitutive equations for distribution parameter and drift velocity in the drift-flux model, and the semi-theoretical correlation for Sauter mean diameter namely interfacial area concentration, which were proposed previously, were validated by local flow parameters obtained in the experiment using the annulus. (authors)

  20. Tribonucleation of bubbles.

    PubMed

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

    2014-07-15

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

  1. Extreme conditions in a dissolving air nanobubble.

    PubMed

    Yasui, Kyuichi; Tuziuti, Toru; Kanematsu, Wataru

    2016-07-01

    Numerical simulations of the dissolution of an air nanobubble in water have been performed taking into account the effect of bubble dynamics (inertia of the surrounding liquid). The presence of stable bulk nanobubbles is not assumed in the present study because the bubble radius inevitably passes the nanoscale in the complete dissolution of a bubble. The bubble surface is assumed to be clean because attachment of hydrophobic materials on the bubble surface could considerably change the gas diffusion rate. The speed of the bubble collapse (the bubble wall speed) increases to about 90 m/s or less. The shape of a bubble is kept nearly spherical because the amplitude of the nonspherical component of the bubble shape is negligible compared to the instantaneous bubble radius. In other words, a bubble never disintegrates into daughter bubbles during the dissolution. At the final moment of the dissolution, the temperature inside a bubble increases to about 3000 K due to the quasiadiabatic compression. The bubble temperature is higher than 1000 K only for the final 19 ps. However, the Knudsen number is more than 0.2 for this moment, and the error associated with the continuum model should be considerable. In the final 2.3 ns, only nitrogen molecules are present inside a bubble as the solubility of nitrogen is the lowest among the gas species. The radical formation inside a bubble is negligible because the probability of nitrogen dissociation is only on the order of 10^{-15}. The pressure inside a bubble, as well as the liquid pressure at the bubble wall, increases to about 5 GPa at the final moment of dissolution. The pressure is higher than 1 GPa for the final 0.7 ns inside a bubble and for the final 0.6 ns in the liquid at the bubble wall. The liquid temperature at the bubble wall increases to about 360 K from 293 K at the final stage of the complete dissolution. PMID:27575216

  2. Extreme conditions in a dissolving air nanobubble

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi; Tuziuti, Toru; Kanematsu, Wataru

    2016-07-01

    Numerical simulations of the dissolution of an air nanobubble in water have been performed taking into account the effect of bubble dynamics (inertia of the surrounding liquid). The presence of stable bulk nanobubbles is not assumed in the present study because the bubble radius inevitably passes the nanoscale in the complete dissolution of a bubble. The bubble surface is assumed to be clean because attachment of hydrophobic materials on the bubble surface could considerably change the gas diffusion rate. The speed of the bubble collapse (the bubble wall speed) increases to about 90 m/s or less. The shape of a bubble is kept nearly spherical because the amplitude of the nonspherical component of the bubble shape is negligible compared to the instantaneous bubble radius. In other words, a bubble never disintegrates into daughter bubbles during the dissolution. At the final moment of the dissolution, the temperature inside a bubble increases to about 3000 K due to the quasiadiabatic compression. The bubble temperature is higher than 1000 K only for the final 19 ps. However, the Knudsen number is more than 0.2 for this moment, and the error associated with the continuum model should be considerable. In the final 2.3 ns, only nitrogen molecules are present inside a bubble as the solubility of nitrogen is the lowest among the gas species. The radical formation inside a bubble is negligible because the probability of nitrogen dissociation is only on the order of 10-15. The pressure inside a bubble, as well as the liquid pressure at the bubble wall, increases to about 5 GPa at the final moment of dissolution. The pressure is higher than 1 GPa for the final 0.7 ns inside a bubble and for the final 0.6 ns in the liquid at the bubble wall. The liquid temperature at the bubble wall increases to about 360 K from 293 K at the final stage of the complete dissolution.

  3. Extreme conditions in a dissolving air nanobubble.

    PubMed

    Yasui, Kyuichi; Tuziuti, Toru; Kanematsu, Wataru

    2016-07-01

    Numerical simulations of the dissolution of an air nanobubble in water have been performed taking into account the effect of bubble dynamics (inertia of the surrounding liquid). The presence of stable bulk nanobubbles is not assumed in the present study because the bubble radius inevitably passes the nanoscale in the complete dissolution of a bubble. The bubble surface is assumed to be clean because attachment of hydrophobic materials on the bubble surface could considerably change the gas diffusion rate. The speed of the bubble collapse (the bubble wall speed) increases to about 90 m/s or less. The shape of a bubble is kept nearly spherical because the amplitude of the nonspherical component of the bubble shape is negligible compared to the instantaneous bubble radius. In other words, a bubble never disintegrates into daughter bubbles during the dissolution. At the final moment of the dissolution, the temperature inside a bubble increases to about 3000 K due to the quasiadiabatic compression. The bubble temperature is higher than 1000 K only for the final 19 ps. However, the Knudsen number is more than 0.2 for this moment, and the error associated with the continuum model should be considerable. In the final 2.3 ns, only nitrogen molecules are present inside a bubble as the solubility of nitrogen is the lowest among the gas species. The radical formation inside a bubble is negligible because the probability of nitrogen dissociation is only on the order of 10^{-15}. The pressure inside a bubble, as well as the liquid pressure at the bubble wall, increases to about 5 GPa at the final moment of dissolution. The pressure is higher than 1 GPa for the final 0.7 ns inside a bubble and for the final 0.6 ns in the liquid at the bubble wall. The liquid temperature at the bubble wall increases to about 360 K from 293 K at the final stage of the complete dissolution.

  4. Variations of bubble cavitation and temperature elevation during lesion formation by high-intensity focused ultrasound.

    PubMed

    Zhou, Yufeng; Gao, Xiaobin Wilson

    2013-08-01

    High-intensity focused ultrasound (HIFU) is emerging as an effective therapeutic modality in both thermal ablations for solid tumor/cancer and soft-tissue fragmentation. Mechanical and thermal effects, which play an important role in the HIFU treatment simultaneously, are dependent on the operating parameters and may vary with the progress of therapy. Mechanical erosion in the shape of a "squid," a "dumbbell" lesion with both mechanical and thermal lesions, or a "tadpole" lesion with mechanical erosion at the center and thermal necrosis on the boundary in the transparent gel phantom could be produced correspondingly with the pulse duration of 5-30 ms, which is much longer than histotripsy burst but shorter than the time for tissue boiling, and pulse repetition frequency (PRF) of 0.2-5 Hz. Meanwhile, variations of bubble cavitation (both inertial and stable cavitation) and temperature elevation in the focal region (i.e., z = -2.5, 0, and 2.5 mm) were measured by passive cavitation detection (PCD) and thermocouples during the therapeutic procedure, respectively. Stable cavitation increased with the pulse duration, PRF, and the number of pulses delivered. However, inertial cavitation was found to increase initially and then decrease with long pulse duration and high PRF. Temperature in the pre-focal region is always higher than those at the focal and post-focal position in all tests. Great variations of PCD signals and temperature elevation are due to the generation and persistence of large bubble, which is resistant to collapse and occurs with the increase of pulse duration and PRF. Similar lesion pattern and variations were also observed in ex vivo porcine kidneys. Hyperechoes in the B-mode ultrasound image were comparable to the shape and size of lesions in the dissected tissue. Thermal lesion volume increased with the increase of pulse duration and PRF, but mechanical erosion reached its maximum volume with the pulse duration of 20 ms and PRF of 1

  5. Role of air in granular jet formation.

    PubMed

    Caballero, Gabriel; Bergmann, Raymond; van der Meer, Devaraj; Prosperetti, Andrea; Lohse, Detlef

    2007-07-01

    A steel ball impacting on a bed of very loose, fine sand results in a surprisingly vigorous jet which shoots up from the surface of the sand [D. Lohse, Phys. Rev. Lett. 93, 198003 (2004)10.1103/PhysRevLett.93.198003]. When the ambient pressure p is reduced, the jet is found to be less vigorous [R. Royer, Nature Phys. 1, 164 (2005)10.1038/nphys175]. In this Letter we show that p also affects the rate of penetration of the ball: Higher pressure increases the rate of penetration, which makes the cavity created by the ball close deeper into the sand bed, where the hydrostatic pressure is stronger, thereby producing a more energetic collapse and jetting. The origin of the deeper penetration under normal ambient pressure is found to lie in the extra sand fluidization caused by the air flow induced by the falling ball.

  6. Role of Air in Granular Jet Formation

    NASA Astrophysics Data System (ADS)

    Caballero, Gabriel; Bergmann, Raymond; van der Meer, Devaraj; Prosperetti, Andrea; Lohse, Detlef

    2007-07-01

    A steel ball impacting on a bed of very loose, fine sand results in a surprisingly vigorous jet which shoots up from the surface of the sand [D. Lohse , Phys. Rev. Lett. 93, 198003 (2004)PRLTAO0031-900710.1103/PhysRevLett.93.198003]. When the ambient pressure p is reduced, the jet is found to be less vigorous [R. Royer , Nature Phys. 1, 164 (2005)1745-248110.1038/nphys175]. In this Letter we show that p also affects the rate of penetration of the ball: Higher pressure increases the rate of penetration, which makes the cavity created by the ball close deeper into the sand bed, where the hydrostatic pressure is stronger, thereby producing a more energetic collapse and jetting. The origin of the deeper penetration under normal ambient pressure is found to lie in the extra sand fluidization caused by the air flow induced by the falling ball.

  7. Technique for air bubble management during endothelial keratoplasty in eyes after penetrating glaucoma surgery.

    PubMed

    Banitt, Michael; Arrieta-Quintero, Esdras; Parel, Jean-Marie; Fantes, Francisco

    2011-02-01

    Our purpose was to develop a technique for maintaining air within the anterior chamber during endothelial keratoplasty in eyes that have previously undergone trabeculectomy or a glaucoma drainage implant. Whole human globes and rabbits underwent penetrating glaucoma surgery to develop the technique. Without the aid of any additional device or manipulation, continuing to inject air into the anterior chamber as it escapes through the sclerostomy or tube eventually fills the subconjunctival space and allows for back pressure. This allows for a full anterior chamber air fill and brief elevation of intraocular pressure. We employed this overfilling technique on 3 patients with previous incisional glaucoma surgery to perform successful Descemet stripping endothelial keratoplasty without complication. We recommend using the overfilling technique when performing Descemet stripping endothelial keratoplasty surgery in eyes with previous penetrating glaucoma surgery because it is a simple technique without the need for pre- or postoperative manipulation.

  8. Bubble stimulation efficiency of dinoflagellate bioluminescence.

    PubMed

    Deane, Grant B; Stokes, M Dale; Latz, Michael I

    2016-02-01

    Dinoflagellate bioluminescence, a common source of bioluminescence in coastal waters, is stimulated by flow agitation. Although bubbles are anecdotally known to be stimulatory, the process has never been experimentally investigated. This study quantified the flash response of the bioluminescent dinoflagellate Lingulodinium polyedrum to stimulation by bubbles rising through still seawater. Cells were stimulated by isolated bubbles of 0.3-3 mm radii rising at their terminal velocity, and also by bubble clouds containing bubbles of 0.06-10 mm radii for different air flow rates. Stimulation efficiency, the proportion of cells producing a flash within the volume of water swept out by a rising bubble, decreased with decreasing bubble radius for radii less than approximately 1 mm. Bubbles smaller than a critical radius in the range 0.275-0.325 mm did not stimulate a flash response. The fraction of cells stimulated by bubble clouds was proportional to the volume of air in the bubble cloud, with lower stimulation levels observed for clouds with smaller bubbles. An empirical model for bubble cloud stimulation based on the isolated bubble observations successfully reproduced the observed stimulation by bubble clouds for low air flow rates. High air flow rates stimulated more light emission than expected, presumably because of additional fluid shear stress associated with collective buoyancy effects generated by the high air fraction bubble cloud. These results are relevant to bioluminescence stimulation by bubbles in two-phase flows, such as in ship wakes, breaking waves, and sparged bioreactors.

  9. Influence of ultrasound power on acoustic streaming and micro-bubbles formations in a low frequency sono-reactor: mathematical and 3D computational simulation.

    PubMed

    Sajjadi, Baharak; Raman, Abdul Aziz Abdul; Ibrahim, Shaliza

    2015-05-01

    This paper aims at investigating the influence of ultrasound power amplitude on liquid behaviour in a low-frequency (24 kHz) sono-reactor. Three types of analysis were employed: (i) mechanical analysis of micro-bubbles formation and their activities/characteristics using mathematical modelling. (ii) Numerical analysis of acoustic streaming, fluid flow pattern, volume fraction of micro-bubbles and turbulence using 3D CFD simulation. (iii) Practical analysis of fluid flow pattern and acoustic streaming under ultrasound irradiation using Particle Image Velocimetry (PIV). In mathematical modelling, a lone micro bubble generated under power ultrasound irradiation was mechanistically analysed. Its characteristics were illustrated as a function of bubble radius, internal temperature and pressure (hot spot conditions) and oscillation (pulsation) velocity. The results showed that ultrasound power significantly affected the conditions of hotspots and bubbles oscillation velocity. From the CFD results, it was observed that the total volume of the micro-bubbles increased by about 4.95% with each 100 W-increase in power amplitude. Furthermore, velocity of acoustic streaming increased from 29 to 119 cm/s as power increased, which was in good agreement with the PIV analysis.

  10. Communicating air quality information: experimental evaluation of alternative formats.

    PubMed

    Johnson, Branden B

    2003-02-01

    A long-running effort in environmental communication is daily publication of a report on local air pollution in many American newspapers based on the Pollutant Standards Index (PSI). A 1998 proposal by the U.S. Environmental Protection Agency (U.S. EPA) to change the PSI prompted a survey experiment with 1,100 adults in Philadelphia, evaluating the proposed change's ability to better inform the populace. The effects of exposure to the old and new versions of the PSI, as well as health cautions and information about groups sensitive to air pollution, were compared with evaluation criteria suggested by Weinstein and Sandman (1993). Sample respondents had strong baseline concerns about air pollution. Descriptors of air quality (e.g., "good; " "unhealthy") were difficult to discriminate, particularly in the New format. Concern rose as hypothetical air pollution levels rose, but the New format (as well as PSI versions without health cautions or sensitive-group information) evoked a sharp discontinuity in concern between below- and above-standard pollution levels. Both Old and New formats reduced concern relative to no provision of PSI information at all, but the New format reduced concern significantly more than the Old version. No PSI format did particularly well at increasing knowledge of air pollution or decreasing intentions to be active outdoors during high pollution, contrary to the agency's aim. Although U.S. EPA has since adopted the new proposal as a national "Air Quality Index" requirement, the experiment's results illuminate the strengths and limitations of the new PSI as a means of informing citizens and motivating them to protect themselves. PMID:12635725

  11. Measurement and modeling on hydrodynamic forces and deformation of an air bubble approaching a solid sphere in liquids.

    PubMed

    Shahalami, Mansoureh; Wang, Louxiang; Wu, Chu; Masliyah, Jacob H; Xu, Zhenghe; Chan, Derek Y C

    2015-03-01

    The interaction between bubbles and solid surfaces is central to a broad range of industrial and biological processes. Various experimental techniques have been developed to measure the interactions of bubbles approaching solids in a liquid. A main challenge is to accurately and reliably control the relative motion over a wide range of hydrodynamic conditions and at the same time to determine the interaction forces, bubble-solid separation and bubble deformation. Existing experimental methods are able to focus only on one of the aspects of this problem, mostly for bubbles and particles with characteristic dimensions either below 100 μm or above 1 cm. As a result, either the interfacial deformations are measured directly with the forces being inferred from a model, or the forces are measured directly with the deformations to be deduced from the theory. The recently developed integrated thin film drainage apparatus (ITFDA) filled the gap of intermediate bubble/particle size ranges that are commonly encountered in mineral and oil recovery applications. Equipped with side-view digital cameras along with a bimorph cantilever as force sensor and speaker diaphragm as the driver for bubble to approach a solid sphere, the ITFDA has the capacity to measure simultaneously and independently the forces and interfacial deformations as a bubble approaches a solid sphere in a liquid. Coupled with the thin liquid film drainage modeling, the ITFDA measurement allows the critical role of surface tension, fluid viscosity and bubble approach speed in determining bubble deformation (profile) and hydrodynamic forces to be elucidated. Here we compare the available methods of studying bubble-solid interactions and demonstrate unique features and advantages of the ITFDA for measuring both forces and bubble deformations in systems of Reynolds numbers as high as 10. The consistency and accuracy of such measurement are tested against the well established Stokes-Reynolds-Young-Laplace model

  12. Measurement and modeling on hydrodynamic forces and deformation of an air bubble approaching a solid sphere in liquids.

    PubMed

    Shahalami, Mansoureh; Wang, Louxiang; Wu, Chu; Masliyah, Jacob H; Xu, Zhenghe; Chan, Derek Y C

    2015-03-01

    The interaction between bubbles and solid surfaces is central to a broad range of industrial and biological processes. Various experimental techniques have been developed to measure the interactions of bubbles approaching solids in a liquid. A main challenge is to accurately and reliably control the relative motion over a wide range of hydrodynamic conditions and at the same time to determine the interaction forces, bubble-solid separation and bubble deformation. Existing experimental methods are able to focus only on one of the aspects of this problem, mostly for bubbles and particles with characteristic dimensions either below 100 μm or above 1 cm. As a result, either the interfacial deformations are measured directly with the forces being inferred from a model, or the forces are measured directly with the deformations to be deduced from the theory. The recently developed integrated thin film drainage apparatus (ITFDA) filled the gap of intermediate bubble/particle size ranges that are commonly encountered in mineral and oil recovery applications. Equipped with side-view digital cameras along with a bimorph cantilever as force sensor and speaker diaphragm as the driver for bubble to approach a solid sphere, the ITFDA has the capacity to measure simultaneously and independently the forces and interfacial deformations as a bubble approaches a solid sphere in a liquid. Coupled with the thin liquid film drainage modeling, the ITFDA measurement allows the critical role of surface tension, fluid viscosity and bubble approach speed in determining bubble deformation (profile) and hydrodynamic forces to be elucidated. Here we compare the available methods of studying bubble-solid interactions and demonstrate unique features and advantages of the ITFDA for measuring both forces and bubble deformations in systems of Reynolds numbers as high as 10. The consistency and accuracy of such measurement are tested against the well established Stokes-Reynolds-Young-Laplace model

  13. Air Plasma Formation in MHD Slipstream Accelerator for Mercury Lightcraft

    SciTech Connect

    Myrabo, L.N.; Raizer, Y.P.; Surzhikov, S.

    2004-03-30

    This paper investigates the physics of air plasma formation at the entrance of the MHD slipstream accelerator for the 'tractor-beam' Mercury Lightcraft. Two scenarios are analyzed. The first addresses the needs of the minimum power airspike assuming that all the power required for air plasma formation must come from the remote laser beam. The second case considers the constant-focus airspike and assumes that the breakdown criteria is satisfied by an on-board auxiliary source (e.g., electric discharge, RF source, microwave source, or E-beam)

  14. Air Plasma Formation in MHD Slipstream Accelerator for Mercury Lightcraft

    NASA Astrophysics Data System (ADS)

    Myrabo, L. N.; Raizer, Y. P.; Surzhikov, S.

    2004-03-01

    This paper investigates the physics of air plasma formation at the entrance of the MHD slipstream accelerator for the `tractor-beam' Mercury Lightcraft. Two scenarios are analyzed. The first addresses the needs of the minimum power airspike assuming that all the power required for air plasma formation must come from the remote laser beam. The second case considers the constant-focus airspike and assumes that the breakdown criteria is satisfied by an on-board auxiliary source (e.g., electric discharge, RF source, microwave source, or E-beam).

  15. Gases in Tektite Bubbles.

    PubMed

    O'keefe, J A; Lowman, P D; Dunning, K L

    1962-07-20

    Spectroscopic analysis of light produced by electrodeless discharge in a tektite bubble showed the main gases in the bubble to be neon, helium, and oxygen. The neon and helium have probably diffused in from the atmosphere, while the oxygen may be atmospheric gas incorporated in the tektite during its formation.

  16. Let Them Blow Bubbles.

    ERIC Educational Resources Information Center

    Korenic, Eileen

    1988-01-01

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

  17. Gases in Tektite Bubbles.

    PubMed

    O'keefe, J A; Lowman, P D; Dunning, K L

    1962-07-20

    Spectroscopic analysis of light produced by electrodeless discharge in a tektite bubble showed the main gases in the bubble to be neon, helium, and oxygen. The neon and helium have probably diffused in from the atmosphere, while the oxygen may be atmospheric gas incorporated in the tektite during its formation. PMID:17801113

  18. Formation, disruption and mechanical properties of a rigid hydrophobin film at an air-water interface

    NASA Astrophysics Data System (ADS)

    Walker, Lynn; Kirby, Stephanie; Anna, Shelley; CMU Team

    Hydrophobins are small, globular proteins with distinct hydrophilic and hydrophobic regions that make them extremely surface active. The behavior of hydrophobins at surfaces has raised interest in their potential industrial applications, including use in surface coatings, food foams and emulsions, and as dispersants. Practical use of hydrophobins requires an improved understanding of the interfacial behavior of these proteins, both individually and in the presence of surfactants. Cerato-ulmin (CU) is a hydrophobin that has been shown to strongly stabilize air bubbles and oil droplets through the formation of a persistent protein film at the interface. In this work, we characterize the adsorption behavior of CU at air/water interfaces by measuring the surface tension and interfacial rheology as a function of adsorption time. CU is found to strongly, irreversibly adsorb at air/water interfaces; the magnitude of the dilatational modulus increases with adsorption time and surface pressure, until the CU eventually forms a rigid film. The persistence of this film is tested through the addition of SDS, a strong surfactant, to the bulk. SDS is found to co-adsorb to interfaces pre-coated with a CU film. At high concentrations, the addition of SDS significantly decreases the dilatational modulus, indicating disruption and displacement of CU. These results lend insight into the complex interfacial interactions between hydrophobins and surfactants. Funding from GoMRI.

  19. Acoustic radiation force on an air bubble and soft fluid spheres in ideal liquids: Example of a high-order Bessel beam of quasi-standing waves

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2009-04-01

    The partial wave series for the scattering of a high-order Bessel beam (HOBB) of acoustic quasi-standing waves by an air bubble and fluid spheres immersed in water and centered on the axis of the beam is applied to the calculation of the acoustic radiation force. A HOBB refers to a type of beam having an axial amplitude null and an azimuthal phase gradient. Radiation force examples obtained through numerical evaluation of the radiation force function are computed for an air bubble, a hexane, a red blood and mercury fluid spheres in water. The examples were selected to illustrate conditions having progressive, standing and quasi-standing waves with appropriate selection of the waves’ amplitude ratio. An especially noteworthy result is the lack of a specific vibrational mode contribution to the radiation force determined by appropriate selection of the HOBB parameters.

  20. Sensitivity of Hollow Fiber Spacesuit Water Membrane Evaporator Systems to Potable Water Constituents, Contaminants and Air Bubbles

    NASA Technical Reports Server (NTRS)

    Bue, Grant C.; Trevino, Luis A.; Fritts, Sharon; Tsioulos, Gus

    2008-01-01

    The Spacesuit Water Membrane Evaporator (SWME) is the baseline heat rejection technology selected for development for the Constellation lunar suit. The first SWME prototype, designed, built, and tested at Johnson Space Center in 1999 used a Teflon hydrophobic porous membrane sheet shaped into an annulus to provide cooling to the coolant loop through water evaporation to the vacuum of space. This present study describes the test methodology and planning and compares the test performance of three commercially available hollow fiber materials as alternatives to the sheet membrane prototype for SWME, in particular, a porous hydrophobic polypropylene, and two variants that employ ion exchange through non-porous hydrophilic modified Nafion. Contamination tests will be performed to probe for sensitivities of the candidate SWME elements to ordinary constituents that are expected to be found in the potable water provided by the vehicle, the target feedwater source. Some of the impurities in potable water are volatile, such as the organics, while others, such as the metals and inorganic ions are nonvolatile. The non-volatile constituents will concentrate in the SWME as evaporated water from the loop is replaced by the feedwater. At some point in the SWME mission lifecycle as the concentrations of the non-volatiles increase, the solubility limits of one or more of the constituents may be reached. The resulting presence of precipitate in the coolant water may begin to plug pores and tube channels and affect the SWME performance. Sensitivity to macroparticles, lunar dust simulant, and air bubbles will also be investigated.

