WorldWideScience

Sample records for bubble distribution acoustic

  1. Distributions of the high temperature and the high pressure inside a single acoustically driven bubble

    Institute of Scientific and Technical Information of China (English)

    应崇福; 安宇

    2002-01-01

    The physical circumstances inside an acoustically driven single gas bubble in water has been intensively explored during the past few years. Starting from the results obtained for a typical case in a well known early paper (Wu, C. C., Roberts, P. H., Phys. Rev. Lett., 1993, 70(22): 3424) and introducing successively several corrections to the physical model, this paper computes in corresponding order the temporal and spatial distributions of significant physical parameters, including the temperature and the pressure, in the bubble around the moment of the bubble's violent collapse, until expectations in consistence with the present points of view are procured. For the peak temperature our results agree with the prevailing belief that in a typical stable single bubble it is of the order of ten thousand degrees.

  2. Resolving size distributions of bubbles with radii less than 30 μm with optical and acoustical methods

    Science.gov (United States)

    Czerski, H.; Twardowski, M.; Zhang, X.; Vagle, S.

    2011-07-01

    Many studies have investigated bubble size distributions in the ocean, but the measured size range does not normally extend to bubbles with a radius below 20 μm. Bubbles smaller than this are thought to have a significant effect on the optical properties of the ocean, potentially affecting remotely sensed measurements of ocean color and the optical detection of particulates and dissolved matter. Such optical data are becoming the major source of oceanic information about algal blooms, primary productivity, sediment loading and the spread of pollutants. The challenges associated with measuring these bubbles are difficulty of calibrating sensors with independent bubble size measurements and lack of knowledge about the organic coating on the bubbles. This paper describes simultaneous oceanic measurements of these small bubbles using independent optical and acoustical techniques. These measurements agree well, and an investigation of the bubble coating parameters was made. Both the optical and acoustical properties of bubbles are affected by this organic coating, and a comparison of these measurements narrows down the choice of possible coating parameters. Our results suggest that the bubbles measured in this study were likely to have a coating with a thickness of 10 nm and a refractive index of 1.18, and that the coating thickness is the more important parameter for optical inversions. The research described here is the first attempt to constrain these parameters in the ocean using two independent techniques and suggests that further studies of this type could result in significant insight into oceanic bubble coatings.

  3. Effects of vapour bubbles on acoustic and temperature distributions of therapeutic ultrasound

    Institute of Scientific and Technical Information of China (English)

    Fan Ting-Bo; Zhang Dong; Zhang Zhe; Ma Yong; Gong Xiu-Fen

    2008-01-01

    This paper describes the evolution of vapour bubbles and its effect on nonlinear ultrnsound propagation and temperature rise through tissues for therapeutic ultrasound.An acoustic-thermo coupling algorithm incorporating nonlinearity,diffraction,and temperature-dependent tissue properties,is employed to describe nonlinear ultrasound propagation and thermal effect.Results demonstrate that an obvious migration of peak pressure toward transducer surface is observed while the position of peak temperature changes little in liver tissue before the generation of vapour bubbles,and that the boiling region enlarges towards the surface of transducer in axial direction but increases slowly in radial direction after the generation of vapour bubbles.

  4. ACOUSTIC MEASUREMENTS BUBBLES IN BIOLOGICAL TIESSURE

    Institute of Scientific and Technical Information of China (English)

    CHAHINE Georges L.; TANGUAY Michel; LORAINE Greg

    2009-01-01

    An acoustic based instrument,the ABS Acoustic Bubble Spectrometer(R)(C)(ABS),was investigated for the detection and quantification of bubbles in biological media.These include viscoelastic media(blood),materials of varying density(bone in tissue),non-homogenous distribution of bubbles(intravenous bubbly flow),and bubbles migrating in tissue(decompression sickness,DCS).The performance of the ABS was demonstrated in a series of laboratory experiments.Validation of the code was performed using a viscoelastic polymer solution,Polyox,in which the bubble size distribution and void fraction were determined by ABS measurements and with image analysis of high speed videos.These tests showed that the accuracy of the ABS was not significantly affected by viscoelasticity for bubbles smaller than 200 microns.The ABS detection and measurement of non-homogenous bubble distributions was demonstrated using a bubbly flow through a simulated vein surrounded by tissue.The scatter of acoustic signals due to bones in the acoustic pathway was also investigated.These in-vitro experiments were done using meat(beef)as a tissue simulant.Decompression experiments were done using beef meat which was held underwater at high pressure(9.9 atm)then rapidly decompressed.Bubble size distributions and void fraction calculations in these experiments were then validated using image analysis of high speed video.In addition,preliminary experiments were performed with the US Navy Medical Research Center,demonstrating the utility of the modified ABS system in detecting the evolution of bubbles in swine undergoing decompression sickness(DCS).These results indicate that the ABS may be used to detect and quantify the evolution of bubbles in-vivo and aid in the monitoring of DCS.

  5. Sonochemistry and the acoustic bubble

    CERN Document Server

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

    2015-01-01

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

  6. Synchrotron x-ray imaging of acoustic cavitation bubbles induced by acoustic excitation

    Science.gov (United States)

    Jung, Sung Yong; Park, Han Wook; Park, Sung Ho; Lee, Sang Joon

    2017-04-01

    The cavitation induced by acoustic excitation has been widely applied in various biomedical applications because cavitation bubbles can enhance the exchanges of mass and energy. In order to minimize the hazardous effects of the induced cavitation, it is essential to understand the spatial distribution of cavitation bubbles. The spatial distribution of cavitation bubbles visualized by the synchrotron x-ray imaging technique is compared to that obtained with a conventional x-ray tube. Cavitation bubbles with high density in the region close to the tip of the probe are visualized using the synchrotron x-ray imaging technique, however, the spatial distribution of cavitation bubbles in the whole ultrasound field is not detected. In this study, the effects of the ultrasound power of acoustic excitation and working medium on the shape and density of the induced cavitation bubbles are examined. As a result, the synchrotron x-ray imaging technique is useful for visualizing spatial distributions of cavitation bubbles, and it could be used for optimizing the operation conditions of acoustic cavitation.

  7. Size distribution estimation of cavitation bubble cloud via bubbles dissolution using an ultrasound wide-beam method

    Science.gov (United States)

    Xu, Shanshan; Zong, Yujin; Liu, Xiaodong; Wan, Mingxi

    2017-03-01

    This paper proposed an acoustic technique to estimate size distribution of a cavitation bubble cloud induced by focused ultrasound (FUS) based on the dissolution of bubble cloud trapped by a wide beam of low acoustic pressure, after the acoustic exposure of FUS is turned off. Dissolution of cavitation bubbles in saline and in phase-shift nanodroplet emulsion diluted with degassed saline or saturated saline has been respectively studied to quantify the effects of pulse duration (PD) and acoustic power (AP) or peak negative pressure (PNP) of FUS on size distribution of cavitation bubbles.

  8. Probing Cell Deformability via Acoustically Actuated Bubbles.

    Science.gov (United States)

    Xie, Yuliang; Nama, Nitesh; Li, Peng; Mao, Zhangming; Huang, Po-Hsun; Zhao, Chenglong; Costanzo, Francesco; Huang, Tony Jun

    2016-02-17

    An acoustically actuated, bubble-based technique is developed to investigate the deformability of cells suspended in microfluidic devices. A microsized bubble is generated by an optothermal effect near the targeted cells, which are suspended in a microfluidic chamber. Subsequently, acoustic actuation is employed to create localized acoustic streaming. In turn, the streaming flow results in hydrodynamic forces that deform the cells in situ. The deformability of the cells is indicative of their mechanical properties. The method in this study measures mechanical biomarkers from multiple cells in a single experiment, and it can be conveniently integrated with other bioanalysis and drug-screening platforms. Using this technique, the mean deformability of tens of HeLa, HEK, and HUVEC cells is measured to distinguish their mechanical properties. HeLa cells are deformed upon treatment with Cytochalasin. The technique also reveals the deformability of each subpopulation in a mixed, heterogeneous cell sample by the use of both fluorescent markers and mechanical biomarkers. The technique in this study, apart from being relevant to cell biology, will also enable biophysical cellular diagnosis.

  9. Laryngeal findings and acoustic changes in hubble-bubble smokers.

    Science.gov (United States)

    Hamdan, Abdul-latif; Sibai, Abla; Oubari, Dima; Ashkar, Jihad; Fuleihan, Nabil

    2010-10-01

    The purpose of our investigation was to evaluate the laryngeal findings and acoustic changes in hubble-bubble smokers. A total of 42 subjects with history of hubble-bubble smoking were recruited for this study. A corresponding group with a history of cigarette smoking and controls were matched. All subjects underwent laryngeal video-endostroboscopic evaluation and acoustic analysis. In the hubble-bubble smoking group, 61.9% were males. The average age was 30.02 +/- 9.48 years and the average number of years of smoking was 8.09 +/- 6.45 years. Three subjects had dysphonia at the time of examination. The incidence of benign lesions of the vocal folds in the hubble-bubble group was 21.5%, with edema being the most common at 16.7% followed by cyst at 4.8%. The incidence of laryngeal findings was significantly higher in the hubble-bubble group compared to controls. In the cigarette-smoking group, the most common finding was vocal fold cyst in 14.8% followed by polyps in 7.4%, and edema, sulcus vocalis and granuloma. These findings were not significantly different from the hubble-bubble group except for the thick mucus, which was significantly higher in the latter. There were no significant changes in any of the acoustic parameters between hubble-bubble smokers and controls except for the VTI and MPT, which were significantly lower in the hubble-bubble group. In comparison with the cigarette-smoking group, hubble-bubble smokers had significantly higher Fundamental frequency and habitual pitch (p value 0.042 and 0.008, respectively). The laryngeal findings in hubble-bubble smokers are comparable to cigarette smokers. These laryngeal findings are not translated acoustically, as all the acoustic parameters are within normal range compared to controls.

  10. Precise measurement technique for the stable acoustic cavitation bubble

    Institute of Scientific and Technical Information of China (English)

    HUANG Wei; CHEN Weizhong; LIU Yanan; GAO Xianxian; JIANG Lian; XU Junfeng; ZHU Yifei

    2005-01-01

    Based on the periodic oscillation of the stable acoustic cavitation bubble, we present a precise measurement technique for the bubble evolution. This technique comprises the lighting engineering of pulsing laser beam whose phase can be digitally shifted, and the long distance microphotographics. We used a laser, an acousto-optic modulator, a pulse generator, and a long distance microscope. The evolution of a levitated bubble can be directly shown by a series of bubble's images at different phases. Numerical simulation in the framework of the Rayleigh-Plesset bubble dynamics well supported the experimental result, and the ambient radius of the bubble, an important parameter related to the mass of the gas inside the bubble, was obtained at the same time.

  11. Bubble Size Distribution in a Vibrating Bubble Column

    Science.gov (United States)

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

    2016-11-01

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

  12. Optimal Acoustic Attenuation of Weakly Compressible Media Permeated with Air Bubbles

    Institute of Scientific and Technical Information of China (English)

    LIANG Bin; CHENG Jian-Chun

    2007-01-01

    Based on fuzzy logic (FL) and genetic algorithm (GA), we present an optimization method to obtain the optimal acoustic attenuation of a longitudinal acoustic wave propagating in a weakly compressible medium permeated with air bubbles. In the optimization, the parameters of the size distribution of bubbles in the medium are optimized for providing uniformly high acoustic attenuation in the frequency band of interest. Compared with other traditional optimization methods, the unique advantage of the present method is that it can locate the global optimum quickly and effectively in need of knowing the mathematical model precisely. As illustrated by a numerical simulation, the method is effective and essential in enhancing the acoustic attenuation of such a medium in an optimal manner. The bubbly medium with optimized structural parameters can effectively attenuate longitudinal waves at intermediate frequencies with an acoustic attenuation approximating a constant value of 10(dB/cm). Such bubbly media with optimal acoustic attenuations may be applied to design acoustic absorbent by controlling broader attenuation band and higher efficiency.

  13. Mixing high-viscosity fluids via acoustically driven bubbles

    Science.gov (United States)

    Orbay, Sinem; Ozcelik, Adem; Lata, James; Kaynak, Murat; Wu, Mengxi; Huang, Tony Jun

    2017-01-01

    We present an acoustofluidic micromixer which can perform rapid and homogeneous mixing of highly viscous fluids in the presence of an acoustic field. In this device, two high-viscosity polyethylene glycol (PEG) solutions were co-injected into a three-inlet PDMS microchannel with the center inlet containing a constant stream of nitrogen flow which forms bubbles in the device. When these bubbles were excited by an acoustic field generated via a piezoelectric transducer, the two solutions mixed homogenously due to the combination of acoustic streaming, droplet ejection, and bubble eruption effects. The mixing efficiency of this acoustofluidic device was evaluated using PEG-700 solutions which are ~106 times more viscous than deionized (DI) water. Our results indicate homogenous mixing of the PEG-700 solutions with a ~0.93 mixing index. The acoustofluidic micromixer is compact, inexpensive, easy to operate, and has the capacity to mix highly viscous fluids within 50 ms.

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

    Science.gov (United States)

    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.

  15. Acoustic Sensor Design for Dark Matter Bubble Chamber Detectors

    Directory of Open Access Journals (Sweden)

    Ivan Felis

    2016-06-01

    Full Text Available Dark matter bubble chamber detectors use piezoelectric sensors in order to detect and discriminate the acoustic signals emitted by the bubbles grown within the superheated fluid from a nuclear recoil produced by a particle interaction. These sensors are attached to the outside walls of the vessel containing the fluid. The acoustic discrimination depends strongly on the properties of the sensor attached to the outer wall of the vessel that has to meet the requirements of radiopurity and size. With the aim of optimizing the sensor system, a test bench for the characterization of the sensors has been developed. The sensor response for different piezoelectric materials, geometries, matching layers, and backing layers have been measured and contrasted with FEM simulations and analytical models. The results of these studies lead us to have a design criterion for the construction of specific sensors for the next generation of dark matter bubble chamber detectors (250 L.

  16. Acoustic Sensor Design for Dark Matter Bubble Chamber Detectors.

    Science.gov (United States)

    Felis, Ivan; Martínez-Mora, Juan Antonio; Ardid, Miguel

    2016-06-10

    Dark matter bubble chamber detectors use piezoelectric sensors in order to detect and discriminate the acoustic signals emitted by the bubbles grown within the superheated fluid from a nuclear recoil produced by a particle interaction. These sensors are attached to the outside walls of the vessel containing the fluid. The acoustic discrimination depends strongly on the properties of the sensor attached to the outer wall of the vessel that has to meet the requirements of radiopurity and size. With the aim of optimizing the sensor system, a test bench for the characterization of the sensors has been developed. The sensor response for different piezoelectric materials, geometries, matching layers, and backing layers have been measured and contrasted with FEM simulations and analytical models. The results of these studies lead us to have a design criterion for the construction of specific sensors for the next generation of dark matter bubble chamber detectors (250 L).

  17. Acoustic characteristics of bubble bursting at the surface of a high-viscosity liquid

    Institute of Scientific and Technical Information of China (English)

    Liu Xiao-Bo; Zhang Jian-Run; Li Pu

    2012-01-01

    An acoustic pressure model of bubble bursting is proposed.An experiment studying the acoustic characteristics of the bursting bubble at the surface of a high-viscosity liquid is reported.It is found that the sudden bursting of a bubble at the high-viscosity liquid surface generates N-shape wave at first,then it transforms into a jet wave.The fundamental frequency of the acoustic signal caused by the bursting bubble decreases linearly as the bubble size increases.The results of the investigation can be used to understand the acoustic characteristics of bubble bursting.

  18. The acoustic bubble: Ocean, cetacean and extraterrestrial acoustics, and cold water cleaning

    Science.gov (United States)

    Leighton, T. G.

    2017-01-01

    This paper summarizes the content of a plenary lecture on the author’s personal research into the interactions between bubbles and sound fields, covering particular topics involving the climatically important gas exchange between atmosphere and ocean, the implications of bubbly ocean water to marine mammals that use sound, and the opportunities afforded by incorporating acoustical sensors onto probes launched to investigate other worlds in our solar system. It closes with recent data on the opportunities of bubble acoustics to investigate methods of cold water cleaning.

  19. Giant frequency down-conversion of the dancing acoustic bubble

    Science.gov (United States)

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

    2016-11-01

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

  20. Instability of interfaces of gas bubbles in liquids under acoustic excitation with dual frequency.

    Science.gov (United States)

    Zhang, Yuning; Du, Xiaoze; Xian, Haizhen; Wu, Yulin

    2015-03-01

    Instability of interfaces of gas bubbles in liquids under acoustic excitation with dual frequency is theoretically investigated. The critical bubble radii dividing stable and unstable regions of bubbles under dual-frequency acoustic excitation are strongly affected by the amplitudes of dual-frequency acoustic excitation rather than the frequencies of dual-frequency excitation. The limitation of the proposed model is also discussed with demonstrating examples.

  1. Evaluation and interpretation of bubble size distributions in pulsed megasonic fields

    Science.gov (United States)

    Hauptmann, M.; Struyf, H.; De Gendt, S.; Glorieux, C.; Brems, S.

    2013-05-01

    The occurrence of acoustic cavitation is incorporating a multitude of interdependent effects that strongly depend on the bubble size. Therefore, bubble size control would be beneficial for biological and industrial processes that rely on acoustic cavitation. A pulsed acoustic field can result in bubble size control and the repeated dissolution and reactivation ("recycling") of potentially active bubbles. As a consequence, a pulsed field can strongly enhance cavitation activity. In this paper, we present a modified methodology for the evaluation of the active bubble size distribution by means of a combination of cavitation noise measurements and ultrasonic pulsing. The key component of this modified methodology is the definition of an upper size limit, below which bubbles—in between subsequent pulses—have to dissolve, in order to be sustainably recycled. This upper limit makes it possible to explain and link the enhancement of cavitation activity to a bubble size distribution. The experimentally determined bubble size distributions for different power densities are interpreted in the frame of numerical calculations of the oscillatory responses of the bubbles to the intermittent driving sound field. The distributions are found to be shaped by the size dependent interplay between bubble pulsations, rectified diffusion, coalescence, and the development of parametrically amplified shape instabilities. Also, a phenomenological reactivation-deactivation model is proposed to explain and quantify the observed enhancement of cavitation activity under pulsed, with respect to continuous sonication. In this model, the pulse-duration determines the magnitude of the reactivation of partially dissolved bubbles and the deactivation of activated bubbles by coalescence. It is shown that the subsequent recycling of previously active bubbles leads to an accumulation of cavitation activity, which saturates after a certain number of pulses. The model is fitted to the experimental

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

    Science.gov (United States)

    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.

  3. 2-D steering and propelling of acoustic bubble-powered microswimmers.

    Science.gov (United States)

    Feng, Jian; Yuan, Junqi; Cho, Sung Kwon

    2016-06-21

    This paper describes bi-directional (linear and rotational) propelling and 2-D steering of acoustic bubble-powered microswimmers that are achieved in a centimeter-scale pool (beyond chip level scale). The core structure of a microswimmer is a microtube with one end open in which a gaseous bubble is trapped. The swimmer is propelled by microstreaming flows that are generated when the trapped bubble is oscillated by an external acoustic wave. The bubble oscillation and thus propelling force are highly dependent on the frequency of the acoustic wave and the bubble length. This dependence is experimentally studied by measuring the resonance behaviors of the testing pool and bubble using a laser Doppler vibrometer (LDV) and by evaluating the generated streaming flows. The key idea in the present 2-D steering is to utilize this dependence. Multiple bubbles with different lengths are mounted on a single microswimmer with a variety of arrangements. By controlling the frequency of the acoustic wave, only frequency-matched bubbles can strongly oscillate and generate strong propulsion. By arranging multiple bubbles of different lengths in parallel but with their openings opposite and switching the frequency of the acoustic wave, bi-directionally linear propelling motions are successfully achieved. The propelling forces are calculated by a CFD analysis using the Ansys Fluent® package. For bi-directional rotations, a similar method but with diagonal arrangement of bubbles on a rectangular swimmer is also applied. The rotation can be easily reversed when the frequency of the acoustic wave is switched. For 2-D steering, short bubbles are aligned perpendicular to long bubbles. It is successfully demonstrated that the microswimmer navigates through a T-junction channel under full control with and without carrying a payload. During the navigation, the frequency is the main control input to select and resonate targeted bubbles. All of these operations are achieved by a single

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

    Science.gov (United States)

    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.

  5. Acoustic emission noise from sodium vapour bubble collapsing: detection, interpretation, modelling and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Dentico, G.; Pacilio, V.; Papalia, B.; Taglienti, S.; Tosi, V.

    1982-01-01

    Sodium vapour bubble collapsing is detected by means of piezoelectric accelorometers coupled to the test section via short waveguides. The output analog signal is processed by transforming it into a time series of pulses through the setting of an amplitude threshold and the shaping of a standard pulse (denominated 'event') every time the signal crosses that border. The number of events is counted in adjacent and equal time duration samples and the waiting time distribution between contiguous events is measured. Up to the moment, six kinetic properties have been found for the mentioned time series. They help in setting a stochastic model in which the subministration of energy into a liquid sodium medium induces the formation of vapour bubbles and their consequent collapsing delivers acoustic pulses. Finally, a simulation procedure is carried out: a Polya's urn model is adopted for simulating event sequences with a priori established requisites.

  6. Modeling and experimental analysis of acoustic cavitation bubbles for Burst Wave Lithotripsy

    Science.gov (United States)

    Maeda, Kazuki; Colonius, Tim; Kreider, Wayne; Maxwell, Adam; Cunitz, Bryan; Bailey, Michael

    2016-01-01

    A combined modeling and experimental study of acoustic cavitation bubbles that are initiated by focused ultrasound waves is reported. Focused ultrasound waves of frequency 335 kHz and peak negative pressure 8 MPa are generated in a water tank by a piezoelectric transducer to initiate cavitation. The resulting pressure field is obtained by direct numerical simulation (DNS) and used to simulate single bubble oscillation. The characteristics of cavitation bubbles observed by high-speed photography qualitatively agree withs the simulation result. Finally, bubble clouds are captured using acoustic B-mode imaging that works in synchronization with high-speed photography. PMID:27087826

  7. Study of acoustic bubble cluster dynamics using a lattice Boltzmann model

    Institute of Scientific and Technical Information of China (English)

    Mahdi Daemi; Mohammad Taeibi-Rahni; Hamidreza Massah

    2015-01-01

    Search for the development of a reliable mathematical model for understanding bubble dynamics behavior is an ongoing endeavor. A long list of complex phenomena underlies physics of this problem. In the past decades, the lattice Boltzmann (LB) method has emerged as a promising tool to address such complexities. In this regard, we have applied a 121-velocity multiphase lattice Boltzmann model (LBM) to an asymmetric cluster of bubbles in an acoustic field. A problem as a benchmark is studied to check the consistency and applicability of the model. The problem of interest is to study the deformation and coalescence phenomena in bubble cluster dynamics, and the screening effect on an acoustic multi-bubble medium. It has been observed that the LB model is able to simulate the combination of the three aforementioned phenomena for a bubble cluster as a whole and for every individual bubble in the cluster.

  8. Acoustic streaming produced by a cylindrical bubble undergoing volume and translational oscillations in a microfluidic channel

    Science.gov (United States)

    Doinikov, Alexander A.; Combriat, Thomas; Thibault, Pierre; Marmottant, Philippe

    2016-09-01

    A theoretical model is developed for acoustic streaming generated by a cylindrical bubble confined in a fluid channel between two planar elastic walls. The bubble is assumed to undergo volume and translational oscillations. The volume oscillation is caused by an imposed acoustic pressure field and generates the bulk scattered wave in the fluid gap and Lamb-type surface waves propagating along the fluid-wall interfaces. The translational oscillation is induced by the velocity field of an external sound source such as another bubble or an oscillatory fluid flow. The acoustic streaming is assumed to result from the interaction of the volume and the translational modes of the bubble oscillations. The general solutions for the linear equations of fluid motion and the equations of acoustic streaming are calculated with no restrictions on the ratio between the viscous penetration depth and the bubble size. Approximate solutions for the limit of low viscosity are provided as well. Simulations of streamline patterns show that the geometry of the streaming resembles flows generated by a source dipole, while the vortex orientation is governed by the driving frequency, bubble size, and the distance of the bubble from the source of translational excitation. Experimental verification of the developed theory is performed using data for streaming generated by bubble pairs.

  9. Acoustic Localization in Weakly Compressible Elastic Media Permeated with Air Bubbles

    Institute of Scientific and Technical Information of China (English)

    LIANG Bin; ZHU Zhe-Min; CHENG Jian-Chun

    2006-01-01

    @@ The propagation of longitudinal acoustic waves in weakly compressible elastic media permeated with air bubbles is investigated on the basis of the radial pulsation equation of a single bubble. The multiple scattering of waves in such media is rigorously described by using a self-consistent approach.

  10. Acoustic streaming produced by a cylindrical bubble undergoing volume and translational oscillations in a microfluidic channel.