  1. Characterization of acoustic droplet vaporization for control of bubble generation under flow conditions.

    PubMed

    Kang, Shih-Tsung; Huang, Yi-Luan; Yeh, Chih-Kuang

    2014-03-01

    This study investigated the manipulation of bubbles generated by acoustic droplet vaporization (ADV) under clinically relevant flow conditions. Optical microscopy and high-frequency ultrasound imaging were used to observe bubbles generated by 2-MHz ultrasound pulses at different time points after the onset of ADV. The dependence of the bubble population on droplet concentration, flow velocity, fluid viscosity and acoustic parameters, including acoustic pressure, pulse duration and pulse repetition frequency, was investigated. The results indicated that post-ADV bubble growth spontaneously driven by air permeation markedly affected the bubble population after insonation. The bubbles can grow to a stable equilibrium diameter as great as twice the original diameter in 0.5-1 s, as predicted by the theoretical calculation. The growth trend is independent of flow velocity, but dependent on fluid viscosity and droplet concentration, which directly influence the rate of gas uptake by bubbles and the rate of gas exchange across the wall of the semipermeable tube containing the bubbles and, hence, the gas content of the host medium. Varying the acoustic pressure does not markedly change the formation of bubbles as long as the ADV thresholds of most droplets are reached. Varying pulse duration and pulse repetition frequency markedly reduces the number of bubbles. Lengthening pulse duration favors the production of large bubbles, but reduces the total number of bubbles. Increasing the PRF interestingly provides superior performance in bubble disruption. These results also suggest that an ADV bubble population cannot be assessed simply on the basis of initial droplet size or enhancement of imaging contrast by the bubbles. Determining the optimal acoustic parameters requires careful consideration of their impact on the bubble population produced for different application scenarios.

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

    PubMed

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

    2015-02-01

    An experimental study of air gasification of rice husk was conducted in a bench-scale fluidized bed gasifier (FBG) having 210 mm diameter and 1600 mm height. Heating of sand bed material was performed using conventional charcoal fuel. Different operating conditions like bed temperature, feeding rate and equivalence ratio (ER) varied in the range of 750-850 °C, 25-31.3 kg/h, and 0.3-0.38, respectively. Flow rate of air was kept constant (37 m(3)/h) during FBG experiments. The carbon conversion efficiencies (CCE), cold gas efficiency, and thermal efficiency were evaluated, where maximum CCE was found as 91%. By increasing ER, the carbon conversion efficiency was decreased. Drastic reduction in electric consumption for initial heating of gasifier bed with charcoal compared to ceramic heater was ∼45%. Hence rice husk is found as a potential candidate to use directly (without any processing) in FBG as an alternative renewable energy source from agricultural field. PMID:25446789

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

    PubMed

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

    2015-02-01

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

  4. Airborne & SAR Synergy Reveals the 3D Structure of Air Bubble Entrainment in Internal Waves and Frontal Zones

    NASA Astrophysics Data System (ADS)

    da Silva, J. C. B.; Magalhaes, J. M.; Batista, M.; Gostiaux, L.; Gerkema, T.; New, A. L.

    2013-03-01

    Internal waves are now recognised as an important mixing mechanism in the ocean. Mixing at the base of the mixed layer and in the seasonal thermocline affects the properties of those water masses which define the exchange of heat and freshwater between the atmosphere and ocean. The breaking of Internal Solitary Waves (ISWs) contributes significantly to turbulent mixing in the near-surface layers, through the continual triggering of instabilities as they propagate and shoal towards the coast or shallow topography. Here we report some results of the EU funded project A.NEW (Airborne observations of Nonlinear Evolution of internal Waves generated by internal tidal beams). The airborne capabilities to observe small scale structure of breaking internal waves in the near-shore zone has been demonstrated in recent studies (e.g. Marmorino et al., 2008). In particular, sea surface thermal signatures of shoaling ISWs have revealed the turbulent character of these structures in the form of surface “boil” features. On the other hand, some in situ measurements of internal waves and theoretical work suggest subsurface entrainment of air bubbles in the convergence zones of ISWs (Serebryany and Galybin, 2009; Grimshaw et al., 2010). We conducted airborne remote sensing observations in the coastal zone off the west Iberian Peninsula (off Lisbon, Portugal) using high resolution imaging sensors: LiDAR (Light Detection And Ranging), hyperspectral cameras (Eagle and Hawk) and thermal infrared imaging (TABI-320). These measurements were planned based on previous SAR observations in the region, which included also near-real time SAR overpasses (ESA project AOPT-2423 and TerraSAR-X project OCE-0056). The airborne measurements were conducted from board the NERC (Natural Environmental Research Centre) Do 228 aircraft in the summer of 2010. The TABI-320 thermal airborne broadband imager can distinguish temperature differences as small as one-twentieth of a degree and operates in the

  5. A survey on air bubble detector placement in the CPB circuit: a 2011 cross-sectional analysis of the practice of Certified Clinical Perfusionists.

    PubMed

    Kelting, T; Searles, B; Darling, E

    2012-07-01

    The ideal location of air bubble detector (ABD) placement on the cardiopulmonary bypass (CPB) circuit is debatable. There is, however, very little data characterizing the prevalence of specific ABD placement preferences by perfusionists. Therefore, the purpose of this study was to survey the perfusion community to collect data describing the primary locations of air bubble detector placement on the CPB circuit. In June 2011, an 18-question on-line survey was conducted. Completed surveys were received from 627 participants. Of these, analysis of the responses from the 559 certified clinical perfusionists (CCP) was performed. The routine use of ABD during CPB was reported by 96.8% of CCPs. Of this group, specific placement of the bubble detector is as follows: distal to the venous reservoir outlet (35.6%), between the arterial pump and oxygenator (3.8%), between the oxygenator and arterial line filter (35.1%), distal to the arterial line filter (ALF) (23.6%), and other (1.8%). Those placing the ABD distal to the venous reservoir predominately argued that an emptied venous reservoir was the most likely place to introduce air into the circuit. Those who placed the ABD between the oxygenator and the arterial line filter commonly reasoned that this placement protects against air exiting the membrane. Those placing the ABD distal to the ALF (23.6%) cited that this location protects from all possible entry points of air. A recent false alarm event from an ABD during a case was reported by 36.1% of CCPs. This study demonstrates that the majority of CCPs use an ABD during the conduct of CPB. The placement of the ABD on the circuit, however, is highly variable across the perfusion community. A strong rationale for the various ABD placements suggests that the adoption of multiple ABD may offer the greatest comprehensive protection against air emboli.

  6. Bubbles formation in helium ion irradiated Cu/W multilayer nanocomposites: Effects on structure and mechanical properties

    NASA Astrophysics Data System (ADS)

    Callisti, M.; Karlik, M.; Polcar, T.

    2016-05-01

    This study investigates the effects of He bubbles on structural and mechanical properties of sputter-deposited Cu/W multilayers. A multilayer with a periodicity of 10 nm was deposited and subjected to helium ion irradiation with two different fluences. He bubbles formed mostly in Cu layers and their distribution was affected by He concentration and radiation damage. According to SRIM calculations, in low He concentration regions bubbles formed mostly along interfaces, while more homogeneously distributed bubbles were found in Cu layers and along columnar grain boundaries in higher He concentration regions. We suggest that the capability of interfaces to annihilate point defects is weakened by the He bubbles shielding effect. Nanoindentation tests revealed a hardness decrease amounting to ∼0.5 and ∼1 GPa for low and high fluences, respectively. The observed softening effect is attributed to He storage-induced changes in residual stresses and columnar grain boundary/interfacial sliding facilitated by He bubbles.

  7. 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.

  8. Clustering in bubbly liquids

    NASA Astrophysics Data System (ADS)

    Figueroa, Bernardo; Zenit, Roberto

    2004-11-01

    We are conducting experiments to determine the amount of clustering that occurs when small gas bubbles ascend in clean water. In particular, we are interested in flows for which the liquid motion around the bubbles can be described, with a certain degree of accuracy, using potential flow theory. This model is applicable for the case of bubbly liquids in which the Reynolds number is large and the Weber number is small. To clearly observe the formation of bubble clusters we propose the use of a Hele-Shaw-type channel. In this thin channel the bubbles cannot overlap in the depth direction, therefore the identification of bubble clusters cannot be misinterpreted. Direct video image analysis is performed to calculate the velocity and size of the bubbles, as well as the formation of clusters. Although the walls do affect the motion of the bubbles, the clustering phenomena does occur and has the same qualitative behavior as in fully three-dimensional flows. A series of preliminary measurements are presented. A brief discussion of our plans to perform PIV measurements to obtain the liquid velocity fields is also presented.

  9. Using MRI to detect and differentiate calcium oxalate and calcium hydroxyapatite crystals in air-bubble-free phantom.

    PubMed

    Mustafi, Devkumar; Fan, Xiaobing; Peng, Bo; Foxley, Sean; Palgen, Jeremy; Newstead, Gillian M

    2015-12-01

    Calcium oxalate (CaOX) crystals and calcium hydroxyapatite (CaHA) crystals were commonly associated with breast benign and malignant lesions, respectively. In this research, CaOX (n = 6) and CaHA (n = 6) crystals in air-bubble-free agarose phantom were studied and characterized by using MRI at 9.4 T scanner. Calcium micro-crystals, with sizes that ranged from 200 to 500 µm, were made with either 99% pure CaOX or CaHA powder and embedded in agar to mimic the dimensions and calcium content of breast microcalcifications in vivo. MRI data were acquired with high spatial resolution T2-weighted (T2W) images and gradient echo images with five different echo times (TEs). The crystal areas were determined by setting the threshold relative to agarose signal. The ratio of crystal areas was calculated by the measurements from gradient echo images divided by T2W images. Then the ratios as a function of TE were fitted with the radical function. The results showed that the blooming artifacts due to magnetic susceptibility between agar and CaHA crystals were more than twice as large as the susceptibility in CaOX crystals (p < 0.05). In addition, larger bright rings were observed on gradient echo images around CaHA crystals compared to CaOX crystals. Our results suggest that MRI may provide useful information regarding breast microcalcifications by evaluating the apparent area of crystal ratios obtained between gradient echo and T2W images.

  10. Ionospheric disturbances during the magnetic storm of 15 July 2000: Role of the fountain effect and plasma bubbles for the formation of large equatorial plasma density depletions

    NASA Astrophysics Data System (ADS)

    Kil, Hyosub; Paxton, Larry J.

    2006-12-01

    We investigate the role of the fountain effect and plasma bubbles for the formation of the large equatorial plasma depletions during the geomagnetic storm of 15 July 2000. The large equatorial plasma depletions are detected in the Atlantic sector on the night of the 15th by the Defense Meteorological Satellite Program (DMSP) F15 and the first Republic of China Satellite (ROCSAT-1). The observations show discontinuous drop of the plasma density at the walls of the depletions, flat plasma density inside the depletions, and persistence or growth of the depletions over night. These properties are not consistent with the trough morphology induced by the fountain effect. The coincident ionospheric observations of DMSP F15 and ROCSAT-1 demonstrate that the large depletions are created in the longitude regions where plasma bubbles are present. The occurrence of the large depletions after sunset, elongation in the north-south direction, formation of steep walls, and colocation with plasma bubbles at lower altitudes or earlier times suggest that the large depletions are closely associated with plasma bubbles.

  11. Contributions to the acoustic excitation of bubbles released from a nozzle.

    PubMed

    Czerski, Helen; Deane, Grant B

    2010-11-01

    It has recently been demonstrated that air bubbles released from a nozzle are excited into volume mode oscillations by the collapse of the neck of air formed at the moment of bubble detachment. A pulse of sound is caused by these breathing mode oscillations, and the sound of air-entraining flows is made up of many such pulses emitted as bubbles are created. This paper is an elaboration on a JASA-EL paper, which examined the acoustical excitation of bubbles released from a nozzle. Here, further details of the collapse of a neck of air formed at the moment of bubble formation and its implications for the emission of sound by newly formed bubbles are presented. The role of fluid surface tension was studied using high-speed photography and found to be consistent with a simple model for neck collapse. A re-entrant fluid jet forms inside the bubble just after detachment, and its role in acoustic excitation is assessed. It is found that for slowly-grown bubbles the jet does make a noticeable difference to the total volume decrease during neck collapse, but that it is not a dominant effect in the overall acoustic excitation. PMID:21110560

  12. The role of air in granular jet formation

    NASA Astrophysics Data System (ADS)

    van der Meer, Devaraj; Bergmann, Raymond; Caballero, Gabriel; Lohse, Detlef

    2006-11-01

    A steel ball impacting on a bed of very loose, fine sand results in a surprisingly vigorous jet which shoots out from the surface of the sand. When the ambient pressure is reduced, the jet is found to be less vigorous, which suggests that air should play an important role in the mechanism of jet formation. In our impact experiments it was found that the penetration depth of the ball strongly decreases with decreasing pressure, whereas all other results are consistent with the gravitational collapse of the cavity that is created upon impact. This limits the influence of air to the stage of void formation, in which the cavity is created by a balance of the initial potential energy of the sphere and the dissipation due to the drag the ball experiences when penetrating into the sand.

  13. Bubble collision with gravitation

    SciTech Connect

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

    2012-07-01

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

  14. Microstructure of HIPed and SPSed 9Cr-ODS steel and its effect on helium bubble formation

    NASA Astrophysics Data System (ADS)

    Lu, Chenyang; Lu, Zheng; Xie, Rui; Liu, Chunming; Wang, Lumin

    2016-06-01

    Two 9Cr-ODS steels with the same nominal composition were consolidated by hot isostatic pressing (HIP, named COS-1) and spark plasma sintering (SPS, named COS-2). Helium ions were implanted into COS-1, COS-2 and non-ODS Eurofer 97 steels up at 673 K. Microstructures before and after helium ion implantations were carefully characterized. The results show a bimodal grain size distribution in COS-2 and a more uniform grain size distribution in COS-1. Nanoscale clusters of GP-zone type Y-Ti-O and Y2Ti2O7 pyrochlore as well as large spinel Mn(Ti)Cr2O4 particles are all observed in the two ODS steels. The Y-Ti-enriched nano-oxides in COS-1 exhibit higher number density and smaller size than in COS-2. The Y-Ti-enriched nano-oxides in fine grains of COS-2 show higher number density and smaller size than that in coarse grains of COS-2. Nano-oxides effectively trap helium atoms and lead to the formation of high density and ultra-fine helium bubbles.

  15. Investigation of the potential for vascular bubble formation in a repetitively diving dolphin.

    PubMed

    Houser, D S; Dankiewicz-Talmadge, L A; Stockard, T K; Ponganis, P J

    2010-01-01

    The production of venous gas emboli (VGE) resulting from altered dive behavior is postulated as contributing to the stranding of beaked whales exposed to mid-frequency active sonar. To test whether nitrogen gas uptake during repetitive breath-hold diving is sufficient for asymptomatic VGE formation in odontocetes, a bottlenose dolphin (Tursiops truncatus Montagu) was trained to perform 10-12 serial dives with 60 s surface intervals to depths of 30, 50, 70 or 100 m. The dolphin remained at the bottom depth for 90 s on each dive. Doppler and/or two-dimensional imaging ultrasound did not detect VGE in the portal and brachiocephalic veins following a dive series. Van Slyke analyses of serial, post-dive blood samples drawn from the fluke yielded blood nitrogen partial pressure (P(N(2))) values that were negligibly different from control samples. Mean heart rate (HR; +/-1 s.d.) recorded during diving was 50+/-3 beats min(-1) and was not significantly different between the 50, 70 and 100 m dive sessions. The absence of VGE and elevated blood P(N(2)) during post-dive periods do not support the hypothesis that N(2) supersaturation during repetitive dives contributes to VGE formation in the dolphin. The diving HR pattern and the presumed rapid N(2) washout during the surface-interval tachycardia probably minimized N(2) accumulation in the blood during dive sessions.

  16. The Dynamics of Bubbles and Bubble Clouds.

    NASA Astrophysics Data System (ADS)

    Smereka, Peter Stenberg

    In an effort to understand acoustic cavitation noise the dynamics of periodically driven single bubbles and bubble clouds are examined. The single bubble equations are written as a perturbation of a Hamiltonian system and the conditions for resonances to occur are found, these can interact with the nonresonant orbit to produce jump and period-doubling bifurcations. To study the chaotic behavior a map which approximates the Poincare map in the resonant band is derived. The Poincare map is computed numerically which shows the formation of strange attractors which suddenly disappear leaving behind Smale horseshoe maps. The bubble cloud is studied using an averaged two-fluid model for bubbly flow with periodic driving at the boundary. The equations are examined both analytically and numerically. Local and global existence of solutions is proved and the existence of an absorbing set is established. An analysis of the linearized equations combined with estimates on the nonlinearity is used to prove the existence of nonlinear periodic orbit. This periodic orbit is a fixed point of the Poincare map and its stability is determined by finding the spectrum of the linearized Poincare map. This calculation combined with the absorbing set proves that the long term dynamics of the bubble cloud is finite dimensional. Numerical computations show the important attractors are a periodic -two orbit and a quasi-periodic orbit.

  17. Blowing magnetic skyrmion bubbles

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  18. Indoor air chemistry: Formation of organic acids and aldehydes

    SciTech Connect

    Zhang, J.; Lioy, P.J. ||; Wilson, W.E.

    1994-12-31

    Laying emphasis on the formation of aldehydes and organic acids, the study has examined the gas-phase reactions of ozone with unsaturated VOCs. The formation of formaldehyde and formic acid was observed for all the three selected unsaturated VOCs: styrene, limonene, and 4-vinylcyclohexene. In addition, benzaldehyde was detected in the styrene-ozone-air reaction system, and acetic acid was also found in limonene-ozone-air system. The study has also examined the gas-phase reactions among formaldehyde, ozone, and nitrogen dioxide and found the formation of formic acid. The nitrate radical was suggested to play an important role in converting formaldehyde into formic acid. Experiments for all the reactions were conducted by using a 4.3 m{sup 3} Teflon chamber. Since the conditions for the reactions were similar to those for indoor environments, the results from the study can be implicated to real indoor situations and can be employed to support the findings and suggestions from the previous studies: certain aldehydes and organic acids could be generated by indoor chemistry.

  19. Recalcitrant bubbles

    PubMed Central

    Shanahan, Martin E. R.; Sefiane, Khellil

    2014-01-01

    We demonstrate that thermocapillary forces may drive bubbles against liquid flow in ‘anomalous' mixtures. Unlike ‘ordinary' liquids, in which bubbles migrate towards higher temperatures, we have observed vapour bubbles migrating towards lower temperatures, therefore against the flow. This unusual behaviour may be explained by the temperature dependence of surface tension of these binary mixtures. Bubbles migrating towards their equilibrium position follow an exponential trend. They finally settle in a stationary position just ‘downstream' of the minimum in surface tension. The exponential trend for bubbles in ‘anomalous' mixtures and the linear trend in pure liquids can be explained by a simple model. For larger bubbles, oscillations were observed. These oscillations can be reasonably explained by including an inertial term in the equation of motion (neglected for smaller bubbles). PMID:24740256

  20. Recalcitrant bubbles.

    PubMed

    Shanahan, Martin E R; Sefiane, Khellil

    2014-04-17

    We demonstrate that thermocapillary forces may drive bubbles against liquid flow in 'anomalous' mixtures. Unlike 'ordinary' liquids, in which bubbles migrate towards higher temperatures, we have observed vapour bubbles migrating towards lower temperatures, therefore against the flow. This unusual behaviour may be explained by the temperature dependence of surface tension of these binary mixtures. Bubbles migrating towards their equilibrium position follow an exponential trend. They finally settle in a stationary position just 'downstream' of the minimum in surface tension. The exponential trend for bubbles in 'anomalous' mixtures and the linear trend in pure liquids can be explained by a simple model. For larger bubbles, oscillations were observed. These oscillations can be reasonably explained by including an inertial term in the equation of motion (neglected for smaller bubbles).

  1. 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

  2. Singular Jets and Bubbles in Drop Impact

    NASA Astrophysics Data System (ADS)

    Bartolo, Denis; Josserand, Christophe; Bonn, Daniel

    2006-03-01

    We show that when water droplets gently impact on a hydrophobic surface, the droplet shoots out a violent jet, the velocity of which can be up to 40 times the drop impact speed. As a function of the impact velocity, two different hydrodynamic singularities are found that correspond to the collapse of the air cavity formed by the deformation of the drop at impact. It is the collapse that subsequently leads to the jet formation. We show that the divergence of the jet velocity can be understood using simple scaling arguments. In addition, we find that very large air bubbles can remain trapped in the drops. The surprising occurrence of the bubbles for low-speed impact is connected with the nature of the singularities, and can have important consequences for drop deposition, e.g., in ink-jet printing.

  3. Neutron detection via bubble chambers.

    PubMed

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

    2005-01-01

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

  4. Star-formation Activity in the Neighborhood of W–R 1503-160L Star in the Mid-infrared Bubble N46

    NASA Astrophysics Data System (ADS)

    Dewangan, L. K.; Baug, T.; Ojha, D. K.; Janardhan, P.; Ninan, J. P.; Luna, A.; Zinchenko, I.

    2016-07-01

    In order to investigate star-formation (SF) processes in extreme environments, we have carried out a multi-wavelength analysis of the mid-infrared bubble N46, which hosts a WN7 Wolf–Rayet (W–R) star. We have used 13CO line data to trace an expanding shell surrounding the W–R star containing about five condensations within the molecular cloud associated with the bubble. The W–R star is associated with a powerful stellar wind having a mechanical luminosity of ˜4 × 1037 erg s‑1. A deviation of the H-band starlight mean polarization angles around the bubble has also been traced, indicating the impact of stellar wind on the surroundings. The Herschel temperature map shows a temperature range of ˜18–24 K toward the five molecular condensations. The photometric analysis reveals that these condensations are associated with the identified clusters of young stellar objects, revealing ongoing SF process. The densest among these five condensations (peak N(H2) ˜9.2 × 1022 cm‑2 and A V ˜ 98 mag) is associated with a 6.7 GHz methanol maser, an infrared dark cloud, and the CO outflow, tracing active massive SF within it. At least five compact radio sources (CRSs) are physically linked with the edges of the bubble, and each of them is consistent with the radio spectral class of a B0V–B0.5V-type star. The ages of the individual infrared counterparts of three CRSs (˜1–2 Myr) and a typical age of WN7 W–R star (˜4 Myr) indicate that the SF activities around the bubble are influenced by the feedback of the W–R star.

  5. Star-formation Activity in the Neighborhood of W-R 1503-160L Star in the Mid-infrared Bubble N46

    NASA Astrophysics Data System (ADS)

    Dewangan, L. K.; Baug, T.; Ojha, D. K.; Janardhan, P.; Ninan, J. P.; Luna, A.; Zinchenko, I.

    2016-07-01

    In order to investigate star-formation (SF) processes in extreme environments, we have carried out a multi-wavelength analysis of the mid-infrared bubble N46, which hosts a WN7 Wolf-Rayet (W-R) star. We have used 13CO line data to trace an expanding shell surrounding the W-R star containing about five condensations within the molecular cloud associated with the bubble. The W-R star is associated with a powerful stellar wind having a mechanical luminosity of ˜4 × 1037 erg s-1. A deviation of the H-band starlight mean polarization angles around the bubble has also been traced, indicating the impact of stellar wind on the surroundings. The Herschel temperature map shows a temperature range of ˜18-24 K toward the five molecular condensations. The photometric analysis reveals that these condensations are associated with the identified clusters of young stellar objects, revealing ongoing SF process. The densest among these five condensations (peak N(H2) ˜9.2 × 1022 cm-2 and A V ˜ 98 mag) is associated with a 6.7 GHz methanol maser, an infrared dark cloud, and the CO outflow, tracing active massive SF within it. At least five compact radio sources (CRSs) are physically linked with the edges of the bubble, and each of them is consistent with the radio spectral class of a B0V-B0.5V-type star. The ages of the individual infrared counterparts of three CRSs (˜1-2 Myr) and a typical age of WN7 W-R star (˜4 Myr) indicate that the SF activities around the bubble are influenced by the feedback of the W-R star.

  6. Tribonucleation of bubbles

    PubMed Central

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

    2014-01-01

    We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for “writing with bubbles,” i.e., creating controlled patterns of microscopic bubbles. PMID:24982169

  7. Toroidal bubble entrapment under an impacting drop

    NASA Astrophysics Data System (ADS)

    Thoraval, Marie-Jean; Thoroddsen, Sigurdur T.; Takehara, Kohsei; Etoh, Takeharu Goji

    2012-11-01

    We use ultra-high-speed imaging and numerical simulations (GERRIS, http://gfs.sf.net) to observe and analyze the formation of up to 14 air tori when a water drop impacts on a thin liquid film of water or other miscible liquids. They form during the early contact between the drop and the pool by the vertical oscillations of the ejecta sheet. They then break in micro-bubble rings by the Rayleigh instability. Their formation is associated with the shedding of an axisymmetric vortex street into the liquid from the free surface. These vorticity structures and their dynamics are made apparent by the dynamics of the micro-bubbles, added seed particles and the difference of refractive index for different liquids in the drop and the pool. More robust entrapments are observed for a thin film of ethanol or methanol. We show that while the non-spherical drop shape is not responsible for the toroidal bubble entrapments, the number of rings is increasing for more oblate drops. Individual bubble entrapments are also observed from azimuthal destabilizations of the neck between the drop and the pool.