    Science.gov (United States)

    Doinikov, Alexander A; Combriat, Thomas; Thibault, Pierre; Marmottant, Philippe

    2016-09-01

    A theoretical model is developed for acoustic streaming generated by a cylindrical bubble confined in a fluid channel between two planar elastic walls. The bubble is assumed to undergo volume and translational oscillations. The volume oscillation is caused by an imposed acoustic pressure field and generates the bulk scattered wave in the fluid gap and Lamb-type surface waves propagating along the fluid-wall interfaces. The translational oscillation is induced by the velocity field of an external sound source such as another bubble or an oscillatory fluid flow. The acoustic streaming is assumed to result from the interaction of the volume and the translational modes of the bubble oscillations. The general solutions for the linear equations of fluid motion and the equations of acoustic streaming are calculated with no restrictions on the ratio between the viscous penetration depth and the bubble size. Approximate solutions for the limit of low viscosity are provided as well. Simulations of streamline patterns show that the geometry of the streaming resembles flows generated by a source dipole, while the vortex orientation is governed by the driving frequency, bubble size, and the distance of the bubble from the source of translational excitation. Experimental verification of the developed theory is performed using data for streaming generated by bubble pairs.

  11. A Demonstration of Underwater Bubble Capture by the Fundamental Acoustic Mode in Spherical Geometry

    Directory of Open Access Journals (Sweden)

    Umaporn KONTHARAK

    2008-01-01

    Full Text Available Nowadays, scientific demonstrations have become a crucial part of scientific learning. Acoustic waves are normally demonstrated in air via Kundt’s tube, but a physical demonstration for underwater acoustic waves is still lacking. In this paper, we address one of the aspects by demonstrating a way to acoustically-trap gas bubbles in a spherical, water-filled flask resonating at its first fundamental mode. The theory of acoustic waves in a spherical geometry, particularly the fundamental mode, is reviewed. The full description of the experimental setup is expressed both acoustically and electronically. By using this method, we show that a gas bubble can be stabilized in the middle of a flask at an acoustic frequency of 21.16 kHz, the acoustic fundamental frequency of the flask.

  12. Propagation of acoustic wave in viscoelastic medium permeated with air bubbles

    Institute of Scientific and Technical Information of China (English)

    Liang Bin; Zhu Zhe-Min; Cheng Jian-Chun

    2006-01-01

    Based on the modification of the radial pulsation equation of an individual bubble, an effective medium method (EMM) is presented for studying propagation of linear and nonlinear longitudinal acoustic waves in viscoelastic medium permeated with air bubbles. A classical theory developed previously by Gaunaurd (Gaunaurd GC and (U)berall H, J. Acoust. Soc. Am., 1978; 63: 1699-1711) is employed to verify the EMM under linear approximation by comparing the dynamic (i.e. frequency-dependent) effective parameters, and an excellent agreement is obtained. The propagation of longitudinal waves is hereby studied in detail. The results illustrate that the nonlinear pulsation of bubbles serves as the source of second harmonic wave and the sound energy has the tendency to be transferred to second harmonic wave. Therefore the sound attenuation and acoustic nonlinearity of the viscoelastic matrix are remarkably enhanced due to the system's resonance induced by the existence of bubbles.

  13. Acoustic waveform of continuous bubbling in a non-Newtonian fluid.

    Science.gov (United States)

    Vidal, Valérie; Ichihara, Mie; Ripepe, Maurizio; Kurita, Kei

    2009-12-01

    We study experimentally the acoustic signal associated with a continuous bubble bursting at the free surface of a non-Newtonian fluid. Due to the fluid rheological properties, the bubble shape is elongated, and, when bursting at the free surface, acts as a resonator. For a given fluid concentration, at constant flow rate, repetitive bubble bursting occurs at the surface. We report a modulation pattern of the acoustic waveform through time. Moreover, we point out the existence of a precursor acoustic signal, recorded on the microphone array, previous to each bursting. The time delay between this precursor and the bursting signal is well correlated with the bursting signal frequency content. Their joint modulation through time is driven by the fluid rheology, which strongly depends on the presence of small satellite bubbles trapped in the fluid due to the yield stress.

  14. Correction of bubble size distributions from transmission electron microscopy observations

    Energy Technology Data Exchange (ETDEWEB)

    Kirkegaard, P.; Eldrup, M.; Horsewell, A.; Skov Pedersen, J.

    1996-01-01

    Observations by transmission electron microscopy of a high density of gas bubbles in a metal matrix yield a distorted size distribution due to bubble overlap and bubble escape from the surface. A model is described that reconstructs 3-dimensional bubble size distributions from 2-dimensional projections on taking these effects into account. Mathematically, the reconstruction is an ill-posed inverse problem, which is solved by regularization technique. Extensive Monte Carlo simulations support the validity of our model. (au) 1 tab., 32 ills., 32 refs.

  15. Phase Transition in Acoustic Localization in a Soft Medium Permeated with Air Bubbles

    Institute of Scientific and Technical Information of China (English)

    LIANG Bin; ZOU Xin-Ye; CHENG Jian-Chun

    2009-01-01

    Propagation of an acoustic wave in a soft medium permeated with air bubbles is theoretically investigated by using a self-consistent approach. The soft medium is assumed to be viscoelastic to estimate the effect of acoustic absorption on the acoustic localization in such a medium. The oscillation phases of bubbles are examined by employing a phase diagram method. A collective oscillation of the bubbles is observed once the acoustic localization occurs, which is known as a phenomenon of 'phase transition', and such a phenomenon persists as we manually increase the viscosity factor of the soft medium. Therefore it is proven that the phenomenon of phase transition may serve as a unique criterion to effectively identify acoustic localization in a bubbly soft medium even in the presence of viscosity, and the directions of the phase vectors help to determine the extent of localization. This is of practical significance for experimental research studying the acoustic localization in such a medium, for which the presence of viscosity generally causes great ambiguity in distinguishing the effects of localization and acoustic absorption.

  16. Nonlinear activity of acoustically driven gas bubble near a rigid boundary

    Energy Technology Data Exchange (ETDEWEB)

    Maksimov, Alexey [Pacific Oceanological Institute, Vladivostok 690041 (Russian Federation)

    2015-10-28

    The presence of a boundary can produce considerable changes in the oscillation amplitude of the bubble and its scattered echo. The present study fills a gap in the literature, in that it is concerned theoretically with the bubble activity at relatively small distances from the rigid boundary. It was shown that the bi-spherical coordinates provide separation of variables and are more suitable for analysis of the dynamics of these constrained bubbles. Explicit formulas have been derived which describe the dependence of the bubble emission near a rigid wall on its size and the separation distance between the bubble and the boundary. As applications, time reversal technique for gas leakage detection and radiation forces that are induced by an acoustic wave on a constrained bubble were analyzed.

  17. Implosion of an underwater spark-generated bubble and acoustic energy evaluation using the Rayleigh model.

    Science.gov (United States)

    Buogo, Silvano; Cannelli, Giovanni B

    2002-06-01

    The growth, collapse, and rebound of a vapor bubble generated by an underwater spark is studied by means of high-speed cinematography, simultaneously acquiring the emitted acoustic signature. Video recordings show that the growth and collapse phases are nearly symmetrical during the first two or three cycles, the bubble shape being approximately spherical. After 2-3 cycles the bubble behavior changes from a collapsing/rebounding regime with sound-emitting implosions to a pulsating regime with no implosions. The motion of the bubble wall during the first collapses was found to be consistent with the Rayleigh model of a cavity in an incompressible liquid, with the inclusion of a vapor pressure term at constant temperature within each bubble cycle. An estimate of the pressure inside the bubble is obtained measuring the collapse time and maximum radius, and the amount of energy converted into acoustical energy upon each implosion is deduced. The resulting value of acoustic efficiency was found to be in agreement with measurements based on the emitted acoustic pulse.

  18. Active acoustic leak detection for LMFBR steam generator. Sound attenuation due to bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Kumagai, Hiromichi; Sakuma, Toshio [Central Research Inst. of Electric Power Industry, Komae, Tokyo (Japan). Komae Research Lab.

    1995-06-01

    In the steam generators (SG) of LMFBR, it is necessary to detect the leakage of water from tubes of heat exchangers as soon as it occurs. The active acoustic detection method has drawn general interest owing to its short response time and reduction of the influence of background noise. In this paper, the application of the active acoustic detection method for SG is proposed, and sound attenuation by bubbles is investigated experimentally. Furthermore, using the SG sector model, sound field characteristics and sound attenuation characteristics due to injection of bubbles are studied. It is clarified that the sound attenuation depends upon bubble size as well as void fraction, that the distance attenuation of sound in the SG model containing heat transfer tubes is 6dB for each two-fold increase of distance, and that emitted sound attenuates immediately upon injection of bubbles. (author).

  19. Concentration distribution around a growing gas bubble in tissue.

    Science.gov (United States)

    Mohammadein, S A; Mohamed, K G

    2010-05-01

    This paper presents the concentration distribution around a growing nitrogen gas bubble in the blood and other tissues of divers who surface too quickly, when the ambient pressure through the decompression process is variable and constant. This effort is a modification of Sirinivasan et al. model (1999) [9]. The mathematical model is solved analytically to find the growth rate of a gas bubble in a tissue after decompression in the ambient pressure. Moreover, the concentration distribution around the growing bubble is introduced. The growth process is affected by ascent rate alpha (t), tissue diffusivity D(T), initial concentration difference DeltaC(0), surface tension sigma and void fraction varphi(0).

  20. Nonlinear scattering of acoustic waves by natural and artificially generated subsurface bubble layers in sea.

    Science.gov (United States)

    Ostrovsky, Lev A; Sutin, Alexander M; Soustova, Irina A; Matveyev, Alexander L; Potapov, Andrey I; Kluzek, Zigmund

    2003-02-01

    The paper describes nonlinear effects due to a biharmonic acoustic signal scattering from air bubbles in the sea. The results of field experiments in a shallow sea are presented. Two waves radiated at frequencies 30 and 31-37 kHz generated backscattered signals at sum and difference frequencies in a bubble layer. A motorboat propeller was used to generate bubbles with different concentrations at different times, up to the return to the natural subsurface layer. Theoretical consideration is given for these effects. The experimental data are in a reasonably good agreement with theoretical predictions.

  1. Variations in the spatial distribution of sonoluminescing bubbles in the presence of an ionic surfactant and electrolyte.

    Science.gov (United States)

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

    2010-03-04

    It has been established that the addition of sodium dodecylsulfate (SDS) to water to a concentration of 1 mM increased the integrated sonoluminescence (SL) intensity to a maximum. Moreover, further increase in the SDS concentration to 10 mM decreased the SL intensity to a level comparable to that obtained for water. Photographic images of water and 10 mM SDS have revealed a localized distribution of SL bubbles near the liquid surface. For 1 mM SDS, a homogeneous distribution of SL bubbles was observed throughout the liquid. In this study, a comprehensive investigation was performed to determine the variations in the spatial distribution of SL bubbles as a function of SDS concentration, with and without the addition of sodium chloride (NaCl). It was found that the integrated SL intensity passed through a local minimum as the distribution of SL bubbles transformed from an isolated to a homogeneous distribution at 0.25 and 2.4 mM SDS. Similar transformations in the spatial distribution of SL bubbles within these SDS solutions were also observed upon the addition of a few millimolar NaCl. These variations in the spatial distribution of SL bubbles in aqueous solutions containing an ionic surfactant and electrolyte were believed to be the result of changes in the coalescence stability of bubbles, the attenuation of the acoustic wave, and the standing wave ratio.

  2. Bubble size distribution in surface wave breaking entraining process

    Institute of Scientific and Technical Information of China (English)

    HAN; Lei; YUAN; YeLi

    2007-01-01

    From the similarity theorem,an expression of bubble population is derived as a function of the air entrainment rate,the turbulent kinetic energy (TKE) spectrum density and the surface tension.The bubble size spectrum that we obtain has a dependence of a-2.5+nd on the bubble radius,in which nd is positive and dependent on the form of TKE spectrum within the viscous dissipation range.To relate the bubble population with wave parameters,an expression about the air entrainment rate is deduced by introducing two statistical relations to wave breaking.The bubble population vertical distribution is also derived,based on two assumptions from two typical observation results.

  3. Measuring Technique of Bubble Size Distributions in Dough

    Science.gov (United States)

    Maeda, Tatsurou; Do, Gab-Soo; Sugiyama, Junichi; Oguchi, Kosei; Tsuta, Mizuki

    A novel technique to recognize bubbles in bread dough and analyze their size distribution was developed by using a Micro-Slicer Image Processing System (MSIPS). Samples were taken from the final stage of the mixing process of bread dough which generally consists of four distinctive stages. Also, to investigate the effect of freeze preservation on the size distribution of bubbles, comparisons were made between fresh dough and the dough that had been freeze preserved at .30°C for three months. Bubbles in the dough samples were identified in the images of MSIPS as defocusing spots due to the difference in focal distance created by vacant spaces. In case of the fresh dough, a total of 910 bubbles were recognized and their maximum diameter ranged from 0.4 to 70.5μm with an average of 11.1μm. On the other hand, a total of 1,195 bubbles were recognized from the freeze-preserved sample, and the maximum diameter ranged from 0.9 to 32.7μm with an average of 6.7μm. Small bubbles with maximum diameters less than 10μm comprised approximately 59% and 78% of total bubbles for fresh and freeze-preserved dough samples, respectively. The results indicated that the bubble size of frozen dough is smaller than that of unfrozen one. The proposed method can provide a novel tool to investigate the effects of mixing and preservation treatments on the size, morphology and distribution of bubbles in bread dough.

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

    Directory of Open Access Journals (Sweden)

    ANDRÉ G. SIMÃO

    2016-06-01

    Full Text Available Abstract 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.

  5. Enhanced and reduced transmission of acoustic waves with bubble meta-screens

    CERN Document Server

    Bretagne, Alice; Leroy, V

    2011-01-01

    We present a class of sonic meta-screens for manipulating air-borne acoustic waves at ultrasonic or audible frequencies. Our screens consist of periodic arrangements of air bubbles in water or possibly embedded in a soft elastic matrix. They can be used for soundproofing, but also for exalting transmission at an air/water interface or even to achieve enhanced absorption.

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

    Science.gov (United States)

    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.

  7. The Distribution of Bubble Sizes During Reionization

    CERN Document Server

    Lin, Yin; Furlanetto, Steven R; Sutter, P M

    2015-01-01

    A key physical quantity during reionization is the size of HII regions. Previous studies found a characteristic bubble size which increases rapidly during reionization, with apparent agreement between simulations and analytic excursion set theory. Using four different methods, we critically examine this claim. In particular, we introduce the use of the watershed algorithm -- widely used for void finding in galaxy surveys -- which we show to be an unbiased method with the lowest dispersion and best performance on Monte-Carlo realizations of a known bubble size PDF. We find that a friends-of-friends algorithm declares most of the ionized volume to be occupied by a network of volume-filling regions connected by narrow tunnels. For methods tuned to detect those volume-filling regions, previous apparent agreement between simulations and theory is spurious, and due to a failure to correctly account for the window function of measurement schemes. The discrepancy is already obvious from visual inspection. Instead, HI...

  8. The distribution of bubble sizes during reionization

    Science.gov (United States)

    Lin, Yin; Oh, S. Peng; Furlanetto, Steven R.; Sutter, P. M.

    2016-09-01

    A key physical quantity during reionization is the size of H II regions. Previous studies found a characteristic bubble size which increases rapidly during reionization, with apparent agreement between simulations and analytic excursion set theory. Using four different methods, we critically examine this claim. In particular, we introduce the use of the watershed algorithm - widely used for void finding in galaxy surveys - which we show to be an unbiased method with the lowest dispersion and best performance on Monte Carlo realizations of a known bubble size probability density function (PDF). We find that a friends-of-friends algorithm declares most of the ionized volume to be occupied by a network of volume-filling regions connected by narrow tunnels. For methods tuned to detect the volume-filling regions, previous apparent agreement between simulations and theory is spurious, and due to a failure to correctly account for the window function of measurement schemes. The discrepancy is already obvious from visual inspection. Instead, H II regions in simulations are significantly larger (by factors of 10-1000 in volume) than analytic predictions. The size PDF is narrower, and evolves more slowly with time, than predicted. It becomes more sharply peaked as reionization progresses. These effects are likely caused by bubble mergers, which are inadequately modelled by analytic theory. Our results have important consequences for high-redshift 21 cm observations, the mean free path of ionizing photons, and the visibility of Lyα emitters, and point to a fundamental failure in our understanding of the characteristic scales of the reionization process.

  9. Bubbles

    DEFF Research Database (Denmark)

    Dholakia, Nikhilesh; Turcan, Romeo V.

    2013-01-01

    A goal of our ongoing research stream is to develop a multidisciplinary metatheory of bubbles. In this viewpoint paper we put forward a typology of bubbles by comparing four types of assets – entertainment, commodities, financial securities (stocks), and housing properties – where bubbles could a...

  10. Effects of acoustic parameters on bubble cloud dynamics in ultrasound tissue erosion (histotripsy).

    Science.gov (United States)

    Xu, Zhen; Hall, Timothy L; Fowlkes, J Brian; Cain, Charles A

    2007-07-01

    High intensity pulsed ultrasound can produce significant mechanical tissue fractionation with sharp boundaries ("histotripsy"). At a tissue-fluid interface, histotripsy produces clearly demarcated tissue erosion and the erosion efficiency depends on pulse parameters. Acoustic cavitation is believed to be the primary mechanism for the histotripsy process. To investigate the physical basis of the dependence of tissue erosion on pulse parameters, an optical method was used to monitor the effects of pulse parameters on the cavitating bubble cloud generated by histotripsy pulses at a tissue-water interface. The pulse parameters studied include pulse duration, peak rarefactional pressure, and pulse repetition frequency (PRF). Results show that the duration of growth and collapse (collapse cycle) of the bubble cloud increased with increasing pulse duration, peak rarefactional pressure, and PRF when the next pulse arrived after the collapse of the previous bubble cloud. When the PRF was too high such that the next pulse arrived before the collapse of the previous bubble cloud, only a portion of histotripsy pulses could effectively create and collapse the bubble cloud. The collapse cycle of the bubble cloud also increased with increasing gas concentration. These results may explain previous in vitro results on effects of pulse parameters on tissue erosion.

  11. Acoustic monitoring of co-seismic changes in gas bubble rupture rate in a hydrothermal reservoir: field evaluation of a possible precursor and mechanism for remote seismic triggering

    Science.gov (United States)

    Crews, J. B.

    2015-12-01

    Remotely triggered seismicity is a phenomenon in which an earthquake at one location triggers others over distances up to thousands of kilometers. The mechanism by which low-amplitude dynamic oscillations of the confining stress can produce such an effect, often after a time delay of minutes-to-days, is unclear, but a concentration of remotely triggered seismic events in carbon-dioxide-rich volcanic and geothermal regions suggests that an increase in pore fluid pressure associated with the nucleation and growth of carbon-dioxide gas bubbles may reduce the effective stress in critically loaded geologic faults. While this hypothesis has been tested in bench-scale laboratory experiments, field detection of seismically initiated gas bubble growth in groundwater may provide further evidence for this remote triggering mechanism. In the present study, a hydrophone continuously records the acoustic power spectrum in CH-10B, a hydrothermal well located in Long Valley Caldera, California - a site that is susceptible to remotely seismic triggering. This well exhibits co-seismic changes in water level in response to near and distant earthquakes, including every magnitude-six or greater at any location on Earth. Exploiting the inverse relationship between gas bubble radius and the peak acoustic frequency emitted when a gas bubble ruptures, this investigation seeks to detect changes in the acoustic power spectrum arising from a shift in the size-distribution or count rate of rupturing gas bubbles, coincident with a distant earthquake. By resolving the timing and intensity of the onset of a change in gas bubble rupture rate after the passage of seismic wave from a distant source, it may be possible to establish the extent to which seismically initiated gas bubble growth contributes to co-seismic borehole water level response, pore fluid pressure perturbations, and the onset of remotely triggered seismicity.

  12. Determination of size distribution of bubbles in a bubbly column two phase flows by ultrasound and neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Baroni, Douglas B.; Lamy, Carlos A.; Bittencourt, Marcelo S.Q.; Pereira, Claudio M.N.A., E-mail: douglasbaroni@ien.gov.b, E-mail: lamy@ien.gov.b, E-mail: bittenc@ien.gov.b, E-mail: cmnap@ien.gov.b [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Cunha Filho, Jurandyr S. [Escola Tecnica Estadual Visconde de Maua (ETEVM/RJ), Rio de Janeiro, RJ (Brazil); Motta, Mauricio S., E-mail: mmotta@cefet-rj.b [Centro Federal de Educacao Tecnologica Celso Suckow da Fonseca (CEFET/RJ), Rio de Janeiro, RJ (Brazil)

    2011-07-01

    The development of advanced nuclear reactor conceptions depends largely on the amount of available data to the designer. Non invasive ultrasonic techniques can contribute to the evaluation of gas-liquid two-phase regimes in the nuclear thermo-hydraulic circuits. A key-point for success of those techniques is the interpretation of the ultrasonic signal. In this work, a methodology based in artificial neural networks (ANN) is proposed to predict size distribution of bubbles in a bubbly flow. To accomplish that, an air feed system control was used to obtain specific bubbly flows in an experimental system utilizing a Plexiglas vertical bubbly column. Four different size distribution of bubbles were generated. The bubbles were photographed and measured. To evaluate the different size distribution of bubbles it was used the ultrasonic reflected echo on the opposite wall of the column. Then, an ANN has been developed for predicting size distribution of bubbles by using the frequency spectra of the ultrasonic signal as input. A trained artificial neural network using ultrasonic signal in the frequency domain can evaluate with a good precision the size distribution of bubbles generated in this system. (author)

  13. Passive acoustic derived bubble flux and applications to natural gas seepage in the Mackenzie Delta, NWT, Canada and Coal Oil Point, CA

    Science.gov (United States)

    Culling, D.; Leifer, I.; Dallimore, S.; Alcala, K.

    2012-12-01

    Methane is a prominent greenhouse gas that escapes naturally from thermogenic reservoirs as seepage from marine and lacustrine biogenic sources as bubble ebullition. Geologic methane emissions are critically important contributors to the global methane budget however, few quantitative flux measurements are available for shallow waters. This gap in knowledge is critical as in these settings gas can easily transit as bubbles through the water column and directly influence global atmospheric budgets. Video and active acoustic (sonar) measurements of bubble flux have spatial limitations requiring predictable bubble emission location. Passive acoustics are less affected by these limitations, in addition, they can provide data in water too shallow for effective sonar bubble observations. Lab tests were undertaken to quantify the acoustic signature of bubbles formed in non-cohesive sediments. specifically focusing on mechanisms that complicate interpretation of acoustic data. Lab tests then were compared to field data to provide measurement calibration/validation. The principles behind the acoustic analysis method are based on the Minnaert equation, which relates a bubble radius and acoustic frequency. Bubble size and the resultant acoustic frequency from known flows and capillary tube diameters are well documented; however changing sediment pathways adds to the complexity of bubble formation and the resultant bubble acoustic signal. These complex signals were investigated in a lab tank with a thick, cohesive fine-grained sediment bed, through which bubbles produced by a syringe pump migrated to the sediment-water interface. Then, the resultant bubbles were diverted into clear water and measured from high speed, high definition video, while the acoustic signature of bubble formation was recorded concurrently by a hydrophone. Bubble formation is influenced by currents, which shifts the acoustical signal towards a higher frequency with a more complex pattern than the

  14. Grain size effects on He bubbles distribution and evolution

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Gao, X.; Gao, N. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Wang, Z.G., E-mail: zhgwang@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Cui, M.H.; Wei, K.F.; Yao, C.F.; Sun, J.R.; Li, B.S.; Zhu, Y.B.; Pang, L.L. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Li, Y.F. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Wang, D. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xie, E.Q. [School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China)

    2015-02-15

    Highlights: • SMAT treated T91 and conventional T91 were implanted by 200 keV He{sup 2+} to 1 × 10{sup 21} He m{sup −2} at room temperature and annealed at 450 °C for 3.5 h. • He bubbles in nanometer-size-grained T91 are smaller in as-implanted case. • The bubbles in the matrix of nanograins were hard to detect and those along the nanograin boundaries coalesced and filled with the grain boundaries after annealing. • Brownian motion and coalescence and Ostwald ripening process might lead to bubbles morphology presented in the nanometer-size-grained T91 after annealing. - Abstract: Grain boundary and grain size effects on He bubble distribution and evolution were investigated by He implantation into nanometer-size-grained T91 obtained by Surface Mechanical Attrition Treatment (SMAT) and the conventional coarse-grained T91. It was found that bubbles in the nanometer-size-grained T91 were smaller than those in the conventional coarse-grained T91 in as-implanted case, and bubbles in the matrix of nanograins were undetectable while those at nanograin boundaries (GBs) coalesced and filled in GBs after heat treatment. These results suggested that the grain size of structural material should be larger than the mean free path of bubble’s Brownian motion and/or denuded zone around GBs in order to prevent bubbles accumulation at GBs, and multiple instead of one type of defects should be introduced into structural materials to effectively reduce the susceptibility of materials to He embrittlement and improve the irradiation tolerance of structural materials.

  15. Numerical Simulation of Sub-cooled Cavitating Flow by Using Bubble Size Distribution

    Institute of Scientific and Technical Information of China (English)

    Yutaka ITO; Hideki WAKAMATSU; Takao NAGASAKI

    2003-01-01

    A new cavitating model by using bubble size distribution based on mass of bubbles is proposed. Liquid phase is treated with Eulerian framework as a mixture containing minute cavitating bubbles. Vapor phase consists of various sizes of minute vapor bubbles, which is distributed to classes based on their mass. The change of bubble number density for each class was solved by considering the change of bubble mass due to phase change as well as generation of new bubbles due to heterogeneous nucleation. In this method the mass of bubbles is treated as an independent variable, in other word, a new coordinate, and dependant variables are solved in Eulerian framework for spatial coordinates and bubble-mass coordinate. The present method is applied to a cavitating flow in a convergent-divergent nozzle, and the two-phase flow with bubble size distribution and phase change was successfully predicted.

  16. Acoustic Characterization of Fluorinert FC-43 Liquid with Helium Gas Bubbles: Numerical Experiments

    Directory of Open Access Journals (Sweden)

    Christian Vanhille

    2017-01-01

    Full Text Available In this work, we define the acoustic characteristics of a biphasic fluid consisting of static helium gas bubbles in liquid Fluorinert FC-43 and study the propagation of ultrasound of finite amplitudes in this medium. Very low sound speed and high sound attenuation are found, in addition to a particularly high acoustic nonlinear parameter. This result suggests the possibility of using this medium as a nonlinear enhancer in various applications. In particular, parametric generation of low ultrasonic frequencies is studied in a resonator cavity as a function of driving pressure showing high conversion efficiency. This work suggests that this medium could be used for applications such as parametric arrays, nondestructive testing, diagnostic medicine, sonochemistry, underwater acoustics, and ultrasonic imaging and to boost the shock formation in fluids.

  17. Nonlinear acoustic propagation in bubbly liquids: Multiple scattering, softening and hardening phenomena.

    Science.gov (United States)

    Doc, Jean-Baptiste; Conoir, Jean-Marc; Marchiano, Régis; Fuster, Daniel

    2016-04-01

    The weakly nonlinear propagation of acoustic waves in monodisperse bubbly liquids is investigated numerically. A hydrodynamic model based on the averaged two-phase fluid equations is coupled with the Rayleigh-Plesset equation to model the dynamics of bubbles at the local scale. The present model is validated in the linear regime by comparing with the Foldy approximation. The analysis of the pressure signals in the linear regime highlights two resonance frequencies: the Minnaert frequency and a multiple scattering resonance that strongly depends on the bubble concentration. For weakly nonlinear regimes, the generation of higher harmonics is observed only for the Minnaert frequency. Linear combinations between the Minnaert harmonics and the multiple scattering resonance are also observed. However, the most significant effect observed is the appearance of softening-hardening effects that share some similarities with those observed for sandstones or cracked materials. These effects are related to the multiple scattering resonance. Downward or upward resonance frequency shifts can be observed depending on the characteristic of the incident wave when increasing the excitation amplitude. It is shown that the frequency shift can be explained assuming that the acoustic wave velocity depends on a law different from those usually encountered for sandstones or cracked materials.

  18. Sound scattering from rough bubbly ocean surface based on modified sea surface acoustic simulator and consideration of various incident angles and sub-surface bubbles' radii

    Science.gov (United States)

    Bolghasi, Alireza; Ghadimi, Parviz; Chekab, Mohammad A. Feizi

    2016-09-01

    The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator (SSAS) developed based on optimization of the Helmholtz-Kirchhoff-Fresnel (HKF) method. The improved acoustic simulator, hereby known as the Modified SSAS (MSSAS), is capable of determining sound scattering from the sea surface and includes an extended Hall-Novarini model and optimized HKF method. The extended Hall-Novarini model is used for considering the effects of sub-surface bubbles over a wider range of radii of sub-surface bubbles compared to the previous SSAS version. Furthermore, MSSAS has the capability of making a three-dimensional simulation of scattered sound from the rough bubbly sea surface with less error than that of the Critical Sea Tests (CST) experiments. Also, it presents scattered pressure levels from the rough bubbly sea surface based on various incident angles of sound. Wind speed, frequency, incident angle, and pressure level of the sound source are considered as input data, and scattered pressure levels and scattering coefficients are provided. Finally, different parametric studies were conducted on wind speeds, frequencies, and incident angles to indicate that MSSAS is quite capable of simulating sound scattering from the rough bubbly sea surface, according to the scattering mechanisms determined by Ogden and Erskine. Therefore, it is concluded that MSSAS is valid for both scattering mechanisms and the transition region between them that are defined by Ogden and Erskine.

  19. Unstable density distribution associated with equatorial plasma bubble

    Science.gov (United States)

    Kherani, E. A.; Bharuthram, R.; Singh, S.; Lakhina, G. S.; de Meneses, F. Carlos

    2016-04-01

    In this work, we present a simulation study of equatorial plasma bubble (EPB) in the evening time ionosphere. The fluid simulation is performed with a high grid resolution, enabling us to probe the steepened updrafting density structures inside EPB. Inside the density depletion that eventually evolves as EPB, both density and updraft are functions of space from which the density as implicit function of updraft velocity or the density distribution function is constructed. In the present study, this distribution function and the corresponding probability distribution function are found to evolve from Maxwellian to non-Maxwellian as the initial small depletion grows to EPB. This non-Maxwellian distribution is of a gentle-bump type, in confirmation with the recently reported distribution within EPB from space-borne measurements that offer favorable condition for small scale kinetic instabilities.

  20. Distributed acoustic sensing with Michelson interferometer demodulation

    Science.gov (United States)

    Liu, Xiaohui; Wang, Chen; Shang, Ying; Wang, Chang; Zhao, Wenan; Peng, Gangding; Wang, Hongzhong

    2016-12-01

    The distributed acoustic sensing (DAS) has been extensively studied and widely used. A distributed acoustic sensing system based on the unbalanced Michelson interferometer with phase generated carrier (PGC) demodulation was designed and tested. The system could directly obtain the phase, amplitude, frequency response, and location information of sound wave at the same time and measurement at all points along the sensing fiber simultaneously. Experiments showed that the system successfully measured the acoustic signals with a phase-pressure sensitivity about-148 dB (re rad/μPa) and frequency response ripple less than 1.5 dB. The further field experiment showed that the system could measure signals at all points along the sensing fiber simultaneously.

  1. Gaseous bubble oscillations in anisotropic non-Newtonian fluids under influence of high-frequency acoustic field

    Science.gov (United States)

    Golykh, R. N.

    2016-06-01

    Progress of technology and medicine dictates the ever-increasing requirements (heat resistance, corrosion resistance, strength properties, impregnating ability, etc.) for non-Newtonian fluids and materials produced on their basis (epoxy resin, coating materials, liquid crystals, etc.). Materials with improved properties obtaining is possible by modification of their physicochemical structure. One of the most promising approaches to the restructuring of non-Newtonian fluids is cavitation generated by high-frequency acoustic vibrations. The efficiency of cavitation in non-Newtonian fluid is determined by dynamics of gaseous bubble. Today, bubble dynamics in isotropic non-Newtonian fluids, in which cavitation bubble shape remains spherical, is most full investigated, because the problem reduces to ordinary differential equation for spherical bubble radius. However, gaseous bubble in anisotropic fluids which are most wide kind of non-Newtonian fluids (due to orientation of macromolecules) deviates from spherical shape due to viscosity dependence on shear rate direction. Therefore, the paper presents the mathematical model of gaseous bubble dynamics in anisotropic non-Newtonian fluids. The model is based on general equations for anisotropic non-Newtonian fluid flow. The equations are solved by asymptotic decomposition of fluid flow parameters. It allowed evaluating bubble size and shape evolution depending on rheological properties of liquid and acoustic field characteristics.

  2. Acoustic imaging for temperature distribution reconstruction

    Science.gov (United States)

    Jia, Ruixi; Xiong, Qingyu; Liang, Shan

    2016-12-01

    For several industrial processes, such as burning and drying, temperature distribution is important because it can reflect the internal running state of industrial equipment and assist to develop control strategy and ensure safety in operation of industrial equipment. The principle of this technique is mainly based on the relationship between acoustic velocity and temperature. In this paper, an algorithm for temperature distribution reconstruction is considered. Compared with reconstruction results of simulation experiments with the least square algorithm and the proposed one, the latter indicates a better information reflection of temperature distribution and relatively higher reconstruction accuracy.

  3. Acoustic imaging for temperature distribution reconstruction

    Directory of Open Access Journals (Sweden)

    Ruixi Jia

    2016-12-01

    Full Text Available For several industrial processes, such as burning and drying, temperature distribution is important because it can reflect the internal running state of industrial equipment and assist to develop control strategy and ensure safety in operation of industrial equipment. The principle of this technique is mainly based on the relationship between acoustic velocity and temperature. In this paper, an algorithm for temperature distribution reconstruction is considered. Compared with reconstruction results of simulation experiments with the least square algorithm and the proposed one, the latter indicates a better information reflection of temperature distribution and relatively higher reconstruction accuracy.

  4. Effect of liquid subcooling on acoustic characteristics during the condensation process of vapor bubbles in a subcooled pool

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Jiguo, E-mail: tangjiguo@sina.cn [Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin, Heilongjiang 150001 (China); Yan, Changqi, E-mail: Changqi_yan@163.com [Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin, Heilongjiang 150001 (China); Sun, Licheng, E-mail: leechengsun@sohu.com [State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu 610065 (China); Li, Ya; Wang, Kaiyuan [Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin, Heilongjiang 150001 (China)

    2015-11-15

    Highlights: • Deviations of signals increase first and then decrease with increase in subcooling. • Two typical waveforms are observed and correspond to bubble split-up and collapse. • Dominant frequency in low frequency region is found for all condensation regimes. • Peaks in high frequency region were only found in capillary wave regime. • Bubble collapse frequency is close to frequency of first peak in amplitude spectra. - Abstract: Sound characteristics of direct contact condensation of vapor bubbles in a subcooled pool were investigated experimentally with a hydrophone and a high-speed video camera. Three different condensation modes were observed, which were referred to as shape oscillation regime, transition regime and capillary wave regime in the paper. Time domain analysis indicated that the acoustic signals were boosted in their maximum amplitude with increase in subcooling, while their standard and average absolute deviations shifted to decrease after reaching a peak value. In addition, two different waveforms were found, possible sources of which were split-up and collapse of bubbles, respectively. From the amplitude spectra obtained by FFT, the first dominant frequency was found at frequency of 150–300 Hz for all condensation regimes, whereas some peaks in high frequency region were observed only for the capillary wave regime. The first dominant frequency was the result of the periodic variation in the vapor bubble volume, and the peaks in high frequency region were due to the high-frequency oscillation of water in pressure caused by sudden bubble collapse. The frequency of first peak was considered to be resulted from the periodic bubble collapse or split-up and thus was close to the bubble collapse frequency obtained from snapshots of bubble condensation. Moreover, according to results of short-time Fourier transform (STFT), the time intervals in which a certain process of bubble condensing occurred could be well known.

  5. An electrochemical and high-speed imaging study of micropore decontamination by acoustic bubble entrapment.

    Science.gov (United States)

    Offin, Douglas G; Birkin, Peter R; Leighton, Timothy G

    2014-03-14

    Electrochemical and high-speed imaging techniques are used to study the abilities of ultrasonically-activated bubbles to clean out micropores. Cylindrical pores with dimensions (diameter × depth) of 500 μm × 400 μm (aspect ratio 0.8), 125 μm × 350 μm (aspect ratio 2.8) and 50 μm × 200 μm (aspect ratio 4.0) are fabricated in glass substrates. Each pore is contaminated by filling it with an electrochemically inactive blocking organic material (thickened methyl salicylate) before the substrate is placed in a solution containing an electroactive species (Fe(CN)6(3-)). An electrode is fabricated at the base of each pore and the Faradaic current is used to monitor the decontamination as a function of time. For the largest pore, decontamination driven by ultrasound (generated by a horn type transducer) and bulk fluid flow are compared. It is shown that ultrasound is much more effective than flow alone, and that bulk fluid flow at the rates used cannot decontaminate the pore completely, but that ultrasound can. In the case of the 125 μm pore, high-speed imaging is used to elucidate the cleaning mechanisms involved in ultrasonic decontamination and reveals that acoustic bubble entrapment is a key feature. The smallest pore is used to explore the limits of decontamination and it is found that ultrasound is still effective at this size under the conditions employed.

  6. Experimental study on bubble size distributions in a direct-contact evaporator

    Directory of Open Access Journals (Sweden)

    Ribeiro Jr. C. P.

    2004-01-01

    Full Text Available Experimental bubble size distributions and bubble mean diameters were obtained by means of a photographic technique for a direct-contact evaporator operating in the quasi-steady-state regime. Four gas superficial velocities and three different spargers were analysed for the air-water system. In order to assure the statistical significance of the determined size distributions, a minimum number of 450 bubbles was analysed for each experimental condition. Some runs were also conducted with an aqueous solution of sucrose to study the solute effect on bubble size distribution. For the lowest gas superficial velocity considered, at which the homogeneous bubbling regime is observed, the size distribution was log-normal and depended on the orifice diameter in the sparger. As the gas superficial velocity was increased, the size distribution progressively acquired a bimodal shape, regardless of the sparger employed. The presence of sucrose in the continuous phase led to coalescence hindrance.

  7. Acoustic CT system for temperature distribution measurement

    Institute of Scientific and Technical Information of China (English)

    Shinji Ohyama; Toyofumi Oga; Kazuo Oshima; Junya Takayama

    2008-01-01

    In this paper,a measurement method for crosssectional temperature distribution is addressed. A novel method based on an acoustic CT technique is proposed. Specifically,the temperature distributions are estimated using the time of flight data of several ultrasonic propagation paths. The times of the flight data contain both temperature and wind effect,and the method to select only temperature component is introduced. A filtered back projection method is applied to reconstruct the temperature distributions from the time of flight data. An experimental system was designed and fabricated to realize simultaneous temperature and wind velocity distribution measurements. Through this system,the effectiveness of the proposed measurement method is confirmed.

  8. Distributed acoustic sensing for pipeline monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Hill, David; McEwen-King, Magnus [OptaSense, QinetiQ Ltd., London (United Kingdom)

    2009-07-01

    Optical fibre is deployed widely across the oil and gas industry. As well as being deployed regularly to provide high bandwidth telecommunications and infrastructure for SCADA it is increasingly being used to sense pressure, temperature and strain along buried pipelines, on subsea pipelines and downhole. In this paper we present results from the latest sensing capability using standard optical fibre to detect acoustic signals along the entire length of a pipeline. In Distributed Acoustic Sensing (DAS) an optical fibre is used for both sensing and telemetry. In this paper we present results from the OptaSense{sup TM} system which has been used to detect third party intervention (TPI) along buried pipelines. In a typical deployment the system is connected to an existing standard single-mode fibre, up to 50km in length, and was used to independently listen to the acoustic / seismic activity at every 10 meter interval. We will show that through the use of advanced array processing of the independent, simultaneously sampled channels it is possible to detect and locate activity within the vicinity of the pipeline and through sophisticated acoustic signal processing to obtain the acoustic signature to classify the type of activity. By combining spare fibre capacity in existing buried fibre optic cables; processing and display techniques commonly found in sonar; and state-of-the-art in fibre-optic distributed acoustic sensing, we will describe the new monitoring capabilities that are available to the pipeline operator. Without the expense of retrofitting sensors to the pipeline, this technology can provide a high performance, rapidly deployable and cost effective method of providing gapless and persistent monitoring of a pipeline. We will show how this approach can be used to detect, classify and locate activity such as; third party interference (including activity indicative of illegal hot tapping); real time tracking of pigs; and leak detection. We will also show how an

  9. Size distribution of air bubbles entering the brain during cardiac surgery.

    Directory of Open Access Journals (Sweden)

    Emma M L Chung

    Full Text Available 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.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.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.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.

  10. Gas distribution effects on waste properties: Viscosities of bubbly slurries

    Energy Technology Data Exchange (ETDEWEB)

    Gauglitz, P.A.; Shah, R.R.; Davis, R.L.

    1994-09-01

    The retention and episodic release of flammable gases are critical safety concerns for double-shell tanks that contain waste slurries. The rheological behavior of the waste, particularly of the settled sludge, is critical to characterizing the tendency of the waste to retain gas bubbles. The presence of gas bubbles is expected to affect the rheology of the sludge, but essentially no literature data are available to assess the effect of bubbles. Accordingly, the objectives of this study are to develop models for the effect of gas bubbles on the viscosity of a particulate slurry, develop an experimental method (capillary rheometer), collect data on the viscosity of a bubbly slurry, and develop a theoretical basis for interpreting the experimental data from the capillary rheometer.

  11. Dynamics of two interacting hydrogen bubbles in liquid aluminum under the influence of a strong acoustic field

    Science.gov (United States)

    Lebon, Gerard S. B.; Pericleous, Koulis; Tzanakis, Iakovos; Eskin, Dmitry G.

    2015-10-01

    Ultrasonic melt processing significantly improves the properties of metallic materials. However, this promising technology has not been successfully transferred to the industry because of difficulties in treating large volumes of melt. To circumvent these difficulties, a fundamental understanding of the efficiency of ultrasonic treatment of liquid metals is required. In this endeavor, the dynamics of two interacting hydrogen bubbles in liquid aluminum are studied to determine the effect of a strong acoustic field on their behavior. It is shown that coalescence readily occurs at low frequencies in the range of 16 to 20 kHz; forcing frequencies at these values are likely to promote degassing. Emitted acoustic pressures from relatively isolated bubbles that resonate with the driving frequency are in the megapascal range and these cavitation shock waves are presumed to promote grain refinement by disrupting the growth of the solidification front.

  12. Measurement of bubble and pellet size distributions: past and current image analysis technology.

    Science.gov (United States)

    Junker, Beth

    2006-08-01

    Measurements of bubble and pellet size distributions are useful for biochemical process optimizations. The accuracy, representation, and simplicity of these measurements improve when the measurement is performed on-line and in situ rather than off-line using a sample. Historical and currently available measurement systems for photographic methods are summarized for bubble and pellet (morphology) measurement applications. Applications to cells, mycelia, and pellets measurements have driven key technological developments that have been applied for bubble measurements. Measurement trade-offs exist to maximize accuracy, extend range, and attain reasonable cycle times. Mathematical characterization of distributions using standard statistical techniques is straightforward, facilitating data presentation and analysis. For the specific application of bubble size distributions, selected bioreactor operating parameters and physicochemical conditions alter distributions. Empirical relationships have been established in some cases where sufficient data have been collected. In addition, parameters and conditions with substantial effects on bubble size distributions were identified and their relative effects quantified. This information was used to guide required accuracy and precision targets for bubble size distribution measurements from newly developed novel on-line and in situ bubble measurement devices.

  13. Inhomogeneous distribution of Chlamydomonas in a cylindrical container with a bubble plume.

    Science.gov (United States)

    Nonaka, Yuki; Kikuchi, Kenji; Numayama-Tsuruta, Keiko; Kage, Azusa; Ueno, Hironori; Ishikawa, Takuji

    2016-01-19

    Swimming microalgae show various taxes, such as phototaxis and gravitaxis, which sometimes result in the formation of a cell-rich layer or a patch in a suspension. Despite intensive studies on the effects of shear flow and turbulence on the inhomogeneous distribution of microalgae, the effect of a bubble plume has remained unclear. In this study, we used Chlamydomonas as model microalgae, and investigated the spatial distribution of cells in a cylindrical container with a bubble plume. The results illustrate that cells become inhomogeneously distributed in the suspension due to their motility and photo-responses. A vortical ring distribution was observed below the free surface when the bubble flow rate was sufficiently small. We performed a scaling analysis on the length scale of the vortical ring, which captured the main features of the experimental results. These findings are important in understanding transport phenomena in a microalgae suspension with a bubble plume.

  14. Discrete particle modeling of granular temperature distribution in a bubbling fluidized bed

    Institute of Scientific and Technical Information of China (English)

    Yurong He; Tianyu Wang; Niels Deen; Martin van Sint Annaland; Hans Kuipers; Dongsheng Wen

    2012-01-01

    The discrete hard sphere particle model (DPM) is applied in this work to study numerically the distributions of particle and bubble granular temperatures in a bubbling fluidized bed.The dimensions of the bed and other parameters are set to correspond to those of Müller et al.(2008).Various drag models and operational parameters are investigated to find their influence on particle and bubble granular temperatures.Various inlet superficial gas velocities are used in this work to obtain their effect on flow characteristics.It is found that the superficial gas velocity has the most important effect on granular temperatures including bubble granular temperature,particle translational granular temperature and particle rotational granular temperature.The drag force model affects more seriously the large scale variables such as the bubble granular temperature.Restitution coefficient influences all granular temperatures to some degree.Simulation results are compared with experimental results by Müller et al.(2008) showing reasonable agreement.

  15. Spatial-temporal dynamics of cavitation bubble clouds in 1.2 MHz focused ultrasound field.

    Science.gov (United States)

    Chen, Hong; Li, Xiaojing; Wan, Mingxi

    2006-09-01

    Cavitation bubbles have been recognized as being essential to many applications of ultrasound. Temporal evolution and spatial distribution of cavitation bubble clouds induced by a focused ultrasound transducer of 1.2 MHz center frequency are investigated by high-speed photography. It is revealed that at a total acoustic power of 72 W the cavitation bubble cloud first emerges in the focal region where cavitation bubbles are observed to generate, grow, merge and collapse during the initial 600 micros. The bubble cloud then grows upward to the post-focal region, and finally becomes visible in the pre-focal region. The structure of the final bubble cloud is characterized by regional distribution of cavitation bubbles in the ultrasound field. The cavitation bubble cloud structure remains stable when the acoustic power is increased from 25 W to 107 W, but it changes to a more violent form when the acoustic power is further increased to 175 W.

  16. Distribution of Acoustic Power Spectra for an Isolated Helicopter Fuselage

    Directory of Open Access Journals (Sweden)

    Kusyumov A.N.

    2016-01-01

    Full Text Available The broadband aerodynamic noise can be studied, assuming isotropic flow, turbulence and decay. Proudman’s approach allows practical calculations of noise based on CFD solutions of RANS or URANS equations at the stage of post processing and analysis of the solution. Another aspect is the broadband acoustic spectrum and the distribution of acoustic power over a range of frequencies. The acoustic energy spectrum distribution in isotropic turbulence is non monotonic and has a maximum at a certain value of Strouhal number. In the present work the value of acoustic power peak frequency is determined using a prescribed form of acoustic energy spectrum distribution presented in papers by S. Sarkar and M. Y. Hussaini and by G. M. Lilley. CFD modelling of the flow around isolated helicopter fuselage model was considered using the HMB CFD code and the RANS equations.

  17. Nonmigrating tidal signature in the distributions of equatorial plasma bubbles and prereversal enhancement

    Science.gov (United States)

    Kil, Hyosub; Kwak, Young-Sil; Lee, Woo Kyoung; Krall, Jonathan; Huba, Joseph D.; Oh, Seung-Jun

    2015-04-01

    Some wave-like features in the longitudinal distribution of equatorial plasma bubbles understood in association with diurnal eastward propagating zonal wave number 3 nonmigrating tide (DE3) in the dayside. However, whether or not the wave features are the daytime DE3 signature has not yet been rigorously investigated. This study investigates (1) the existence of the DE3 signature in the longitudinal distribution of bubbles by analyzing the first Republic of China (ROCSAT-1) satellite data acquired in 2000-2002 and (2) the role of daytime DE3 in the creation of bubbles by examining the linear growth rate of the generalized Rayleigh-Taylor (R-T) instability. The linear growth rate is derived from the "Sami2 is Another Model of the Ionosphere" model simulation results. In the longitudinal distribution of bubbles derived from ROCSAT-1 observations, the wave number 4 component, the representative characteristic of DE3, is a weak feature. In addition, the amplitude and phase of the wave number 4 component do not show a consistent behavior in comparison with those of DE3. Our numerical calculation results show that the linear growth rate of the R-T instability is not sensitive to the variation of the daytime vertical plasma drift. These results indicate that the DE3 signature in the occurrence rate of bubbles is not obvious and the effect of daytime DE3 on the creation of bubbles is negligible.

  18. Enhancement of channel wall vibration due to acoustic excitation of an internal bubbly flow

    NARCIS (Netherlands)

    Zhang, M.M.; Katz, J.; Prosperetti, A.