  8. Hydrocarbon-oil encapsulated air bubble flotation of fine coal. Technical progress report for the third quarter, April 1, 1991--June 30, 1991

    SciTech Connect

    Peng, F.F.

    1995-01-01

    This report is concerned with the progress made during the third period of the two year project. A significant portion of this reporting period has been consumed in measurement of induction time of oil-free and oil-coated bubbles, modification of collector gasifier, hydrocarbon oil encapsulated flotation tests and float and sink analyses of various rank of coal samples, building a 1-inch column cell, as well as building the ultrasound collector emulsification apparatus. Induction time has been measured using an Electronic Induction Timer. The results indicate that alteration of chemical properties of air bubble by applying hydrocarbon oil or reagent can drastically improve the rate of flotation process. Various techniques have been employed in hydrocarbon oil encapsulated flotation processes to further enhance the selectivity of the process, which include: (1) gasified collector flotation with addition of gasified collector into the air stream in the initial stage; (2) two-stage (rougher-cleaner) gasified collector flotation; and (3) starvation gasified collector flotation by addition of gasified collector at various flotation times. Among these, three techniques used in hydrocarbon oil encapsulated flotation process, the starvation flotation technique provides the best selectivity.

  9. Endothelial dysfunction correlates with decompression bubbles in rats.

    PubMed

    Zhang, Kun; Wang, Dong; Jiang, Zhongxin; Ning, Xiaowei; Buzzacott, Peter; Xu, Weigang

    2016-09-12

    Previous studies have documented that decompression led to endothelial dysfunction with controversial results. This study aimed to clarify the relationship between endothelial dysfunction, bubble formation and decompression rate. Rats were subjected to simulated air dives with one of four decompression rates: one slow and three rapid. Bubble formation was detected ultrasonically following decompression for two hours, before measurement of endothelial related indices. Bubbles were found in only rapid-decompressed rats and the amount correlated with decompression rate with significant variability. Serum levels of ET-1, 6-keto-PGF1α, ICAM-1, VCAM-1 and MDA, lung Wet/Dry weight ratio and histological score increased, serum NO decreased following rapid decompression. Endothelial-dependent vasodilatation to Ach was reduced in pulmonary artery rings among rapid-decompressed rats. Near all the above changes correlated significantly with bubble amounts. The results suggest that bubbles may be the causative agent of decompression-induced endothelial damage and bubble amount is of clinical significance in assessing decompression stress. Furthermore, serum levels of ET-1 and MDA may serve as sensitive biomarkers with the capacity to indicate endothelial dysfunction and decompression stress following dives.

  10. Endothelial dysfunction correlates with decompression bubbles in rats.

    PubMed

    Zhang, Kun; Wang, Dong; Jiang, Zhongxin; Ning, Xiaowei; Buzzacott, Peter; Xu, Weigang

    2016-01-01

    Previous studies have documented that decompression led to endothelial dysfunction with controversial results. This study aimed to clarify the relationship between endothelial dysfunction, bubble formation and decompression rate. Rats were subjected to simulated air dives with one of four decompression rates: one slow and three rapid. Bubble formation was detected ultrasonically following decompression for two hours, before measurement of endothelial related indices. Bubbles were found in only rapid-decompressed rats and the amount correlated with decompression rate with significant variability. Serum levels of ET-1, 6-keto-PGF1α, ICAM-1, VCAM-1 and MDA, lung Wet/Dry weight ratio and histological score increased, serum NO decreased following rapid decompression. Endothelial-dependent vasodilatation to Ach was reduced in pulmonary artery rings among rapid-decompressed rats. Near all the above changes correlated significantly with bubble amounts. The results suggest that bubbles may be the causative agent of decompression-induced endothelial damage and bubble amount is of clinical significance in assessing decompression stress. Furthermore, serum levels of ET-1 and MDA may serve as sensitive biomarkers with the capacity to indicate endothelial dysfunction and decompression stress following dives. PMID:27615160

  11. Endothelial dysfunction correlates with decompression bubbles in rats

    PubMed Central

    Zhang, Kun; Wang, Dong; Jiang, Zhongxin; Ning, Xiaowei; Buzzacott, Peter; Xu, Weigang

    2016-01-01

    Previous studies have documented that decompression led to endothelial dysfunction with controversial results. This study aimed to clarify the relationship between endothelial dysfunction, bubble formation and decompression rate. Rats were subjected to simulated air dives with one of four decompression rates: one slow and three rapid. Bubble formation was detected ultrasonically following decompression for two hours, before measurement of endothelial related indices. Bubbles were found in only rapid-decompressed rats and the amount correlated with decompression rate with significant variability. Serum levels of ET-1, 6-keto-PGF1α, ICAM-1, VCAM-1 and MDA, lung Wet/Dry weight ratio and histological score increased, serum NO decreased following rapid decompression. Endothelial-dependent vasodilatation to Ach was reduced in pulmonary artery rings among rapid-decompressed rats. Near all the above changes correlated significantly with bubble amounts. The results suggest that bubbles may be the causative agent of decompression–induced endothelial damage and bubble amount is of clinical significance in assessing decompression stress. Furthermore, serum levels of ET-1 and MDA may serve as sensitive biomarkers with the capacity to indicate endothelial dysfunction and decompression stress following dives. PMID:27615160

  12. The temperature dependence of void and bubble formation and growth in aluminium during 600 MeV proton irradiation

    NASA Astrophysics Data System (ADS)

    Victoria, M.; Green, W. V.; Singh, B. N.; Leffers, T.

    1984-05-01

    As a part of a continuing program, we report in the present paper results obtained from irradiating pure aluminium samples in the PIREX facility installed in the 600 MeV proton beam of the accelerator at the Swiss Institute for Nuclear Research (SIN). The aluminium foils have been irradiated at 8 different temperatures in the range from 130°-430°C, to displacement doses of up to 5 dpa and helium contents of over 1000 appm. The TEM examinations have shown that at all irradiation temperatures and displacement doses, helium bubbles are formed uniformly through the whole grain interior. No voids are observed at temperatures above 160° C. At all temperatures, irradiation induced dislocations have been observed, most of them linked to bubbles. At higher temperatures and doses, clear evidence of irradiation induced precipitation has been observed; the precipitates are normally decorated with helium bubbles.

  13. 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

  14. 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.

  15. Observations on biofilm formation in industrial air-cooling units

    SciTech Connect

    Liebert, C.A.; Hood, M.A.; Winter, P.A.; Singleton, F.L.

    1983-01-01

    Observations on biofilm formation in industrial air-cooling units were made over a 60-day operational period. Methods employed included: epifluorescent direct counts of water and slime samples, enumeration of culturable bacteria in water and slime samples, and ultrastructural observations of microbial attachment to formvar coated grids and epoxy resin blocks. Acridine orange direct counts and culturable counts of bacteria in water samples remained constant over the 60-day cycle, while culturable counts in slime samples increased with time. Interfering fluorescent materials present in the slime made accurate direct counts difficult to obtain. Initial increases in numbers of bacteria on formvar coated grids and culturable counts of slime samples were positively correlated with time. However, after 14 days, the formvar deteriorated and direct transmission electron microscopic bacterial counts could no longer be obtained. Submersion of epoxy resin blocks, especially those with pitted surfaces, provided an excellent method for the observation of bacterial attachment and colonization. 21 references, 3 figures.

  16. Large Eddy Simulation of Bubbly Flow and Slag Layer Behavior in Ladle with Discrete Phase Model (DPM)-Volume of Fluid (VOF) Coupled Model

    NASA Astrophysics Data System (ADS)

    Li, Linmin; Liu, Zhongqiu; Cao, Maoxue; Li, Baokuan

    2015-07-01

    In the ladle metallurgy process, the bubble movement and slag layer behavior is very important to the refining process and steel quality. For the bubble-liquid flow, bubble movement plays a significant role in the phase structure and causes the unsteady complex turbulent flow pattern. This is one of the most crucial shortcomings of the current two-fluid models. In the current work, a one-third scale water model is established to investigate the bubble movement and the slag open-eye formation. A new mathematical model using the large eddy simulation (LES) is developed for the bubble-liquid-slag-air four-phase flow in the ladle. The Eulerian volume of fluid (VOF) model is used for tracking the liquid-slag-air free surfaces and the Lagrangian discrete phase model (DPM) is used for describing the bubble movement. The turbulent liquid flow is induced by bubble-liquid interactions and is solved by LES. The procedure of bubble coming out of the liquid and getting into the air is modeled using a user-defined function. The results show that the present LES-DPM-VOF coupled model is good at predicting the unsteady bubble movement, slag eye formation, interface fluctuation, and slag entrainment.

  17. Bubble Detachment in Variable Gravity Under the Influence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, Cila; Chang, Shinan; Iacona, Estelle

    2002-01-01

    The objective of the research is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Situations were considered with both uniform and nonuniform electric fields. Bubble formation and detachment were visualized in terrestrial gravity as well as for several levels of reduced gravity (lunar, martian and microgravity) using a high-speed video camera. Bubble volume, dimensions and contact angles at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment in an initially uniform electric field was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. The results of the study indicate that the level of gravity and the electric field magnitude significantly affect bubble behavior as well as shape, volume and dimensions.

  18. Nanodiamond formation via thermal radiation from an air shock

    NASA Astrophysics Data System (ADS)

    de Carli, Paul

    2013-06-01

    Nanodiamonds have recently been found in sediments of Younger Dryas age, about 12,900 years ago. Carbon isotope ratios imply that the source of carbon was terrestrial organic matter and rule out the possibility that the diamond was of cosmic origin, e.g., from an influx of meteorites. The nanodiamonds are associated with mineral spherules (and other shapes) that have compositions and textures consistent with the rapid melting and solidification of local soil. The inferred temperatures are much too high for natural events such as forest fires. Similar deposits of nanodiamond have been found in the 65 million year old K-Pg layer associated with the ca. 200 km diameter Chicxulub impact crater. Nanodiamond have also been reported in the vicinity of the Tunguska event, presumed to be the result of an air shock produced by the interaction of a rapidly moving cosmic body with the Earth's atmosphere. We infer that the nanodiamonds were formed when the thermal radiation from the air shock pyrolyzed surface organic matter. Rapid reaction locally depleted the atmosphere of oxygen and the remaining carbon could condense as nanodiamond. A similar mechanism can be invoked to account for the formation of nanodiamond as a froduct of the detonation of ozygen-deficient high explosives.

  19. Bubble baryogenesis

    NASA Astrophysics Data System (ADS)

    Cheung, Clifford; Dahlen, Alex; Elor, Gilly

    2012-09-01

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

  20. Helium bubble bursting in tungsten

    SciTech Connect

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

    2013-12-28

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

  1. Formation of a Rigid Hydrophobin Film and Disruption by an Anionic Surfactant at an Air/Water Interface.

    PubMed

    Kirby, Stephanie M; Zhang, Xujun; Russo, Paul S; Anna, Shelley L; Walker, Lynn M

    2016-06-01

    Hydrophobins are amphiphilic proteins produced by fungi. Cerato-ulmin (CU) is a hydrophobin that has been associated with Dutch elm disease. Like other hydrophobins, CU stabilizes air bubbles and oil droplets through the formation of a persistent protein film at the interface. The behavior of hydrophobins at surfaces has raised interest in their potential applications, including use in surface coatings, food foams, and emulsions and as dispersants. The practical use of hydrophobins requires an improved understanding of the interfacial behavior of these proteins, alone and in the presence of added surfactants. In this study, the adsorption behavior of CU at air/water interfaces is characterized by measuring the surface tension and interfacial rheology as a function of adsorption time. CU is found to adsorb irreversibly at air/water interfaces. The magnitude of the dilatational modulus increases with adsorption time and surface pressure until CU eventually forms a rigid film. The persistence of this film is tested through the sequential addition of strong surfactant sodium dodecyl sulfate (SDS) to the bulk liquid adjacent to the interface. SDS is found to coadsorb to interfaces precoated with a CU film. At high concentrations, the addition of SDS significantly decreases the dilatational modulus, indicating disruption and displacement of CU by SDS. Sequential adsorption results in mixed layers with properties not observed in interfaces generated from complexes formed in the bulk. These results lend insight to the complex interfacial interactions between hydrophobins and surfactants. PMID:27164189

  2. 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)

  3. Sound synchronization of bubble trains in a viscous fluid: experiment and modeling.

    PubMed

    Pereira, Felipe Augusto Cardoso; Baptista, Murilo da Silva; Sartorelli, José Carlos

    2014-10-01

    We investigate the dynamics of formation of air bubbles expelled from a nozzle immersed in a viscous fluid under the influence of sound waves. We have obtained bifurcation diagrams by measuring the time between successive bubbles, having the air flow (Q) as a parameter control for many values of the sound wave amplitude (A), the height (H) of the solution above the top of the nozzle, and three values of the sound frequency (fs). Our parameter spaces (Q,A) revealed a scenario for the onset of synchronization dominated by Arnold tongues (frequency locking) which gives place to chaotic phase synchronization for sufficiently large A. The experimental results were accurately reproduced by numerical simulations of a model combining a simple bubble growth model for the bubble train and a coupling term with the sound wave added to the equilibrium pressure.

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

    NASA Astrophysics Data System (ADS)

    Marchisio, Daniele; Karimi, Mohsen

    2015-11-01

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

  5. Experimental Results for Direct Electron Irradiation of a Uranyl Sulfate Solution: Bubble Formation and Thermal Hydraulics Studies

    SciTech Connect

    Chemerisov, Sergey; Gromov, R.; Makarashvili, Vakhtang; Heltemes, Thad; Sun, Zaijing; Wardle, Kent E.; Bailey, James; Stepinski, Dominique; Jerden, James; Vandegrift, George F.

    2015-01-30

    In support of the development of accelerator-driven production of fission product Mo-99 as proposed by SHINE Medical Technologies, a 35 MeV electron linac was used to irradiate depleted-uranium (DU) uranyl sulfate dissolved in pH 1 sulfuric acid at average power densities of 6 kW, 12 kW, and 15 kW. During these irradiations, gas bubbles were generated in the solution due to the radiolytic decomposition of water molecules in the solution. Multiple video cameras were used to record the behavior of bubble generation and transport in the solution. Seven six-channel thermocouples were used to record temperature gradients in the solution from self-heating. Measurements of hydrogen and oxygen concentrations in a helium sweep gas were recorded by a gas chromatograph to estimate production rates during irradiation. These data are being used to validate a computational fluid dynamics (CFD) model of the experiment that includes multiphase flow and a custom bubble injection model for the solution region.

  6. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  7. Double Bubble? No Trouble!

    ERIC Educational Resources Information Center

    Shaw, Mike I.; Smith, Greg F.

    1995-01-01

    Describes a soap-solution activity involving formation of bubbles encasing the students that requires only readily available materials and can be adapted easily for use with various grade levels. Discusses student learning outcomes including qualitative and quantitative observations and the concept of surface tension. (JRH)

  8. Vortex-ring-induced large bubble entrainment during drop impact.

    PubMed

    Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T

    2016-03-01

    For a limited set of impact conditions, a drop impacting onto a pool can entrap an air bubble as large as its own size. The subsequent rise and rupture of this large bubble plays an important role in aerosol formation and gas transport at the air-sea interface. The large bubble is formed when the impact crater closes up near the pool surface and is known to occur only for drops that are prolate at impact. Herein we use experiments and numerical simulations to show that a concentrated vortex ring, produced in the neck between the drop and the pool, controls the crater deformations and pinchoff. However, it is not the strongest vortex rings that are responsible for the large bubbles, as they interact too strongly with the pool surface and self-destruct. Rather, it is somewhat weaker vortices that can deform the deeper craters, which manage to pinch off the large bubbles. These observations also explain why the strongest and most penetrating vortex rings emerging from drop impacts are not produced by oblate drops but by more prolate drop shapes, as had been observed in previous experiments. PMID:27078468

  9. Vortex-ring-induced large bubble entrainment during drop impact.

    PubMed

    Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T

    2016-03-01

    For a limited set of impact conditions, a drop impacting onto a pool can entrap an air bubble as large as its own size. The subsequent rise and rupture of this large bubble plays an important role in aerosol formation and gas transport at the air-sea interface. The large bubble is formed when the impact crater closes up near the pool surface and is known to occur only for drops that are prolate at impact. Herein we use experiments and numerical simulations to show that a concentrated vortex ring, produced in the neck between the drop and the pool, controls the crater deformations and pinchoff. However, it is not the strongest vortex rings that are responsible for the large bubbles, as they interact too strongly with the pool surface and self-destruct. Rather, it is somewhat weaker vortices that can deform the deeper craters, which manage to pinch off the large bubbles. These observations also explain why the strongest and most penetrating vortex rings emerging from drop impacts are not produced by oblate drops but by more prolate drop shapes, as had been observed in previous experiments.

  10. Vortex-ring-induced large bubble entrainment during drop impact

    NASA Astrophysics Data System (ADS)

    Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T.

    2016-03-01

    For a limited set of impact conditions, a drop impacting onto a pool can entrap an air bubble as large as its own size. The subsequent rise and rupture of this large bubble plays an important role in aerosol formation and gas transport at the air-sea interface. The large bubble is formed when the impact crater closes up near the pool surface and is known to occur only for drops that are prolate at impact. Herein we use experiments and numerical simulations to show that a concentrated vortex ring, produced in the neck between the drop and the pool, controls the crater deformations and pinchoff. However, it is not the strongest vortex rings that are responsible for the large bubbles, as they interact too strongly with the pool surface and self-destruct. Rather, it is somewhat weaker vortices that can deform the deeper craters, which manage to pinch off the large bubbles. These observations also explain why the strongest and most penetrating vortex rings emerging from drop impacts are not produced by oblate drops but by more prolate drop shapes, as had been observed in previous experiments.

  11. Micro bubbles at interfaces

    NASA Astrophysics Data System (ADS)

    Keshavarzi, Gholamreza; Wang, Anna; Barber, Tracie; Manoharan, Vinothan

    2014-03-01

    The behaviour of a small micron sized bubbles close to an interface is vital to various interface interaction applications in several industries. Previous studies have focused on understanding the behaviour of large millimetric bubbles reaching an interface. Some of these millimetric bubbles are shown to bounce back, while others penetrate and burst on the interface resulting in possible small micron sized bubbles. However, small micron sized bubble may act different. It has been observed that small microbubbles can act as if they are stabilized at the interface without merging to the fluid over the interface. The dynamics of the microbubble adsorption close to an interface has yet to be well understood.In this study we used digital holography microscopy to explore detailed information on the behaviour of the air microbubble at the interface. This study investigates the position and shape of a microbubble with respect to the interface. The dynamic behavior close to the interface along with where the small microbubble is positioned near an interface will help us in understanding the probability of penetration and merging back to the fluid on top.

  12. Adsorption of egg phosphatidylcholine to an air/water and triolein/water bubble interface: use of the 2-dimensional phase rule to estimate the surface composition of a phospholipid/triolein/water surface as a function of surface pressure.

    PubMed

    Mitsche, Matthew A; Wang, Libo; Small, Donald M

    2010-03-11

    Phospholipid monolayers play a critical role in the structure and stabilization of biological interfaces, including all membranes, the alveoli of the lungs, fat droplets in adipose tissue, and lipoproteins. The behavior of phospholipids in bilayers and at an air-water interface is well understood. However, the study of phospholipids at oil-water interfaces is limited due to technical challenges. In this study, egg phosphatidylcholine (EPC) was deposited from small unilamellar vesicles onto a bubble of either air or triolein (TO) formed in a low-salt buffer. The surface tension (gamma) was measured using a drop tensiometer. We observed that EPC binds irreversibly to both interfaces and at equilibrium exerts approximately 12 and 15 mN/m of pressure (Pi) at an air and TO interface, respectively. After EPC was bound to the interface, the unbound EPC was washed out of the cuvette, and the surface was compressed to study the Pi/area relationship. To determine the surface concentration (Gamma), which cannot be measured directly, compression isotherms from a Langmuir trough and drop tensiometer were compared. The air-water interfaces had identical characteristics using both techniques; thus, Gamma on the bubble can be determined by overlaying the two isotherms. Both TO and EPC are surface-active, so in a mixed TO/EPC monolayer, both molecules will be exposed to water. Since TO is less surface-active than EPC, as Pi increases, the TO is progressively ejected. To understand the Pi/area isotherm of EPC on a TO bubble, a variety of TO-EPC mixtures were spread at the air-water interface. The isotherms show an abrupt break in the curve caused by the ejection of TO from the monolayer into a new bulk phase. By overlaying the compression isotherm above the ejection point with a TO bubble compression isotherm, Gamma can be estimated. This allows determination of Gamma of EPC on a TO bubble as a function of Pi.

  13. Coalescence of bubbles translating through a tube.

    PubMed

    Almatroushi, Eisa; Borhan, Ali

    2006-09-01

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

  14. Oscillations of soap bubbles

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

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

  15. Tuning bubbly structures in microchannels.

    PubMed

    Vuong, Sharon M; Anna, Shelley L

    2012-06-01

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

  16. Mechanism of bubble detachment from vibrating walls

    SciTech Connect

    Kim, Dongjun; Park, Jun Kwon Kang, Kwan Hyoung; Kang, In Seok

    2013-11-15

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

  17. Vapor-Gas Bubble Evolution and Growth in Extremely Viscous Fluids Under Vacuum

    NASA Technical Reports Server (NTRS)

    Kizito, John; Balasubramaniam, R.; Nahra, Henry; Agui, Juan; Truong, Duc

    2008-01-01

    Formation of vapor and gas bubbles and voids is normal and expected in flow processes involving extremely viscous fluids in normal gravity. Practical examples of extremely viscous fluids are epoxy-like filler materials before the epoxy fluids cure to their permanent form to create a mechanical bond between two substrates. When these fluids flow with a free liquid interface exposed to vacuum, rapid bubble expansion process may ensue. Bubble expansion might compromise the mechanical bond strength. The potential sources for the origin of the gases might be incomplete out-gassing process prior to filler application; regasification due to seal leakage in the filler applicator; and/or volatiles evolved from cure reaction products formed in the hardening process. We embarked on a study that involved conducting laboratory experiments with imaging diagnostics in order to deduce the seriousness of bubbling caused by entrained air and volatile fluids under space vacuum and low gravity environment. We used clear fluids with the similar physical properties as the epoxy-like filler material to mimic the dynamics of bubbles. Another aspect of the present study was to determine the likelihood of bubbling resulting from dissolved gases nucleating from solution. These experimental studies of the bubble expansion are compared with predictions using a modified Rayleigh- Plesset equation, which models the bubble expansion.

  18. 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.

  19. Frequency and Size of Strombolian Eruptions from the Phonolitic Lava Lake at Erebus Volcano, Antarctica: Insights from Infrasound and Seismic Observations on Bubble Formation and Ascent

    NASA Astrophysics Data System (ADS)

    Rotman, H. M. M.; Kyle, P. R.; Fee, D.; Curtis, A.

    2015-12-01

    Erebus, an active intraplate volcano on Ross Island, commonly produces bubble burst Strombolian explosions from a long-lived, convecting phonolitic lava lake. Persistent lava lakes are rare, and provide direct insights into their underlying magmatic system. Erebus phonolite is H2O-poor and contains ~30% anorthoclase megacrysts. At shallow depths lab measurements suggest the magma has viscosities of ~107 Pa s. This has implications for magma and bubble ascent rates through the conduit and into the lava lake. The bulk composition and matrix glass of Erebus ejecta has remained uniform for many thousands of years, but eruptive activity varies on decadal and shorter time scales. Over the last 15 years, increased activity took place in 2005-2007, and more recently in the 2013 austral summer. In the 2014 austral summer, new infrasound sensors were installed ~700 m from the summit crater hosting the lava lake. These sensors, supplemented by the Erebus network seismic stations, recorded >1000 eruptions between 1 January and 7 April 2015, with an average infrasound daily uptime of 9.6 hours. Over the same time period, the CTBT infrasound station IS55, ~25 km from Erebus, detected ~115 of the >1000 locally observed eruptions with amplitude decreases of >100x. An additional ~200 eruptions were recorded during local infrasound downtime. This represents an unusually high level of activity from the Erebus lava lake, and while instrument noise influences the minimum observable amplitude each day, the eruption infrasound amplitudes may vary by ~3 orders of magnitude over the scale of minutes to hours. We use this heightened period of variable activity and associated seismic and acoustic waveforms to examine mechanisms for bubble formation and ascent, such as rise speed dependence and collapsing foam; repose times for the larger eruptions; and possible eruption connections to lava lake cyclicity.

  20. Cylindrical bubbles and blobs from a Class II Hydrophobin

    NASA Astrophysics Data System (ADS)

    Russo, Paul; Pham, Michael; Blalock, Brad

    2012-02-01

    Cerato ulmin is a class II hydrophobin. In aqueous suspensions, it easily forms cylindrical air bubbles and cylindrical oil blobs. The conditions for formation of these unusual structures will be discussed, along with scattering and microscopic investigations of their remarkable stability. Possible applications in diverse fields including polymer synthesis and oil spill remediation will be considered. Acknowledgment is made to Dr. Wayne C. Richards of the Canadian Forest Service for the gift of Cerato ulmin.

  1. Breaking waves and near-surface sea spray aerosol dependence on changing winds: Wave breaking efficiency and bubble-related air-sea interaction processes

    NASA Astrophysics Data System (ADS)

    Hwang, P. A.; Savelyev, I. B.; Anguelova, M. D.

    2016-05-01

    Simultaneous measurements of sea spray aerosol (SSA), wind, wave, and microwave brightness temperature are obtained in the open ocean on-board Floating Instrument Platform (FLIP). These data are analysed to clarify the ocean surface processes important to SSA production. Parameters are formulated to represent surface processes with characteristic length scales spanning a broad range. The investigation reveals distinct differences of the SSA properties in rising winds and falling winds, with higher SSA volume in falling winds. Also, in closely related measurements of whitecap coverage, higher whitecap fraction as a function of wind speed is found in falling winds than in rising winds or in older seas than in younger seas. Similar trend is found in the short scale roughness reflected in the microwave brightness temperature data. In the research of length and velocity scales of breaking waves, it has been observed that the length scale of wave breaking is shorter in mixed seas than in wind seas. For example, source function analysis of short surface waves shows that the characteristic length scale of the dissipation function shifts toward higher wavenumber (shorter wavelength) in mixed seas than in wind seas. Similarly, results from feature tracking or Doppler analysis of microwave radar sea spikes, which are closely associated with breaking waves, show that the magnitude of the average breaking wave velocity is smaller in mixed seas than in wind seas. Furthermore, breaking waves are observed to possess geometric similarity. Applying the results of breaking wave analyses to the SSA and whitecap observations described above, it is suggestive that larger air cavities resulting from the longer breakers are entrained in rising high winds. The larger air cavities escape rapidly due to buoyancy before they can be fully broken down into small bubbles for the subsequent SSA production or whitecap manifestation. In contrast, in falling winds (with mixed seas more likely), the

  2. Tiny Bubbles.

    ERIC Educational Resources Information Center

    Kim, Hy

    1985-01-01

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

  3. Leverage bubble

    NASA Astrophysics Data System (ADS)

    Yan, Wanfeng; Woodard, Ryan; Sornette, Didier

    2012-01-01

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

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

    PubMed

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

    2015-01-01

    In the present work, stable clusters made of multiple sonoluminescent bubbles are experimentally and theoretically studied. Argon bubbles were acoustically generated and trapped using bi-frequency driving within a cylindrical chamber filled with a sulfuric acid aqueous solution (SA85w/w). The intensity of the acoustic pressure field was strong enough to sustain, during several minutes, a large number of positionally and spatially fixed (without pseudo-orbits) sonoluminescent bubbles over an ellipsoidally-shaped tridimensional array. The dimensions of the ellipsoids were studied as a function of the amplitude of the applied low-frequency acoustic pressure (PAc(LF)) and the static pressure in the fluid (P0). In order to explain the size and shape of the bubble clusters, we performed a series of numerical simulations of the hydrodynamic forces acting over the bubbles. In both cases the observed experimental behavior was in excellent agreement with the numerical results. The simulations revealed that the positionally stable region, mainly determined by the null primary Bjerknes force (F→Bj), is defined as the outer perimeter of an axisymmetric ellipsoidal cluster centered in the acoustic field antinode. The role of the high-frequency component of the pressure field and the influence of the secondary Bjerknes force are discussed. We also investigate the effect of a change in the concentration of dissolved gas on the positional and spatial instabilities through the cluster dimensions. The experimental and numerical results presented in this paper are potentially useful for further understanding and modeling numerous current research topics regarding multi-bubble phenomena, e.g. forces acting on the bubbles in multi-frequency acoustic fields, transient acoustic cavitation, bubble interactions, structure formation processes, atomic and molecular emissions of equal bubbles and nonlinear or unsteady acoustic pressure fields in bubbly media. PMID:24974006

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

    PubMed

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

    2015-01-01

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

  6. 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.

  7. 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.

  8. 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. PMID:26943558

  9. Generation of Bubbly Suspensions in Low Gravity

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  10. Magnetism. Blowing magnetic skyrmion bubbles.

    PubMed

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

    2015-07-17

    The formation of soap bubbles from thin films is accompanied by topological transitions. Here we show how a magnetic topological structure, a skyrmion bubble, can be generated in a solid-state system in a similar manner. Using an inhomogeneous in-plane current in a system with broken inversion symmetry, we experimentally "blow" magnetic skyrmion bubbles from a geometrical constriction. The presence of a spatially divergent spin-orbit torque gives rise to instabilities of the magnetic domain structures that are reminiscent of Rayleigh-Plateau instabilities in fluid flows. We determine a phase diagram for skyrmion formation and reveal the efficient manipulation of these dynamically created skyrmions, including depinning and motion. The demonstrated current-driven transformation from stripe domains to magnetic skyrmion bubbles could lead to progress in skyrmion-based spintronics. PMID:26067256

  11. Magnetism. Blowing magnetic skyrmion bubbles.

    PubMed

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

    2015-07-17

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

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

    PubMed

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

    2011-12-01

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

  13. Drops and Bubble in Materials Science

    NASA Technical Reports Server (NTRS)

    Doremus, R. H.

    1982-01-01

    The formation of extended p-n junctions in semiconductors by drop migration, mechanisms and morphologies of migrating drops and bubbles in solids and nucleation and corrections to the Volmer-Weber equations are discussed. Bubble shrinkage in the processing of glass, the formation of glass microshells as laser-fusion targets, and radiation-induced voids in nuclear reactors were examined.

  14. Submarine rescue decompression procedure from hyperbaric exposures up to 6 bar of absolute pressure in man: effects on bubble formation and pulmonary function.

    PubMed

    Blatteau, Jean-Eric; Hugon, Julien; Castagna, Olivier; Meckler, Cédric; Vallée, Nicolas; Jammes, Yves; Hugon, Michel; Risberg, Jan; Pény, Christophe

    2013-01-01

    Recent advances in submarine rescue systems have allowed a transfer under pressure of crew members being rescued from a disabled submarine. The choice of a safe decompression procedure for pressurised rescuees has been previously discussed, but no schedule has been validated when the internal submarine pressure is significantly increased i.e. exceeding 2.8 bar absolute pressure. This study tested a saturation decompression procedure from hyperbaric exposures up to 6 bar, the maximum operating pressure of the NATO submarine rescue system. The objective was to investigate the incidence of decompression sickness (DCS) and clinical and spirometric indices of pulmonary oxygen toxicity. Two groups were exposed to a Nitrogen-Oxygen atmosphere (pO2 = 0.5 bar) at either 5 bar (N = 14) or 6 bar (N = 12) for 12 h followed by 56 h 40 min resp. 60 h of decompression. When chamber pressure reached 2.5 bar, the subjects breathed oxygen intermittently, otherwise compressed air. Repeated clinical examinations, ultrasound monitoring of venous gas embolism and spirometry were performed during decompression. During exposures to 5 bar, 3 subjects had minor subjective symptoms i.e. sensation of joint discomfort, regressing spontaneously, and after surfacing 2 subjects also experienced joint discomfort disappearing without treatment. Only 3 subjects had detectable intravascular bubbles during decompression (low grades). No bubbles were detected after surfacing. About 40% of subjects felt chest tightness when inspiring deeply during the initial phase of decompression. Precordial burning sensations were reported during oxygen periods. During decompression, vital capacity decreased by about 8% and forced expiratory flow rates decreased significantly. After surfacing, changes in the peripheral airways were still noticed; Lung Diffusion for carbon monoxide was slightly reduced by 1% while vital capacity was normalized. The procedure did not result in serious symptoms of DCS or

  15. Submarine Rescue Decompression Procedure from Hyperbaric Exposures up to 6 Bar of Absolute Pressure in Man: Effects on Bubble Formation and Pulmonary Function

    PubMed Central

    Blatteau, Jean-Eric; Hugon, Julien; Castagna, Olivier; Meckler, Cédric; Vallée, Nicolas; Jammes, Yves; Hugon, Michel; Risberg, Jan; Pény, Christophe

    2013-01-01

    Recent advances in submarine rescue systems have allowed a transfer under pressure of crew members being rescued from a disabled submarine. The choice of a safe decompression procedure for pressurised rescuees has been previously discussed, but no schedule has been validated when the internal submarine pressure is significantly increased i.e. exceeding 2.8 bar absolute pressure. This study tested a saturation decompression procedure from hyperbaric exposures up to 6 bar, the maximum operating pressure of the NATO submarine rescue system. The objective was to investigate the incidence of decompression sickness (DCS) and clinical and spirometric indices of pulmonary oxygen toxicity. Two groups were exposed to a Nitrogen-Oxygen atmosphere (pO2 = 0.5 bar) at either 5 bar (N = 14) or 6 bar (N = 12) for 12 h followed by 56 h 40 min resp. 60 h of decompression. When chamber pressure reached 2.5 bar, the subjects breathed oxygen intermittently, otherwise compressed air. Repeated clinical examinations, ultrasound monitoring of venous gas embolism and spirometry were performed during decompression. During exposures to 5 bar, 3 subjects had minor subjective symptoms i.e. sensation of joint discomfort, regressing spontaneously, and after surfacing 2 subjects also experienced joint discomfort disappearing without treatment. Only 3 subjects had detectable intravascular bubbles during decompression (low grades). No bubbles were detected after surfacing. About 40% of subjects felt chest tightness when inspiring deeply during the initial phase of decompression. Precordial burning sensations were reported during oxygen periods. During decompression, vital capacity decreased by about 8% and forced expiratory flow rates decreased significantly. After surfacing, changes in the peripheral airways were still noticed; Lung Diffusion for carbon monoxide was slightly reduced by 1% while vital capacity was normalized. The procedure did not result in serious symptoms of DCS or

  16. Submarine rescue decompression procedure from hyperbaric exposures up to 6 bar of absolute pressure in man: effects on bubble formation and pulmonary function.

    PubMed

    Blatteau, Jean-Eric; Hugon, Julien; Castagna, Olivier; Meckler, Cédric; Vallée, Nicolas; Jammes, Yves; Hugon, Michel; Risberg, Jan; Pény, Christophe

    2013-01-01

    Recent advances in submarine rescue systems have allowed a transfer under pressure of crew members being rescued from a disabled submarine. The choice of a safe decompression procedure for pressurised rescuees has been previously discussed, but no schedule has been validated when the internal submarine pressure is significantly increased i.e. exceeding 2.8 bar absolute pressure. This study tested a saturation decompression procedure from hyperbaric exposures up to 6 bar, the maximum operating pressure of the NATO submarine rescue system. The objective was to investigate the incidence of decompression sickness (DCS) and clinical and spirometric indices of pulmonary oxygen toxicity. Two groups were exposed to a Nitrogen-Oxygen atmosphere (pO2 = 0.5 bar) at either 5 bar (N = 14) or 6 bar (N = 12) for 12 h followed by 56 h 40 min resp. 60 h of decompression. When chamber pressure reached 2.5 bar, the subjects breathed oxygen intermittently, otherwise compressed air. Repeated clinical examinations, ultrasound monitoring of venous gas embolism and spirometry were performed during decompression. During exposures to 5 bar, 3 subjects had minor subjective symptoms i.e. sensation of joint discomfort, regressing spontaneously, and after surfacing 2 subjects also experienced joint discomfort disappearing without treatment. Only 3 subjects had detectable intravascular bubbles during decompression (low grades). No bubbles were detected after surfacing. About 40% of subjects felt chest tightness when inspiring deeply during the initial phase of decompression. Precordial burning sensations were reported during oxygen periods. During decompression, vital capacity decreased by about 8% and forced expiratory flow rates decreased significantly. After surfacing, changes in the peripheral airways were still noticed; Lung Diffusion for carbon monoxide was slightly reduced by 1% while vital capacity was normalized. The procedure did not result in serious symptoms of DCS or

  17. 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.

  18. 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. PMID:26565252

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  20. Application of the ultrasonic technique and high-speed filming for the study of the structure of air-water bubbly flows

    SciTech Connect

    Carvalho, R.D.M.; Venturini, O.J.; Tanahashi, E.I.; Neves, F. Jr.; Franca, F.A.

    2009-10-15

    Multiphase flows are very common in industry, oftentimes involving very harsh environments and fluids. Accordingly, there is a need to determine the dispersed phase holdup using noninvasive fast responding techniques; besides, knowledge of the flow structure is essential for the assessment of the transport processes involved. The ultrasonic technique fulfills these requirements and could have the capability to provide the information required. In this paper, the potential of the ultrasonic technique for application to two-phase flows was investigated by checking acoustic attenuation data against experimental data on the void fraction and flow topology of vertical, upward, air-water bubbly flows in the zero to 15% void fraction range. The ultrasonic apparatus consisted of one emitter/receiver transducer and three other receivers at different positions along the pipe circumference; simultaneous high-speed motion pictures of the flow patterns were made at 250 and 1000 fps. The attenuation data for all sensors exhibited a systematic interrelated behavior with void fraction, thereby testifying to the capability of the ultrasonic technique to measure the dispersed phase holdup. From the motion pictures, basic gas phase structures and different flows patterns were identified that corroborated several features of the acoustic attenuation data. Finally, the acoustic wave transit time was also investigated as a function of void fraction. (author)

  1. Aluminum colloid formation and its effect on co-precipitation of zinc during acid rock drainage remediation with clinoptilolite in a slurry bubble column

    NASA Astrophysics Data System (ADS)

    Xu, W.; Li, L. Y.; Grace, J. R.

    2012-04-01

    Zinc and other metal ions were adsorbed in a laboratory slurry bubble column (SBC) by natural clinoptilolite sorbent particles. During the remediation process, significant white precipitates were sometimes observed. Both zinc and aluminum were detected in the colloidal mixtures. It is shown that Al leached from clinoptilolite during the agitation, contributing to the precipitate. As a result of the Al leaching and increase of pH during the remediation process, the formation of an Al colloid and zinc adsorption onto it could significantly improve ARD remediation, given the high adsorption capacity of the colloid. Sorption of cations increased with increasing colloid formation. Various conditions were tested to investigate their impact on (a) dealumination of clinoptilolite; (b) Al hydrolysis/colloid formation; and (c) adsorption onto the colloidal mixture. The test results indicate that dealumination contributes to the excess aluminum in the aqueous phase and to precipitates. The excess dealumination varies with pH and agitation time. Al hydrolysis occurs with increasing pH due to the neutralization effect of clinoptilolite. A significant proportion of zinc adsorbed onto the collectible aluminum precipitates.

  2. The impacts of replacing air bubbles with microspheres for the clarification of algae from low cell-density culture.

    PubMed

    Ometto, Francesco; Pozza, Carlo; Whitton, Rachel; Smyth, Beatrice; Gonzalez Torres, Andrea; Henderson, Rita K; Jarvis, Peter; Jefferson, Bruce; Villa, Raffaella

    2014-04-15

    Dissolved Air Flotation (DAF) is a well-known coagulation-flotation system applied at large scale for microalgae harvesting. Compared to conventional harvesting technologies DAF allows high cell recovery at lower energy demand. By replacing microbubbles with microspheres, the innovative Ballasted Dissolved Air Flotation (BDAF) technique has been reported to achieve the same algae cell removal efficiency, while saving up to 80% of the energy required for the conventional DAF unit. Using three different algae cultures (Scenedesmus obliquus, Chlorella vulgaris and Arthrospira maxima), the present work investigated the practical, economic and environmental advantages of the BDAF system compared to the DAF system. 99% cells separation was achieved with both systems, nevertheless, the BDAF technology allowed up to 95% coagulant reduction depending on the algae species and the pH conditions adopted. In terms of floc structure and strength, the inclusion of microspheres in the algae floc generated a looser aggregate, showing a more compact structure within single cell alga, than large and filamentous cells. Overall, BDAF appeared to be a more reliable and sustainable harvesting system than DAF, as it allowed equal cells recovery reducing energy inputs, coagulant demand and carbon emissions.

  3. Retinal angiography: noninvasive, real-time bubble assessment from the ocular fundus.

    PubMed

    Parsons, J Travis; Smith, Cameron R; Zhu, Jiepei; Spiess, Bruce D

    2009-01-01

    Formation of bubbles in tissue and vasculature from a sudden reduction in ambient pressure is likely an underlying cause of the clinical symptoms of decompression sickness (DCS). Thus, tools detecting bubbles in the vasculature may be important for evaluating DCS. Sheep were air-compressed to 6.0 ATA (30 minutes bottom time) then rapidly decompressed to the surface. A fundus camera was quickly positioned for continuous observation of the retinal vasculature. Bubbles were observed in the retinal vasculature of 25.8% (n = 31) of the sheep. Bubble onset time ranged from 5-22 minutes post-chamber and lodge time ranged from 0-70+ minutes. Bubbles were visualized mostly in the arteries of the retinal circulation. Severe vasoconstriction was captured using red-free angiography in two sheep. In two other sheep, fluorescein angiography demonstrated occluded blood flow caused by arterial gas emboli. This study demonstrates that retinal angiography is a practical tool for real-time, noninvasive detection of bubbles in the retinal circulation, a visible window to the cerebral circulation. Thus retinal angiography may prove invaluable in the early detection of arterial gas emboli in the cerebral circulation, the resolution of which is imperative to favorable neurological outcomes. This study also presents for the first time images of bubbles in the retinal circulation associated with DCS captured by a fundus camera.

  4. Fuel system bubble dissipation device

    SciTech Connect

    Iseman, W.J.

    1987-11-03

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

  5. The Minnaert Bubble: An Acoustic Approach

    ERIC Educational Resources Information Center

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude; Leroy, Valentin

    2008-01-01

    We propose an "ab initio" introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian…

  6. Experimental study of the effect of a small bubble at the nose of a larger bubble in a Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Ikeda, E.; Maxworthy, T.

    1990-04-01

    The effect of a small air bubble attached to the nose of a much larger air bubble in a viscous liquid in a Hele-Shaw cell has been studied. The Hele-Shaw cell was tilted to an angle alpha, measured from the horizontal, so that the buoyancy force allowed the bubbles to rise. The larger bubble became elongated to a nearly elliptical shape and its velocity increased above the value for a circular bubble of the same area. For a given size of main bubble, as the size of the nose bubble decreased, the aspect ratio and velocity of the larger bubble increased. The velocity for a given size bubble could be approximated by the theory presented by Maxworthy (1986) for small values of the bubble ellipticity and large values of alpha. At small values of alpha, modification of the bubble drag by gravitational distortion could partially explain the deviation from the simpler theory.

  7. Detailed Jet Dynamics in a Collapsing Bubble

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  8. Bernoulli Suction Effect on Soap Bubble Blowing?

    NASA Astrophysics Data System (ADS)

    Davidson, John; Ryu, Sangjin

    2015-11-01

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

  9. Circulating venous bubbles in children after diving.

    PubMed

    Lemaitre, Frederic; Carturan, Daniel; Tourney-Chollet, Claire; Gardette, Bernard

    2009-02-01

    Doppler ultrasonic detection of circulating venous bubbles after a scuba dive is a useful index of decompression safety in adults, since a relationship between bubbles and the risk of decompression sickness has been documented. No study, however, has investigated circulating venous bubbles in young recreational divers after their usual dives. The aim of this study was to determine whether these bubbles would be detected in children who performed a single dive without any modification in their diving habits. Ten young recreational divers (13.1 +/- 2.3 years) performed their usual air dive. They were Doppler-monitored 20 min before the dive (12 +/- 3 m for 26 +/- 7 min) and for 60 min after surfacing, at 20-min intervals. No circulating venous bubbles were detected after the children surfaced. The results showed that during a usual shallow diving session, venous bubbles were not detected in children.

  10. Arrested Bubble Rise in a Narrow Tube

    NASA Astrophysics Data System (ADS)

    Lamstaes, Catherine; Eggers, Jens

    2016-06-01

    If a long air bubble is placed inside a vertical tube closed at the top it can rise by displacing the fluid above it. However, Bretherton found that if the tube radius, R, is smaller than a critical value Rc=0.918 ℓ_c , where ℓ_c=√{γ /ρ g} is the capillary length, there is no solution corresponding to steady rise. Experimentally, the bubble rise appears to have stopped altogether. Here we explain this observation by studying the unsteady bubble motion for Rbubble and the tube goes to zero in limit of large t like t^{-4/5} , leading to a rapid slow-down of the bubble's mean speed U ∝ t^{-2} . As a result, the total bubble rise in infinite time remains very small, giving the appearance of arrested motion.

  11. Measurements of electron avalanche formation time in W-band microwave air breakdown

    SciTech Connect

    Cook, Alan M.; Hummelt, Jason S.; Shapiro, Michael A.; Temkin, Richard J.

    2011-08-15

    We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are {approx}0.1-2 {mu}s over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

  12. Measurements of electron avalanche formation time in W-band microwave air breakdown

    NASA Astrophysics Data System (ADS)

    Cook, Alan M.; Hummelt, Jason S.; Shapiro, Michael A.; Temkin, Richard J.

    2011-08-01

    We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are ˜0.1-2 μs over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

  13. 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. ...

  14. Discrete Bubble Modeling for Cavitation Bubbles

    NASA Astrophysics Data System (ADS)

    Choi, Jin-Keun; Chahine, Georges; Hsiao, Chao-Tsung

    2007-03-01

    Dynaflow, Inc. has conducted extensive studies on non-spherical bubble dynamics and interactions with solid and free boundaries, vortical flow structures, and other bubbles. From these studies, emerged a simplified Surface Averaged Pressure (SAP) spherical bubble dynamics model and a Lagrangian bubble tracking scheme. In this SAP scheme, the pressure and velocity of the surrounding flow field are averaged on the bubble surface, and then used for the bubble motion and volume dynamics calculations. This model is implemented using the Fluent User Defined Function (UDF) as Discrete Bubble Model (DBM). The Bubble dynamics portion can be solved using an incompressible liquid modified Rayleigh-Plesset equation or a compressible liquid modified Gilmore equation. The Discrete Bubble Model is a very suitable tool for the studies on cavitation inception of foils and turbo machinery, bubble nuclei effects, noise from the bubbles, and can be used in many practical problems in industrial and naval applications associated with flows in pipes, jets, pumps, propellers, ships, and the ocean. Applications to propeller cavitation, wake signatures of waterjet propelled ships, bubble-wake interactions, modeling of cavitating jets, and bubble entrainments around a ship will be presented.

  15. Particle-bubble interaction inside a Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Mines, John M.; Lee, Sungyon; Jung, Sunghwan

    2016-08-01

    Hydrodynamic interactions between air bubbles and particles have wide applications in multiphase separation and reaction processes. In the present work, we explore the fundamental mechanism of such complex processes by studying the collision of a single bubble with a fixed solid particle inside a Hele-Shaw cell. Physical experiments show that an air bubble either splits or slides around the particle depending on the initial transverse distance between the bubble and particle centroids. An air bubble splits into two daughter bubbles at small transverse distances, and slides around the particle at large distances. In order to predict the critical transverse distance that separates these two behaviors, we also develop a theoretical model by estimating the rate of the bubble volume transfer from one side of the particle to the other based on Darcy's law, which is in good agreement with experiments.

  16. Particle-bubble interaction inside a Hele-Shaw cell.

    PubMed

    Zhang, Peng; Mines, John M; Lee, Sungyon; Jung, Sunghwan

    2016-08-01

    Hydrodynamic interactions between air bubbles and particles have wide applications in multiphase separation and reaction processes. In the present work, we explore the fundamental mechanism of such complex processes by studying the collision of a single bubble with a fixed solid particle inside a Hele-Shaw cell. Physical experiments show that an air bubble either splits or slides around the particle depending on the initial transverse distance between the bubble and particle centroids. An air bubble splits into two daughter bubbles at small transverse distances, and slides around the particle at large distances. In order to predict the critical transverse distance that separates these two behaviors, we also develop a theoretical model by estimating the rate of the bubble volume transfer from one side of the particle to the other based on Darcy's law, which is in good agreement with experiments. PMID:27627397

  17. Nonlinear ultrasonic waves in bubbly liquids with nonhomogeneous bubble distribution: Numerical experiments.

    PubMed

    Vanhille, Christian; Campos-Pozuelo, Cleofé

    2009-06-01

    This paper deals with the nonlinear propagation of ultrasonic waves in mixtures of air bubbles in water, but for which the bubble distribution is nonhomogeneous. The problem is modelled by means of a set of differential equations which describes the coupling of the acoustic field and bubbles vibration, and solved in the time domain via the use and adaptation of the SNOW-BL code. The attenuation and nonlinear effects are assumed to be due to the bubbles exclusively. The nonhomogeneity of the bubble distribution is introduced by the presence of bubble layers (or clouds) which can act as acoustic screens, and alters the behaviour of the ultrasonic waves. The effect of the spatial distribution of bubbles on the nonlinearity of the acoustic field is analyzed. Depending on the bubble density, dimension, shape, and position of the layers, its effects on the acoustic field change. Effects such as shielding and resonance of the bubbly layers are especially studied. The numerical experiments are carried out in two configurations: linear and nonlinear, i.e. for low and high excitation pressure amplitude, respectively, and the features of the phenomenon are compared. The parameters of the medium are chosen such as to reproduce air bubbly water involved in the stable cavitation process.