    2010-01-01

    The effect of an internal turbulent bubbly flow on vibrations of a channel wall is investigated experimentally and theoretically. Our objective is to determine the spectrum and attenuation rate of sound propagating through a bubbly liquid flow in a channel, and connect these features with the vibrat

  19. Microneedles with Controlled Bubble Sizes and Drug Distributions for Efficient Transdermal Drug Delivery

    Science.gov (United States)

    Wang, Qi Lei; Zhu, Dan Dan; Liu, Xu Bo; Chen, Bo Zhi; Guo, Xin Dong

    2016-01-01

    Drug loaded dissolving microneedles (DMNs) fabricated with water soluble polymers have received increasing attentions as a safe and efficient transdermal drug delivery system. Usually, to reach a high drug delivery efficiency, an ideal drug distribution is gathering more drugs in the tip or the top part of DMNs. In this work, we introduce an easy and new method to introduce a bubble with controlled size into the body of DMNs. The introduction of bubbles can prevent the drug diffusion into the whole body of the MNs. The heights of the bubbles are well controlled from 75 μm to 400 μm just by changing the mass concentrations of polymer casting solution from 30 wt% to 10 wt%. The drug-loaded bubble MNs show reliable mechanical properties and successful insertion into the skins. For the MNs prepared from 15 wt% PVA solution, bubble MNs achieve over 80% of drug delivery efficiency in 20 seconds, which is only 10% for the traditional solid MNs. Additionally, the bubble microstructures in the MNs are also demonstrated to be consistent and identical regardless the extension of MN arrays. These scalable bubble MNs may be a promising carrier for the transdermal delivery of various pharmaceuticals. PMID:27929104

  20. Decompression vs. Decomposition: Distribution, Amount, and Gas Composition of Bubbles in Stranded Marine Mammals.

    Science.gov (United States)

    de Quirós, Yara Bernaldo; González-Diaz, Oscar; Arbelo, Manuel; Sierra, Eva; Sacchini, Simona; Fernández, Antonio

    2012-01-01

    Gas embolic lesions linked to military sonar have been described in stranded cetaceans including beaked whales. These descriptions suggest that gas bubbles in marine mammal tissues may be more common than previously thought. In this study we have analyzed gas amount (by gas score) and gas composition within different decomposition codes using a standardized methodology. This broad study has allowed us to explore species-specific variability in bubble prevalence, amount, distribution, and composition, as well as masking of bubble content by putrefaction gases. Bubbles detected within the cardiovascular system and other tissues related to both pre- and port-mortem processes are a common finding on necropsy of stranded cetaceans. To minimize masking by putrefaction gases, necropsy, and gas sampling must be performed as soon as possible. Before 24 h post mortem is recommended but preferably within 12 h post mortem. At necropsy, amount of bubbles (gas score) in decomposition code 2 in stranded cetaceans was found to be more important than merely presence vs. absence of bubbles from a pathological point of view. Deep divers presented higher abundance of gas bubbles, mainly composed of 70% nitrogen and 30% CO(2), suggesting a higher predisposition of these species to suffer from decompression-related gas embolism.

  1. The Milky Way Project and ATLASGAL: The distribution and physical properties of cold clumps near infrared bubbles

    CERN Document Server

    Kendrew, S; Simpson, R; Csengeri, T; Wienen, M; Lintott, C J; Povich, M S; Beaumont, C; Schuller, F

    2016-01-01

    We present a statistical study of the distribution and physical properties of cold dense material in and around the inner Galactic Plane near infrared bubbles as catalogued by the Milky Way Project citizen scientists. Using data from the ATLASGAL 870 um survey, we show that 48 +/- 2% of all cold clumps in the studied survey region (|l| <= 65 degrees, |b| <= 1 degree) are found in close proximity to a bubble, and 25 +/- 2% appear directly projected towards a bubble rim. A two-point correlation analysis confirms the strong correlation of massive cold clumps with expanding bubbles. It shows an overdensity of clumps along bubble rims that grows with increasing bubble size, which shows how interstellar medium material is reordered on large scales by bubble expansion around regions of massive star formation. The highest column density clumps appear resistent to the expansion, remaining overdense towards the bubbles' interior rather than being swept up by the expanding edge. Spectroscopic observations in ammon...

  2. Study on demodulated signal distribution and acoustic pressure phase sensitivity of a self-interfered distributed acoustic sensing system

    Science.gov (United States)

    Shang, Ying; Yang, Yuan-Hong; Wang, Chen; Liu, Xiao-Hui; Wang, Chang; Peng, Gang-Ding

    2016-06-01

    We propose a demodulated signal distribution theory for a self-interfered distributed acoustic sensing system. The distribution region of Rayleigh backscattering including the acoustic sensing signal in the sensing fiber is investigated theoretically under different combinations of both the path difference and pulse width Additionally we determine the optimal solution between the path difference and pulse width to obtain the maximum phase change per unit length. We experimentally test this theory and realize a good acoustic pressure phase sensitivity of  -150 dB re rad/(μPa·m) of fiber in the frequency range from 200 Hz to 1 kHz.

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

    Science.gov (United States)

    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.

  4. SYS 2: Acoustic ENSBox A System of Self Calibrating Distributed Acoustic Arrays

    OpenAIRE

    Lewis Girod; Martin Lukac; Vlad Trifa; Deborah Estrin

    2006-01-01

    The Acoustic Embedded Networked Sensing Box, is a platform for prototyping rapid-deployable distributed acoustic sensing systems, particularly distributed source localization. Each ENSBox integrates an ARM processor running Linux and supports key facilities required for source localization: a sensor array, wireless network services, time synchronization, and precise self-calibration of array position and orientation. The ENSBoxs integrated high precision self-calibration facility sets it ap...

  5. Bubble cloud dynamics in a high-pressure spherical resonator

    Science.gov (United States)

    Anderson, Phillip Andrew

    A bubble cloud is a population of bubbles confined to a region within a fluid. Bubble clouds play a large role in a variety of naturally occurring phenomena and man-made applications (e.g., ocean noise, cavitation damage, sonoluminescence, ultrasonic cleaning, drug delivery, lithotripsy). It is important, therefore, to understand the behavior of bubble clouds so that their effects may be enhanced or diminished as desired. This work explores and characterizes the properties of bubble clouds nucleated inside a high-pressure spherical acoustic resonator, in connection with recent interest in acoustic inertial confinement fusion (acoustic ICF). A laser system was developed to repeatably nucleate a cloud of bubbles inside the resonator. The resulting events were then observed, primarily with schlieren imaging methods. Preliminary studies of the bubble cloud dynamics showed the sensitivity of the initial cloud to nucleation parameters including the phase of nucleation, the laser energy, and the acoustic power. After many acoustic cycles, some bubble clouds are observed to evolve into a tight cluster. The formation of these clusters correlates with initial bubble distributions which have a large cloud interaction parameter, β. Cluster dynamics are seen to be largely driven by reconverging shock waves from previous collapses reflected from the resonator's interior surface. Initial expansion of the cluster boundary is on the order of 8 mm/µs and the maximum radius approaches 3 mm. Shock pressures are estimated to be > 10 GPa at a radius of 100 µm using weak shock theory.

  6. The efficiency and stability of bubble formation by acoustic vaporization of submicron perfluorocarbon droplets.

    Science.gov (United States)

    Reznik, Nikita; Shpak, Oleksandr; Gelderblom, Erik C; Williams, Ross; de Jong, Nico; Versluis, Michel; Burns, Peter N

    2013-09-01

    Submicron droplets of liquid perfluorocarbon converted into microbubbles with applied ultrasound have been studied, for a number of years, as potential next generation extravascular ultrasound contrast agents. In this work, we conduct an initial ultra-high-speed optical imaging study to examine the vaporization of submicron droplets and observe the newly created microbubbles in the first microseconds after vaporization. It was estimated that single pulses of ultrasound at 10 MHz with pressures within the diagnostic range are able to vaporize on the order of at least 10% of the exposed droplets. However, only part of the newly created microbubbles survives immediately following vaporization - the bubbles may recondense back into the liquid droplet state within microseconds of nucleation. The probability of bubble survival within the first microseconds of vaporization was shown to depend on ultrasound excitation pressure as well as on bubble coalescence during vaporization, a behavior influenced by the presence of coating material on the newly created bubbles. The results of this study show for the first time that although initial vaporization of droplets is necessary to create echogenic bubbles, additional factors, such as coalescence and bubble shell properties, are important and should be carefully considered for the production of microbubbles for use in medical imaging.

  7. Constraints on Methane Distribution from Acoustic Profiles of Shallow Sediments Across the Alaska Shelf

    Science.gov (United States)

    Wood, W. T.; Hart, P. E.; Greinert, J.; de Batist, M. A.; Rose, K.; Coffin, R. B.

    2009-12-01

    In September of 2009 the U. S. Naval Research Laboratory, U. S. Dept of Energy, and Royal Netherlands Institute for Sea Research conducted piston coring, acoustic profiling, and water sampling on the Alaskan Arctic shelf from the U. S. Coast Guard icebreaker Polar Sea, as part of the MITAS (Methane In The Arctic Shelf) project. The overall project objective is to determine the role of methane in arctic shelf processes by determining the source, distribution, and concentration of shallow (0-30m methane accumulations as well as active and potential methane seeps along selected transects across and along the Alaskan Beaufort Sea shelf. The specific objective of the acoustic program is to delineate gas (methane) by mapping bubble release into the water column (flare detection), and free gas indications as acoustic blanking and gas fronts in the sediment. The data consist of 3.5 kHz, 12 kHz profiles acquired using hull-mounted transducers on the Polar Sea, in conjunction with 3.5 kHz sub-bottom profiler and 180 kHz multi-beam data acquired from the Polar Sea's ASB (Arctic Service Boat). Acoustic profiles and images, as well as preliminary interpretations are discussed in the presentation.

  8. Cumulative distribution functions associated with bubble-nucleation processes in cavitation

    KAUST Repository

    Watanabe, Hiroshi

    2010-11-15

    Bubble-nucleation processes of a Lennard-Jones liquid are studied by molecular dynamics simulations. Waiting time, which is the lifetime of a superheated liquid, is determined for several system sizes, and the apparent finite-size effect of the nucleation rate is observed. From the cumulative distribution function of the nucleation events, the bubble-nucleation process is found to be not a simple Poisson process but a Poisson process with an additional relaxation time. The parameters of the exponential distribution associated with the process are determined by taking the relaxation time into account, and the apparent finite-size effect is removed. These results imply that the use of the arithmetic mean of the waiting time until a bubble grows to the critical size leads to an incorrect estimation of the nucleation rate. © 2010 The American Physical Society.

  9. A stochastic model of bubble distribution in gas-solid fluidized beds

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    On the basis of the Langevin equation and the Fokker-Planck equation, a stochastic model of bubble distribution in a gas-solid fluidized bed was developed. A fluidized bed with a cross section of 0.3 m×0.02 m and a height of 0.8m was used to investigate the bubble distribution with the photographic method. Two distributors were used with orifice diameters of 3 and 6 mm and opening ratios of 6.4% and 6.8%, respectively. The particles were color glass beads with diameters of 0.3, 0.5 and 0.8 mm (Geldart group B particles). The model predictions are reasonable in accordance with the experiment data. The research results indicated that the distribution of bubble concentration was affected by the particle diameter, the fluidizing velocity, and the distributor style. The fluctuation extension of the distribution of bubble concentration narrowed as the particle diameter, fluidizing velocity and opening ratio of the distributor increased. For a given distributor and given particles the distribution was relatively steady along the bed height as the fluidizing velocity changed.

  10. Can diving-induced tissue nitrogen supersaturation increase the chance of acoustically driven bubble growth in marine mammals?

    Science.gov (United States)

    Houser, D S; Howard, R; Ridgway, S

    2001-11-21

    The potential for acoustically mediated causes of stranding in cetaceans (whales and dolphins) is of increasing concern given recent stranding events associated with anthropogenic acoustic activity. We examine a potentially debilitating non-auditory mechanism called rectified diffusion. Rectified diffusion causes gas bubble growth, which in an insonified animal may produce emboli, tissue separation and high, localized pressure in nervous tissue. Using the results of a dolphin dive study and a model of rectified diffusion for low-frequency exposure, we demonstrate that the diving behavior of cetaceans prior to an intense acoustic exposure may increase the chance of rectified diffusion. Specifically, deep diving and slow ascent/descent speed contributes to increased gas-tissue saturation, a condition that amplifies the likelihood of rectified diffusion. The depth of lung collapse limits nitrogen uptake per dive and the surface interval duration influences the amount of nitrogen washout from tissues between dives. Model results suggest that low-frequency rectified diffusion models need to be advanced, that the diving behavior of marine mammals of concern needs to be investigated to identify at-risk animals, and that more intensive studies of gas dynamics within diving marine mammals should be undertaken.

  11. High-speed imaging of an ultrasound-driven bubble in contact with a wall: " Narcissus" effect and resolved acoustic streaming

    NARCIS (Netherlands)

    Marmottant, Philippe; Versluis, Michel; Jong, de Nico; Hilgenfeldt, Sascha; Lohse, Detlef

    2006-01-01

    We report microscopic observations of the primary flow oscillation of an acoustically driven bubble in contact with a wall, captured with the ultra high-speed camera Brandaris 128 (Chin et al. 2003). The driving frequency is up to 200 kHz, and the imaging frequency is up to 25 MHz. The details of th

  12. Acoustically tuneable optical transmission through a subwavelength hole with a bubble

    CERN Document Server

    Maksymov, Ivan S

    2016-01-01

    Efficient manipulation of light with sound in subwavelength-sized volumes is important for applications in photonics, phononics and biophysics, but remains elusive. We theoretically demonstrate the control of light with MHz-range ultrasound in a subwavelength, 300 nm wide water-filled hole with a 100 nm radius air bubble. Ultrasound-driven pulsations of the bubble modulate the effective refractive index of the hole aperture, which gives rise to spectral tuning of light transmission through the hole. This control mechanism opens up novel opportunities for tuneable acousto-optic and optomechanical metamaterials, and all-optical ultrasound transduction.

  13. Mechanisms of surface pressure distribution within a laminar separation bubble at different Reynolds numbers

    Science.gov (United States)

    Lee, Donghwi; Kawai, Soshi; Nonomura, Taku; Anyoji, Masayuki; Aono, Hikaru; Oyama, Akira; Asai, Keisuke; Fujii, Kozo

    2015-02-01

    Mechanisms behind the pressure distribution and skin friction within a laminar separation bubble (LSB) are investigated by large-eddy simulations around a 5% thickness blunt flat plate at the chord length based Reynolds number 5.0 × 103, 6.1 × 103, 1.1 × 104, and 2.0 × 104. The characteristics inside the LSB change with the Reynolds number; a steady laminar separation bubble (LSB_S) at the Reynolds number 5.0 × 103 and 6.1 × 103, and a steady-fluctuating laminar separation bubble (LSB_SF) at the Reynolds number 1.1 × 104, and 2.0 × 104. Different characteristics of pressure and skin friction distributions are observed by increasing the Reynolds number, such that a gradual monotonous pressure recovery in the LSB_S and a plateau pressure distribution followed by a rapid pressure recovery region in the LSB_SF. The reasons behind the different characteristics of pressure distributions at different Reynolds numbers are discussed by deriving the Reynolds averaged pressure gradient equation. It is confirmed that the viscous stress distributions near the surface play an important role in determining the formation of different pressure distributions. Depending on the Reynolds numbers, the viscous stress distributions near the surface are affected by the development of a separated laminar shear layer or the Reynolds shear stress. In addition, we show that the same analyses can be applied to the flows around a NACA0012 airfoil.

  14. A dynamic pressure view cell for acoustic stimulation of fluids—Micro-bubble generation and fluid movement in porous media

    Science.gov (United States)

    Stewart, Robert A.; Shaw, J. M.

    2015-09-01

    The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10-5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest.

  15. Sound source localization using distributed elevated acoustic sensors

    Science.gov (United States)

    Di, Xiao; Wagstaff, Ronald A.; Anderson, John D.; Gilbert, Kenneth E.

    2009-05-01

    Detecting and localizing impulsive acoustic sources in the daytime using distributed elevated acoustic sensors with large baseline separations has distinct advantages over small ground-based arrays. There are generally two reasons for this: first, during the daytime, because of more direct and less encumbered propagation paths, signal levels are generally larger at altitude than near the ground. Second, larger baselines provide improved localization accuracy. Results are reported from a distributed array of acoustic sensors deployed during an experiment near Bourges, France during June of 2008. The distributed array consisted of microphones and GPS receivers attached to the tether lines of three widely separated aerostats. The sound sources were various impulsive devices. Results from the measurements are presented and discussed. Localization errors (GPS accuracy, propagation calculation, and aerostat motion, etc) are discussed. Possible ways to improve the localization accuracy are suggested.

  16. Acoustic transmission through a single layer of bubbly gel%含泡胶质体层的声透射特性研究

    Institute of Scientific and Technical Information of China (English)

    胡洁; 刘云飞

    2013-01-01

    对包含有限数目气泡的单层胶质体模型,在理论上研究了垂直入射的平面纵波的透射特性.利用计及多重散射效应的自洽场方法,严格求解了该模型中的声传播问题并得到了声透射系数.数值计算结果证明声波可在略高于气泡本征频率的频段内发生局域化,且局域化现象在气泡含量较小时已经出现.此外,采用等效媒质方法对该模型进行均匀化近似后求解了其声透射系数.在不同结构参数下,分析比较了两种方法所得结果的差异,考察了等效媒质方法的适用性.结果表明多重散射效应在气泡含量较低时已显著影响当前模型的声透射特性,尽管等效媒质方法在气泡含量极低(~10-5)时可简便的得到基本有效的计算结果,但当气泡含量变高(~10-4)时,忽略多重散射效应的等效媒质方法已不能正确的描述此类媒质的声传播特性.%For a single slab fabricated by elastic gel which contains randomly-distributed air bubbles,the propagation of normally incident longitudinal plane wave is theoretically studied.The wave propagation is solved rigorously by using a selfconsistent method,with the multiple scattering effects fully 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.The sensibility of the features of localization to the structure parameters is numerically investigated.Comparisons are performed between the results obtained by using the effective medium method and self-consistent method for different structure parameters.The results show that the multiple scattering is very important for bubbly gel even when the volume concentration of bubble is low.It is convenient to accurately describe the acoustic transmission in the present model by using effective medium method when the concentration is extremely low (~ 10

  17. Sound Scattering From Rough Bubbly Ocean Surface Based on Modified Sea Surface Acoustic Simulator and Consideration of Various Incident Angles and Sub-surface Bubbles’ Radii

    Institute of Scientific and Technical Information of China (English)

    Alireza Bolghasi; Parviz Ghadimi; Mohammad A. Feizi Chekab

    2016-01-01

    The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator (SSAS) developed based on optimization of the Helmholtz–Kirchhoff–Fresnel (HKF) method. The improved acoustic simulator, hereby known as the Modified SSAS (MSSAS), is capable of determining sound scattering from the sea surface and includes an extended Hall–Novarini model and optimized HKF method. The extended Hall–Novarini model is used for considering the effects of sub-surface bubbles over a wider range of radii of sub-surface bubbles compared to the previous SSAS version. Furthermore, MSSAS has the capability of making a three-dimensional simulation of scattered sound from the rough bubbly sea surface with less error than that of the Critical Sea Tests (CST) experiments. Also, it presents scattered pressure levels from the rough bubbly sea surface based on various incident angles of sound. Wind speed, frequency, incident angle, and pressure level of the sound source are considered as input data, and scattered pressure levels and scattering coefficients are provided. Finally, different parametric studies were conducted on wind speeds, frequencies, and incident angles to indicate that MSSAS is quite capable of simulating sound scattering from the rough bubbly sea surface, according to the scattering mechanisms determined by Ogden and Erskine. Therefore, it is concluded that MSSAS is valid for both scattering mechanisms and the transition region between them that are defined by Ogden and Erskine.

  18. Stream-wise distribution of skin-friction drag reduction on a flat plate with bubble injection

    Science.gov (United States)

    Qin, Shijie; Chu, Ning; Yao, Yan; Liu, Jingting; Huang, Bin; Wu, Dazhuan

    2017-03-01

    To investigate the stream-wise distribution of skin-friction drag reduction on a flat plate with bubble injection, both experiments and simulations of bubble drag reduction (BDR) have been conducted in this paper. Drag reductions at various flow speeds and air injection rates have been tested in cavitation tunnel experiments. Visualization of bubble flow pattern is implemented synchronously. The computational fluid dynamics (CFD) method, in the framework of Eulerian-Eulerian two fluid modeling, coupled with population balance model (PBM) is used to simulate the bubbly flow along the flat plate. A wide range of bubble sizes considering bubble breakup and coalescence is modeled based on experimental bubble distribution images. Drag and lift forces are fully modeled based on applicable closure models. Both predicted drag reductions and bubble distributions are in reasonable concordance with experimental results. Stream-wise distribution of BDR is revealed based on CFD-PBM numerical results. In particular, four distinct regions with different BDR characteristics are first identified and discussed in this study. Thresholds between regions are extracted and discussed. And it is highly necessary to fully understand the stream-wise distribution of BDR in order to establish a universal scaling law. Moreover, mechanism of stream-wise distribution of BDR is analysed based on the near-wall flow parameters. The local drag reduction is a direct result of near-wall max void fraction. And the near-wall velocity gradient modified by the presence of bubbles is considered as another important factor for bubble drag reduction.

  19. Bubble diagnostics

    Science.gov (United States)

    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. Active acoustic leak detection for LMFBR steam generator. Pt. 5. Experiment for detection of bubbles using the SG full sector model

    Energy Technology Data Exchange (ETDEWEB)

    Kumagai, Hiromichi [Central Research Inst. of Electric Power Industry, Komae, Tokyo (Japan). Komae Research Lab.

    1997-05-01

    In order to prevent the expansion of tube damages and to maintain structural safety in steam generators (SG) of fast breeder reactors (FBR), it is necessary to detect precisely and immediately the leakage of water from tubes of heat exchangers. Therefore, an active acoustic method, which detects the sound attenuation due to bubbles generated in the sodium-water reactions, it being developed. In this paper, the attenuation characteristics of sound attenuated by bubbles and influence of background noise are investigated experimentally by using an SG full sector model (diameter ratio about 1/1, height ratio about 1/7) simulating the actual SG. As an experimental result, the received sound attenuation for ten seconds was more than 10 dB from air bubble injection when injected bubble of 10 l/s (equivalence water leak rate about 10 g/s). The attenuation of sound are least affected by bubble injection position of heat exchanger tube bunch department. And the time was about 25 seconds till the sound attenuation became 10 dB in case of quantity of air bubble 1 l/s (equivalent water leak rate about 1 g/s). It is clarified that the background noise hardly influenced water leak detection performance as a result of having examined influence of background noise. (author)

  1. Active acoustic leak detection for LMFBR steam generators. Pt. 4. Experimental results for detection of bubble using the SG full sector model

    Energy Technology Data Exchange (ETDEWEB)

    Kumagai, Hiromichi [Central Research Inst. of Electric Power Industry, Komae, Tokyo (Japan). Komae Research Lab.

    1996-06-01

    In order to prevent the expansion of tube damages and to maintain structural safety in steam generators (SG) of fast breeder reactor (FBR), it is necessary to detect precisely and immediately the leakage of water from tubes of heat exchangers. The active acoustic method, which detects the sound attenuation due to bubbles generated at the sodium-water reactions, is being developed. In this paper, the attenuation characteristics of sound attenuated by bubbles are investigated experimentally by using the SG full sector model simulating the actual SG. An emitter and a receiver sensor are attached to the SG shell, and the attenuation of sounds due to passing of bubbles through the sound field is detected and measured. As a experimental result, it is clarified that the received sound attenuates immediately upon injection of bubbles, and the attenuation of sound are 2-5 dB at after 10 seconds from bubble injection of 10 l/s. The attenuation of sound are least affected by bubble injection location. (author)

  2. Solar wind driven dust acoustic instability with Lorentzian kappa distribution

    Energy Technology Data Exchange (ETDEWEB)

    Arshad, Kashif [National Center for Physics (NCP), Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore, Islamabad and University of Wah, Wah Cantt 47040 (Pakistan); Ehsan, Zahida, E-mail: Ehsan.zahida@gmail.com [National Center for Physics (NCP), Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Universita degli Studi del Molise, 86090 Pesche - IS (Italy); INFN Sezione di Napoli, 80126 Napoli (Italy); Department of Physics, COMSATS Institute of Information Technology (CIIT), Defence Road, Off Raiwind Road, Lahore 86090 (Pakistan); Khan, S. A. [National Center for Physics (NCP), Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Mahmood, S. [Theoretical Plasma Physics Division, PINSTEC, PO Box Nilore, Islamabad 44000 (Pakistan)

    2014-02-15

    In a three species electron-ion-dust plasma following a generalized non-Maxwellian distribution function (Lorentzian or kappa), it is shown that a kinetic instability of dust-acoustic mode exists. The instability threshold is affected when such (quasineutral) plasma permeates through another static plasma. Such case is of interest when the solar wind is streaming through the cometary plasma in the presence of interstellar dust. In the limits of phase velocity of the waves larger and smaller than the thermal velocity of dust particles, the dispersion properties and growth rate of dust-acoustic mode are investigated analytically with validation via numerical analysis.