  18. Light scattering by bubbles in a bubble chamber.

    PubMed

    Withrington, R J

    1968-01-01

    A discussion of the angular scattering expected from small bubbles in liquids of refractive indices 1.1 and 1.025 is given ogether with the inverse, i.e., of small spheres of the liquids in air. The similarities between the two scattering functions are compared with a view to the simulation of bubble chamber tracks using readily available materials. Fraunhofer scattering is significant on axis while larger angle scattering is geometrical. Some experimental verification of the scattering functions is also reported.

  19. The Effect of the Saharan Air Layer on the Formation of Hurricane Isabel (2003) Simulated with AIRS Data

    NASA Technical Reports Server (NTRS)

    Wu, iguang; Braun, Scott A.; Qu, John J.

    2006-01-01

    The crucial physics of how the atmosphere really accomplishes the tropical cyclogenesis process is still poorly understood. The presence of the Saharan Air Layer (SAL), an elevated mixed layer of warm and dry air that extends from Africa to the tropical Atlantic and contains a substantial amount of mineral dust, adds more complexity to the tropical cyclogenesis process in the Atlantic basin. The impact of the SAL on tropical cyclogenesis is still uncertain. Karyampudi and Carlson (1988) conclude that a strong SAL can potentially aid tropical cyclone development while Dunion and Velden (2004) argue that the SAL generally inhibits tropical cyclogenesis and intensification. Advancing our understanding of the physical mechanisms of tropical cyclogenesis and the associated roles of the SAL strongly depends on the improvement in the observations over the data-sparse ocean areas. After the Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU), and the microwave Humidity Sounder of Brazil (HSB) were launched with the NASA Aqua satellite in 2002, new data products retrieved from the AIRS suite became available for studying the effect of the warm, dry air mass associated with the SAL (referred to as the thermodynamic effect). The vertical profiles of the AIRS retrieved temperature and humidity provide an unprecedented opportunity to examine the thermodynamic effect of the SAL. The observational data can be analyzed and assimilated into numerical models, in which the model thermodynamic state is allowed to relax to the observed state from AIRS data. The objective of this study is to numerically demonstrate that the thermodynamic effect of the SAL on the formation of Hurricane Isabel (2003) can be largely simulated through nudging of the AIRS data.

  20. Liquid jet pumped by rising gas bubbles

    NASA Technical Reports Server (NTRS)

    Hussain, N. A.; Siegel, R.

    1975-01-01

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

  1. Videotaping the Lifespan of a Soap Bubble.

    ERIC Educational Resources Information Center

    Ramme, Goran

    1995-01-01

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

  2. Bubbles and foams in microfluidics.

    PubMed

    Huerre, Axel; Miralles, Vincent; Jullien, Marie-Caroline

    2014-09-28

    Microfluidics offers great tools to produce highly-controlled dispersions of gas into liquid, from isolated bubbles to organized microfoams. Potential technological applications are manifold, from novel materials to scaffolds for tissue engineering or enhanced oil recovery. More fundamentally, microfluidics makes it possible to investigate the physics of complex systems such as foams at scales where the capillary forces become dominant, in model experiments involving few well-controlled parameters. In this context, this review does not have the ambition to detail in a comprehensive manner all the techniques and applications involving bubbles and foams in microfluidics. Rather, it focuses on particular consequences of working at the microscale, under confinement, and hopes to provide insight into the physics of such systems. The first part of this work focuses on bubbles, and more precisely on (i) bubble generation, where the confinement can suppress capillary instabilities while inertial effects may play a role, and (ii) bubble dynamics, paying special attention to the lubrication film between bubble and wall and the influence of confinement. The second part addresses the formation and dynamics of microfoams, emphasizing structural differences from macroscopic foams and the influence of the confinement.

  3. Moving with bubbles: a review of the interactions between bubbles and the microorganisms that surround them.

    PubMed

    Walls, Peter L L; Bird, James C; Bourouiba, Lydia

    2014-12-01

    Bubbles are ubiquitous in biological environments, emerging during the complex dynamics of waves breaking in the open oceans or being intentionally formed in bioreactors. From formation, through motion, until death, bubbles play a critical role in the oxygenation and mixing of natural and artificial ecosystems. However, their life is also greatly influenced by the environments in which they emerge. This interaction between bubbles and microorganisms is a subtle affair in which surface tension plays a critical role. Indeed, it shapes the role of bubbles in mixing or oxygenating microorganisms, but also determines how microorganisms affect every stage of the bubble's life. In this review, we guide the reader through the life of a bubble from birth to death, with particular attention to the microorganism-bubble interaction as viewed through the lens of fluid dynamics. PMID:25096288

  4. Moving with bubbles: a review of the interactions between bubbles and the microorganisms that surround them.

    PubMed

    Walls, Peter L L; Bird, James C; Bourouiba, Lydia

    2014-12-01

    Bubbles are ubiquitous in biological environments, emerging during the complex dynamics of waves breaking in the open oceans or being intentionally formed in bioreactors. From formation, through motion, until death, bubbles play a critical role in the oxygenation and mixing of natural and artificial ecosystems. However, their life is also greatly influenced by the environments in which they emerge. This interaction between bubbles and microorganisms is a subtle affair in which surface tension plays a critical role. Indeed, it shapes the role of bubbles in mixing or oxygenating microorganisms, but also determines how microorganisms affect every stage of the bubble's life. In this review, we guide the reader through the life of a bubble from birth to death, with particular attention to the microorganism-bubble interaction as viewed through the lens of fluid dynamics.

  5. Single Bubble Sonoluminescence

    NASA Astrophysics Data System (ADS)

    Farley, Jennifer; Hough, Shane

    2003-05-01

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

  6. Characteristics of micro-nano bubbles and potential application in groundwater bioremediation.

    PubMed

    Li, Hengzhen; Hu, Liming; Song, Dejun; Lin, Fei

    2014-09-01

    Content of oxygen in water is a critical factor in increasing bioremediation efficiency for contaminated groundwater. Micro-nano bubbles (MNBs) injection seems to be an effective technique for increasing oxygen in water compared with traditional air sparging technology with macrobubbles. Micro-nano bubbles have larger interfacial area, higher inner pressure and density, and lower rising velocity in water, superior to that of macrobubbles. In this paper, MNBs with diameters ranging from 500 nm to 100 microm are investigated, with a specific focus on the oxygen mass transfer coefficient from inner bubbles to surrounding water. The influence of surfactant on the bubbles formation and dissolution is studied as well. The stability of MNBs is further investigated by means of zeta potential measurements and rising velocity analysis. The results show that MNBs can greatly increase oxygen content in water. Higher surfactant concentration in water will decrease the bubbles size, reduce the dissolution rate, and increase the zeta potential. Moreover, MNBs with greater zeta potential value tend to be more stable. Besides, the low rising velocity of MNBs contributes to the long stagnation in water. It is suggested that micro-nano bubble aeration, a potential in groundwater remediation technology, can largely enhance the bioremediation effect.

  7. Evidence for Air-Seeding: Watching the Formation of Embolism in Conifer Xylem

    PubMed Central

    Mayr, S.; Kartusch, B.; Kikuta, S.

    2016-01-01

    Water transport in plants is based on a metastable system as the xylem “works” at negative water potentials (ψ). At critically low ψ, water columns can break and cause embolism. According to the air-seeding hypothesis, this occurs by air entry via the pits. We studied the formation of embolism in dehydrating xylem sections of Juniperus virginiana (Cupressaceae), which were monitored microscopically and via ultrasonic emission analyses. After replacement of water by air in outer tracheid layers, a complex movement of air-water menisci into tracheids was found. With decreasing ψ, pits started to aspirate and the speed of menisci movements increased. In one experiment, an airseeding event could be detected at a pit. The onset of ultrasonic activity was observed when pits started to close, and ultrasonic emission ceased at intense dehydration. Experiments clearly indicated that predictions of the air-seeding hypothesis are correct: At low ψ, pit mechanisms to prevent air entry failed and air spread into tracheids. ψ fluctuations caused complex movements of air-water menisci and pits, and at low ψ, air-seeding caused ultrasonic emissions. Main insights are presented in a video.

  8. Effect of pressure on structure and NO sub X formation in CO-air diffusion flames

    NASA Technical Reports Server (NTRS)

    Maahs, H. G.; Miller, I. M.

    1979-01-01

    A study was made of nitric oxide formation in a laminar CO-air diffusion flame over a pressure range from 1 to 50 atm. The carbon monoxide (CO) issued from a 3.06 mm diameter port coaxially into a coflowing stream of air confined within a 20.5 mm diameter chimney. Nitric oxide concentrations from the flame were measured at two carbon monoxide (fuel) flow rates: 73 standard cubic/min and 146 sccm. Comparison of the present data with data in the literature for a methane-air diffusion flame shows that for flames of comparable flame height (8 to 10 mm) and pseudoequivalence ratio (0.162), the molar emission index of a CO-air flame is significantly greater than that of a methane-air flame.

  9. Bubble chamber as a trace chemical detector

    SciTech Connect

    Luo, X.; McCreary, E.I.; Atencio, J.H.; McCown, A.W.; Sander, R.K.

    1998-08-01

    A novel concept for trace chemical analysis in liquid has been demonstrated. The technique utilizes light absorption in a superheated liquid. Although a superheated liquid is thermodynamically unstable, a high degree of superheating can be dynamically achieved for a short period of time. During this time the superheated liquid is extremely sensitive to boiling at nucleation sites produced by energy deposition. Observation of bubbles in the superheated liquid in some sense provides amplification of the initial energy deposition. Bubble chambers containing superheated liquids have been used to detect energetic particles; now a bubble chamber is used to detect a trace chemical in superheated liquid propane by observing bubble formation initiated by optical absorption. Crystal violet is used as a test case and can be detected at the subpart-per-10{sup 12} level by using a Nd:YAG laser. The mechanism for bubble formation and ideas for further improvement are discussed. {copyright} 1998 Optical Society of America

  10. Bubble chamber as a trace chemical detector.

    PubMed

    Luo, X; McCreary, E I; Atencio, J H; McCown, A W; Sander, R K

    1998-08-20

    A novel concept for trace chemical analysis in liquids has been demonstrated. The technique utilizes light absorption in a superheated liquid. Although a superheated liquid is thermodynamically unstable, a high degree of superheating can be dynamically achieved for a short period of time. During this time the superheated liquid is extremely sensitive to boiling at nucleation sites produced by energy deposition. Observation of bubbles in the superheated liquid in some sense provides amplification of the initial energy deposition. Bubble chambers containing superheated liquids have been used to detect energetic particles; now a bubble chamber is used to detect a trace chemical in superheated liquid propane by observing bubble formation initiated by optical absorption. Crystal violet is used as a test case and can be detected at the subpart-per-10(12) level by using a Nd:YAG laser. The mechanism for bubble formation and ideas for further improvement are discussed.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Nunn, J. A.

    2013-12-01

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

  13. Molecular emission from single-bubble sonoluminescence.

    PubMed

    Didenko, Y T; McNamara, W B; Suslick, K S

    2000-10-19

    Ultrasound can drive a single gas bubble in water into violent oscillation; as the bubble is compressed periodically, extremely short flashes of light (about 100 ps) are generated with clock-like regularity. This process, known as single-bubble sonoluminescence, gives rise to featureless continuum emission in water (from 200 to 800 nm, with increasing intensity into the ultraviolet). In contrast, the emission of light from clouds of cavitating bubbles at higher acoustic pressures (multi-bubble sonoluminescence) is dominated by atomic and molecular excited-state emission at much lower temperatures. These observations have spurred intense effort to uncover the origin of sonoluminescence and to generalize the conditions necessary for its creation. Here we report a series of polar aprotic liquids that generate very strong single-bubble sonoluminescence, during which emission from molecular excited states is observed. Previously, single-bubble sonoluminescence from liquids other than water has proved extremely elusive. Our results give direct proof of the existence of chemical reactions and the formation of molecular excited states during single-bubble cavitation, and provide a spectroscopic link between single- and multi-bubble sonoluminescence.

  14. OH Production Enhancement in Bubbling Pulsed Discharges

    SciTech Connect

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

    2010-10-13

    The generation of active species, such as H{sub 2}O{sub 2}, O{sup *}, OH*, HO{sub 2}*, O{sub 3}, N{sub 2}{sup *}, etc, produced in aqueous solutions by HV pulsed discharges was studied in order to find the most efficient way in waste water treatment taking into account that these species are almost stronger oxidizers than ozone. Plasma was generated inside gas bubbles formed by the argon, air and oxygen gas flow between the special designed electrodes. The pulse width and pulse frequency influence was studied in order to increase the efficiency of the OH active species formation. The produced active species were investigated by optical emission spectroscopy and correlated with electrical parameters of the discharges (frequency, pulse width, amplitude, and rise and decay time).

  15. Excess air formation as a mechanism for delivering oxygen to groundwater

    NASA Astrophysics Data System (ADS)

    Mächler, L.; Peter, S.; Brennwald, M. S.; Kipfer, R.

    2013-10-01

    The temporal dynamics and spatial distribution of the concentrations of dissolved gases (He, Ar, Kr, N2, O2, and CO2) in an infiltrating groundwater system fed by the peri-alpine river Thur (Switzerland) were analyzed before, during and after a single, well-defined flood event. The analysis was based on measurements taken in five different groundwater observation wells that were located approximately 10 m apart and tapped the same groundwater body, but were situated in three different riparian zones. The input of O2 into the groundwater as a result of the formation of excess air was found to be of the same order of magnitude as that resulting from the advection of river water, although the amount of excess air formed and the amount of O2 delivered varied significantly among the riparian zones. The results suggest that the input of O2 into groundwater as a result of excess air formation is controlled not only by the hydraulic conditions prevailing in the river and the groundwater, but also by the thickness of the confining bed at the top of the aquifer. The sandy gravel aquifer itself is too coarse to trap a significant amount of air during the water level rise. The clay layer confining the aquifer, however, acts as a barrier hindering the escape of air from the subsoil to the surface, and hence is likely to be a key factor controlling the trapping and dissolution of air in groundwater.

  16. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  17. Bubble Detachment in Variable Gravity Under the Influence of a Non-Uniform Electric Field

    NASA Technical Reports Server (NTRS)

    Chang, Shinan; Herman, Cila; Iacona, Estelle

    2002-01-01

    The objective of the study reported in this paper is to investigate the effects of variable, reduced gravity on the formation and detachment behavior of individual air bubbles under the influence of a non-uniform electric field. For this purpose, variable gravity experiments were carried out in parabolic nights. The non-uniform electric field was generated by a spherical electrode and a plate electrode. The effect of the magnitude of the non-uniform electric field and gravity level on bubble formation, development and detachment at an orifice was investigated. An image processing code was developed that allows the measurement of bubble volume, dimensions and contact angle at detachment. The results of this research can be used to explore the possibility of enhancing boiling heat transfer in the variable and low gravity environments by substituting the buoyancy force with a force induced by the electric field. The results of experiments and measurements indicate that the level of gravity significantly affects bubble shape, size and frequency. The electric field magnitude also influences bubble detachment, however, its impact is not as profound as that of variable gravity for the range of electric field magnitudes investigated in the present study.

  18. The interaction of positive streamers with bubbles floating on a liquid surface

    NASA Astrophysics Data System (ADS)

    Akishev, Yu; Arefi-Khonsari, F.; Demir, A.; Grushin, M.; Karalnik, V.; Petryakov, A.; Trushkin, N.

    2015-12-01

    This paper reports the results of a preliminary investigation on the interaction of a streamer discharge in air with bubbles filled with air and floating on a liquid surface. The bubbles are formed of tap water and transformer oil. It was shown that the strike of the streamer in a bubble is followed by the full bubble destroying. However, scenarios of the streamer discharge interaction with a conductive water bubble and dielectric oil bubble are different in their concrete details. A positive streamer smoothly and slowly slides on an external surface of a water bubble, but the streamer striking in an oil bubble quickly perforates it and penetrates into the bubble. The mechanisms for water and oil bubble destroying are discussed. The applicability of the results obtained to plasma-liquid systems based on the use of foam is discussed as well.

  19. Critical angle refractometry and sizing of bubble clouds.

    PubMed

    Onofri, Fabrice; Krysiek, Mariusz; Mroczka, Janusz

    2007-07-15

    The principle of the critical angle refractometry and sizing technique is extended to characterize the size distribution and the mean refractive index of clouds of bubbles. For a log-normal bubble-size distribution, simulations show that the mean size, the relative width of the size distribution, and the mean refractive index of the bubbles have a particular and easily identified influence on the critical scattering patterns. Preliminary experimental results on air bubble/water flows clearly demonstrate the potential and robustness of this new technique for bubbly flow characterization.

  20. Steady State Vapor Bubble in Pool Boiling.

    PubMed

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

    2016-02-03

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

  1. Steady State Vapor Bubble in Pool Boiling

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  2. Steady State Vapor Bubble in Pool Boiling

    PubMed Central

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

    2016-01-01

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

  3. A High-Latitude Winter Continental Low Cloud Feedback Suppresses Arctic Air Formation in Warmer Climates

    NASA Astrophysics Data System (ADS)

    Cronin, T.; Tziperman, E.; Li, H.

    2015-12-01

    High latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. It has also been found that the high-latitude lapse rate feedback plays an important role in Arctic amplification of climate change in climate model simulations, but we have little understanding of why lapse rates at high latitudes change so strongly with warming. To better understand these problems, we study Arctic air formation - the process by which a high-latitude maritime air mass is advected over a continent during polar night, cooled at the surface by radiation, and transformed into a much colder continental polar air mass - and its sensitivity to climate warming. We use a single-column version of the WRF model to conduct two-week simulations of the cooling process across a wide range of initial temperature profiles and microphysics schemes, and find that a low cloud feedback suppresses Arctic air formation in warmer climates. This cloud feedback consists of an increase in low cloud amount with warming, which shields the surface from radiative cooling, and increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ~10 days for initial maritime surface air temperatures of 20 oC. Given that this is about the time it takes an air mass starting over the Pacific to traverse the north American continent, this suggests that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates. We find that CMIP5 climate model runs show large increases in cloud water path and surface cloud longwave forcing in warmer climates, consistent with the proposed low-cloud feedback

  4. Dynamics of Single Hydrogen Bubbles at a Platinum Microelectrode.

    PubMed

    Yang, Xuegeng; Karnbach, Franziska; Uhlemann, Margitta; Odenbach, Stefan; Eckert, Kerstin

    2015-07-28

    Bubble dynamics, including the formation, growth, and detachment, of single H2 bubbles was studied at a platinum microelectrode during the electrolysis of 1 M H2SO4 electrolyte. The bubbles were visualized through a microscope by a high-speed camera. Electrochemical measurements were conducted in parallel to measure the transient current. The periodic current oscillations, resulting from the periodic formation and detachment of single bubbles, allow the bubble lifetime and size to be predicted from the transient current. A comparison of the bubble volume calculated from the current and from the recorded bubble image shows a gas evolution efficiency increasing continuously with the growth of the bubble until it reaches 100%. Two different substrates, glass and epoxy, were used to embed the Pt wire. While nearly no difference was found with respect to the growth law for the bubble radius, the contact angle differs strongly for the two types of cell. Data provided for the contact point evolution further complete the image of single hydrogen bubble growth. Finally, the velocity field driven by the detached bubble was measured by means of PIV, and the effects of the convection on the subsequent bubble were evaluated.

  5. Dynamics of Single Hydrogen Bubbles at a Platinum Microelectrode.

    PubMed

    Yang, Xuegeng; Karnbach, Franziska; Uhlemann, Margitta; Odenbach, Stefan; Eckert, Kerstin

    2015-07-28

    Bubble dynamics, including the formation, growth, and detachment, of single H2 bubbles was studied at a platinum microelectrode during the electrolysis of 1 M H2SO4 electrolyte. The bubbles were visualized through a microscope by a high-speed camera. Electrochemical measurements were conducted in parallel to measure the transient current. The periodic current oscillations, resulting from the periodic formation and detachment of single bubbles, allow the bubble lifetime and size to be predicted from the transient current. A comparison of the bubble volume calculated from the current and from the recorded bubble image shows a gas evolution efficiency increasing continuously with the growth of the bubble until it reaches 100%. Two different substrates, glass and epoxy, were used to embed the Pt wire. While nearly no difference was found with respect to the growth law for the bubble radius, the contact angle differs strongly for the two types of cell. Data provided for the contact point evolution further complete the image of single hydrogen bubble growth. Finally, the velocity field driven by the detached bubble was measured by means of PIV, and the effects of the convection on the subsequent bubble were evaluated. PMID:26133052

  6. The bubble coalescence model of radiation blistering

    NASA Astrophysics Data System (ADS)

    Yadava, R. D. S.

    1981-05-01

    The existence of overpressurized gas bubbles, and a suitable mechanism for bubble growth during low temperature ion implantations, are the essential ingredients for the validity of a gas-driven blister formation mechanism. In this paper, taking into account the difference between the formation energy of helium interstitials and the free energy change of a bubble per helium atom added, we have theoretically shown that such bubbles indeed exist, and their growth is driven by their bias for vacancies and anti-bias for interstitials which arise because of the overpressure-induced compressive stress field around them. The relations for helium density in bubbles and the bubble overpressure are derived. The role of interbubble interaction and the effect of bubbles on the elastic properties of the material have been taken into account to determine the dose dependence of the integrated lateral stress and the critical conditions for interbubble coalescence/fracture. It is shown that the observed sublinearity and the relief of integrated lateral stress are a natural consequence of the attractive interbubble interaction and do not uniquely relate to the blister formation as considered in the stress model. The derived conditions for coalescence agree well with the available data. It is argued that the present treatment provides a sound theoretical basis for the gas pressure model of radiation blistering.

  7. Forces on ellipsoidal bubbles in a turbulent shear layer

    NASA Astrophysics Data System (ADS)

    Ford, Barry; Loth, Eric

    1998-01-01

    The objective of this research was to gain fundamental knowledge of the drag and lift forces on ellipsoidal air bubbles in water in a turbulent flow. This was accomplished by employing a cinematic two-phase particle image velocimetry (PIV) system to evaluate bubbly flow in a two-stream, turbulent, planar free shear layer of filtered tap water. Ellipsoidal air bubbles with nominal diameters from 1.5 to 4.5 mm were injected directly into the shear layer through a single slender tube. The cinematic PIV allowed for high resolution of the unsteady liquid velocity vector field. Triple-pulsed bubble images were obtained in a temporal sequence, such that the bubble size and bubble trajectory could be accurately determined. The bubble's oscillation characteristics, velocity, acceleration, and buoyancy force were obtained from the trajectory data. A bubble dynamic equation was then applied to allow determination of the time-evolving lift and drag forces acting upon bubbles within the shear layer. The results indicate that for a fixed bubble diameter (and fixed Bond and Morton numbers), the drag coefficient decreases for an increasing Reynolds number. This is fundamentally different than the increasing drag coefficient trend seen for ellipsoidal bubbles rising in quiescent baths for increasing diameter (and increasing Bond number), but is qualitatively consistent with the trend for spherical bubbles. A new empirical expression for the dependence of the drag coefficient on Reynolds number for air bubbles in tap water for both quiescent and turbulent flows is constructed herein. Finally, the instantaneous side forces measured in this study were dominated by the inherent deformation-induced vortex shedding of the bubble wake rather than the inviscid lift force based on the background fluid vorticity.

  8. Daughter bubble cascades produced by folding of ruptured thin films.

    PubMed

    Bird, James C; de Ruiter, Riëlle; Courbin, Laurent; Stone, Howard A

    2010-06-10

    Thin liquid films, such as soap bubbles, have been studied extensively for over a century because they are easily formed and mediate a wide range of transport processes in physics, chemistry and engineering. When a bubble on a liquid-gas or solid-gas interface (referred to herein as an interfacial bubble) ruptures, the general expectation is that the bubble vanishes. More precisely, the ruptured thin film is expected to retract rapidly until it becomes part of the interface, an event that typically occurs within milliseconds. The assumption that ruptured bubbles vanish is central to theories on foam evolution and relevant to health and climate because bubble rupture is a source for aerosol droplets. Here we show that for a large range of fluid parameters, interfacial bubbles can create numerous small bubbles when they rupture, rather than vanishing. We demonstrate, both experimentally and numerically, that the curved film of the ruptured bubble can fold and entrap air as it retracts. The resulting toroidal geometry of the trapped air is unstable, leading to the creation of a ring of smaller bubbles. The higher pressure associated with the higher curvature of the smaller bubbles increases the absorption of gas into the liquid, and increases the efficiency of rupture-induced aerosol dispersal.