  3. Dependence of pulsed focused ultrasound induced thrombolysis on duty cycle and cavitation bubble size distribution.

    Science.gov (United States)

    Xu, Shanshan; Zong, Yujin; Feng, Yi; Liu, Runna; Liu, Xiaodong; Hu, Yaxin; Han, Shimin; Wan, Mingxi

    2015-01-01

    In this study, we investigated the relationship between the efficiency of pulsed, focused ultrasound (FUS)-induced thrombolysis, the duty cycle (2.3%, 9%, and 18%) and the size distribution of cavitation bubbles. The efficiency of thrombolysis was evaluated through the degree of mechanical fragmentation, namely the number, mass, and size of clot debris particles. First, we found that the total number and mass of clot debris particles were highest when a duty cycle of 9% was used and that the mean diameter of clot debris particles was smallest. Second, we found that the size distribution of cavitation bubbles was mainly centered around the linear resonance radius (2.5μm) of the emission frequency (1.2MHz) of the FUS transducer when a 9% duty cycle was used, while the majority of cavitation bubbles became smaller or larger than the linear resonance radius when a 2.3% or 18% duty cycle was used. In addition, the inertial cavitation dose from the treatment performed at 9% duty cycle was much higher than the dose obtained with the other two duty cycles. The data presented here suggest that there is an optimal duty cycle at which the thrombolysis efficiency and cavitation activity are strongest. They further indicate that using a pulsed FUS may help control the size distribution of cavitation nuclei within an active size range, which we found to be near the linear resonance radius of the emission frequency of the FUS transducer.

  4. Investigation of liquid phase axial dispersion in Taylor bubble flow by radiotracer residence time distribution analysis

    Directory of Open Access Journals (Sweden)

    Jin J.H.

    2013-05-01

    Full Text Available A gas-liquid Taylor bubble flow occurs in small diameter channels in which gas bubbles are separated by slugs of pure liquid. This type of flow regime is well suited for solid catalyzed gas-liquid reactors in which the reaction efficiency is a strong function of axial dispersion in the regions of pure liquid. This paper presents an experimental study of liquid phase axial dispersion in a Taylor bubble flow developed in a horizontal tube using high speed photography and radiotracer residence time distribution (RTD analysis. A parametric dependence of axial dispersion on average volume fraction of gas phase was also investigated by varying the relative volumetric flow rates of the two phases. 137mBa produced from a 137Cs/137mBa radionuclide generator was used as radiotracer and measurements were made using the NaI(Tl scintillation detectors. Validation of 137mBa in the form of barium chloride as aqueous phase radiotracer was also carried out. Axial Dispersion Model (ADM was used to simulate the hydrodynamics of the system and the results of the experiment are presented. It was observed that the system is characterized by very high values of Peclet Number (Pe∼102 which reveals an approaching plug type flow. The experimental and model estimated values of mean residence times were observed in agreement with each other.

  5. Experimental study on upward bubble velocity and pierce length distributions in a water model of copper converter

    Institute of Scientific and Technical Information of China (English)

    Bin Du; Jiayun Zhang; Tuping Zhou; Qifeng Shu

    2003-01-01

    The upward bubble velocity and the pierce length distributions in a sectional water model of the copper convener in Guixi Smelter in Jiangxi, China, were measured using a two-contact electro-resistivity probe. In the case of using a single tuyere, the bubble velocity distribution along longitudinal direction was similar to that derived from Guassian function. Beyond the center of the longitudinal range, the bubble pierce length exhibited a sudden increase. The upward bubble velocity at a specified location could go up to meters per second. Its probability at a fixed location obeys a lognormal function; the bubble pierce length there varies bellow a few centimeters. In the case of using multi-tuyeres, the upward bubble velocity was roughly uniform right above the tuyeres and showed a slow decrease beyond this region. The bubble pierce length within both of these two regions was roughly uniform. Its average value in the former region, however, was found to be somewhat lower than that in the later.

  6. The concentration distribution around a growing gas bubble in a bio tissue under the effect of suction process.

    Science.gov (United States)

    Mohammadein, S A

    2014-07-01

    The concentration distribution around a growing nitrogen gas bubble in the blood and other bio tissues of divers who ascend to surface too quickly is obtained by Mohammadein and Mohamed model (2010) for variant and constant ambient pressure through the decompression process. In this paper, the growing of gas bubbles and concentration distribution under the effect of suction process are studied as a modification of Mohammadein and Mohamed model (zero suction). The growth of gas bubble is affected by ascent rate, tissue diffusivity, initial concentration difference, surface tension and void fraction. Mohammadein and Mohamed model (2010) is obtained as a special case from the present model. Results showed that, the suction process activates the systemic blood circulation and delay the growth of gas bubbles in the bio tissues to avoid the incidence of decompression sickness (DCS).

  7. Electron acoustic solitary waves with kappa-distributed electrons

    Energy Technology Data Exchange (ETDEWEB)

    Devanandhan, S; Singh, S V; Lakhina, G S, E-mail: satyavir@iigs.iigm.res.in [Indian Institute of Geomagnetism, New Panvel (West), Navi Mumbai (India)

    2011-08-01

    Electron acoustic solitary waves are studied in a three-component, unmagnetized plasma composed of hot electrons, fluid cold electrons and ions having finite temperatures. Hot electrons are assumed to have kappa distribution. The Sagdeev pseudo-potential technique is used to study the arbitrary amplitude electron-acoustic solitary waves. It is found that inclusion of cold electron temperature shrinks the existence regime of the solitons, and soliton electric field amplitude decreases with an increase in cold electron temperature. A decrease in spectral index, {kappa}, i.e. an increase in the superthermal component of hot electrons, leads to a decrease in soliton electric field amplitude as well as the soliton velocity range. The soliton solutions do not exist beyond T{sub c}/T{sub h}>0.13 for {kappa}=3.0 and Mach number M=0.9 for the dayside auroral region parameters.

  8. Acoustical properties of individual liposome-loaded microbubbles.

    Science.gov (United States)

    Luan, Ying; Faez, Telli; Gelderblom, Erik; Skachkov, Ilya; Geers, Bart; Lentacker, Ine; van der Steen, Ton; Versluis, Michel; de Jong, Nico

    2012-12-01

    A comparison between phospholipid-coated microbubbles with and without liposomes attached to the microbubble surface was performed using the ultra-high-speed imaging camera (Brandaris 128). We investigated 73 liposome-loaded microbubbles (loaded microbubbles) and 41 microbubbles without liposome loading (unloaded microbubbles) with a diameter ranging from 3-10 μm at frequencies ranging from 0.6-3.8 MHz and acoustic pressures ranging from 5-100 kPa. The experimental data showed nearly the same shell elasticity for the loaded and unloaded bubbles, but the shell viscosity was higher for loaded bubbles compared with unloaded bubbles. For loaded bubbles, a higher pressure threshold for the bubble vibrations was noticed. In addition, an "expansion-only" behavior was observed for up to 69% of the investigated loaded bubbles, which mostly occurred at low acoustic pressures (≤30 kPa). Finally, fluorescence imaging showed heterogeneity of liposome distributions of the loaded bubbles.

  9. Distribution theory approach to implementing directional acoustic sensors.

    Science.gov (United States)

    Schmidlin, Dean J

    2010-01-01

    The objective of directional acoustic sensors is to provide high directivity while occupying a small amount of space. An idealized point sensor achieves this objective from a knowledge of the spatial partial derivatives of acoustic pressure at a point in space. Direct measurement of these derivatives is difficult in practice. Consequently, it is expedient to come up with indirect methods. The use of pressure sensors to construct finite-difference approximations is an example of such a method. This paper utilizes the theory of distributions to derive another indirect method for estimating the various spatial partial derivatives of the pressure. This alternate method is then used to construct a multichannel filter which processes the acoustic pressure by mean of three-dimensional integral transforms throughout a 6epsilon-length cube centered at the origin. The output of the multichannel filter is a spatially and temporally filtered version of the pressure at the origin. The temporal filter is a lowpass Gaussian filter whose bandwidth is inversely proportional to epsilon. Finally, the lattice method for numerical multiple integration is utilized to develop a discrete-spatial version of the multichannel filter.

  10. Passive acoustic inversion to estimate bedload size distribution in rivers

    Science.gov (United States)

    Petrut, Teodor; Geay, Thomas; Belleudy, Philippe; Gervaise, Cédric

    2016-04-01

    The knowledge of sediment transport rate in rivers is related to issues like changes in channel forms, inundation risks and river's ecological functions. The passive acoustic method introduced here measures the bedload processes by recording the noise generated by the inter-particle collisions. In this research, an acoustic inversion is proposed to estimate the size distribution of mobile particles. The theoretical framework of Hertz's impact between two solids rigid is used to model the sediment-generated noise. This model combined with the acoustical power spectrum density gives the information on the particle sizes. The sensitivity of the method is performed and finally the experimental validation is done through a series of tests in the laboratory as well in a natural stream. The limitations of the proposed inversion method are drawn assuming the wave propagation effects in the channel. It is stated that propagation effects limit the applicability of the method to large rivers, like fluvial channels, in the detriment of mountain torrents.

  11. Single bubble sonoluminescence and stable cavitation

    Institute of Scientific and Technical Information of China (English)

    CHEN Qian; QIAN Menglu

    2004-01-01

    A single bubble trapped at an antinode of an acoustic standing wave field in water can emit 50ps-140ps light pulses, called "single bubble sonoluminescence" (SBSL). It arouses much interest in physical acoustics because of its highly non-linear characteristics, high concentration of energy, and stable cavitation behavior. In this paper, bubble stability, the dynamic behavior of bubbles, non-invasive measurement of driving acoustic pressure and Mie scattering method are introduced.

  12. Room Acoustical Simulation Algorithm Based on the Free Path Distribution

    Science.gov (United States)

    VORLÄNDER, M.

    2000-04-01

    A new algorithm is presented which provides estimates of impulse responses in rooms. It is applicable to arbitrary shaped rooms, thus including non-diffuse spaces like workrooms or offices. In the latter cases, for instance, sound propagation curves are of interest to be applied in noise control. In the case of concert halls and opera houses, the method enables very fast predictions of room acoustical criteria like reverberation time, strength or clarity. The method is based on a low-resolved ray tracing and recording of the free paths. Estimates of impulse responses are derived from evaluation of the free path distribution and of the free path transition probabilities.

  13. Reconstruction and prediction of multi-source acoustic field with the distributed source boundary point method based nearfield acoustic holography

    Institute of Scientific and Technical Information of China (English)

    BI; Chuanxing; CHEN; Jian; CHEN; Xinzhao

    2004-01-01

    In a multi-source acoustic field, the actual measured pressure is a scalar sum of pressures from all the sources. The pressure belonging to every source cannot be separated out with the existing techniques. Consequently, routine formulas cannot be used to reconstruct the acoustic source and predict the acoustic field directly. In this paper, a novel theoretical model of reconstruction and prediction of multi-source acoustic field in the distributed source boundary point method (DSBPM) based nearfield acoustic holography (NAH) is established. Three different methods, namely combination method with single surface measurement, combination method with multi-surface measurement and elimination method with multi-surface measurement, are proposed to realize the holographic reconstruction of sources. With these methods, the problem of reconstruction and prediction of acoustic field existing multiple coherent sources synchronously is solved effectively. Using the particular solutions constructed by the DSBPM to establish the vibro-acoustic transfer matrix, the calculation time, calculation precision and calculation stability are improved. These methods are valuable in localizing acoustic source and predicting acoustic field in engineering field.

  14. Single bubble sonoluminescence

    NARCIS (Netherlands)

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

    2002-01-01

    Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light ten

  15. Modelling of the Bubble Size Distribution in an Aerated Stirred Tank: Theoretical and Numerical Comparison of Different Breakup Models

    Directory of Open Access Journals (Sweden)

    Kálal Zbyněk

    2014-09-01

    Full Text Available The main topic of this study is the mathematical modelling of bubble size distributions in an aerated stirred tank using the population balance method. The air-water system consisted of a fully baffled vessel with a diameter of 0.29 m, which was equipped with a six-bladed Rushton turbine. The secondary phase was introduced through a ring sparger situated under the impeller. Calculations were performed with the CFD software CFX 14.5. The turbulent quantities were predicted using the standard k-ε turbulence model. Coalescence and breakup of bubbles were modelled using the MUSIG method with 24 bubble size groups. For the bubble size distribution modelling, the breakup model by Luo and Svendsen (1996 typically has been used in the past. However, this breakup model was thoroughly reviewed and its practical applicability was questioned. Therefore, three different breakup models by Martínez-Bazán et al. (1999a, b, Lehr et al. (2002 and Alopaeus et al. (2002 were implemented in the CFD solver and applied to the system. The resulting Sauter mean diameters and local bubble size distributions were compared with experimental data.

  16. Pulsed electro-acoustic (PEA) measurements of embedded charge distributions

    Science.gov (United States)

    Dennison, J. R.; Pearson, Lee H.

    2013-09-01

    Knowledge of the spatial distribution and evolution of embedded charge in thin dielectric materials has important applications in semiconductor, high-power electronic device, high-voltage DC power cable insulation, high-energy and plasma physics apparatus, and spacecraft industries. Knowing how, where, and how much charge accumulates and how it redistributes and dissipates can predict destructive charging effects. Pulsed Electro-acoustic (PEA) measurements— and two closely related methods, Pressure Wave Propagation (PWP) and Laser Intensity Modulation (LIMM)— nondestructively probe such internal charge distributions. We review the instrumentation, methods, theory and signal processing of simple PEA experiments, as well as the related PPW and LIMM methods. We emphasize system improvements required to achieve high spatial resolution for in vacuo measurements of thin dielectrics charged using electron beam injection.

  17. Mechanisms Of Pressure Distributions Within Laminar Separation Bubble At Different Reynolds Numbers

    Science.gov (United States)

    Lee, Donghwi; Kawai, Soshi; Nonomura, Taku; Oyama, Akira; Fujii, Kozo

    2014-11-01

    Large-eddy simulation around 5 % thickness flat plate at Re = 5 , 000 , 6 , 100 , 11 , 000 and 20 , 000 are performed and the physical mechanisms of the pressure distributions (Cp) in laminar separation bubbles are analyzed. Depending on the Reynolds number, a gradual pressure recovery and plateau pressure distribution are observed as experiments by Anyoji et al. [AIAA paper 2011-0852]. The causes of the pressure distributions are quantitatively shown by deriving the pressure gradient (momentum budget) equation from the steady momentum equation. From the results, we identify that the viscous diffusion term near the surface has a major contribution to the pressure gradients, and a different growth of the separated shear layer relying on the Reynolds numbers affects the viscous stress near the surface. The gradual pressure recovery at the lower Reynolds numbers is caused by the progressive development of separated shear layer due to the viscous stress which makes a non-negligible viscous stress. On the other hand, a thin laminar separated shear layer is created at the higher Reynolds numbers because of the relatively small viscous diffusion effects, which results in a negligible shear stress distribution. It makes dp / dx ~ 0 and the plateau pressure distribution is generated. Asahi Glass Scholarship.

  18. Acoustically enhanced bubble growth at low frequencies and its implications for human diver and marine mammal safety.

    Science.gov (United States)

    Crum, L A; Mao, Y

    1996-05-01

    Computations are made of the conditions necessary to obtain bubble growth by rectified diffusion under a variety of conditions associated with low-frequency sonar propagation in the ocean. The complex issue of microbubble nuclei stabilization is treated by assuming either a sufficient level of supersaturation to stabilize the initial bubble size, or by examining a microbubble nucleus with zero surface tension. The bubble growth rates and thresholds are obtained for a ranged of sound-pressure levels (re: 1 microPa) from 150-220 dB, for initial bubble radii from 1-10 microns, and for levels of the dissolved gas concentration from 100% to 223% of saturation. It was determined that for the range of conditions examined, it was necessary to utilize three different formulations of the equations for bubble growth. The results of these calculations (and assumptions concerning nuclei stabilization) indicate that for SPL's in excess of 210 dB, significant bubble growth can be expected to occur, and divers and marine mammals exposed to these conditions could be at risk. For SPL's below about 190 dB, however, except under relatively extreme conditions of supersaturation, significant bubble growth is unexpected.

  19. Distribution of lateral acoustic energy in Mudejar Gothic churches

    Science.gov (United States)

    Girón, S.; Galindo, M.; Zamarreño, T.

    2008-09-01

    In this work, the physical measures of spatial impression are considered in 12 Mudejar-Gothic churches in the city of Seville in the south of Spain. This study describes the spatial distribution of the early and late lateral acoustic energy, through monaural parameters derived from impulse response analysis using a maximum length sequence measurement system in each church. In the first time analysis, the two early lateral energy measures, early lateral fraction (LF) and early lateral fraction cosine (LFC) are taken in order to assess apparent source width (ASW), and the late lateral level (GLL) in the second to assess listener envelopment (LEV) are conducted. Parameters have been studied spectrally in each temple and were averaged at low- and mid-frequency values in their different naves in order to study how these two attributes of sound perception vary with source-receiver distance. Experimental results have been compared with the theoretical early lateral energy fractions and late lateral level, both of which are derived by assuming that reflected energy in these places of worship is solely dependent on source-receiver distance. This comparison is carried out in accordance with the μ-model proposed by the authors in an earlier paper in order to describe the dependence of acoustic monaural omnidirectional energy parameters on source-receiver distance. Thus, it is supposed that the directional distribution of reflections is similar to a diffuse distribution. To conclude, these spatially averaged monoaural parameters have been correlated with geometric variables by using linear regression and only weak correlations with the mean width of the churches and with the height/width ratio have been found.

  20. Collapse and rebound of a gas-filled spherical bubble immersed in a diagnostic ultrasonic field.

    Science.gov (United States)

    Aymé-Bellegarda, E J

    1990-08-01

    This work is concerned with the influence of the finite-amplitude distortion of a driving diagnostic ultrasonic field on the collapse and rebound of a gas-filled spherical microbubble, present in the exposed compressible liquid. Such an analysis is especially important since one of the mechanisms for cavitation damage comes from the very large gas pressures generated at bubble collapse and in the subsequent pressure wave formed by bubble rebound. Gilmore's model [F.R. Gilmore, "The growth or collapse of a spherical bubble in a viscous compressible liquid," Hydrodynamics Lab. Rep. No. 26-4, California Institute of Technology, Pasadena, CA (1952)] for bubble dynamics is used to obtain the motion of the bubble interface when subjected to a pulsed diagnostic ultrasonic field of large amplitude. Knowledge of the bubble motion allows one to derive the pressure distribution around the bubble. Numerical results over a range of initial bubble sizes, acoustic pressures, and frequencies relevant to medical use show that the strength of the pressure spikes radiated by the rebounding bubble depends upon (i) the acoustic frequency (f), (ii) the initial bubble size (R0), and (iii) the magnitude of the pressure amplitude of the fundamental (PF) in a Fourier series description of the distorted pulse. As the pressure spikes propagate outward from the bubble wall, their strength is attenuated as the reciprocal of the distance from the center of collapse.

  1. Numerical simulation of bubble plumes and an analysis of their seismic attributes

    Science.gov (United States)

    Li, Canping; Gou, Limin; You, Jiachun

    2017-04-01

    To study the bubble plume's seismic response characteristics, the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theory based on an analysis of both the acoustic characteristics of a bubble-contained water body and the actual features of a plume. The finite difference method is used for forward modelling, and the single-shot seismic record exhibits the characteristics of a scattered wave field generated by a plume. A meaningful conclusion is obtained by extracting seismic attributes from the pre-stack shot gather record of a plume. The values of the amplitude-related seismic attributes increase greatly as the bubble content goes up, and changes in bubble radius will not cause seismic attributes to change, which is primarily observed because the bubble content has a strong impact on the plume's acoustic velocity, while the bubble radius has a weak impact on the acoustic velocity. The above conclusion provides a theoretical reference for identifying hydrate plumes using seismic methods and contributes to further study on hydrate decomposition and migration, as well as on distribution of the methane bubble in seawater.

  2. Distributed acoustic fibre optic sensors for condition monitoring of pipelines

    Science.gov (United States)

    Hussels, Maria-Teresa; Chruscicki, Sebastian; Habib, Abdelkarim; Krebber, Katerina

    2016-05-01

    Industrial piping systems are particularly relevant to public safety and the continuous availability of infrastructure. However, condition monitoring systems based on many discrete sensors are generally not well-suited for widespread piping systems due to considerable installation effort, while use of distributed fibre-optic sensors would reduce this effort to a minimum. Specifically distributed acoustic sensing (DAS) is employed for detection of third-party threats and leaks in oil and gas pipelines in recent years and can in principle also be applied to industrial plants. Further possible detection routes amenable by DAS that could identify damage prior to emission of medium are subject of a current project at BAM, which aims at qualifying distributed fibre optic methods such as DAS as a means for spatially continuous monitoring of industrial piping systems. Here, first tests on a short pipe are presented, where optical fibres were applied directly to the surface. An artificial signal was used to define suitable parameters of the measurement system and compare different ways of applying the sensor.

  3. Can airborne ultrasound monitor bubble size in chocolate?

    Science.gov (United States)

    Watson, N.; Hazlehurst, T.; Povey, M.; Vieira, J.; Sundara, R.; Sandoz, J.-P.

    2014-04-01

    Aerated chocolate products consist of solid chocolate with the inclusion of bubbles and are a popular consumer product in many countries. The volume fraction and size distribution of the bubbles has an effect on their sensory properties and manufacturing cost. For these reasons it is important to have an online real time process monitoring system capable of measuring their bubble size distribution. As these products are eaten by consumers it is desirable that the monitoring system is non contact to avoid food contaminations. In this work we assess the feasibility of using an airborne ultrasound system to monitor the bubble size distribution in aerated chocolate bars. The experimental results from the airborne acoustic experiments were compared with theoretical results for known bubble size distributions using COMSOL Multiphysics. This combined experimental and theoretical approach is used to develop a greater understanding of how ultrasound propagates through aerated chocolate and to assess the feasibility of using airborne ultrasound to monitor bubble size distribution in these systems. The results indicated that a smaller bubble size distribution would result in an increase in attenuation through the product.

  4. Global bubble distribution seen from ROCSAT-1 and its association with the evening prereversal enhancement

    Science.gov (United States)

    Kil, Hyosub; Paxton, Larry J.; Oh, Seung-Jun

    2009-06-01

    The occurrence statistics of equatorial plasma bubbles (EPBs) obtained from low-inclination orbit satellites are significantly affected by the way the data are sampled and the way that the EPBs are counted. To resolve the discrepancy between the EPB occurrence frequency determined by ground-based observations and in situ sampling of plasma density from spacecraft, we have developed a new EPB detection method that minimizes the dependence of the EPB occurrence rate on the data processing method. The global EPB distribution maps are created by analyzing the measurements of the ion density from the first Republic of China satellite (ROCSAT-1) during March 1999 to June 2004. The EPB occurrence probability obtained using our new EPB detection method is a few times greater than that obtained using the conventional method. Our results are comparable to the ground observations. The good agreement of the global EPB distribution with the global morphology of the evening prereversal enhancement (PRE) of vertical ion velocity supports the notion that the PRE is an important factor on a global scale in the generation of EPBs. However, the generation of EPBs is not guaranteed by the occurrence of an intense PRE. Other mechanisms, in addition to the PRE, should be considered as an explanation for the occurrence of EPBs on the topside.

  5. Dust-acoustic waves and stability in the permeating dust plasma: II. Power-law distributions

    CERN Document Server

    Gong, Jingyu; Du, Jiulin

    2012-01-01

    The dust-acoustic waves and their stability driven by a flowing dust plasma when it cross through a static (target) dust plasma (the so-called permeating dust plasma) are investigated when the components of the dust plasma obey the power-law q-distributions in nonextensive statistics. The frequency, the growth rate and the stability condition of the dust-acoustic waves are derived under this physical situation, which express the effects of the nonextensivity as well as the flowing dust plasma velocity on the dust-acoustic waves in this dust plasma. The numerical results illustrate some new characteristics of the dust-acoustic waves, which are different from those in the permeating dust plasma when the plasma components are the Maxwellian distribution. In addition, we show that the flowing dust plasma velocity has a significant effect on the dust-acoustic waves in the permeating dust plasma with the power-law q-distribution.

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

    Science.gov (United States)

    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.

  7. Seismic wave detection system based on fully distributed acoustic sensing

    Science.gov (United States)

    Jiang, Yue; Xu, Tuanwei; Feng, Shengwen; Huang, Jianfen; Yang, Yang; Guo, Gaoran; Li, Fang

    2016-11-01

    This paper presents a seismic wave detection system based on fully distributed acoustic sensing. Combined with Φ- OTDR and PGC demodulation technology, the system can detect and acquire seismic wave in real time. The system has a frequency response of 3.05 dB from 5 Hz to 1 kHz, whose sampling interval of each channel of 1 meter on total sensing distance up to 10 km. By comparing with the geophone in laboratory, the data show that in the time domain and frequency domain, two waveforms coincide consistently, and the correlation coefficient could be larger than 0.98. Through the analysis of the data of the array experiment and the oil well experiment, DAS system shows a consistent time domain and frequency domain response and a clearer trail of seismic wave signal as well as a higher signal-noise rate which indicate that the system we proposed is expected to become the next generation of seismic exploration equipment.

  8. Bubble Clouds in Coastal Waters and Their Role in Air-Water Gas Exchange of CO2

    Directory of Open Access Journals (Sweden)

    Joseph R. Crosswell

    2015-08-01

    Full Text Available Bubbles generated by breaking waves can drive significant gas exchange between the ocean and atmosphere, but the role of bubble-mediated gas transfer in estuaries is unknown. Here, backscatter data from 41 acoustic Doppler current profiler stations was analyzed to assess subsurface bubble distributions in nine estuaries along the U.S. East and Gulf Coast. Wind speed, wind direction, and current velocity were the dominant controls on bubble entrainment, but the relative importance of these physical drivers depended on local geomorphology. Bubble entrainment in high-current or shallow, long-fetch estuaries began at wind speeds <5 m s−1. In deep or fetch-limited estuaries, bubble entrainment was less frequent and generally began at higher wind speeds. Data observed during several storms suggests that episodic bubble-driven gas exchange may be an important component of annual CO2 fluxes in large, shallow estuaries but would be less significant in other coastal systems.

  9. Distributions of crystals and gas bubbles in reservoir ice during winter growth period

    Directory of Open Access Journals (Sweden)

    Zhi-jun LI

    2011-06-01

    Full Text Available In order to understand the dominant factors of ice physical properties for ice thermodynamics and mechanics, in-situ observations of ice growth and decay processes were carried out. Two samplings were done, in the stages of fast ice growth and steady ice growth. These ice samples were used to observe ice crystals and gas bubbles in ice, and to measure ice density. Vertical profiles of the ice crystal type, ice crystal size, gas bubble shape and size, gas bubble content, as well as ice density were ontained. The results reveal that the upper part of the samples is granular ice and the lower part is columnar ice, the average grain size increases along ice depth and keeps steady within fast and steady ice growth stages; the shape of gas bubbles in ice upper layer is spherical with higher total content, and the shape in the middle and lower layers is cylinder with lower total content; the gas bubble size and content are active along with the ice growth stage; ice density decreases with the gas content increasing.

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

    Science.gov (United States)

    Leighton, Timothy G.

    2004-11-01

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

  11. Ion acoustic solitons in a solar wind magnetoplasma with Kappa distributed electrons

    Science.gov (United States)

    Devanandhan, Selvaraj; Singh, Satyavir; Singh Lakhina, Gurbax; Sreeraj, T.

    2016-07-01

    In many space plasma environments, the velocity distribution of particles often deviates from Maxwellian and is well-modelled by a kappa distribution function. We have analyzed the ion acoustic soliton in a magnetized consisting of plasma Protons, Helium ions, an electron beam and superthermal hot electrons following kappa distribution function. Under the assumption of weak nonlinearity, the ion-acoustic solitons are described by the Korteweg-de-Vries-Zakharov-Kuznetsov (KdV-ZK) equation. The solution of KdV-ZK equation is used to model the characteristics of the ion acoustic solitary waves in a solar wind magnetoplasma observed at 1 AU. We have found both slow and fast ion acoustic solitons in our study. It is found that the superthermality of hot electrons greatly influence the existence regime of the solitary waves. The numerical results of this study to explain solar wind observations will be discussed in detail.

  12. Acoustic Estimates of Distribution and Biomass of Different Acoustic Scattering Types Between the New England Shelf Break and Slope Waters

    KAUST Repository

    McLaren, Alexander

    2011-11-01

    Due to their great ecological significance, mesopelagic fishes are attracting a wider audience on account of the large biomass they represent. Data from the National Marine Fisheries Service (NMFS) provided the opportunity to explore an unknown region of the North-West Atlantic, adjacent to one of the most productive fisheries in the world. Acoustic data collected during the cruise required the identification of acoustically distinct scattering types to make inferences on the migrations, distributions and biomass of mesopelagic scattering layers. Six scattering types were identified by the proposed method in our data and traces their migrations and distributions in the top 200m of the water column. This method was able to detect and trace the movements of three scattering types to 1000m depth, two of which can be further subdivided. This process of identification enabled the development of three physically-derived target-strength models adapted to traceable acoustic scattering types for the analysis of biomass and length distribution to 1000m depth. The abundance and distribution of acoustic targets varied closely in relation to varying physical environments associated with a warm core ring in the New England continental Shelf break region. The continental shelf break produces biomass density estimates that are twice as high as the warm core ring and the surrounding continental slope waters are an order of magnitude lower than either estimate. Biomass associated with distinct layers is assessed and any benefits brought about by upwelling at the edge of the warm core ring are shown not to result in higher abundance of deepwater species. Finally, asymmetric diurnal migrations in shelf break waters contrasts markedly with the symmetry of migrating layers within the warm ring, both in structure and density estimates, supporting a theory of predatorial and nutritional constraints to migrating pelagic species.

  13. Bubble Formation in Basalt-like Melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Keding, Ralf; Yue, Yuanzheng

    2011-01-01

    The effect of the melting temperature on bubble size and bubble formation in an iron bearing calcium aluminosilicate melt is studied by means of in-depth images acquired by optical microscopy. The bubble size distribution and the total bubble volume are determined by counting the number of bubble...

  14. Bubble Formation in Basalt-like Melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Keding, Ralf; Yue, Yuanzheng

    2011-01-01

    The effect of the melting temperature on bubble size and bubble formation in an iron bearing calcium aluminosilicate melt is studied by means of in-depth images acquired by optical microscopy. The bubble size distribution and the total bubble volume are determined by counting the number of bubbles...

  15. The Bubble Box: Towards an Automated Visual Sensor for 3D Analysis and Characterization of Marine Gas Release Sites.

    Science.gov (United States)

    Jordt, Anne; Zelenka, Claudius; von Deimling, Jens Schneider; Koch, Reinhard; Köser, Kevin

    2015-12-05

    Several acoustic and optical techniques have been used for characterizing natural and anthropogenic gas leaks (carbon dioxide, methane) from the ocean floor. Here, single-camera based methods for bubble stream observation have become an important tool, as they help estimating flux and bubble sizes under certain assumptions. However, they record only a projection of a bubble into the camera and therefore cannot capture the full 3D shape, which is particularly important for larger, non-spherical bubbles. The unknown distance of the bubble to the camera (making it appear larger or smaller than expected) as well as refraction at the camera interface introduce extra uncertainties. In this article, we introduce our wide baseline stereo-camera deep-sea sensor bubble box that overcomes these limitations, as it observes bubbles from two orthogonal directions using calibrated cameras. Besides the setup and the hardware of the system, we discuss appropriate calibration and the different automated processing steps deblurring, detection, tracking, and 3D fitting that are crucial to arrive at a 3D ellipsoidal shape and rise speed of each bubble. The obtained values for single bubbles can be aggregated into statistical bubble size distributions or fluxes for extrapolation based on diffusion and dissolution models and large scale acoustic surveys. We demonstrate and evaluate the wide baseline stereo measurement model using a controlled test setup with ground truth information.

  16. The Bubble Box: Towards an Automated Visual Sensor for 3D Analysis and Characterization of Marine Gas Release Sites

    Directory of Open Access Journals (Sweden)

    Anne Jordt

    2015-12-01

    Full Text Available Several acoustic and optical techniques have been used for characterizing natural and anthropogenic gas leaks (carbon dioxide, methane from the ocean floor. Here, single-camera based methods for bubble stream observation have become an important tool, as they help estimating flux and bubble sizes under certain assumptions. However, they record only a projection of a bubble into the camera and therefore cannot capture the full 3D shape, which is particularly important for larger, non-spherical bubbles. The unknown distance of the bubble to the camera (making it appear larger or smaller than expected as well as refraction at the camera interface introduce extra uncertainties. In this article, we introduce our wide baseline stereo-camera deep-sea sensor bubble box that overcomes these limitations, as it observes bubbles from two orthogonal directions using calibrated cameras. Besides the setup and the hardware of the system, we discuss appropriate calibration and the different automated processing steps deblurring, detection, tracking, and 3D fitting that are crucial to arrive at a 3D ellipsoidal shape and rise speed of each bubble. The obtained values for single bubbles can be aggregated into statistical bubble size distributions or fluxes for extrapolation based on diffusion and dissolution models and large scale acoustic surveys. We demonstrate and evaluate the wide baseline stereo measurement model using a controlled test setup with ground truth information.

  17. Study on resonance frequency distribution of high-overtone bulk acoustic resonators

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hui; WANG Zuoqing; ZHANG Shuyi

    2005-01-01

    Based on the method of characterizing piezo-films by the resonance frequency distributions, the factors influencing the resonance frequency distribution of a High-overtone Bulk Acoustic Resonator (HBAR) consisting of a piezoelectric thin film with twoelectrodes and a substrate are studied. Some HBARs are simulated. The results manifest that changing the acoustic impedance ratio of the substrate to piezo-film the distribution of the space of the parallel resonance frequency and the effective electromechanical coupling factor are changed. When the fundamental mode of the piezo-film is at high frequency, changing the acoustic impedance ratio of the electrode to piezo-film and the thickness of the electrodes make the resonance frequency distribution of HBARs change. These results manifest that the HBARs can be resonant at specified frequencies by means of adjusting the factors affecting the resonance frequency distribution.

  18. Receptivity of Hypersonic Boundary Layers to Distributed Roughness and Acoustic Disturbances

    Science.gov (United States)

    Balakumar, P.

    2013-01-01

    Boundary-layer receptivity and stability of Mach 6 flows over smooth and rough seven-degree half-angle sharp-tipped cones are numerically investigated. The receptivity of the boundary layer to slow acoustic disturbances, fast acoustic disturbances, and vortical disturbances is considered. The effects of three-dimensional isolated roughness on the receptivity and stability are also simulated. The results for the smooth cone show that the instability waves are generated in the leading edge region and that the boundary layer is much more receptive to slow acoustic waves than to the fast acoustic waves. Vortical disturbances also generate unstable second modes, however the receptivity coefficients are smaller than that of the slow acoustic wave. Distributed roughness elements located near the nose region decreased the receptivity of the second mode generated by the slow acoustic wave by a small amount. Roughness elements distributed across the continuous spectrum increased the receptivity of the second mode generated by the slow and fast acoustic waves and the vorticity wave. The largest increase occurred for the vorticity wave. Roughness elements distributed across the synchronization point did not change the receptivity of the second modes generated by the acoustic waves. The receptivity of the second mode generated by the vorticity wave increased in this case, but the increase is lower than that occurred with the roughness elements located across the continuous spectrum. The simulations with an isolated roughness element showed that the second mode waves generated by the acoustic disturbances are not influenced by the small roughness element. Due to the interaction, a three-dimensional wave is generated. However, the amplitude is orders of magnitude smaller than the two-dimensional wave.

  19. Kinetic study of ion acoustic twisted waves with kappa distributed electrons

    Science.gov (United States)

    Arshad, Kashif; Aman-ur-Rehman, Mahmood, Shahzad

    2016-05-01

    The kinetic theory of Landau damping of ion acoustic twisted modes is developed in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons and Maxwellian ions. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the ion acoustic twisted waves in a non-thermal plasma. The strong damping effects of ion acoustic twisted waves at low values of temperature ratio of electrons and ions are also obtained by using exact numerical method and illustrated graphically, where the weak damping wave theory fails to explain the phenomenon properly. The obtained results of Landau damping rates of the twisted ion acoustic wave are discussed at different values of azimuthal wave number and non-thermal parameter kappa for electrons.

  20. Pitch and TDOA-Based Localization of Acoustic Sources with Distributed Arrays

    DEFF Research Database (Denmark)

    Hansen, Martin Weiss; Jensen, Jesper Rindom; Christensen, Mads Græsbøll

    2015-01-01

    In this paper, a method for acoustic source localization using distributed microphone arrays based on time-differences of arrival (TDOAs) is presented. The TDOAs are used to estimate the location of an acoustic source using a recently proposed method, based on a 4D parameter space defined by the 3D...... location of the source, and the TDOAs. The performance of the proposed method for acoustic source localization is compared to the performance of a method based on generalized cross-correlation with phase transform (GCC-PHAT) using synthetic and speech signals with varying source position. Results show...

  1. Numerical investigation of bubble nonlinear dynamics characteristics

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-10-28

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

  2. The relation between pre-eruptive bubble size distribution, ash particle morphology, and their internal density: Implications to volcanic ash transport and dispersion models

    Science.gov (United States)

    Proussevitch, Alexander

    2014-05-01

    Parameterization of volcanic ash transport and dispersion (VATD) models strongly depends on particle morphology and their internal properties. Shape of ash particles affects terminal fall velocities (TFV) and, mostly, dispersion. Internal density combined with particle size has a very strong impact on TFV and ultimately on the rate of ash cloud thinning and particle sedimentation on the ground. Unlike other parameters, internal particle density cannot be measured directly because of the micron scale sizes of fine ash particles, but we demonstrate that it varies greatly depending on the particle size. Small simple type ash particles (fragments of bubble walls, 5-20 micron size) do not contain whole large magmatic bubbles inside and their internal density is almost the same as that of volcanic glass matrix. On the other side, the larger compound type ash particles (>40 microns for silicic fine ashes) always contain some bubbles or the whole spectra of bubble size distribution (BSD), i.e. bubbles of all sizes, bringing their internal density down as compared to simple ash. So, density of the larger ash particles is a function of the void fraction inside them (magmatic bubbles) which, in turn, is controlled by BSD. Volcanic ash is a product of the fragmentation of magmatic foam formed by pre-eruptive bubble population and characterized by BSD. The latter can now be measured from bubble imprints on ash particle surfaces using stereo-scanning electron microscopy (SSEM) and BubbleMaker software developed at UNH, or using traditional high-resolution X-Ray tomography. In this work we present the mathematical and statistical formulation for this problem connecting internal ash density with particle size and BSD, and demonstrate how the TFV of the ash population is affected by variation of particle density.

  3. Planar dust-acoustic waves in electron-positron-ion-dust plasmas with dust size distribution

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hong-Yan; Zhang, Kai-Biao [Sichuan University of Science and Engineering, Zigong (China)

    2014-06-15

    Nonlinear dust-acoustic solitary waves which are described with a Kortweg-de vries (KdV) equation by using the reductive perturbation method, are investigated in a planar unmagnetized dusty plasma consisting of electrons, positrons, ions and negatively-charged dust particles of different sizes and masses. The effects of the power-law distribution of dust and other plasma parameters on the dust-acoustic solitary waves are studied. Numerical results show that the dust size distribution has a significant influence on the propagation properties of dust-acoustic solitons. The amplitudes of solitary waves in the case of a power-law distribution is observed to be smaller, but the soliton velocity and width are observed to be larger, than those of mono-sized dust grains with an average dust size. Our results indicate that only compressed solitary waves exist in dusty plasma with different dust species. The relevance of the present investigation to interstellar clouds is discussed.

  4. Decoding Group Vocalizations: The Acoustic Energy Distribution of Chorus Howls Is Useful to Determine Wolf Reproduction

    Science.gov (United States)

    López-Bao, José Vicente; Llaneza, Luis; Fernández, Carlos; Font, Enrique

    2016-01-01

    Population monitoring is crucial for wildlife management and conservation. In the last few decades, wildlife researchers have increasingly applied bioacoustics tools to obtain information on several essential ecological parameters, such as distribution and abundance. One such application involves wolves (Canis lupus). These canids respond to simulated howls by emitting group vocalizations known as chorus howls. These responses to simulated howls reveal the presence of wolf litters during the breeding period and are therefore often used to determine the status of wolf populations. However, the acoustic structure of chorus howls is complex and discriminating the presence of pups in a chorus is sometimes difficult, even for experienced observers. In this study, we evaluate the usefulness of analyses of the acoustic energy distribution in chorus howls to identify the presence of pups in a chorus. We analysed 110 Iberian wolf chorus howls with known pack composition and found that the acoustic energy distribution is concentrated at higher frequencies when there are pups vocalizing. We built predictive models using acoustic energy distribution features to determine the presence of pups in a chorus, concluding that the acoustic energy distribution in chorus howls can be used to determine the presence of wolf pups in a pack. The method we outline here is objective, accurate, easily implemented, and independent of the observer's experience. These advantages are especially relevant in the case of broad scale surveys or when many observers are involved. Furthermore, the analysis of the acoustic energy distribution can be implemented for monitoring other social canids that emit chorus howls such as jackals or coyotes, provides an easy way to obtain information on ecological parameters such as reproductive success, and could be useful to study other group vocalizations. PMID:27144887

  5. 结构设计及气泡型填料对水声吸声材料的影响综述%Review for influence of structure design and packings containing air bubble on underwater acoustic absorption materials

    Institute of Scientific and Technical Information of China (English)

    孙卫红; 晏欣

    2012-01-01

    The status of structure design of the underwater acoustic absorption materials and the research survey of the materials modified with packings containing air bubble were summarized, the progress in the research of synthetic resin micro-particles which was expected to be an acoustic absorption ma- terials was introduced with 54 references. The trend of novel underwater acoustic absorption materials was pointed out.%综述了水声吸声材料的结构设计现状以及气泡型填科改性水声吸声材料的研究概况,介绍了有望作为水声吸声材料的高分子树脂颗粒吸声材料的研究进展,指出了新型水下吸声材料的发展趋势.

  6. Science Bubbles

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella; Pedersen, David Budtz

    2013-01-01

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

  7. Vertical distribution of giant jellyfish, Nemopilema nomurai using acoustics and optics

    Science.gov (United States)

    Kim, Seonghun; Lee, Kyounghoon; Yoon, Won Duk; Lee, Hyungbeen; Hwang, Kangseok

    2016-03-01

    Nemopilema nomurai jellyfish, which are believed to complete their development in the East China Sea, have started migrating into the Yellow Sea in recent years. We obtained biomass estimates of this species in the Yellow Sea using bottom trawl fishing gear and sighting surveys over a 5-year period. These methods are effective for obtaining N. nomurai jellyfish density estimates and information about the community distribution near the bottom or surface of the sea. To verify the vertical distributions of giant jellyfish between, we used hydroacoustic equipment, including an optical stereo camera system attached to a towed sledge and an echo counting method with scientific echosounder system. Acoustic and optical data were collected while the vessel moved at 3 knots, from which the distribution and density of N. nomurai jellyfish were analyzed. Subsequently, the camera system was towed from a 7 m mean depth to sea level, with the detection range of the acoustic system extending from an 8 m depth to the bottom surface. The optical and acoustic methods indicated the presence of vertical distribution of 0.113 (inds/m3) and 0.064 (inds/m3), respectively. However, the vertical distribution indicated that around 93% of individuals occurred at a depth range of 10-40 m; thus, a 2.4-fold greater density was estimated by acoustic echo counting compared to the optical method.

  8. RISING BUBBLE DISTRIBUTION IN STAGNANT LIQUID%静止液相中气泡上升过程的分布特性

    Institute of Scientific and Technical Information of China (English)

    孙奇; 赵华; 杨瑞昌

    2003-01-01

    It is significant for the development of multidimensional two-phase models to study the measurement technology and distribution characteristics of local parameters in two-phase flow. The radial distribution of a rising bubble in stagnant liquid is investigated through the radial measurement in a vertical tube using the dual-sensor optical probe. The analyses of probe signals show that optical probe is very sensitive to the bubble signals and satisfactory measurement results can be obtained. Besides, the effect of the up-stream sensor on the down-stream one is studied in this paper.

  9. Vapor Bubbles

    Science.gov (United States)

    Prosperetti, Andrea

    2017-01-01

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

  10. Characteristics of bubble plumes, bubble-plume bubbles and waves from wind-steepened wave breaking

    NARCIS (Netherlands)

    Leifer, I.; Caulliez, G.; Leeuw, G. de

    2007-01-01

    Observations of breaking waves, associated bubble plumes and bubble-plume size distributions were used to explore the coupled evolution of wave-breaking, wave properties and bubble-plume characteristics. Experiments were made in a large, freshwater, wind-wave channel with mechanical wind-steepened w

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

    NARCIS (Netherlands)

    Leifer, I.; Leeuw, G. de

    2006-01-01

    Measurements of bubble plumes from paddle-amplified, wind stress breaking waves were made in a large wind-wave channel during the LUMINY experiment in fresh (but not clean) water. Bubble plumes exhibited considerable variability with respect to dynamics, bubble size distribution, and physical extent

  12. An Euler-Lagrange method considering bubble radial dynamics for modeling sonochemical reactors.

    Science.gov (United States)

    Jamshidi, Rashid; Brenner, Gunther

    2014-01-01

    Unsteady numerical computations are performed to investigate the flow field, wave propagation and the structure of bubbles in sonochemical reactors. The turbulent flow field is simulated using a two-equation Reynolds-Averaged Navier-Stokes (RANS) model. The distribution of the acoustic pressure is solved based on the Helmholtz equation using a finite volume method (FVM). The radial dynamics of a single bubble are considered by applying the Keller-Miksis equation to consider the compressibility of the liquid to the first order of acoustical Mach number. To investigate the structure of bubbles, a one-way coupling Euler-Lagrange approach is used to simulate the bulk medium and the bubbles as the dispersed phase. Drag, gravity, buoyancy, added mass, volume change and first Bjerknes forces are considered and their orders of magnitude are compared. To verify the implemented numerical algorithms, results for one- and two-dimensional simplified test cases are compared with analytical solutions. The results show good agreement with experimental results for the relationship between the acoustic pressure amplitude and the volume fraction of the bubbles. The two-dimensional axi-symmetric results are in good agreement with experimentally observed structure of bubbles close to sonotrode.

  13. Evaluation of near-surface stress distributions in dissimilar welded joint by scanning acoustic microscopy.

    Science.gov (United States)

    Kwak, Dong Ryul; Yoshida, Sanichiro; Sasaki, Tomohiro; Todd, Judith A; Park, Ik Keun

    2016-04-01

    This paper presents the results from a set of experiments designed to ultrasonically measure the near surface stresses distributed within a dissimilar metal welded plate. A scanning acoustic microscope (SAM), with a tone-burst ultrasonic wave frequency of 200 MHz, was used for the measurement of near surface stresses in the dissimilar welded plate between 304 stainless steel and low carbon steel. For quantitative data acquisition such as leaky surface acoustic wave (leaky SAW) velocity measurement, a point focus acoustic lens of frequency 200 MHz was used and the leaky SAW velocities within the specimen were precisely measured. The distributions of the surface acoustic wave velocities change according to the near-surface stresses within the joint. A three dimensional (3D) finite element simulation was carried out to predict numerically the stress distributions and compare with the experimental results. The experiment and FE simulation results for the dissimilar welded plate showed good agreement. This research demonstrates that a combination of FE simulation and ultrasonic stress measurements using SAW velocity distributions appear promising for determining welding residual stresses in dissimilar material joints.

  14. Distributed acoustic mapping based on interferometry of phase optical time-domain reflectometry

    Science.gov (United States)

    Wang, Chang; Wang, Chen; Shang, Ying; Liu, Xiaohui; Peng, Gangding

    2015-07-01

    We demonstrate the design and characterization of a distributed optical fiber sensing system based on Michelson interferometer of the phase sensitive optical time domain reflectometer (φ-OTDR) for acoustic measurement. Phase, amplitude, frequency response and location information can be directly obtained at the same time by using the passive 3×3 coupler demodulation. In order to simulate sound profiles of seismic or hydroacoustic imaging, experiments on detection of multiple piezoelectric transducers (PZT) are carried out. The result shows that our system can well demodulate different acoustic sources with different intensities.

  15. Distributed acoustic sensing system using an identical weak fiber Bragg grating array

    Science.gov (United States)

    Liu, Sheng; Han, Xinying; Wen, Hongqiao

    2016-10-01

    We propose and experimentally demonstrate a distributed acoustic sensing system using an identical weak fiber Bragg grating array. Phase, frequency and location information of vibration can be demodulated by using a path-match interferometry method. 3×3 coupler demodulation technique is employed to eliminate signal fading in interferometer. Experiments on detecting acoustic wave generated by PZT show that the system is capable of measuring vibrations of up to 1000 Hz over 1.6 km with 2.5m spatial resolution.

  16. Prediction of Fluid Velocity Distribution near a Rising Bubble%上升气泡附近液体速度分布的预测

    Institute of Scientific and Technical Information of China (English)

    成弘; 周明

    2002-01-01

    A model is presented for predicting the fluid velocity distribution around a rising bubble which startsfrom rest on a distillation column tray by considering the unsteady fluid flow based on the method of streamfunction. Experimental measurement of the velocity distribution by using whole field digitized PIV (particle imagevelocimetry) method is briefly described. The velocity distribution predicted by the present model is in betteragreement with the measurements than the others models published in literature.

  17. Quasi-distributed acoustic sensing based on identical low-reflective fiber Bragg gratings

    Science.gov (United States)

    Shang, Ying; Yang, Yuan-Hong; Wang, Chen; Liu, Xiao-Hui; Wang, Chang; Peng, Gang-Ding

    2017-01-01

    A quasi-distributed acoustic sensing (QDAS) scheme based on identical low-reflective fiber Bragg grating is proposed and analyzed theoretically and experimentally. We realize the acoustic demodulation of different location and different frequency simultaneously by using imbalanced Michelson interferometer of φ-OTDR and Phase Generated Carrier technology with 600 identical low-reflective fiber Bragg gratings(FBGs) written on-line during drawing of the ordinary signal mode fibers in an equal separation of 2 m. We further obtain the 1.4 dB of frequency response flatness at the range of 200 Hz-1500 Hz and proportional character of demodulated intensity of acoustic sources with different drive voltage of underwater speaker in the experiment.