  9. Daughter bubble cascades produced by folding of ruptured thin films.

    PubMed

    Bird, James C; de Ruiter, Riëlle; Courbin, Laurent; Stone, Howard A

    2010-06-10

    Thin liquid films, such as soap bubbles, have been studied extensively for over a century because they are easily formed and mediate a wide range of transport processes in physics, chemistry and engineering. When a bubble on a liquid-gas or solid-gas interface (referred to herein as an interfacial bubble) ruptures, the general expectation is that the bubble vanishes. More precisely, the ruptured thin film is expected to retract rapidly until it becomes part of the interface, an event that typically occurs within milliseconds. The assumption that ruptured bubbles vanish is central to theories on foam evolution and relevant to health and climate because bubble rupture is a source for aerosol droplets. Here we show that for a large range of fluid parameters, interfacial bubbles can create numerous small bubbles when they rupture, rather than vanishing. We demonstrate, both experimentally and numerically, that the curved film of the ruptured bubble can fold and entrap air as it retracts. The resulting toroidal geometry of the trapped air is unstable, leading to the creation of a ring of smaller bubbles. The higher pressure associated with the higher curvature of the smaller bubbles increases the absorption of gas into the liquid, and increases the efficiency of rupture-induced aerosol dispersal. PMID:20535206

  10. Dynamics of charged hemispherical soap bubbles

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  11. Format and basic geometry of a perspective display of air traffic for the cockpit

    NASA Technical Reports Server (NTRS)

    Mcgreevy, Michael Wallace; Ellis, Stephen R.

    1991-01-01

    The design and implementation of a perspective display of air traffic for the cockpit is discussed. Parameters of the perspective are variable and interactive so that the appearance of the projected image can be widely varied. This approach makes allowances for exploration of perspective parameters and their interactions. The display was initially used to study the cases of horizontal maneuver biases found in experiments involving a plan view air traffic display format. Experiments to determine the effect of perspective geometry on spatial judgements have evolved from the display program. Several scaling techniques and other adjustments to the perspective are used to tailor the geometry for effective presentation of 3-D traffic situations.

  12. 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

  13. 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.

  14. Neutron Detection via Bubble Chambers

    SciTech Connect

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

    2005-10-06

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

  15. Fuel Spray and Flame Formation in a Compression-Ignition Engine Employing Air Flow

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1937-01-01

    The effects of air flow on fuel spray and flame formation in a high-speed compression-ignition engine have been investigated by means of the NACA combustion apparatus. The process was studied by examining high-speed motion pictures taken at the rate of 2,200 frames a second. The combustion chamber was of the flat-disk type used in previous experiments with this apparatus. The air flow was produced by a rectangular displacer mounted on top of the engine piston. Three fuel-injection nozzles were tested: a 0.020-inch single-orifice nozzle, a 6-orifice nozzle, and a slit nozzle. The air velocity within the combustion chamber was estimated to reach a value of 425 feet a second. The results show that in no case was the form of the fuel spray completely destroyed by the air jet although in some cases the direction of the spray was changed and the spray envelope was carried away by the moving air. The distribution of the fuel in the combustion chamber of a compression-ignition engine can be regulated to some extent by the design of the combustion chamber, by the design of the fuel-injection nozzle, and by the use of air flow.

  16. Soap Bubbles and Logic.

    ERIC Educational Resources Information Center

    Levine, Shellie-helane; And Others

    1986-01-01

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

  17. Spherical bubble motion in a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Felton, Keith; Loth, Eric

    2001-09-01

    Monodisperse dilute suspensions of spherical air bubbles in a tap-water turbulent vertical boundary layer were experimentally studied to note their motion and distribution. Bubbles with diameters of 0.37-1.2 mm were injected at various transverse wall-positions for free-stream velocities between 0.4 and 0.9 m/s. The bubbles were released from a single injector at very low frequencies such that two-way coupling and bubble-bubble interaction were negligible. The experimental diagnostics included ensemble-averaged planar laser intensity profiles for bubble concentration distribution, as well as Cinematic Particle Image Velocimetry with bubble tracking for bubble hydrodynamic forces. A variety of void distributions within the boundary layer were found. For example, there was a tendency for bubbles to collect along the wall for higher Stokes number conditions, while the lower Stokes number conditions produced Gaussian-type profiles throughout the boundary layer. In addition, three types of bubble trajectories were observed—sliding bubbles, bouncing bubbles, and free-dispersion bubbles. Instantaneous liquid forces acting on individual bubbles in the turbulent flow were also obtained to provide the drag and lift coefficients (with notable experimental uncertainty). These results indicate that drag coefficient decreases with increasing Reynolds number as is conventionally expected but variations were observed. In general, the instantaneous drag coefficient (for constant bubble Reynolds number) tended to be reduced as the turbulence intensity increased. The averaged lift coefficient is higher than that given by inviscid theory (and sometimes even that of creeping flow theory) and tends to decrease with increasing bubble Reynolds number.

  18. Modeling of bubble dynamics in relation to medical applications

    SciTech Connect

    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.

  19. Colliding interstellar bubbles in the direction of l = 54°

    NASA Astrophysics Data System (ADS)

    Zychová, L.; Ehlerová, S.

    2016-10-01

    Context. Interstellar bubbles are structures in the interstellar medium with diameters of a few to tens of parsecs. Their progenitors are stellar winds, intense radiation of massive stars, or supernova explosions. Star formation and young stellar objects are commonly associated with these structures. Aims: We compare infrared observations of bubbles N115, N116 and N117 with atomic, molecular and ionized gas in this region. While determining the dynamical properties of the bubbles, we also look into their ambient environment to understand their formation in a wider context. Methods: To find bubbles in HI (Very Large Array Galactic Plane Survey) and CO data (Galactic Ring Survey), we used the images from the Galactic Legacy Infrared Mid-Plane Survey. We manually constructed masks based on the appearance of the bubbles in the IR images and applied them to the HI and CO data. We determined kinematic distance, size, expansion velocity, mass, original density of the maternal cloud, age, and energy input of the bubbles. Results: We identified two systems of bubbles: the first, the background system, is formed by large structures G053.9+0.2 and SNR G054.4-0.3 and the infrared bubble N116+117. The second, the foreground system, includes the infrared bubble N115 and two large HI bubbles, which we discovered in the HI data. Both systems are independent, lying at different distances, but look similar. They are both formed by two large colliding bubbles with radii around 20-30 pc and ages of a few million years. A younger and smaller ( 4 pc, less than a million years) infrared bubble lies at the position of the collision. Conclusions: We found that both infrared bubbles N115 and N116+117 are associated with the collisions of larger and older bubbles. We propose that such collisions increase the probability of further star formation, probably by squeezing the interstellar material, suggesting that they are an important mechanism for star formation.

  20. Preheating in bubble collisions

    SciTech Connect

    Zhang Jun; Piao Yunsong

    2010-08-15

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

  1. Low clouds suppress Arctic air formation and amplify high-latitude continental winter warming

    PubMed Central

    Cronin, Timothy W.; Tziperman, Eli

    2015-01-01

    High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. We use an idealized single-column atmospheric model across a range of conditions to study the polar night process of air mass transformation from high-latitude maritime air, with a prescribed initial temperature profile, to much colder high-latitude continental air. We find that a low-cloud feedback—consisting of a robust increase in the duration of optically thick liquid clouds with warming of the initial state—slows radiative cooling of the surface and amplifies continental warming. This low-cloud feedback increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature, effectively suppressing Arctic air formation. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ∼10 d for initial maritime surface air temperatures of 20 °C. These results, supplemented by an analysis of Coupled Model Intercomparison Project phase 5 climate model runs that shows large increases in cloud water path and surface cloud longwave forcing in warmer climates, suggest that the “lapse rate feedback” in simulations of anthropogenic climate change may be related to the influence of low clouds on the stratification of the lower troposphere. The results also indicate that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates. PMID:26324919

  2. Low clouds suppress Arctic air formation and amplify high-latitude continental winter warming.

    PubMed

    Cronin, Timothy W; Tziperman, Eli

    2015-09-15

    High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. We use an idealized single-column atmospheric model across a range of conditions to study the polar night process of air mass transformation from high-latitude maritime air, with a prescribed initial temperature profile, to much colder high-latitude continental air. We find that a low-cloud feedback--consisting of a robust increase in the duration of optically thick liquid clouds with warming of the initial state--slows radiative cooling of the surface and amplifies continental warming. This low-cloud feedback increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature, effectively suppressing Arctic air formation. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ∼ 10 d for initial maritime surface air temperatures of 20 °C. These results, supplemented by an analysis of Coupled Model Intercomparison Project phase 5 climate model runs that shows large increases in cloud water path and surface cloud longwave forcing in warmer climates, suggest that the "lapse rate feedback" in simulations of anthropogenic climate change may be related to the influence of low clouds on the stratification of the lower troposphere. The results also indicate that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates.

  3. Interaction of equal-size bubbles in shear flow.

    PubMed

    Prakash, Jai; Lavrenteva, Olga M; Byk, Leonid; Nir, Avinoam

    2013-04-01

    The inertia-induced forces on two identical spherical bubbles in a simple shear flow at small but finite Reynolds number, for the case when the bubbles are within each other's inner viscous region, are calculated making use of the reciprocal theorem. This interaction force is further employed to model the dynamics of air bubbles injected to a viscous fluid sheared in a Couette device at the first shear flow instability where the bubbles are trapped inside the stable Taylor vortex. It was shown that, during a long time scale, the inertial interaction between the bubbles in the primary shear flow drives them away from each other and, as a result, equal-size bubbles eventually assume an ordered string with equal separation distances between all neighbors. We report on experiments showing the dynamic evolution of various numbers of bubbles. The results of the theory are in good agreement with the experimental observations.

  4. Effects of Air-Fuel Spray and Flame Formation in a Compression-Ignition Engine

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1937-01-01

    High-speed motion pictures were taken at the rate of 2,500 frames per second of the fuel spray and flame formation in the combustion chamber of the NACA combustion apparatus. The compression ratio was 13.2 and the speed 1,500 revolutions per minute. An optical indicator was used to record the time-pressure relationship in the combustion chamber. The air-fuel ratio was varied from 10.4 to 365. The results showed that as the air-fuel ratio was increased definite stratification of the charge occurred in the combustion chamber even though moderate air flow existed. The results also showed the rate of vapor diffusion to be relatively slow.

  5. Brut: Automatic bubble classifier

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  6. Bursting the Taylor cone bubble

    NASA Astrophysics Data System (ADS)

    Pan, Zhao; Truscott, Tadd

    2014-11-01

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

  7. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  8. Interactions of fire emissions and urban pollution over California: Ozone formation and air quality simulations

    NASA Astrophysics Data System (ADS)

    Singh, H. B.; Cai, C.; Kaduwela, A.; Weinheimer, A.; Wisthaler, A.

    2012-09-01

    An instrumented DC-8 aircraft was employed to perform airborne observations in rural and urban environs of California during the summer 2008 NASA ARCTAS-CARB campaign. The fortuitous occurrence of large wildfire episodes in Northern California allowed for studies of fire emissions, their composition, and their interactions with rural and urban air. Relative to CO, emissions of HCN were shown to vary non-linearly with fire characteristics while those of CH3CN were nearly unchanged, making the latter a superior quantitative tracer of biomass combustion. Although some fire plumes over California contained little NOx and virtually no O3 enhancement, others contained ample VOCs and sufficient NOx, largely from urban influences, to result in significant ozone formation. The highest observed O3 mixing ratios (170 ppb) were also in fire-influenced urban air masses. Attempts to simulate these interactions using CMAQ, a high-resolution state of the art air quality model, were only minimally successful and indicated several shortcomings in simulating fire emission influences on urban smog formation. A variety of secondary oxidation products (e.g. O3, PAN, HCHO) were substantially underestimated in fire-influenced air masses. Available data involving fire plumes and anthropogenic pollution interactions are presently quite sparse and additional observational and mechanistic studies are needed.

  9. Experimental investigation on flame pattern formations of DME-air mixtures in a radial microchannel

    SciTech Connect

    Fan, Aiwu; Maruta, Kaoru; Nakamura, Hisashi; Kumar, Sudarshan; Liu, Wei

    2010-09-15

    Flame pattern formations of premixed DME-air mixture in a heated radial channel with a gap distance of 2.5 mm were experimentally investigated. The DME-air mixture was introduced into the radial channel through a delivery tube which connected with the center of the top disk. With an image-intensified high-speed video camera, rich flame pattern formations were identified in this configuration. Regime diagram of all these flame patterns was drawn based on the experimental findings in the equivalence ratio range of 0.6-2.0 and inlet velocity range of 1.0-5.0 m/s. Compared with our previous study on premixed methane-air flames, there are several distinct characteristics for the present study. First, Pelton-wheel-like rotary flames and traveling flames with kink-like structures were observed for the first time. Second, in most cases, flames can be stabilized near the inlet port of the channel, exhibiting a conical or cup-like shape, while the conventional circular flame was only observed under limited conditions. Thirdly, an oscillating flame phenomenon occurred under certain conditions. During the oscillation process, a target appearance was seen at some instance. These pattern formation characteristics are considered to be associated with the low-temperature oxidation of DME. (author)

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

    PubMed

    Randsoe, Thomas; Hyldegaard, Ole

    2012-08-01

    The standard treatment of altitude decompression sickness (aDCS) caused by nitrogen bubble formation is oxygen breathing and recompression. However, micro air bubbles (containing 79% nitrogen), injected into adipose tissue, grow and stabilize at 25 kPa regardless of continued oxygen breathing and the tissue nitrogen pressure. To quantify the contribution of oxygen to bubble growth at altitude, micro oxygen bubbles (containing 0% nitrogen) were injected into the adipose tissue of rats depleted from nitrogen by means of preoxygenation (fraction of inspired oxygen = 1.0; 100%) and the bubbles studied at 101.3 kPa (sea level) or at 25 kPa altitude exposures during continued oxygen breathing. In keeping with previous observations and bubble kinetic models, we hypothesize that oxygen breathing may contribute to oxygen bubble growth at altitude. Anesthetized rats were exposed to 3 h of oxygen prebreathing at 101.3 kPa (sea level). Micro oxygen bubbles of 500-800 nl were then injected into the exposed abdominal adipose tissue. The oxygen bubbles were studied for up to 3.5 h during continued oxygen breathing at either 101.3 or 25 kPa ambient pressures. At 101.3 kPa, all bubbles shrank consistently until they disappeared from view at a net disappearance rate (0.02 mm(2) × min(-1)) significantly faster than for similar bubbles at 25 kPa altitude (0.01 mm(2) × min(-1)). At 25 kPa, most bubbles initially grew for 2-40 min, after which they shrank and disappeared. Four bubbles did not disappear while at 25 kPa. The results support bubble kinetic models based on Fick's first law of diffusion, Boyles law, and the oxygen window effect, predicting that oxygen contributes more to bubble volume and growth during hypobaric conditions. As the effect of oxygen increases, the lower the ambient pressure. The results indicate that recompression is instrumental in the treatment of aDCS. PMID:22653987

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

    PubMed

    Randsoe, Thomas; Hyldegaard, Ole

    2012-08-01

    The standard treatment of altitude decompression sickness (aDCS) caused by nitrogen bubble formation is oxygen breathing and recompression. However, micro air bubbles (containing 79% nitrogen), injected into adipose tissue, grow and stabilize at 25 kPa regardless of continued oxygen breathing and the tissue nitrogen pressure. To quantify the contribution of oxygen to bubble growth at altitude, micro oxygen bubbles (containing 0% nitrogen) were injected into the adipose tissue of rats depleted from nitrogen by means of preoxygenation (fraction of inspired oxygen = 1.0; 100%) and the bubbles studied at 101.3 kPa (sea level) or at 25 kPa altitude exposures during continued oxygen breathing. In keeping with previous observations and bubble kinetic models, we hypothesize that oxygen breathing may contribute to oxygen bubble growth at altitude. Anesthetized rats were exposed to 3 h of oxygen prebreathing at 101.3 kPa (sea level). Micro oxygen bubbles of 500-800 nl were then injected into the exposed abdominal adipose tissue. The oxygen bubbles were studied for up to 3.5 h during continued oxygen breathing at either 101.3 or 25 kPa ambient pressures. At 101.3 kPa, all bubbles shrank consistently until they disappeared from view at a net disappearance rate (0.02 mm(2) × min(-1)) significantly faster than for similar bubbles at 25 kPa altitude (0.01 mm(2) × min(-1)). At 25 kPa, most bubbles initially grew for 2-40 min, after which they shrank and disappeared. Four bubbles did not disappear while at 25 kPa. The results support bubble kinetic models based on Fick's first law of diffusion, Boyles law, and the oxygen window effect, predicting that oxygen contributes more to bubble volume and growth during hypobaric conditions. As the effect of oxygen increases, the lower the ambient pressure. The results indicate that recompression is instrumental in the treatment of aDCS.

  12. Time-dependent bubble motion through a liquid filled compliant channel

    NASA Astrophysics Data System (ADS)

    Halpern, David; Gaver, Donald; Jensen, Oliver

    2000-11-01

    Pulmonary airway closure occurs when the liquid lining layer occludes the airway and obstructs airflow. Meniscus formation is the result of a surface-tension driven instability within the liquid layer. Airway 'compliant collapse' may result, which leads to tube buckling with airway walls held in apposition. Airway closure is common in premature neonates who do not produce sufficient surfactant and those suffering from emphysema. To model the reopening of a collapsed airway flooded with fluid, we consider the time-dependent motion of an air-bubble driven by a positive bubble pressure Pb through a liquid filled compliant channel. The governing Stokes equations are solved using the boundary element method near the bubble tip, and lubrication theory sufficiently far ahead of the buble where the channel walls have a gentle taper. Results show that for Pb > P_crit, the bubble moves forward and converges to a steady velocity as the airway walls 'peel' open. For Pb < P_crit, no steady solutions are found because fluid continuously accummulates ahead of the bubble tip. This result validates the stability analysis of the previously steady wall peeling solution branch. The impact of the flow field on transport of surfactant and the applied shear and normal stresses on the wall as they relate to pulmonary reopening are also discussed.

  13. In situ secondary organic aerosol formation from ambient pine forest air using an oxidation flow reactor

    NASA Astrophysics Data System (ADS)

    Palm, B. B.; Campuzano-Jost, P.; Ortega, A. M.; Day, D. A.; Kaser, L.; Jud, W.; Karl, T.; Hansel, A.; Hunter, J. F.; Cross, E. S.; Kroll, J. H.; Peng, Z.; Brune, W. H.; Jimenez, J. L.

    2015-11-01

    Ambient air was oxidized by OH radicals in an oxidation flow reactor (OFR) located in a montane pine forest during the BEACHON-RoMBAS campaign to study biogenic secondary organic aerosol (SOA) formation and aging. High OH concentrations and short residence times allowed for semi-continuous cycling through a large range of OH exposures ranging from hours to weeks of equivalent (eq.) atmospheric aging. A simple model is derived and used to account for the relative time scales of condensation of low volatility organic compounds (LVOCs) onto particles, condensational loss to the walls, and further reaction to produce volatile, non-condensing fragmentation products. More SOA production was observed in the OFR at nighttime (average 4 μg m-3 when LVOC fate corrected) compared to daytime (average 1 μg m-3 when LVOC fate corrected), with maximum formation observed at 0.4-1.5 eq. days of photochemical aging. SOA formation followed a similar diurnal pattern to monoterpenes, sesquiterpenes, and toluene + p-cymene concentrations, including a substantial increase just after sunrise at 07:00 LT. Higher photochemical aging (> 10 eq. days) led to a decrease in new SOA formation and a loss of preexisting OA due to heterogeneous oxidation followed by fragmentation and volatilization. When comparing two different commonly used methods of OH production in OFRs (OFR185 and OFR254), similar amounts of SOA formation were observed. We recommend the OFR185 mode for future forest studies. Concurrent gas-phase measurements of air after OH oxidation illustrate the decay of primary VOCs, production of small oxidized organic compounds, and net production at lower ages followed by net consumption of terpenoid oxidation products as photochemical age increased. New particle formation was observed in the reactor after oxidation, especially during times when precursor gas concentrations and SOA formation were largest. Approximately 6 times more SOA was formed in the reactor from OH oxidation than

  14. Transient bubble oscillations near an elastic membrane in water

    NASA Astrophysics Data System (ADS)

    Turangan, C. K.; Khoo, B. C.

    2015-12-01

    We present a study of transient oscillating bubble-elastic membrane interaction by means of an experiment and a numerical simulation to study the dynamics of bubble's inertial collapse near an elastic interface. The bubble is generated very close to a thin elastic membrane using an electric spark, and their interaction is observed using high speed photography. The high pressure and temperature plasma from the dielectric breakdown precedes the bubble formation. The bubble then expands and creates a dimple on the membrane. After reaching its maximum size, the bubble begins to collapse. The membrane retracts back, transmitting a perturbation on the bubble surface. The coupling between bubble contraction and this perturbation strengthens the collapse and leads to the formation of a mushroom-shaped bubble, bubble pinching and splitting. Towards the end of the collapse, the water inertia surrounding the bubble pulls the membrane upwards forming a relatively sharp conical hump. The dynamics of this interaction is well predicted by the boundary element method (BEM) simulation.

  15. Wintertime Air Quality Impacts from Oil and Natural Gas Drilling Operations in the Bakken Formation Region

    NASA Astrophysics Data System (ADS)

    Evanoski-Cole, Ashley; Sive, Barkley; Zhou, Yong; Prenni, Anthony; Schurman, Misha; Day, Derek; Sullivan, Amy; Li, Yi; Hand, Jenny; Gebhart, Kristi; Schichtel, Bret; Collett, Jeffrey

    2016-04-01

    Oil and natural gas extraction has dramatically increased in the last decade in the United States due to the increased use of unconventional drilling techniques which include horizontal drilling and hydraulic fracturing. The impact of these drilling activities on local and regional air quality in oil and gas basins across the country are still relatively unknown, especially in recently developed basins such as the Bakken shale formation. This study is the first to conduct a comprehensive characterization of the regional air quality in the Bakken region. The Bakken shale formation, part of the Williston basin, is located in North Dakota and Montana in the United States and Saskatchewan and Manitoba in Canada. Oil and gas drilling operations can impact air quality in a variety of ways, including the generation of atmospheric particulate matter (PM), hazardous air pollutants, ozone, and greenhouse gas emissions. During the winter especially, PM formation can be enhanced and meteorological conditions can favor increased concentrations of PM and other pollutants. In this study, ground-based measurements throughout the Bakken region in North Dakota and Montana were collected over two consecutive winters to gain regional trends of air quality impacts from the oil and gas drilling activities. Additionally, one field site had a comprehensive suite of instrumentation operating at high time resolution to gain detailed characterization of the atmospheric composition. Measurements included organic carbon and black carbon concentrations in PM, the characterization of inorganic PM, inorganic gases, volatile organic compounds (VOCs), precipitation and meteorology. These elevated PM episodes were further investigated using the local meteorological conditions and regional transport patterns. Episodes of elevated concentrations of nitrogen oxides and sulfur dioxide were also detected. The VOC concentrations were analyzed and specific VOCs that are known oil and gas tracers were used

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

    NASA Astrophysics Data System (ADS)

    Wu, Chengtian

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

  17. Interacting bubble clouds and their sonochemical production.

    PubMed

    Stricker, Laura; Dollet, Benjamin; Fernández Rivas, David; Lohse, Detlef

    2013-09-01

    An acoustically driven air pocket trapped in a pit etched on a surface can emit a bubble cluster. When several pits are present, the resulting bubble clusters interact in a nontrivial way. Fernández Rivas et al. [Angew. Chem. Int. Ed. 49, 9699-9701 (2010)] observed three different behaviors at increasing driving power: clusters close to their "mother" pits, clusters attracting each other but still well separated, and merging clusters. The last is highly undesirable for technological purposes as it is associated with a reduction of the radical production and an enhancement of the erosion of the reactor walls. In this paper, the conditions for merging to occur are quantified in the case of two clusters, as a function of the following control parameters: driving pressure, distance between the two pits, cluster radius, and number of bubbles within each cluster. The underlying mechanism, governed by the secondary Bjerknes forces, is strongly influenced by the nonlinearity of the bubble oscillations and not directly by the number of nucleated bubbles. The Bjerknes forces are found to dampen the bubble oscillations, thus reducing the radical production. Therefore, the increased number of bubbles at high power could be the key to understanding the experimental observation that, above a certain power threshold, any further increase of the driving does not improve the sonochemical efficiency.

  18. Kinetics of Bubble Generation in Mafic Enclaves

    NASA Astrophysics Data System (ADS)

    Jackson, B. A.; Gardner, J. E.