  18. Characterization and modeling of bubbles size distribution in mechanical flotation cells; Caracterizacion y modelacion de las distribuciones de tamano de burbujas en celdas de flotacion con agitacion mecanica

    Energy Technology Data Exchange (ETDEWEB)

    Vallebuona, G.; Casali, A.; Kracht, W.

    2005-07-01

    In this work, bubble size distribution is determined for tests in a batch flotation cells, for different impeller speed and air flowrate. Bubbles are sampled and their sizes are measured using image analysis. Size distributions by surface are expressed as cumulative percent passing as well as percent retained. The distributions show a common shape for all tests and are represented with a unique model, selected due to its goodness of fit. This model corresponds to an equation used in heavy media separation and considers two parameters: x{sub 5}0, the 50% passing size, and 1, an adjustable parameter. The correlation coefficient for all tests averages 0.999 for the cumulative distributions and 0.912 for the retained distributions. (Author) 15 refs.

  19. 球状泡群内气泡的耦合振动∗%Coupled oscillation of bubbles in a spherical bubble cluster

    Institute of Scientific and Technical Information of China (English)

    王成会; 莫润阳; 胡静; 陈时

    2015-01-01

    The pressure wave emitted by a pulsating bubble affects the motions of other bubbles, so in an acoustic field bubbles are in a state of coupled oscillation. In this paper, a cluster with cavitation bubbles inside is considered, and a mathematical model is developed to describe the dynamics of the bubbles of the same radius inside a spherical cluster when the effects of coupled oscillation are included. Based on this new model, the nonlinear acoustic response of cavitation bubbles is analyzed numerically. Comparison of our model with those in the literature, shows that bubbles are suppressed heavily. Because of the coupled oscillations of bubbles, the motions of a bubble are affected by more constraints in the system, which cause the decrease of natural frequency of the bubbles. The nonlinear acoustical response of bubbles is improved by the coupled oscillation in a bubble cluster. With the rise in number density of the cluster, the suppression of bubble oscillation is enhanced. For a cluster of 1 mm radius, when the bubble number is below 500, the change of bubble number may cause a sharp decrease of maximum radial displacement of the bubbles. In cavitation region, there are bubble clusters and large-sized bubble, and the moving large bubble can absorb small bubbles from the surface of bubble cluster, so the bubble numbers inside a cluster varies with time, which may change the acoustic response of coupled oscillating bubbles. The increase of the liquid static pressure can suppress the oscillation of bubbles too, and there is a sensitive region (1–2 atm) that affects remarkably the acoustical response of bubbles. Driving ultrasound can affect the motion of bubble greatly. The range of cavitation bubble size is narrowed when the wave frequency increases. The bubbles whose initial radii are close to 5 µm are easy to be activated by ultrasound under given acoustic conditions, i.e. sizes of bubble cluster, surrounding liquid and inner gas. The cluster oscillation of

  20. Bubble rupture in bubble electrospinning

    Directory of Open Access Journals (Sweden)

    Chen Rouxi

    2015-01-01

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

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

    Science.gov (United States)

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

    2016-07-01

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

  2. Determination of Surface Stress Distributions in Steel Using Laser-Generated Surface Acoustic Waves

    Science.gov (United States)

    Shi; Yifei; Ni; Chenyin; Shen; Zhonghua; Ni; Xiaowu; Lu; Jian

    2008-05-01

    High frequency surface acoustic waves (SAWs) are excited by a pulsed laser and detected by a specially designed poly(vinylidene fluoride) (PVDF) transducer to investigate surface stress distribution. Two kinds of stressed surfaces are examined experimentally. One is a steel plate elastically deformed under simple bending forces, where the surface stress varies slowly. The other is a welded steel plate for which the surface stress varies very rapidly within a small area near the welding seam. Applying a new signal processing method developed from correlation technique, the velocity distribution of the SAWs, which reflects the stress distribution, is obtained in these two samples with high resolution.

  3. Spherical Kadomtsev–Petviashviliequation for dust acoustic waves with dust size distribution and two-charges-ions

    Indian Academy of Sciences (India)

    K Annou; S Bahamida; R Annou

    2011-03-01

    The nonlinear dust acoustic waves in dusty plasmas with negative as well as positive ions and the combined effects of bounded spherical geometry and the transverse perturbation and the size distribution of dust grains are studied. Using the perturbation method, a spherical Kadomtsev–Petviashvili (SKP) equation that describes the dust acoustic waves is deduced.

  4. Phase distribution in horizontal gas-liquid two-phase bubbly flow

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    An investigation on phase distribution in air-water two-phaseflow in horizontal circular channel was conducted by using the double-sensor resistivity probe. The variations of phase distribution with variations ofgas and liquid volumetric fluxes were analyzed and the present data werecompared with some of other researcher's data and existing models. It wasfound there exists more complicated phase distribution pattern in horizontalflow system than in vertical flow. The radial local void fraction profilesare similar at the same measurement angle with various gas and liquid flowrates. However, an asymmetric profile can be observed at a given slice ofthe pipe cross-section.

  5. Manipulating bubbles with secondary Bjerknes forces

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-23

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

  6. Asymmetric transmission of acoustic waves in a layer thickness distribution gradient structure using metamaterials

    Science.gov (United States)

    Chen, Jung-San; Chang, I.-Ling; Huang, Wan-Ting; Chen, Lien-Wen; Huang, Guan-Hua

    2016-09-01

    This research presents an innovative asymmetric transmission design using alternate layers of water and metamaterial with complex mass density. The directional transmission behavior of acoustic waves is observed numerically inside the composite structure with gradient layer thickness distribution and the rectifying performance of the present design is evaluated. The layer thickness distributions with arithmetic and geometric gradients are considered and the effect of gradient thickness on asymmetric wave propagation is systematically investigated using finite element simulation. The numerical results indicate that the maximum pressure density and transmission through the proposed structure are significantly influenced by the wave propagation direction over a wide range of audible frequencies. Tailoring the thickness of the layered structure enables the manipulation of asymmetric wave propagation within the desired frequency range. In conclusion, the proposed design offers a new possibility for developing directional-dependent acoustic devices.

  7. Distributed Acoustic Sensing Technology in a Magmatic Geothermal Field - First Results From a Survey in Iceland

    Science.gov (United States)

    Reinsch, Thomas; Jousset, Philippe; Henninges, Jan; Blanck, Hanna

    2016-04-01

    Seismic methods are particularly suited for investigating the Earth's subsurface. Compared to surface-measurements , wellbore measurements can be used to acquire more detailed information about rock properties and possible fluid pathways within a geothermal reservoir. For high temperature geothermal wells, however, ambient temperatures are often far above the operating temperature range of conventional geophones. One way to overcome this limitation is the application of fiber optic sensor systems, where only the passive optical fiber is subjected to downhole conditions. Their applicability is thus determined by the operating temperature range of the optical fiber. Choosing appropriate fibers, such sensor systems can be operated at temperatures far above 200°C. Along an optical fiber, the distributed acoustic sensing technology (DAS) can be used to acquire acoustic signals with a high spatial and temporal resolution. Previous experiments have shown that the DAS technology is well suited for active seismic measurements. Within the framework of the EC funded project IMAGE, a fiber optic cable was deployed in a newly drilled geothermal well (RN-34) within the Reykjanes geothermal field, Iceland. Additionally, a >15 km fiber optic cable, already available at the surface, was connected to a DAS read-out unit. Acoustic data was acquired continuously for 9 days. Hammer shots were performed at the wellhead as well as along the surface cable in order to locate individual acoustic traces and calibrate the spatial distribution of the acoustic information. During the monitoring period both signals from on- and offshore explosive sources and natural seismic events could be recorded. We compare the fiber optic data to conventional seismic records from a dense seismic network deployed on the Reykjanes in the course of the IMAGE project. Here, first results from the seismic survey will be presented.

  8. Interacting bubble clouds and their sonochemical production

    NARCIS (Netherlands)

    Stricker, L.; Dollet, B.; Fernandez Rivas, D.; Lohse, D.

    2013-01-01

    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 incre

  9. Bubble systems

    CERN Document Server

    Avdeev, Alexander A

    2016-01-01

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

  10. Numerical prediction of underwater noise reduction during offshore pile driving by a Small Bubble Curtain

    DEFF Research Database (Denmark)

    Göttsche, Klaus Marco; Juhl, Peter Møller; Steinhagen, Ulrich

    2013-01-01

    Small Bubble Curtains are an effective technique to reduce the underwater noise being emitted during offshore pile driving. In order to protect the marine fauna, noise reduction becomes even more important, since the increasing contribution of offshore wind energy leads to a rising number......, a method is presented in order to predict the rate of noise attenuation achieved by a Small Bubble Curtain. For this purpose, the bubble distribution is determined with Computational Fluid Dynamics. The noise radiation during pile driving is simulated by Finite Element Analysis and an Effective Medium...... Approach considers the acoustic effects within the Bubble Curtain. The pressure level at an arbitrary distance from the pile is determined by a Parabolic Equation method. Furthermore, comparisons between simulations and offshore measurements are presented. This combination of four methods provides...

  11. Velocity distribution of the flow field in the cyclonic zone of cyclone-static micro-bubble flotation column

    Institute of Scientific and Technical Information of China (English)

    Deng Xiao-wei; Liu Jiong-tian; Wang Yong-tian; Cao Yi-jun

    2013-01-01

    Laboratory experiments have been conducted to study the flow field in a cyclone static micro-bubble flotation column.The method of Particle Image Velocimetry (PIV) was used.The flow field velocity distribution in both cross section and longitudinal section within cyclonic zone was studied for different circulating volumes.The cross sectional vortex was also analyzed.The results show that in cross section as the circulating volume increases from 0.187 to 0.350 m3/h,the flow velocity ranges from 0 to 0.68 m/s.The flow field is mainly a non-vortex potential flow that forms a free vortex without outside energy input.In the cyclonic region the vortex deviates from the center of the flotation column because a single tangential opening introduces circulating fluid into the column.The tangential component of the velocity plays a defining role in the cross section.In the longitudinal section the velocity ranges from 0 to 0.08 m/s.The flow velocity increases as does the circulating volume.Advantageous mineral separation conditions arise from the combined effects of cyclonic flow in cross and longitudinal section.

  12. Bubble-bubble interaction: A potential source of cavitation noise

    CERN Document Server

    Ida, Masato

    2009-01-01

    The interaction between microbubbles through pressure pulses has been studied to show that it can be a source of cavitation noise. A recent report demonstrated that the acoustic noise generated by a shrimp originates from the collapse of a cavitation bubble produced when the shrimp closes its snapper claw. The recorded acoustic signal contains a broadband noise that consists of positive and negative pulses, but a theoretical model for single bubbles fails to reproduce the negative ones. Using a nonlinear multibubble model we have shown here that the negative pulses can be explained by considering the interaction of microbubbles formed after the cavitation bubble has collapsed and fragmented: Positive pulses produced at the collapse of the microbubbles hit and impulsively compress neighboring microbubbles to generate reflected pulses whose amplitudes are negative. Discussing the details of the noise generation process, we have found that no negative pulses are generated if the internal pressure of the reflecti...

  13. Ion-acoustic cnoidal waves in plasmas with warm ions and kappa distributed electrons and positrons

    Energy Technology Data Exchange (ETDEWEB)

    Kaladze, T. [Department of Physics, Government College University (GCU), Lahore 54000 (Pakistan); I.Vekua Institute of Applied Mathematics, Tbilisi State University, 0186 Georgia (United States); Mahmood, S., E-mail: shahzadm100@gmail.com [Theoretical Physics Division (TPD), PINSTECH P.O. Nilore Islamabad 44000 (Pakistan); National Center for Physics (NCP), Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan)

    2014-03-15

    Electrostatic ion-acoustic periodic (cnoidal) waves and solitons in unmagnetized electron-positron-ion (EPI) plasmas with warm ions and kappa distributed electrons and positrons are investigated. Using the reductive perturbation method, the Korteweg-de Vries (KdV) equation is derived with appropriate boundary conditions for periodic waves. The corresponding analytical and various numerical solutions are presented with Sagdeev potential approach. Differences between the results caused by the kappa and Maxwell distributions are emphasized. It is revealed that only hump (compressive) structures of the cnoidal waves and solitons are formed. It is shown that amplitudes of the cnoidal waves and solitons are reduced in an EPI plasma case in comparison with the ordinary electron-ion plasmas. The effects caused by the temperature variations of the warm ions are also discussed. It is obtained that the amplitude of the cnoidal waves and solitons decreases for a kappa distributed (nonthermal) electrons and positrons plasma case in comparison with the Maxwellian distributed (thermal) electrons and positrons EPI plasmas. The existence of kappa distributed particles leads to decreasing of ion-acoustic frequency up to thermal ions frequency.

  14. Complete velocity distribution in river cross-sections measured by acoustic instruments

    Science.gov (United States)

    Cheng, R.T.; Gartner, J.W.; ,

    2003-01-01

    To fully understand the hydraulic properties of natural rivers, velocity distribution in the river cross-section should be studied in detail. The measurement task is not straightforward because there is not an instrument that can measure the velocity distribution covering the entire cross-section. Particularly, the velocities in regions near the free surface and in the bottom boundary layer are difficult to measure, and yet the velocity properties in these regions play the most significant role in characterizing the hydraulic properties. To further characterize river hydraulics, two acoustic instruments, namely, an acoustic Doppler current profiler (ADCP), and a "BoogieDopp" (BD) were used on fixed platforms to measure the detailed velocity profiles across the river. Typically, 20 to 25 stations were used to represent a river cross-section. At each station, water velocity profiles were measured independently and/or concurrently by an ADCP and a BD. The measured velocity properties were compared and used in computation of river discharge. In a tow-tank evaluation of a BD, it has been confirmed that BD is capable of measuring water velocity at about 11 cm below the free-surface. Therefore, the surface velocity distribution across the river was extracted from the BD velocity measurements and used to compute the river discharge. These detailed velocity profiles and the composite velocity distribution were used to assess the validity of the classic theories of velocity distributions, conventional river discharge measurement methods, and for estimates of channel bottom roughness.

  15. Ion-acoustic cnoidal waves in plasmas with warm ions and kappa distributed electrons and positrons

    Science.gov (United States)

    Kaladze, T.; Mahmood, S.

    2014-03-01

    Electrostatic ion-acoustic periodic (cnoidal) waves and solitons in unmagnetized electron-positron-ion (EPI) plasmas with warm ions and kappa distributed electrons and positrons are investigated. Using the reductive perturbation method, the Korteweg-de Vries (KdV) equation is derived with appropriate boundary conditions for periodic waves. The corresponding analytical and various numerical solutions are presented with Sagdeev potential approach. Differences between the results caused by the kappa and Maxwell distributions are emphasized. It is revealed that only hump (compressive) structures of the cnoidal waves and solitons are formed. It is shown that amplitudes of the cnoidal waves and solitons are reduced in an EPI plasma case in comparison with the ordinary electron-ion plasmas. The effects caused by the temperature variations of the warm ions are also discussed. It is obtained that the amplitude of the cnoidal waves and solitons decreases for a kappa distributed (nonthermal) electrons and positrons plasma case in comparison with the Maxwellian distributed (thermal) electrons and positrons EPI plasmas. The existence of kappa distributed particles leads to decreasing of ion-acoustic frequency up to thermal ions frequency.

  16. Robust Distributed Noise Reduction in Hearing Aids with External Acoustic Sensor Nodes

    Directory of Open Access Journals (Sweden)

    Marc Moonen

    2009-01-01

    Full Text Available The benefit of using external acoustic sensor nodes for noise reduction in hearing aids is demonstrated in a simulated acoustic scenario with multiple sound sources. A distributed adaptive node-specific signal estimation (DANSE algorithm, that has a reduced communication bandwidth and computational load, is evaluated. Batch-mode simulations compare the noise reduction performance of a centralized multi-channel Wiener filter (MWF with DANSE. In the simulated scenario, DANSE is observed not to be able to achieve the same performance as its centralized MWF equivalent, although in theory both should generate the same set of filters. A modification to DANSE is proposed to increase its robustness, yielding smaller discrepancy between the performance of DANSE and the centralized MWF. Furthermore, the influence of several parameters such as the DFT size used for frequency domain processing and possible delays in the communication link between nodes is investigated.

  17. Distributed Remote Vector Gaussian Source Coding for Wireless Acoustic Sensor Networks

    DEFF Research Database (Denmark)

    Zahedi, Adel; Østergaard, Jan; Jensen, Søren Holdt;

    2014-01-01

    In this paper, we consider the problem of remote vector Gaussian source coding for a wireless acoustic sensor network. Each node receives messages from multiple nodes in the network and decodes these messages using its own measurement of the sound field as side information. The node’s measurement...... and the estimates of the source resulting from decoding the received messages are then jointly encoded and transmitted to a neighboring node in the network. We show that for this distributed source coding scenario, one can encode a so-called conditional sufficient statistic of the sources instead of jointly...... encoding multiple sources. We focus on the case where node measurements are in form of noisy linearly mixed combinations of the sources and the acoustic channel mixing matrices are invertible. For this problem, we derive the rate-distortion function for vector Gaussian sources and under covariance...

  18. Memory-Effect on Acoustic Cavitation

    OpenAIRE

    Yavaṣ, Oğuz; Leiderer, Paul; Park, Hee K.; Grigoropoulos, Costas P.; Poon, Chie C.; Tam, Andrew C.

    1994-01-01

    The formation of bubbles at a liquid-solid interface due to acoustic cavitation depends particularly on the preconditions of the interface. Here, it wiIl be shown that following laser-induced bubble formation at the interface the acoustic cavitation efficiency is strongly enhanced. Optical reflectance measurements reveal that this observed enhancement of acoustic cavitation due to preceding laser-induced bubble formation, which could be termed as memory effect, decays in a few hundred microse...

  19. Effect of wind-generated bubbles on fixed range acoustic attenuation in shallow water at 1-4 kHz

    NARCIS (Netherlands)

    Ainslie, M.A.

    2005-01-01

    Long-range acoustic propagation in isothermal conditions is considered, involving multiple reflections from the sea surface. If the sea is calm there is almost perfect reflection and hence little loss of acoustic energy or coherence. The effect of wind is to increase propagation loss due to rough su

  20. Analysis of Bubble Plume Distributions to Evaluate Methane Hydrate Decomposition on the Cascadia Margin

    Science.gov (United States)

    Miller, U. K.; Johnson, H. P.; Salmi, M.; Solomon, E. A.

    2015-12-01

    Methane gas is formed within the sediments of accretionary prisms by the biological and thermal degradation of organic matter. Some of this methane is trapped as solid-phase methane hydrate, the stability of which is temperature and pressure-dependent. Past fluctuations in global temperatures have resulted in the decomposition of continental margin gas hydrate reservoirs and subsequent emissions of methane, creating a positive feedback to global warming with additional impacts on the marine environment. Temperature data collected over the past four decades show that bottom water on the upper slope of the Washington State continental margin has undergone systematic warming. Thermal models of this heat propagation into the sediments indicate a 40 meter deepening of the methane hydrate stability depth (MHDS) that if correct, would suggest a preferential release of methane into the water column from these depths on the Cascadia margin. Location data for over 100 active methane seeps on the Cascadia margin were compiled from a variety of sources including research cruises, published literature, and local fishermen. Emission site locations show anomalous plume densities at depths associated with the MHDS, which lies at approximately 500 meters water depth in the NE Pacific. This supports the hypothesis that warming of seawater at intermediate depths due to contemporary climate change has begun to destabilize the Cascadia margin gas hydrate reservoir. While relatively small sample size and incomplete coverage due to the ad-hoc nature of data acquisition limit confidence in any conclusions drawn from this dataset, this study provides a framework for future analysis of methane plume distributions and supports the need for a comprehensive and systematic geophysical and geochemical examination of the Cascadia margin.

  1. Cylindrical and spherical dust-acoustic wave modulations in dusty plasmas with non-extensive distributions

    Indian Academy of Sciences (India)

    M Eghbali; B Farokhi

    2015-04-01

    The nonlinear wave modulation of planar and non-planar (cylindrical and spherical) dust-acoustic waves (DAW) propagating in dusty plasmas, in the presence of non-extensive distributions for ions and electrons is investigated. By employing multiple scales technique, a cylindrically and spherically modified nonlinear Schrödinger equation (NLSE) is derived. The presence of hot non-extensive -distributed ions and electron is shown to influence the modulational instability (MI) of the waves. It is shown that the properties of the MI of DAW in cylindrical and spherical geometries differ from those in a planar one-dimensional geometry. Furthermore, it is observed that the non-extensive distributed ions have more effect on the MI of the DAW than electrons. Also, it is found that there is a MI period for cylindrical and spherical wave modulations, which does not exist in the one-dimensional case.

  2. Dust-acoustic solitons in quantum plasma with kappa-distributed ions

    Indian Academy of Sciences (India)

    Mehran Shahmansouri

    2013-02-01

    Arbitrary amplitude dust-acoustic (DA) solitary waves in an unmagnetized and collisionless quantum dusty plasma comprising cold dust particles, kappa ()-distributed ions and degenerate electrons are investigated. The influence of suprathermality and quantum effects on the linear dispersion relation of DA waves is investigated. Then, the effect of -distributed ions and degenerate electrons on the existence domain of solitons is discussed in the space of (, ). The comparison of the existence domain for higher and lower values of shows that suprathermality results in propagation of solitons with lower values of Mach number, and the quantum effects, lead to a higher values of Mach number. The existence domain of solitons for nondegenerate -distributed electrons is considered for comparison with effect of degenerate electrons. Also, we found that the Sagdeev potential well becomes deeper and wider as $_{F-i}$ decreases, as for lower values, the influence of quantum effects on the Sagdeev pseudopotential profile is smaller.

  3. Localizing Near and Far Field Acoustic Sources with Distributed Microhone Arrays

    DEFF Research Database (Denmark)

    Hansen, Martin Weiss; Jensen, Jesper Rindom; Christensen, Mads Græsbøll

    2014-01-01

    In this paper, we consider the problem of acoustic source localization using distributed microphone arrays. Time differences of arrival (TDOAs) are estimated using a recently proposed method based on joint direction of arrival (DOA) and range estimation. The TDOAs are used to estimate the location...... on joint DOA and pitch estimation, using synthesized harmonic signals with varying source position. Results show a decrease in the error of the estimated position when joint DOA and range estimation is used for TDOA estimation, compared to the GCC-PHAT and joint DOA and pitch methods....

  4. Ambient Noise Surface Wave Tomography for Geotechnical Monitoring Using "Large N" Distributed Acoustic Sensing

    Science.gov (United States)

    Ajo Franklin, J. B.; Lindsey, N.; Martin, E. R.; Wagner, A. M.; Robertson, M.; Bjella, K.; Gelvin, A.; Ulrich, C.; Wu, Y.; Freifeld, B. M.; Daley, T. M.; Dou, S.

    2015-12-01

    Surface wave tomography using ambient noise sources has found broad application at the regional scale but has not been adopted fully for geotechnical applications despite the abundance of noise sources in this context. The recent development of Distributed Acoustic Sensing (DAS) provides a clear path for inexpensively recording high spatial resolution (survey as well as direct-push data on ice content. We also compare vintages of ambient noise DAS data to evaluate the short-term repeatability of the technique in the face of changing noise environments. The resulting dataset demonstrates the utility of using DAS for real-time shear-modulus monitoring in support of critical infrastructure.

  5. Bubble coalescence in breathing DNA

    DEFF Research Database (Denmark)

    Novotný, Tomas; Pedersen, Jonas Nyvold; Ambjörnsson, Tobias;

    2007-01-01

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

  6. The statistical distributed source boundary point method to calculate the acoustic radiation from the random vibrating body

    Institute of Scientific and Technical Information of China (English)

    WANGXiufeng; CHENXinzhao; LIUZhao

    2003-01-01

    The statistical distributed source boundary point method (SDSBPM) put forward is applied to calculate the acoustic radiation from the random vibrating body. A detailed description of this method is presented. A test for the SDSBPM is carried out through the random vibrating sphere and the random vibrating cuboid. An experiment on the exterior acoustic radiation of a random vibrating simulation axial box of the lathe tool is performed in a semi-anechoic chamber.

  7. The effects of surfactants on the lateral migration of bubbles and the bubble clustering phenomenon in a bubbly channel flow

    Science.gov (United States)

    Takagi, Shu; Ogasawara, Toshiyuki; Matsumoto, Yoichiro

    2004-11-01

    The behaviors of bubbles in an upward channel flow are experimentally investigated. Two kinds of surfactant, 3-pentanol and Triton X-100 are added in the bubbly flow. Addition of surfactant prevents the bubble coalescence and mono-dispersed 1mm spherical bubbles were obtained, although these surfactants do not modify the single-phase turbulence statistics. At the condition of high Reynolds number (Re=8200) with 20-60ppm 3-Pentanol, bubbles migrated towards the wall. These bubbles highly accumulated near the wall and formed crescent like shaped horizontal bubble clusters of 10-40mm length. On the other hand, bubble clusters did not appear in the 2ppm Triton-X100 aqueous solution. By the addition of the small amount of Triton-X100, bubble coalescences were also preventable and the bubble size and its distribution became almost the same as in the case of 60ppm 3-Pentanol aqueous solution. However, the tendency of the lateral migration of bubbles towards the wall weakened and the bubbles did not accumulated near the wall. And this is the main reason of the disapperance of bubble cluster. We discuss this phenomenon, related to the lift force acting on bubbles and particles.