    2014-12-01

    Volcanically erupted mafic enclaves are typically vesicular, with the bubbles forming when the mafic magma cools after it is injected and disaggregated into a cooler silicic magma. This study uses hydrothermal experiments to investigate the kinetics of pre-eruptive bubble nucleation and growth within mafic magmas, focused on the efficiency of nucleation on different minerals, and to quantify the growth rate of bubbles with varying cooling rates. Starting materials are natural mafic enclaves from Southwest Trident, Alaska. Experiments were initially equilibrated with H2O at 85 MPa and 1065 °C for 2 hours, producing a melt with blocky crystals of plagioclase and pyroxene, and spherical bubbles with a mean 30 μm diameter and number density (Nv) of 7.2x104 cm-3. Upon cooling to 1015 °C at 2 °C/h, the mineralogy and Nv did not change (although total crystallinity increased), while the mean bubble diameter increased to 90 μm. Cooling further to 985 °C at 2 °C/h, resulted in the crystallization of Fe-Ti oxides, along with an abrupt Nv increase (3.0x105 cm-3) of bubbles with a mean diameter of 60 μm. This abrupt bubble nucleation event, coinciding with the formation of Fe-Ti oxides, suggests that plagioclase and pyroxene are poor bubble nucleation sites in mafic melts, and that Fe-Ti oxides are good bubble nucleation sites, similar to previous results using rhyolite melts. Additionally, the occurrence of this nucleation event suggests that cooling related diffusive growth of bubbles in mafic enclaves, under magma chamber conditions, is too slow to keep up with increasing volatile saturation in the melt, and that the melt may become supersaturated until nucleation sites for new bubbles become available. Rapid cooling (1065-985 °C at 110 °C/h) produced abundant acicular plagioclase and pyroxene crystals (no Fe-Ti oxides), and bubbles with a nearly identical mean diameter and Nv to experiments equilibrated at 1065 °C. It is therefore likely that bubbles will not

  19. Nanoemulsions obtained via bubble-bursting at a compound interface

    NASA Astrophysics Data System (ADS)

    Feng, Jie; Roché, Matthieu; Vigolo, Daniele; Arnaudov, Luben N.; Stoyanov, Simeon D.; Gurkov, Theodor D.; Tsutsumanova, Gichka G.; Stone, Howard A.

    2014-08-01

    Bursting of bubbles at an air/liquid interface is a familiar occurrence relevant to foam stability, cell cultures in bioreactors and ocean-atmosphere mass transfer. In the latter case, bubble-bursting leads to the dispersal of sea-water aerosols in the surrounding air. Here we show that bubbles bursting at a compound air/oil/water-with-surfactant interface can disperse submicrometre oil droplets in water. Dispersal results from the detachment of an oil spray from the bottom of the bubble towards water during bubble collapse. We provide evidence that droplet size is selected by physicochemical interactions between oil molecules and the surfactants rather than by hydrodynamics. We demonstrate the unrecognized role that this dispersal mechanism may play in the fate of the sea surface microlayer and of pollutant spills by dispersing petroleum in the water column. Finally, our system provides an energy-efficient route, with potential upscalability, for applications in drug delivery, food production and materials science.

  20. Bubble bursting as an aerosol generation mechanism during an oil spill in the deep-sea environment: molecular dynamics simulations of oil alkanes and dispersants in atmospheric air/salt water interfaces.

    PubMed

    Liyana-Arachchi, Thilanga P; Zhang, Zenghui; Ehrenhauser, Franz S; Avij, Paria; Valsaraj, Kalliat T; Hung, Francisco R

    2014-01-01

    Potential of mean force (PMF) calculations and molecular dynamics (MD) simulations were performed to investigate the properties of oil n-alkanes [i.e., n-pentadecane (C15), n-icosane (C20) and n-triacontane (C30)], as well as several surfactant species [i.e., the standard anionic surfactant sodium dodecyl sulfate (SDS), and three model dispersants similar to the Tween and Span species present in Corexit 9500A] at air/salt water interfaces. This study was motivated by the 2010 Deepwater Horizon (DWH) oil spill, and our simulation results show that, from the thermodynamic point of view, the n-alkanes and the model dispersants have a strong preference to remain at the air/salt water interface, as indicated by the presence of deep free energy minima at these interfaces. The free energy minimum of these n-alkanes becomes deeper as their chain length increases, and as the concentration of surfactant species at the interface increases. The n-alkanes tend to adopt a flat orientation and form aggregates at the bare air/salt water interface. When this interface is coated with surfactants, the n-alkanes tend to adopt more tilted orientations with respect to the vector normal to the interface. These simulation results are consistent with the experimental findings reported in the accompanying paper [Ehrenhauser et al., Environ. Sci.: Processes Impacts 2013, in press, (DOI: 10.1039/c3em00390f)]. The fact that these long-chain n-alkanes show a strong thermodynamic preference to remain at the air/salt water interfaces, especially if these interfaces are coated with surfactants, makes these species very likely to adsorb at the surface of bubbles or droplets and be ejected to the atmosphere by sea surface processes such as whitecaps (breaking waves) and bubble bursting. Finally, the experimental finding that more oil hydrocarbons are ejected when Corexit 9500A is present in the system is consistent with the deeper free energy minima observed for the n-alkanes at the air/salt water

  1. 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.

  2. 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. PMID:24401119

  3. The pharyngeal organ in the buccal cavity of the male Siamese fighting fish, Betta splendens, supplies mucus for building bubble nests.

    PubMed

    Kang, Chao-Kai; Lee, Tsung-Han

    2010-11-01

    The male Siamese fighting fish, Betta splendens, builds a bubble nest on the water surface to care for offspring during the reproductive period. To our knowledge, this study is the first to determine the composition of the bubble nest and to compare the pharyngeal organs of male and female Siamese fighting fish to determine the relationship between the pharyngeal organ and the ability to make bubble nests. Dot blots of the bubble nest probed with periodic acid-Schiff's (PAS) staining and Ponceau S solution revealed that the contents of the nest are glycoprotein rich. Dissection of the heads of Siamese fighting fish showed that the pharyngeal organ is located in the position through which inhaled air passes. The epithelial structure of the pharyngeal organ of the Siamese fighting fish, like that of other teleosts, has numerous wrinkles and papillae. Mucous goblet cells were observed on the epithelium of pharyngeal organs in male and female fish. The pharyngeal organ was found to be larger in male than in female fish. In addition, the epithelium of the pharyngeal organ in male fish has a greater number of mucous goblet cells than that in female fish. In Siamese fighting fish, this sexual dimorphism of the pharyngeal organ suggests that the male fish secretes more glycoprotein-rich mucus to build the bubble nest. Future work will focus on the type of mucous cells found in the epithelium of the pharyngeal organ that contributes to bubble formation and will determine the components of the mucus in the bubble nest.

  4. On the mechanism of zirconium nitride formation by zirconium, zirconia and yttria burning in air

    NASA Astrophysics Data System (ADS)

    Malikova, Ekaterina; Pautova, Julia; Gromov, Alexander; Monogarov, Konstantin; Larionov, Kirill; Teipel, Ulrich

    2015-10-01

    The combustion of Zr and (Zr+ZrO2) powdery mixtures in air was accompanied by major ZrN stabilization. The synthesis of cheap ZrN with the high yield in air was facile and utile. The influence of Y2O3 additive on the content of ZrN the solid combustion products (SCP) was investigated. The reagents and SCP were analyzed by BET, DTA-TGA, XRD, SEM and EDS. Burning temperature was measured by thermal imager. The yield of ZrN in the SCP has been varied by the time regulation of the combustion process. The burning samples were quenched at a certain time to avoid the re-oxidation of the obtained ZrN by oxygen. The quenching of the burned (Zr+ZrO2) samples with the Y2O3 additive was allowed increasing the ZrN yield in SCP up to 66 wt%. The chemical mechanism of ZrN formation in air was discussed and the probable source of ZrN massive formation is suggested.

  5. Formation and growth of indoor air aerosol particles as a result of D-limonene oxidation

    NASA Astrophysics Data System (ADS)

    Vartiainen, E.; Kulmala, M.; Ruuskanen, T. M.; Taipale, R.; Rinne, J.; Vehkamäki, H.

    Oxidation of D-limonene, which is a common monoterpene, can lead to new aerosol particle formation in indoor environments. Thus, products containing D-limonene, such as citrus fruits, air refresheners, household cleaning agents, and waxes, can act as indoor air aerosol particle sources. We released D-limonene into the room air by peeling oranges and measured the concentration of aerosol particles of three different size ranges. In addition, we measured the concentration of D-limonene, the oxidant, and the concentration of ozone, the oxidizing gas. Based on the measurements we calculated the growth rate of the small aerosol particles, which were 3-10 nm in diameter, to be about 6300nmh-1, and the losses of the aerosol particles that were due to the coagulation and condensation processes. From these, we further approximated the concentration of the condensable vapour and its source rate and then calculated the formation rate of the small aerosol particles. For the final result, we calculated the nucleation rate and the maximum number of molecules in a critical cluster. The nucleation rate was in the order of 105cm-3s-1 and the number of molecules in a critical-sized cluster became 1.2. The results were in agreement with the activation theory.

  6. 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. PMID:26172798

  7. Nonlinear Bubble Interactions in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Barbat, Tiberiu; Ashgriz, Nasser; Liu, Ching-Shi

    1996-01-01

    The systems consisting of a two-phase mixture, as clouds of bubbles or drops, have shown many common features in their responses to different external force fields. One of particular interest is the effect of an unsteady pressure field applied to these systems, case in which the coupling of the vibrations induced in two neighboring components (two drops or two bubbles) may result in an interaction force between them. This behavior was explained by Bjerknes by postulating that every body that is moving in an accelerating fluid is subjected to a 'kinetic buoyancy' equal with the product of the acceleration of the fluid multiplied by the mass of the fluid displaced by the body. The external sound wave applied to a system of drops/bubbles triggers secondary sound waves from each component of the system. These secondary pressure fields integrated over the surface of the neighboring drop/bubble may result in a force additional to the effect of the primary sound wave on each component of the system. In certain conditions, the magnitude of these secondary forces may result in significant changes in the dynamics of each component, thus in the behavior of the entire system. In a system containing bubbles, the sound wave radiated by one bubble at the location of a neighboring one is dominated by the volume oscillation mode and its effects can be important for a large range of frequencies. The interaction forces in a system consisting of drops are much smaller than those consisting of bubbles. Therefore, as a first step towards the understanding of the drop-drop interaction subject to external pressure fluctuations, it is more convenient to study the bubble interactions. This paper presents experimental results and theoretical predictions concerning the interaction and the motion of two levitated air bubbles in water in the presence of an acoustic field at high frequencies (22-23 KHz).

  8. Dynamics of two-dimensional bubbles

    NASA Astrophysics Data System (ADS)

    Piedra, Saúl; Ramos, Eduardo; Herrera, J. Ramón

    2015-06-01

    The dynamics of two-dimensional bubbles ascending under the influence of buoyant forces is numerically studied with a one-fluid model coupled with the front-tracking technique. The bubble dynamics are described by recording the position, shape, and orientation of the bubbles as functions of time. The qualitative properties of the bubbles and their terminal velocities are described in terms of the Eötvos (ratio of buoyancy to surface tension) and Archimedes numbers (ratio of buoyancy to viscous forces). The terminal Reynolds number result from the balance of buoyancy and drag forces and, consequently, is not an externally fixed parameter. In the cases that yield small Reynolds numbers, the bubbles follow straight paths and the wake is steady. A more interesting behavior is found at high Reynolds numbers where the bubbles follow an approximately periodic zigzag trajectory and an unstable wake with properties similar to the Von Karman vortex street is formed. The dynamical features of the motion of single bubbles are compared to experimental observations of air bubbles ascending in a water-filled Hele-Shaw cell. Although the comparison is not strictly valid in the sense that the effect of the lateral walls is not incorporated in the model, most of the dynamical properties observed are in good qualitative agreement with the numerical calculations. Hele-Shaw cells with different gaps have been used to determine the degree of approximation of the numerical calculation. It is found that for the relation between the terminal Reynolds number and the Archimedes number, the numerical calculations are closer to the observations of bubble dynamics in Hele-Shaw cells of larger gaps.

  9. 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.

  10. Effect of inlet-air humidity on the formation of oxides of nitrogen in a gas-turbine combustor

    NASA Technical Reports Server (NTRS)

    Marchionna, N. R.

    1973-01-01

    Tests were conducted to determine the effect of inlet-air humidity on the formation of oxides of nitrogen from a gas-turbine combustor. Combustor inlet-air temperature ranged from 450 F to 1050 F. The tests were run at a constant pressure of 6 atmospheres and reference Mach number of 0.065. The NO sub x emission index was found to decrease with increasing inlet-air humidity at a constant exponential rate of 19 percent per mass percent water vapor in the air. This decrease of NO sub x emission index with increasing humidity was found to be independent of inlet-air temperature.

  11. Effects of flow on insulin fibril formation at an air/water interface

    NASA Astrophysics Data System (ADS)

    Posada, David; Heldt, Caryn; Sorci, Mirco; Belfort, Georges; Hirsa, Amir

    2009-11-01

    The amyloid fibril formation process, which is implicated in several diseases such as Alzheimer's and Huntington's, is characterized by the conversion of monomers to oligomers and then to fibrils. Besides well-studied factors such as pH, temperature and concentration, the kinetics of this process are significantly influenced by the presence of solid or fluid interfaces and by flow. By studying the nucleation and growth of a model system (insulin fibrils) in a well-defined flow field with an air/water interface, we can identify the flow conditions that impact protein aggregation kinetics both in the bulk solution and at the air/water interface. The present flow system (deep-channel surface viscometer) consists of an annular region bounded by stationary inner and outer cylinders, an air/water interface, and a floor driven at constant rotation. We show the effects of Reynolds number on the kinetics of the fibrillation process both in the bulk solution and at the air/water interface, as well as on the structure of the resultant amyloid aggregates.

  12. Bubbles in live-stranded dolphins.

    PubMed

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

    2012-04-01

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

  13. Bubbles in live-stranded dolphins

    PubMed Central

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

    2012-01-01

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

  14. In situ secondary organic aerosol formation from ambient pine forest air using an oxidation flow reactor

    DOE PAGES

    Palm, Brett B.; Campuzano-Jost, Pedro; Ortega, Amber M.; Day, Douglas A.; Kaser, Lisa; Jud, Werner; Karl, Thomas; Hansel, Armin; Hunter, James F.; Cross, Eben S.; et al

    2016-03-08

    An oxidation flow reactor (OFR) is a vessel inside which the concentration of a chosen oxidant can be increased for the purpose of studying SOA formation and aging by that oxidant. During the BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen–Rocky Mountain Biogenic Aerosol Study) field campaign, ambient pine forest air was oxidized by OH radicals in an OFR to measure the amount of SOA that could be formed from the real mix of ambient SOA precursor gases, and how that amount changed with time as precursors changed. High OH concentrations and short residence times allowed formore » semicontinuous cycling through a large range of OH exposures ranging from hours to weeks of equivalent (eq.) atmospheric aging. A simple model is derived and used to account for the relative timescales of condensation of low-volatility organic compounds (LVOCs) onto particles; condensational loss to the walls; and further reaction to produce volatile, non-condensing fragmentation products. More SOA production was observed in the OFR at nighttime (average 3 µg m−3 when LVOC fate corrected) compared to daytime (average 0.9 µg m−3 when LVOC fate corrected), with maximum formation observed at 0.4–1.5 eq. days of photochemical aging. SOA formation followed a similar diurnal pattern to monoterpenes, sesquiterpenes, and toluene+p-cymene concentrations, including a substantial increase just after sunrise at 07:00 local time. Higher photochemical aging (> 10 eq. days) led to a decrease in new SOA formation and a loss of preexisting OA due to heterogeneous oxidation followed by fragmentation and volatilization. When comparing two different commonly used methods of OH production in OFRs (OFR185 and OFR254-70), similar amounts of SOA formation were observed. We recommend the OFR185 mode for future forest studies. Concurrent gas-phase measurements of air after OH oxidation illustrate the decay of primary VOCs, production of

  15. In situ secondary organic aerosol formation from ambient pine forest air using an oxidation flow reactor

    NASA Astrophysics Data System (ADS)

    Palm, Brett B.; Campuzano-Jost, Pedro; Ortega, Amber M.; Day, Douglas A.; Kaser, Lisa; Jud, Werner; Karl, Thomas; Hansel, Armin; Hunter, James F.; Cross, Eben S.; Kroll, Jesse H.; Peng, Zhe; Brune, William H.; Jimenez, Jose L.

    2016-03-01

    An oxidation flow reactor (OFR) is a vessel inside which the concentration of a chosen oxidant can be increased for the purpose of studying SOA formation and aging by that oxidant. During the BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen-Rocky Mountain Biogenic Aerosol Study) field campaign, ambient pine forest air was oxidized by OH radicals in an OFR to measure the amount of SOA that could be formed from the real mix of ambient SOA precursor gases, and how that amount changed with time as precursors changed. High OH concentrations and short residence times allowed for semicontinuous cycling through a large range of OH exposures ranging from hours to weeks of equivalent (eq.) atmospheric aging. A simple model is derived and used to account for the relative timescales of condensation of low-volatility organic compounds (LVOCs) onto particles; condensational loss to the walls; and further reaction to produce volatile, non-condensing fragmentation products. More SOA production was observed in the OFR at nighttime (average 3 µg m-3 when LVOC fate corrected) compared to daytime (average 0.9 µg m-3 when LVOC fate corrected), with maximum formation observed at 0.4-1.5 eq. days of photochemical aging. SOA formation followed a similar diurnal pattern to monoterpenes, sesquiterpenes, and toluene+p-cymene concentrations, including a substantial increase just after sunrise at 07:00 local time. Higher photochemical aging (> 10 eq. days) led to a decrease in new SOA formation and a loss of preexisting OA due to heterogeneous oxidation followed by fragmentation and volatilization. When comparing two different commonly used methods of OH production in OFRs (OFR185 and OFR254-70), similar amounts of SOA formation were observed. We recommend the OFR185 mode for future forest studies. Concurrent gas-phase measurements of air after OH oxidation illustrate the decay of primary VOCs, production of small oxidized organic

  16. Shock Separation and Dead-Zone Formation from Detonations in an Internal Air-Well Geometry

    NASA Astrophysics Data System (ADS)

    Molitoris, John; Andreski, Henry; Garza, Raul; Batteux, Jan; Vitello, Peter; Souers, Clark

    2007-06-01

    Here we report on measurements of dead-zone formation due to shock separation from detonations attempting to corner-turn in an internal air-well geometry. This geometry is also known as a ``hockey-puck'' configuration. These measurements were performed on detonations in LX-17 and PBX9502 using time sequence radiography to image the event with surface contact timing pins as an additional diagnostic. In addition to an open corner in the high-explosive component we also examined the effects of steel defining the corner. In these experiments we find a long lived dead-zone consisting of shocked explosive that persists to very late times. Data and numerical modeling will be presented in addition to a comparison with previous work using an external air well. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  17. On the mechanism of zirconium nitride formation by zirconium, zirconia and yttria burning in air

    SciTech Connect

    Malikova, Ekaterina; Pautova, Julia; Gromov, Alexander; Monogarov, Konstantin; Larionov, Kirill; Teipel, Ulrich

    2015-10-15

    The combustion of Zr and (Zr+ZrO{sub 2}) powdery mixtures in air was accompanied by major ZrN stabilization. The synthesis of cheap ZrN with the high yield in air was facile and utile. The influence of Y{sub 2}O{sub 3} additive on the content of ZrN the solid combustion products (SCP) was investigated. The reagents and SCP were analyzed by BET, DTA–TGA, XRD, SEM and EDS. Burning temperature was measured by thermal imager. The yield of ZrN in the SCP has been varied by the time regulation of the combustion process. The burning samples were quenched at a certain time to avoid the re-oxidation of the obtained ZrN by oxygen. The quenching of the burned (Zr+ZrO{sub 2}) samples with the Y{sub 2}O{sub 3} additive was allowed increasing the ZrN yield in SCP up to 66 wt%. The chemical mechanism of ZrN formation in air was discussed and the probable source of ZrN massive formation is suggested. - Highlights: • Combustion of Zr, (Zr+ZrO{sub 2}) and (Zr+ZrO{sub 2}+Y{sub 2}O{sub 3}) powdery mixtures in air was studied. • The new combustion phenomenon has been found: metal (Zr) chemically reacts with its oxide (ZrO{sub 2}) in the burning wave. • The effective influence of Y{sub 2}O{sub 3} additive (2–3 wt%) on ZrN yield in combustion products is shown. • The yield of ZrN in the combustion products can be varied by the burning time regulation (quenching)

  18. Circulatory bubble dynamics: from physical to biological aspects.

    PubMed

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

    2014-04-01

    Bubbles can form in the body during or after decompression from pressure exposures such as those undergone by scuba divers, astronauts, caisson and tunnel workers. Bubble growth and detachment physics then becomes significant in predicting and controlling the probability of these bubbles causing mechanical problems by blocking vessels, displacing tissues, or inducing an inflammatory cascade if they persist for too long in the body before being dissolved. By contrast to decompression induced bubbles whose site of initial formation and exact composition are debated, there are other instances of bubbles in the bloodstream which are well-defined. Gas emboli unwillingly introduced during surgical procedures and ultrasound microbubbles injected for use as contrast or drug delivery agents are therefore also discussed. After presenting the different ways that bubbles can end up in the human bloodstream, the general mathematical formalism related to the physics of bubble growth and detachment from decompression is reviewed. Bubble behavior in the bloodstream is then discussed, including bubble dissolution in blood, bubble rheology and biological interactions for the different cases of bubble and blood composition considered. PMID:24534474

  19. Circulatory bubble dynamics: from physical to biological aspects.

    PubMed

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

    2014-04-01

    Bubbles can form in the body during or after decompression from pressure exposures such as those undergone by scuba divers, astronauts, caisson and tunnel workers. Bubble growth and detachment physics then becomes significant in predicting and controlling the probability of these bubbles causing mechanical problems by blocking vessels, displacing tissues, or inducing an inflammatory cascade if they persist for too long in the body before being dissolved. By contrast to decompression induced bubbles whose site of initial formation and exact composition are debated, there are other instances of bubbles in the bloodstream which are well-defined. Gas emboli unwillingly introduced during surgical procedures and ultrasound microbubbles injected for use as contrast or drug delivery agents are therefore also discussed. After presenting the different ways that bubbles can end up in the human bloodstream, the general mathematical formalism related to the physics of bubble growth and detachment from decompression is reviewed. Bubble behavior in the bloodstream is then discussed, including bubble dissolution in blood, bubble rheology and biological interactions for the different cases of bubble and blood composition considered.

  20. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix J

    NASA Technical Reports Server (NTRS)

    Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2001-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation--O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  1. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix C

    NASA Technical Reports Server (NTRS)

    Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2000-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation-O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  2. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix H

    NASA Technical Reports Server (NTRS)

    Xu, F.; Faeth, G. M.; Yuan, Z.-G. (Technical Monitor); Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2001-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation-O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  3. Formation of calcium in the products of iron oxide-aluminum thermite combustion in air

    NASA Astrophysics Data System (ADS)

    Gromov, A. A.; Gromov, A. M.; Popenko, E. M.; Sergienko, A. V.; Sabinskaya, O. G.; Raab, B.; Teipel, U.

    2016-10-01

    The composition of condensed products resulting from the combustion of thermite mixtures (Al + Fe2O3) in air is studied by precise methods. It is shown that during combustion, calcium is formed and stabilized in amounts of maximal 0.55 wt %, while is missing from reactants of 99.7 wt % purity. To explain this, it is hypothesized that a low-energy nuclear reaction takes place alongside the reactions of aluminum oxidation and nitridation, resulting in the formation of calcium (Kervran-Bolotov reaction).

  4. 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.

  5. Are there really bubbles in oil prices?

    NASA Astrophysics Data System (ADS)

    Balcilar, Mehmet; Ozdemir, Zeynel Abidin; Yetkiner, Hakan

    2014-12-01

    The aim of this paper is to identify bubbles in oil prices by using the “exponential fitting” methodology proposed by Watanabe et al. (2007) [28,29]. We use the daily US dollar closing crude oil prices of West Texas Intermediate (WTI) covering the 1986:01:02-2013:07:09 and the Brent for the 1987:05:20-2013:07:09 periods. The distinguishing feature of this study from the previous studies is that this is the first study in the literature showing the existence of bubbles in crude oil prices. We found that there are four distinct periods of persistent bubbles in the crude oil prices since 1986. Two of these persistent bubbles are before 2000 and two of them are after 2000. We conclude that further research is needed to understand better how futures markets may impact the oil price formation.

  6. Using sound to study bubble coalescence.

    PubMed

    Kracht, W; Finch, J A

    2009-04-01

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

  7. MAGNETIC TOPOLOGY OF BUBBLES IN QUIESCENT PROMINENCES

    SciTech Connect

    Dudik, J.; Aulanier, G.; Schmieder, B.; Zapior, M.; Heinzel, P.

    2012-12-10

    We study a polar-crown prominence with a bubble and its plume observed in several coronal filters by the SDO/AIA and in H{alpha} by the MSDP spectrograph in Bialkow (Poland) to address the following questions: what is the brightness of prominence bubbles in EUV with respect to the corona outside of the prominence and the prominence coronal cavity? What is the geometry and topology of the magnetic field in the bubble? What is the nature of the vertical threads seen within prominences? We find that the brightness of the bubble and plume is lower than the brightness of the corona outside of the prominence, and is similar to that of the coronal cavity. We constructed linear force-free models of prominences with bubbles, where the flux rope is perturbed by inclusion of parasitic bipoles. The arcade field lines of the bipole create the bubble, which is thus devoid of magnetic dips. Shearing the bipole or adding a second one can lead to cusp-shaped prominences with bubbles similar to the observed ones. The bubbles have complex magnetic topology, with a pair of coronal magnetic null points linked by a separator outlining the boundary between the bubble and the prominence body. We conjecture that plume formation involves magnetic reconnection at the separator. Depending on the viewing angle, the prominence can appear either anvil-shaped with predominantly horizontal structures, or cusp-shaped with predominantly vertical structuring. The latter is an artifact of the alignment of magnetic dips with respect to the prominence axis and the line of sight.

  8. Advection fog formation and aerosols produced by combustion-originated air pollution

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Liaw, G. S.; Vaughan, O. H., Jr.

    1980-01-01

    The way in which pollutants produced by the photochemical reaction of NO(X) and SO(X) affect the quality of the human environment through such phenomena as the formation of advection fog is considered. These pollutants provide the major source of condensation nuclei for the formation of fog in highways, airports and seaports. Results based on the monodisperse, multicomponent aerosol model show that: (1) condensation nuclei can grow and form a dense fog without the air having attained supersaturation; (2) the mass concentration range for NO(X) is one-third that of SO(X); and (3) the greater the mass concentration, the particle concentration, and the radius of condensation nuclei, the denser the fog that is formed.

  9. Thermal decomposition of captan and formation pathways of toxic air pollutants.

    PubMed

    Chen, Kai; Mackie, John C; Kennedy, Eric M; Dlugogorski, Bogdan Z

    2010-06-01

    This study investigates the thermal decomposition of a widely used fungicide, captan, under gas phase conditions, similar to those occurring in fires, cigarette burning, and combustion of biomass treated or contaminated with pesticides. The laboratory-scale apparatus consisted of a plug flow reactor equipped with sampling trains for gaseous, volatile organic compounds (VOC) and condensed products, with analysis performed by Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS), respectively. Under oxidative conditions, the thermal decomposition of captan generated gaseous pollutants including carbon disulfide, thiophosgene, phosgene, and hydrogen cyanide. The VOC analysis revealed the formation of tetrachloroethylene, hexachloroethane, and benzonitrile. Quantum chemical calculations indicated that captan decomposes unimolecularly, via fission of the C-S bond, with the ensuing radicals reacting with O(2). The results of the present study provide an improved understanding of the formation pathways of toxic air pollutants in the accidental or deliberate combustion of captan.

  10. A Feasibility Study on Operating Large Scale Compressed Air Energy Storage in Porous Formations

    NASA Astrophysics Data System (ADS)

    Wang, B.; Pfeiffer, W. T.; Li, D.; Bauer, S.

    2015-12-01

    Compressed air energy storage (CAES) in porous formations has been considered as one promising option of large scale energy storage for decades. This study, hereby, aims at analyzing the feasibility of operating large scale CAES in porous formations and evaluating the performance of underground porous gas reservoirs. To address these issues quantitatively, a hypothetic CAES scenario with a typical anticline structure in northern Germany was numerically simulated. Because of the rapid growth in photovoltaics, the period of extraction in a daily cycle was set to the early morning and the late afternoon in order to bypass the massive solar energy production around noon. The gas turbine scenario was defined referring to the specifications of the Huntorf CAES power plant. The numerical simulations involved two stages, i.e. initial fill and cyclic operation, and both were carried out using the Eclipse E300 simulator (Schlumberger). Pressure loss in the gas wells was post analyzed using an analytical solution. The exergy concept was applied to evaluate the potential energy amount stored in the specific porous formation. The simulation results show that porous formations prove to be a feasible solution of large scale CAES. The initial fill with shut-in periods determines the spatial distribution of the gas phase and helps to achieve higher gas saturation around the wells, and thus higher deliverability. The performance evaluation shows that the overall exergy flow of stored compressed air is also determined by the permeability, which directly affects the deliverability of the gas reservoir and thus the number of wells required.

  11. Effect of nitrous oxide on gas bubble volume in the anterior chamber.

    PubMed

    Wolf, G L; Capuano, C; Hartung, J

    1985-03-01

    Nitrous oxide is often used as anesthesia during ophthalmic surgery that requires intraocular injection of sulfur hexafluoride gas or air. Ventilation with N2O is known to increase intraocular pressure in the presence of intraocular bubbles, but little is known about the effect of N2O on intraocular bubble volume. Accordingly, we have compared the effect of N2O:O2 ventilation (66% N2O, balance O2) with that of air ventilation and oxygen ventilation on intraocular bubbles of SF6 or air. Aspiration of anterior chamber gas after 180 minutes of N2O:O2 ventilation in cats showed an increase in bubble volume of more than threefold when the original intraocular bubble was SF6 and an increase of more than twofold when the original intraocular bubble was air. In contrast, during air ventilation, intraocular SF6 bubble volume increased by 50%, and intraocular air bubble volume increased by only 7.5%. During O2 ventilation, intraocular SF6 bubble volume increased by 35%, and intraocular air bubble volume decreased by 13%. Our results indicate that N2O is contraindicated when gas is injected into the closed eye.

  12. Electric Field Effect on Bubble Detachment in Variable Gravity Environment

    NASA Technical Reports Server (NTRS)

    Iacona, Estelle; Herman, Cila; Chang, Shinan

    2003-01-01

    The subject of the present study, the process of bubble detachment from an orifice in a plane surface, shows some resemblance to bubble departure in boiling. Because of the high heat transfer coefficients associated with phase change processes, boiling is utilized in many industrial operations and is an attractive solution to cooling problems in aerospace engineering. In terrestrial conditions, buoyancy is responsible for bubble removal from the surface. In space, the gravity level being orders of magnitude smaller than on earth, bubbles formed during boiling remain attached at the surface. As a result, the amount of heat removed from the heated surface can decrease considerably. The use of electric fields is proposed to control bubble behavior and help bubble removal from the surface on which they form. The objective of the study is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Bubble cycle life were visualized in terrestrial conditions and for several reduced gravity levels. Bubble volume, dimensions and contact angle at detachment were measured and analyzed for different parameters as gravity level and electric field magnitude. Situations were considered with uniform or non-uni form electric field. Results show that these parameters significantly affect bubble behavior, shape, volume and dimensions.

  13. The relationship between ozone formation and air temperature in the atmospheric surface layer

    NASA Astrophysics Data System (ADS)

    Belan, Boris D.; Savkin, Denis; Tolmachev, Gennadii

    2016-04-01

    Studying the formation and dynamics of ozone in the atmosphere is important due to several reasons. First, the contribution of tropospheric ozone to the global greenhouse effect is only slightly less than that of water vapor, carbon dioxide, and methane. Second, tropospheric ozone acts as a strong poison that has negative effects on human health, animals, and vegetation. Third, being a potent oxidizer, ozone destroys almost all materials, including platinum group metals and compounds. Fourthly, ozone is formed in situ from precursors as a result of photochemical processes, but not emitted into the atmosphere by any industrial enterprises directly. In this work, we present some results of the study aimed at the revealing relationship between ozone formation rate and surface air temperature in the background atmosphere. It has been found that this relationship is nonlinear. Analysis of the possible reasons showed that the nonlinear character of this relationship may be due to a nonlinear increase in the reaction constants versus air temperature and a quadratic increase in the concentration of hydrocarbons with increasing temperature. This work was supported by the Ministry of Education and Science contract no.14.613.21.0013 (ID: RFMEFI61314X0013).

  14. Biofilm Formation Derived from Ambient Air and the Characteristics of Apparatus

    NASA Astrophysics Data System (ADS)

    Kanematsu, H.; Kougo, H.; Kuroda, D.; Itho, H.; Ogino, Y.; Yamamoto, Y.

    2013-04-01

    Biofilm is a kind of thin film on solidified matters, being derived from bacteria. Generally, planktonic bacteria float in aqueous environments, soil or air, most of which can be regarded as oligotrophic environments. Since they have to survive by instinct, they seek for nutrients that would exist on materials surfaces as organic matters. Therefore, bacteria attach materials surfaces reversibly. The attachment and detachment repeat for a while and finally, they attach on them irreversibly and the number of bacteria on them increases. At a threshold number, bacteria produce polymeric matters at the same time by quorum sensing mechanism and the biofilm produces on material surfaces. The biofilm produced in that way generally contains water (more than 80%), EPS (Exopolymeric Substance) and bacteria themselves. And they might bring about many industrial problems, fouling, corrosion etc. Therefore, it is very important for us to control and prevent the biofilm formation properly. However, it is generally very hard to produce biofilm experimentally and constantly in ambient atmosphere on labo scale. The authors invented an apparatus where biofilm could form on specimen's surfaces from house germs in the ambient air. In this experiment, we investigated the basic characteristics of the apparatus, reproducibility, the change of biofilm with experimental time, the quality change of water for biofilm formation and their significance for biofilm research.

  15. Interaction of lithotripter shockwaves with single inertial cavitation bubbles.

    PubMed

    Klaseboer, Evert; Fong, Siew Wan; Turangan, Cary K; Khoo, Boo Cheong; Szeri, Andrew J; Calvisi, Michael L; Sankin, Georgy N; Zhong, Pei

    2007-01-01

    The dynamic interaction of a shockwave (modelled as a pressure pulse) with an initially spherically oscillating bubble is investigated. Upon the shockwave impact, the bubble deforms non-spherically and the flow field surrounding the bubble is determined with potential flow theory using the boundary-element method (BEM). The primary advantage of this method is its computational efficiency. The simulation process is repeated until the two opposite sides of the bubble surface collide with each other (i.e. the formation of a jet along the shockwave propagation direction). The collapse time of the bubble, its shape and the velocity of the jet are calculated. Moreover, the impact pressure is estimated based on water-hammer pressure theory. The Kelvin impulse, kinetic energy and bubble displacement (all at the moment of jet impact) are also determined. Overall, the simulated results compare favourably with experimental observations of lithotripter shockwave interaction with single bubbles (using laser-induced bubbles at various oscillation stages). The simulations confirm the experimental observation that the most intense collapse, with the highest jet velocity and impact pressure, occurs for bubbles with intermediate size during the contraction phase when the collapse time of the bubble is approximately equal to the compressive pulse duration of the shock wave. Under this condition, the maximum amount of energy of the incident shockwave is transferred to the collapsing bubble. Further, the effect of the bubble contents (ideal gas with different initial pressures) and the initial conditions of the bubble (initially oscillating vs. non-oscillating) on the dynamics of the shockwave-bubble interaction are discussed.

  16. Modeling of surface cleaning by cavitation bubble dynamics and collapse.

    PubMed

    Chahine, Georges L; Kapahi, Anil; Choi, Jin-Keun; Hsiao, Chao-Tsung

    2016-03-01

    Surface cleaning using cavitation bubble dynamics is investigated numerically through modeling of bubble dynamics, dirt particle motion, and fluid material interaction. Three fluid dynamics models; a potential flow model, a viscous model, and a compressible model, are used to describe the flow field generated by the bubble all showing the strong effects bubble explosive growth and collapse have on a dirt particle and on a layer of material to remove. Bubble deformation and reentrant jet formation are seen to be responsible for generating concentrated pressures, shear, and lift forces on the dirt particle and high impulsive loads on a layer of material to remove. Bubble explosive growth is also an important mechanism for removal of dirt particles, since strong suction forces in addition to shear are generated around the explosively growing bubble and can exert strong forces lifting the particles from the surface to clean and sucking them toward the bubble. To model material failure and removal, a finite element structure code is used and enables simulation of full fluid-structure interaction and investigation of the effects of various parameters. High impulsive pressures are generated during bubble collapse due to the impact of the bubble reentrant jet on the material surface and the subsequent collapse of the resulting toroidal bubble. Pits and material removal develop on the material surface when the impulsive pressure is large enough to result in high equivalent stresses exceeding the material yield stress or its ultimate strain. Cleaning depends on parameters such as the relative size between the bubble at its maximum volume and the particle size, the bubble standoff distance from the particle and from the material wall, and the excitation pressure field driving the bubble dynamics. These effects are discussed in this contribution.

  17. Shock response of He bubbles in single crystal Cu

    SciTech Connect

    Li, B.; Wang, L.; E, J. C.; Luo, S. N.; Ma, H. H.

    2014-12-07

    With large-scale molecular dynamics simulations, we investigate shock response of He nanobubbles in single crystal Cu. For sufficient bubble size or internal pressure, a prismatic dislocation loop may form around a bubble in unshocked Cu. The internal He pressure helps to stabilize the bubble against plastic deformation. However, the prismatic dislocation loops may partially heal but facilitate nucleation of new shear and prismatic dislocation loops. For strong shocks, the internal pressure also impedes internal jetting, while a bubble assists local melting; a high speed jet breaks a He bubble into pieces dispersed among Cu. Near-surface He bubbles may burst and form high velocity ejecta containing atoms and small fragments, while the ejecta velocities do not follow the three-dimensional Maxwell-Boltzmann distributions expected for thermal equilibrium. The biggest fragment size deceases with increasing shock strength. With a decrease in ligament thickness or an increase in He bubble size, the critical shock strength required for bubble bursting decreases, while the velocity range, space extension and average velocity component along the shock direction, increase. Small bubbles are more efficient in mass ejecting. Compared to voids and perfect single crystal Cu, He bubbles have pronounced effects on shock response including bubble/void collapse, Hugoniot elastic limit (HEL), deformation mechanisms, and surface jetting. HEL is the highest for perfect single crystal Cu with the same orientations, followed by He bubbles without pre-existing prismatic dislocation loops, and then voids. Complete void collapse and shear dislocations occur for embedded voids, as opposed to partial collapse, and shear and possibly prismatic dislocations for He bubbles. He bubbles lower the threshhold shock strength for ejecta formation, and increase ejecta velocity and ejected mass.

  18. [Relationship between the state of intravascular bubbles and microcirculation system].

    PubMed

    Yuan, J; Pan, L; Wang, Q; Ji, Z; Gao, J

    1996-08-01

    To confirm the hypothesis that air bubbles were unable to block the blood vessels and that the state of the intravascular bubbles was determined by the function of the circulatory system, 35 guinea pigs were pressurized then were decompressed to normal pressure. Microscopic observation was made of the bulbar conjunctival, dorsum auricular and subcutaneous vessels in 33 surviving animals. Air bubbles of different amounts, sizes and shapes were found in the dorsum auricular and subcutaneous vein of all the amimals and in the bulbar conjunctival oriridal artery of 16 animals, and in some cases the vessels were even filled with bubbles. The bubbles ran in the same direction and at the same speed as the blood flow. They could run in a backward, to-and-fro or sluggish flow. The bubbles looked shapeless and tended to break and divided into branch flows where the vessel branches. The bubbles were motionless at the proximal end of the artery occluded due to spasm or when the blood was stagnated. Under the action of the blood pressure the bubbles could expand the vessel and push forward. The bubbles showed a tendency of flowing with ease with the function of the vessel recovered. The results suggest that bubbles of any size in the vessel could easily change their shape under the action of the blood flow and pressure, and pass through vessels of any diameter and circulate with the blood. Only when a vessel was occluded due to spasm or the blood in a vessel was stagnated could the bubbles be motionless, but it was not that the bubbles blocked the vessel.

  19. Prospects for bubble fusion

    SciTech Connect

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

    1995-09-01

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

  20. Dynamics of Rear Stagnant Cap formation at the surface of spherical bubbles rising in surfactant solutions at large Reynolds numbers under conditions of small Marangoni number and slow sorption kinetics.

    PubMed

    Dukhin, S S; Kovalchuk, V I; Gochev, G G; Lotfi, M; Krzan, M; Malysa, K; Miller, R

    2015-08-01

    On the surface of bubbles rising in a surfactant solution the adsorption process proceeds and leads to the formation of a so called Rear Stagnant Cap (RSC). The larger this RSC is the stronger is the retardation of the rising velocity. The theory of a steady RSC and steady retarded rising velocity, which sets in after a transient stage, has been generally accepted. However, a non-steady process of bubble rising starting from the initial zero velocity represents an important portion of the trajectory of rising, characterized by a local velocity profile (LVP). As there is no theory of RSC growth for large Reynolds numbers Re » 1 so far, the interpretation of LVPs measured in this regime was impossible. It turned out, that an analytical theory for a quasi-steady growth of RSC is possible for small Marangoni numbers Ma « 1, i.e. when the RSC is almost completely compressed, which means a uniform surface concentration Γ(θ)=Γ(∞) within the RSC. Hence, the RSC angle ψ(t) is obtained as a function of the adsorption isotherm parameters and time t. From the steady velocity v(st)(ψ), the dependence of non-steady velocity on time is obtained by employing v(st)[ψ(t)] via a quasi-steady approximation. The measurement of LVP creates a promising new opportunity for investigation of the RSC dynamics and adsorption kinetics. While adsorption and desorption happen at the same localization in the classical methods, in rising bubble experiments desorption occurs mainly within RSC while adsorption on the mobile part of the bubble surface. The desorption flux from RSC is proportional to αΓ(∞), while it is usually αΓ. The adsorption flux at the mobile surface above RSC can be assumed proportional to βC0, while it is usually βC0(1-Γ/Γ(∞)). These simplifications may become favorable in investigations of the adsorption kinetics for larger molecules, in particular for globular proteins, which essentially stay at an interface once adsorbed.

  1. Dynamics of Rear Stagnant Cap formation at the surface of spherical bubbles rising in surfactant solutions at large Reynolds numbers under conditions of small Marangoni number and slow sorption kinetics.

    PubMed

    Dukhin, S S; Kovalchuk, V I; Gochev, G G; Lotfi, M; Krzan, M; Malysa, K; Miller, R

    2015-08-01

    On the surface of bubbles rising in a surfactant solution the adsorption process proceeds and leads to the formation of a so called Rear Stagnant Cap (RSC). The larger this RSC is the stronger is the retardation of the rising velocity. The theory of a steady RSC and steady retarded rising velocity, which sets in after a transient stage, has been generally accepted. However, a non-steady process of bubble rising starting from the initial zero velocity represents an important portion of the trajectory of rising, characterized by a local velocity profile (LVP). As there is no theory of RSC growth for large Reynolds numbers Re » 1 so far, the interpretation of LVPs measured in this regime was impossible. It turned out, that an analytical theory for a quasi-steady growth of RSC is possible for small Marangoni numbers Ma « 1, i.e. when the RSC is almost completely compressed, which means a uniform surface concentration Γ(θ)=Γ(∞) within the RSC. Hence, the RSC angle ψ(t) is obtained as a function of the adsorption isotherm parameters and time t. From the steady velocity v(st)(ψ), the dependence of non-steady velocity on time is obtained by employing v(st)[ψ(t)] via a quasi-steady approximation. The measurement of LVP creates a promising new opportunity for investigation of the RSC dynamics and adsorption kinetics. While adsorption and desorption happen at the same localization in the classical methods, in rising bubble experiments desorption occurs mainly within RSC while adsorption on the mobile part of the bubble surface. The desorption flux from RSC is proportional to αΓ(∞), while it is usually αΓ. The adsorption flux at the mobile surface above RSC can be assumed proportional to βC0, while it is usually βC0(1-Γ/Γ(∞)). These simplifications may become favorable in investigations of the adsorption kinetics for larger molecules, in particular for globular proteins, which essentially stay at an interface once adsorbed. PMID:25455807

  2. Effect of nitric oxide on photochemical ozone formation in mixtures of air with molecular chlorine and with trichlorofluoromethane

    NASA Technical Reports Server (NTRS)

    Bittker, D. A.; Wong, E. L.

    1978-01-01

    Ozone formation in a reaction chamber at room temperature and atmospheric pressure were studied for the photolysis of mixtures of NO with either Cl2 or CFCl3 in air. Both Cl2 + NO and CFCl3 + NO in air strongly inhibited O3 formation during the entire 3 to 4 hour reaction. A chemical mechanism that explains the results was presented. An important part of this mechanism was the formation and destruction of chlorine nitrate. Computations were performed with this same mechanism for CFCl3-NO-air mixtures at stratospheric temperatures, pressures, and concentrations. Results showed large reductions in steady-state O3 concentrations in these mixtures as compared with pure air.

  3. On thermonuclear processes in cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Nigmatulin, R. I.; Lahey, R. T., Jr.; Taleyarkhan, R. P.; West, C. D.; Block, R. C.

    2014-09-01

    The theoretical and experimental foundations of so-called bubble nuclear fusion are reviewed. In the nuclear fusion process, a spherical cavitation cluster ˜ 10-2 m in diameter is produced of spherical bubbles at the center of a cylindrical chamber filled with deuterated acetone using a focused acoustic field having a resonant frequency of about 20 kHz. The acoustically-forced bubbles effectuate volume oscillations with sharp collapses during the compression stage. At the final stages of collapse, the bubble cluster emits 2.5 MeV D-D fusion neutron pulses at a rate of ˜ 2000 per second. The neutron yield is ˜ 10^5 s -1. In parallel, tritium nuclei are produced at the same yield. It is shown numerically that, for bubbles having sufficient molecular mass, spherical shock waves develop in the center of the cluster and that these spherical shock waves (microshocks) produce converging shocks within the interior bubbles, which focus energy on the centers of the bubbles. When these shock waves reflect from the centers of the bubbles, extreme conditions of temperature ( ˜ 10^8 K) and density ( ˜ 10^4 kg m -3) arise in a (nano)spherical region ( ˜ 10-7 m in size) that last for ˜ 10-12 s, during which time about ten D-D fusion neutrons and tritium nuclei are produced in the region. A paradoxical result in our experiments is that it is bubble cluster (not streamer) cavitation and the sufficiently high molecular mass of (and hence the low sound speed in) D-acetone ( C3D6O) vapor (as compared, for example, to deuterated water D2O) which are necessary conditions for the formation of convergent spherical microshock waves in central cluster bubbles. It is these waves that allow the energy to be sufficiently focused in the nanospherical regions near the bubble centers for fusion events to occur. The criticism to which the concept of 'bubble fusion' has been subjected in the literature, in particular, most recently in Uspekhi Fizicheskikh Nauk (Physics - Uspekhi) journal, is

  4. Sonoluminescence: Why fiery bubbles have eternal life

    NASA Astrophysics Data System (ADS)

    Lohse, Detlef; Brenner, Michael; Hilgenfeldt, Sascha

    1996-11-01

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

  5. Bias structure to efficiently package a magnetic bubble domain device

    NASA Technical Reports Server (NTRS)

    Chen, Thomas T. (Inventor)

    1978-01-01

    A single, compact bias structure to efficiently package a plurality of magnetic bubble domain device chips having different bias requirements. The vertical magnetic field distribution within the bias structure air gap is selectively controlled by a magnetically soft field adjusting assembly suitably attached within the bias structure. The size and configuration of the field adjusting assembly tailors local field variations within the air gap to correspond with the bias requirements of the bubble domain chips disposed therein.

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

    NASA Technical Reports Server (NTRS)

    Pais, S. C.; Kamotani, Y.; Bhunia, A.; Ostrach, S.

    1999-01-01

    The present investigation reports a study of bubble generation under reduced gravity conditions, using both a co-flow and a cross-flow configuration. This study may be used in the conceptual design of a space-based thermal management system. Ensuing two-phase flow void fraction can be accurately monitored using a single nozzle gas injection system within a continuous liquid flow conduit, as utilized in the present investigation. Accurate monitoring of void fraction leads to precise control of heat and mass transfer coefficients related to a thermal management system; hence providing an efficient and highly effective means of removing heat aboard spacecraft or space stations. Our experiments are performed in parabolic flight aboard the modified DC-9 Reduced Gravity Research Aircraft at NASA Lewis Research Center, using an air-water system. For the purpose of bubble dispersion in a flowing liquid, we use both a co-flow and a cross-flow configuration. In the co-flow geometry, air is introduced through a nozzle in the same direction with the liquid flow. On the other hand, in the cross-flow configuration, air is injected perpendicular to the direction of water flow, via a nozzle protruding inside the two-phase flow conduit. Three different flow conduit (pipe) diameters are used, namely, 1.27 cm, 1.9 cm and 2.54 cm. Two different ratios of nozzle to pipe diameter (D(sub N))sup * are considered, namely (D(sub N))sup * = 0.1 and 0.2, while superficial liquid velocities are varied from 8 to 70 cm/s depending on flow conduit diameter. It is experimentally observed that by holding all other flow conditions and geometry constant, generated bubbles decrease in size with increase in superficial liquid velocity. Detached bubble diameter is shown to increase with air injection nozzle diameter. Likewise, generated bubbles grow in size with increasing pipe diameter. Along the same lines, it is shown that bubble frequency of formation increases and hence the time to detachment of a

  7. 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

  8. 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 aviatio