  8. Exploring Bubbles

    Science.gov (United States)

    O'Geary, Melissa A.

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

  9. Antigravitating bubbles

    CERN Document Server

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

    1995-01-01

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

  10. Numerical simulation of the nonlinear ultrasonic pressure wave propagation in a cavitating bubbly liquid inside a sonochemical reactor.

    Science.gov (United States)

    Dogan, Hakan; Popov, Viktor

    2016-05-01

    We investigate the acoustic wave propagation in bubbly liquid inside a pilot sonochemical reactor which aims to produce antibacterial medical textile fabrics by coating the textile with ZnO or CuO nanoparticles. Computational models on acoustic propagation are developed in order to aid the design procedures. The acoustic pressure wave propagation in the sonoreactor is simulated by solving the Helmholtz equation using a meshless numerical method. The paper implements both the state-of-the-art linear model and a nonlinear wave propagation model recently introduced by Louisnard (2012), and presents a novel iterative solution procedure for the nonlinear propagation model which can be implemented using any numerical method and/or programming tool. Comparative results regarding both the linear and the nonlinear wave propagation are shown. Effects of bubble size distribution and bubble volume fraction on the acoustic wave propagation are discussed in detail. The simulations demonstrate that the nonlinear model successfully captures the realistic spatial distribution of the cavitation zones and the associated acoustic pressure amplitudes.

  11. Multiple concurrent sources localization based on a two-node distributed acoustic sensor network

    Science.gov (United States)

    Xu, Jiaxin; Zhao, Zhao; Chen, Chunzeng; Xu, Zhiyong

    2017-01-01

    In this work, we propose a new approach to localize multiple concurrent sources using a distributed acoustic sensor network. Only two node-arrays are required in this sensor network, and each node-array consists of only two widely spaced sensors. Firstly, direction-of-arrivals (DOAs) of multiple sources are estimated at each node-array by utilizing a new pooled angular spectrum proposed in this paper, which can implement the spatial aliasing suppression effectively. Based on minimum variance distortionless response (MVDR) beamforming and the DOA estimates of the sources, the time-frequency spectra containing the corresponding energy distribution features associated with those sources are reconstructed in each node-array. Then, scale invariant feature transform (SIFT) is employed to solve the DOA association problem. Performance evaluation is conducted with field recordings and experimental results prove the effectivity and feasibility of the proposed method.

  12. Generalized Faxén's theorem: Evaluating first-order (hydrodynamic drag) and second-order (acoustic radiation) forces on finite-sized rigid particles, bubbles and droplets in arbitrary complex flows

    Science.gov (United States)

    Annamalai, Subramanian; Balachandar, S.

    2016-11-01

    In recent times, study of complex disperse multiphase problems involving several million particles (e.g. volcanic eruptions, spray control etc.) is garnering momentum. The objective of this work is to present an accurate model (termed generalized Faxén's theorem) to predict the hydrodynamic forces on such inclusions (particles/bubbles/droplets) without having to solve for the details of flow around them. The model is developed using acoustic theory and the force obtained as a summation of infinite series (monopole, dipole and higher sources). The first-order force is the time-dependent hydrodynamic drag force arising from the dipole component due to interaction between the gas and the inclusion at the microscale level. The second-order force however is a time-averaged differential force (contributions arise both from monopole and dipole), also known as the acoustic radiation force primarily used to levitate particles. In this work, the monopole and dipole strengths are represented in terms of particle surface and volume averages of the incoming flow properties and therefore applicable to particle sizes of the order of fluid length scale and subjected to any arbitrary flow. Moreover, this model can also be used to account for inter-particle coupling due to neighboring particles. U.S. DoE, NNSA, Advanced Simulation and Computing Program, Cooperative Agreement under PSAAP-II, Contract No. DE-NA0002378.

  13. Pressure waves in a supersaturated bubbly magma

    Science.gov (United States)

    Kurzon, I.; Lyakhovsky, V.; Navon, O.; Chouet, B.

    2011-01-01

    We study the interaction of acoustic pressure waves with an expanding bubbly magma. The expansion of magma is the result of bubble growth during or following magma decompression and leads to two competing processes that affect pressure waves. On the one hand, growth in vesicularity leads to increased damping and decreased wave amplitudes, and on the other hand, a decrease in the effective bulk modulus of the bubbly mixture reduces wave velocity, which in turn, reduces damping and may lead to wave amplification. The additional acoustic energy originates from the chemical energy released during bubble growth. We examine this phenomenon analytically to identify conditions under which amplification of pressure waves is possible. These conditions are further examined numerically to shed light on the frequency and phase dependencies in relation to the interaction of waves and growing bubbles. Amplification is possible at low frequencies and when the growth rate of bubbles reaches an optimum value for which the wave velocity decreases sufficiently to overcome the increased damping of the vesicular material. We examine two amplification phase-dependent effects: (1) a tensile-phase effect in which the inserted wave adds to the process of bubble growth, utilizing the energy associated with the gas overpressure in the bubble and therefore converting a large proportion of this energy into additional acoustic energy, and (2) a compressive-phase effect in which the pressure wave works against the growing bubbles and a large amount of its acoustic energy is dissipated during the first cycle, but later enough energy is gained to amplify the second cycle. These two effects provide additional new possible mechanisms for the amplification phase seen in Long-Period (LP) and Very-Long-Period (VLP) seismic signals originating in magma-filled cracks.

  14. Dynamics of micro-bubble sonication inside a phantom vessel

    KAUST Repository

    Qamar, Adnan

    2013-01-10

    A model for sonicated micro-bubble oscillations inside a phantom vessel is proposed. The model is not a variant of conventional Rayleigh-Plesset equation and is obtained from reduced Navier-Stokes equations. The model relates the micro-bubble oscillation dynamics with geometric and acoustic parameters in a consistent manner. It predicts micro-bubble oscillation dynamics as well as micro-bubble fragmentation when compared to the experimental data. For large micro-bubble radius to vessel diameter ratios, predictions are damped, suggesting breakdown of inherent modeling assumptions for these cases. Micro-bubble response with acoustic parameters is consistent with experiments and provides physical insight to the micro-bubble oscillation dynamics.

  15. Effect of internal bubbly flow on pipe vibrations

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper presents an experimental investigation on wall vibrations of a pipe due to injection of a uniform bubble cloud into the pipe flow. For different bubble void fractions and averaged bubble sizes, the vibrations were measured using accelerometers. To understand the underlying physics, the evolution of the vibration spectra along the streamwise direction was examined. Results showed that wall vibrations were greatly enhanced up to 25 dB, compared with no bubble case. The characteristics of the vibration were mainly dependent on void fraction. These vibrations were believed to be caused by two mechanisms: acoustic resonance and normal modes of the bubble cloud. The former, originating from the interaction between the first mode of the bubble cloud and the first acoustic mode of the pipe, persisted along the entire pipe to enhance the vibration over a broad band frequency range, while the later, due to the process of bubble formation, successively decayed in the streamwise direction.

  16. Evaluation of dispersive mixing, extension rate and bubble size distribution using numerical simulation of a non-Newtonian fluid in a twin-screw mixer

    Science.gov (United States)

    Rathod, Maureen L.

    Initially 3D FEM simulation of a simplified mixer was used to examine the effect of mixer configuration and operating conditions on dispersive mixing of a non-Newtonian fluid. Horizontal and vertical velocity magnitudes increased with increasing mixer speed, while maximum axial velocity and shear rate were greater with staggered paddles. In contrast, parallel paddles produced an area of efficient dispersive mixing between the center of the paddle and the barrel wall. This study was expanded to encompass the complete nine-paddle mixing section using power-law and Bird-Carreau fluid models. In the center of the mixer, simple shear flow was seen, corresponding with high [special character omitted]. Efficient dispersive mixing appeared near the barrel wall at all flow rates and near the barrel center with parallel paddles. Areas of backflow, improving fluid retention time, occurred with staggered paddles. The Bird-Carreau fluid showed greater influence of paddle motion under the same operating conditions due to the inelastic nature of the fluid. Shear-thinning behavior also resulted in greater maximum shear rate as shearing became easier with decreasing fluid viscosity. Shear rate distributions are frequently calculated, but extension rate calculations have not been made in a complex geometry since Debbaut and Crochet (1988) defined extension rate as the ratio of the third to the second invariant of the strain rate tensor. Extension rate was assumed to be negligible in most studies, but here extension rate is shown to be significant. It is possible to calculate maximum stable bubble diameter from capillary number if shear and extension rates in a flow field are known. Extension rate distributions were calculated for Newtonian and non-Newtonian fluids. High extension and shear rates were found in the intermeshing region. Extension is the major influence on critical capillary number and maximum stable bubble diameter, but when extension rate values are low shear rate has

  17. The effect of q-distributed electrons on the head-on collision of ion acoustic solitary waves

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Uday Narayan; Chatterjee, Prasanta [Department of Mathematics, Siksha Bhavana Visva Bharati University, Santiniketan 731235 (India); Roychoudhury, Rajkumar [Physics and Applied Mathematics, ISI, Kolkata 700009 (India)

    2012-01-15

    The head-on collision of ion acoustic solitary waves (IASWs) in two component plasma comprising nonextensive distributed electrons is investigated. Two opposite directional Kortewg-de-vries (KdV) equations are derived and the phase shift due to collision is obtained using the extended version of Poincare-Lighthill-Kuo method. Different ranges of nonextensive parameter q are considered and their effects on phase shifts are observed. It is found that the presence of nonextensive distributed electrons plays a significant role on the nature of collision of ion acoustic solitary waves.

  18. Ion-acoustic solitons in negative ion plasma with two-electron temperature distributions

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, M. K.; Tiwari, R. S.; Chawla, J. K. [Department of Physics, University of Rajasthan, Jaipur-302004 (India)

    2012-06-15

    Ion-acoustic solitons in a warm positive and negative ion species with different masses, concentrations, and charge states with two electron temperature distributions are studied. Using reductive perturbation method, Korteweg de-Vries (KdV) and modified-KdV (m-KdV) equations are derived for the system. The soliton solution of the KdV and m-KdV equations is discussed in detail. It is found that if the ions have finite temperatures, then there exist two types of modes, namely slow and fast ion-acoustic modes. It is also investigated that the parameter determining the nature of soliton (i.e., whether the system will support compressive or rarefactive solitons) is different for slow and fast modes. For the slow mode, the parameter is the relative temperature of the two ion species; whereas for the fast mode, it is the relative concentration of the two ion species. At a critical concentration of negative ions, both compressive and rarefactive solitons coexist. The amplitude and width of the solitons are discussed in detail at critical concentration for m-KdV solitons. The effect of the relative temperature of the two-electron and cold-electron concentration on the characteristics of the solitons are also discussed.

  19. Microphone Clustering and BP Network based Acoustic Source Localization in Distributed Microphone Arrays

    Directory of Open Access Journals (Sweden)

    CHEN, Z.

    2013-11-01

    Full Text Available A microphone clustering and back propagation (BP neural network based acoustic source localization method using distributed microphone arrays in an intelligent meeting room is proposed. In the proposed method, a novel clustering algorithm is first used to divide all microphones into several clusters where each one corresponds to a specified BP network. Afterwards, the energy-based cluster selecting scheme is applied to select clusters which are small and close to the source. In each chosen cluster, the time difference of arrival of each microphone pair is estimated, and then all estimated time delays act as input of the corresponding BP network for position estimation. Finally, all estimated positions from the chosen clusters are fused for global position estimation. Only subsets rather than all the microphones are responsible for acoustic source localization, which leads to less computational cost; moreover, the local estimation in each selected cluster can be processed in parallel, which expects to improve the localization speed potentially. Simulation results from comparison with other related localization approaches confirm the validity of the proposed method.

  20. Acoustic Source Localization via Distributed Sensor Networks using Tera-scale Optical-Core Devices

    Energy Technology Data Exchange (ETDEWEB)

    Imam, Neena [ORNL; Barhen, Jacob [ORNL; Wardlaw, Michael [Office of Naval Research

    2008-01-01

    For real-time acoustic source localization applications, one of the primary challenges is the considerable growth in computational complexity associated with the emergence of ever larger, active or passive, distributed sensor networks. The complexity of the calculations needed to achieve accurate source localization increases dramatically with the size of sensor arrays, resulting in substantial growth of computational requirements that cannot be met with standard hardware. One option to meet this challenge builds upon the emergence of digital optical-core devices. The objective of this work was to explore the implementation of key building block algorithms used in underwater source localization on an optical-core digital processing platform recently introduced by Lenslet Inc. They investigate key concepts of threat-detection algorithms such as Time Difference Of Arrival (TDOA) estimation via sensor data correlation in the time domain with the purpose of implementation on the optical-core processor. they illustrate their results with the aid of numerical simulation and actual optical hardware runs. The major accomplishments of this research, in terms of computational speedup and numerical accurcy achieved via the deployment of optical processing technology, should be of substantial interest to the acoustic signal processing community.

  1. Bubbling Threat

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

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

  2. Relation between Local Acoustic Parameters and Protein Distribution in Human and Porcine Eye Lenses

    NARCIS (Netherlands)

    Korte, de C.L.; Steen, van der A.F.W.; Thijssen, J.M.; Duindam, J.J.; Otto, Cees; Puppels, G.J.

    1994-01-01

    The purpose of this study is to characterize the eye lens (human, porcine) by acoustic measurements and to investigate whether relations exist with the local protein content. The acoustic measurements were performed with a 'scanning acoustic microscope' (SAM), operating at a frequency of 20 MHz. At

  3. Measurement of Acoustic Intensity Distribution and Radiation Power of Flat-Plate Phased-Array Sound Source

    Science.gov (United States)

    Yokoyama, Tomoki; Takahashi, Kumiko; Seki, Daizaburou; Hasegawa, Akio

    2002-05-01

    The acoustic intensity distribution and radiation power of a flat-plate phased-array sound source consisting of Tonpilz-type transducers were measured. This study shows that the active acoustic intensity is skewed in the direction of wave propagation. In addition, it clarifies that if the measurement is carried out in the immediate vicinity of the sound source, the reactive acoustic intensity distribution is effective for identifying the positions of the individual sound source elements. Experimental values of active radiation power agree well with theoretical values. Conversely, experimental values of reactive radiation power do not agree with theoretical values; it is clear that they fluctuate significantly with distance from the radiating surface. The reason for this is explained in the case of a point sound source.

  4. Colloidal Plasmas : Effect of nonthermal ion distribution and dust temperature on nonlinear dust acoustic solitary waves

    Indian Academy of Sciences (India)

    Tarsem Singh Gill; Harvinder Kaur

    2000-11-01

    The effects of nonthermal ion distribution and finite dust temperature are incorporated in the investigation of nonlinear dust acoustic waves in an unmagnetized dusty plasma. Sagdeev pseudopotential method which takes into account the full nonlinearity of plasma equations, is used here to study solitary wave solutions. Possibility of co-existence of refractive and compressive solitons as a function of Mach number, dust temperature and concentration of nonthermal ions, is considered. For the fixed value of nonthermal ions, it is found that the effect of increase in dust temperature is to reduce the range of co-existence of compressive and refractive solitons. Particular concentration of nonthermal ions results in disappearance of refractive solitons while the decrease in dust temperature, at this concentration restores the lost refractive solitons.

  5. Ion acoustic shock waves in plasmas with warm ions and kappa distributed electrons and positrons

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, S.; Mahmood, S.; Hafeez Ur-Rehman [Theoretical Plasma Physics Division, PINSTECH, P.O. Nilore, Islamabad 44000, Pakistan and Department of Physics and Applied Mathematics, PIEAS, P.O. Nilore, Islamabad 44000 (Pakistan)

    2013-06-15

    The monotonic and oscillatory ion acoustic shock waves are investigated in electron-positron-ion plasmas (e-p-i) with warm ions (adiabatically heated) and nonthermal kappa distributed electrons and positrons. The dissipation effects are included in the model due to kinematic viscosity of the ions. Using reductive perturbation technique, the Kadomtsev-Petviashvili-Burgers (KPB) equation is derived containing dispersion, dissipation, and diffraction effects (due to perturbation in the transverse direction) in e-p-i plasmas. The analytical solution of KPB equation is obtained by employing tangent hyperbolic (Tanh) method. The analytical condition for the propagation of oscillatory and monotonic shock structures are also discussed in detail. The numerical results of two dimensional monotonic shock structures are obtained for graphical representation. The dependence of shock structures on positron equilibrium density, ion temperature, nonthermal spectral index kappa, and the kinematic viscosity of ions are also discussed.

  6. Leverage bubble

    Science.gov (United States)

    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.

  7. Tuning bubbly structures in microchannels.

    Science.gov (United States)

    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.

  8. 低温向上倾斜管内Taylor泡初始形成位置分布的实验研究%Experimental study on the initial position distribution of Taylor bubbles in cryorenic upward inclined tubes

    Institute of Scientific and Technical Information of China (English)

    张华; 王淑华; 刘夷平; 王经

    2009-01-01

    An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using the high speed digital cerera.The tubes in the experiment ale 0.018 m and 0.014 m in inner diameter and 1.0 m in length.The range ofthe inclination angles is 0-45°from the vertical.The statistical method iS employed to analyze the experimental data.The experiment was focused on the effect of the inelination angle on the initial position distribution of Taylor bubbles.The formation criterion of Taylor bubbles was confirmed by analyzing the images of Taylor bubbles.The experimental results show that the initial position of Taylor bubble increased first.and then decreased with the increasing inclination angle,with the maximum at 30.The standard deviation of the initial position of Taylor bubble in tubes was different with difierent inner diameters.The lognormal shape was fined to the measured the initial position distributions of Taylor bubbles in the cryogenic tubes.

  9. Supercoiling induces denaturation bubbles in circular DNA.

    Science.gov (United States)

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

    2010-11-12

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

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

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

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

  11. Interacting bubble clouds and their sonochemical production

    CERN Document Server

    Stricker, Laura; Rivas, David Fernandez; Lohse, Detlef

    2013-01-01

    Acoustically driven air pockets trapped in artificial crevices on a sur- face can emit bubbles which organize in (interacting) bubble clusters. With increasing driving power Fernandez Rivas et al. [Angew. Chem. Int. Ed., 2010] observed three different behaviors: clusters close to the very pits out of which they had been created, clusters pointing toward each other, and merging clusters. The latter behavior is highly undesired for technological purposes as it is associated with a reduction of the radical production and an enhancement of the erosion of the reactor walls. The dependence on the control parameters such as the distance of the pits and the conditions for cluster-merging are examined. The underlying mechanism, governed by the secondary Bjerknes forces, turns out to be 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, th...

  12. Laboratory Studies of the Impact of Fish School Density and Individual Distribution on Acoustic Propagation and Scattering

    Science.gov (United States)

    2012-09-30

    obtained, all below resonance. Fig. 5. The 1-D acoustic resonator with live zebra fish (Danio rerio). Fig. 6. Preliminary measured...of one of the zebra fish used in the resonator measurements is shown. This data was processed to show bones in reddish/pink/white colors and the...DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Laboratory Studies of the Impact of Fish School Density and

  13. Bubble drag reduction requires large bubbles

    CERN Document Server

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

    2016-01-01

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

  14. Bubble Drag Reduction Requires Large Bubbles

    Science.gov (United States)

    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.

  15. Fractal analysis on the spatial distribution of acoustic emission in the failure process of rock specimens

    Institute of Scientific and Technical Information of China (English)

    Rui-fu Yuan; Yuan-hui Li

    2009-01-01

    The spatial distribution of acoustic emission (AE) events in the failure process of several rock specimens was acquired us-ing an advanced AE acquiring and analyzing system.The box counting method (BCM) was employed to calculate the fractal dimen-sion (FD) of AE spatial distribution.There is a similar correlation between the fractal dimension and the load strength for different rock specimens.The fractal dimension presents a decreasing trend with the increase of load strength.For the same kind of specimens,their FD values will decrease to the level below a relatively same value when they reach failure.This value can be regarded as the critical value,which implies that the specimen will reach failure soon.The results reflect that it is possible to correlate the damage of rock with a macroscopic parameter,the FD value of AE signals.Furthermore,the FD value can be also used to forecast the final fail-ure of rock.This conclusion allows identifying or predicting the damage in rock with a great advantage over the classic theory and is very crucial for forecasting rockburst or other dynamic disasters in mines.

  16. Blowing bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Casteel, K.

    1999-04-01

    The article, based on a series of interviews with column flotation equipment suppliers, reviews and comments on the progress of bubble generator design. Developments mentioned include the Air/Water sparger from Cominco, the SparJet and SlamJet from CPT, the CISA sparger from Sevala CISA, Microcel flotation columns from Birtley Engineering, Flotaire column flotation cells from LMC International, and the Variable Gap Sparger from MinnovEX. 1 fig., 2 photo.

  17. Experimental and Theoretical Measurements of Concentration Distributions in Acoustic Focusing Devices

    Energy Technology Data Exchange (ETDEWEB)

    Rose, K A; Fisher, K; Jung, B; Ness, K; Mariella Jr., R P

    2008-06-16

    We describe a modeling approach to capture the particle motion within an acoustic focusing microfluidic device. Our approach combines finite element models for the acoustic forces with analytical models for the fluid motion and uses these force fields to calculate the particle motion in a Brownian dynamics simulation. We compare results for the model with experimental measurements of the focusing efficiency within a microfabricated device. The results show good qualitative agreement over a range of acoustic driving voltages and particle sizes.

  18. Characterization of HIFU transducers designed for sonochemistry application: Acoustic streaming.

    Science.gov (United States)

    Hallez, L; Touyeras, F; Hihn, J-Y; Bailly, Y

    2016-03-01

    Cavitation distribution in a High Intensity Focused Ultrasound sonoreactors (HIFU) has been extensively described in the recent literature, including quantification by an optical method (Sonochemiluminescence SCL). The present paper provides complementary measurements through the study of acoustic streaming generated by the same kind of HIFU transducers. To this end, results of mass transfer measurements (electrodiffusional method) were compared to optical method ones (Particle Image Velocimetry). This last one was used in various configurations: with or without an electrode in the acoustic field in order to have the same perturbation of the wave propagation. Results show that the maximum velocity is not located at the focal but shifted near the transducer, and that this shift is greater for high powers. The two cavitation modes (stationary and moving bubbles) are greatly affect the hydrodynamic behavior of our sonoreactors: acoustic streaming and the fluid generated by bubble motion. The results obtained by electrochemical measurements show the same low hydrodynamic activity in the transducer vicinity, the same shift of the active focal toward the transducer, and the same absence of activity in the post-focal axial zone. The comparison with theoretical Eckart's velocities (acoustic streaming in non-cavitating media) confirms a very high activity at the "sonochemical focal", accounted for by wave distortion, which induced greater absorption coefficients. Moreover, the equivalent liquid velocities are one order of magnitude larger than the ones measured by PIV, confirming the enhancement of mass transfer by bubbles oscillation and collapse close to the surface, rather than from a pure streaming effect.

  19. Cosmological HII Bubble Growth During Reionization

    CERN Document Server

    Shin, Min-Su; Cen, Renyue

    2007-01-01

    We present general properties of ionized hydrogen (HII) bubbles and their growth based on a state-of-the-art large-scale (100 Mpc/h) cosmological radiative transfer simulation. The simulation resolves all halos with atomic cooling at the relevant redshifts and simultaneously performs radiative transfer and dynamical evolution of structure formation. Our major conclusions include: (1) for significant HII bubbles, the number distribution is peaked at a volume of ~ 0.6 Mpc^3/h^3 at all redshifts. But, at z 10 even the largest HII bubbles have a balanced ionizing photon contribution from Pop II and Pop III stars, while at z < 8 Pop II stars start to dominate the overall ionizing photon production for large bubbles, although Pop III stars continue to make a non-negligible contribution. (6) The relationship between halo number density and bubble size is complicated but a strong correlation is found between halo number density and bubble size for for large bubbles.

  20. Bubbles in inkjet printheads : analytical and numerical models

    NARCIS (Netherlands)

    Jeurissen, Roger Josef Maria

    2009-01-01

    The phenomenon of nozzle failure of an inkjet printhead due to entrainment of air bubbles was studies using analytical and numerical models. The studied inkjet printheads consist of many channels in which an acoustic field is generated to eject a droplet. When an air bubble is entrained, it disrupts

  1. Flow velocity measurement with the nonlinear acoustic wave scattering

    Science.gov (United States)

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    2015-10-01

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  2. Flow velocity measurement with the nonlinear acoustic wave scattering

    Energy Technology Data Exchange (ETDEWEB)

    Didenkulov, Igor, E-mail: din@appl.sci-nnov.ru [Institute of Applied Physics, 46 Ulyanov str., Nizhny Novgorod, 603950 (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 23 Gagarin ave., Nizhny Novgorod, 603950 (Russian Federation); Pronchatov-Rubtsov, Nikolay, E-mail: nikvas@rf.unn.ru [Lobachevsky State University of Nizhny Novgorod, 23 Gagarin ave., Nizhny Novgorod, 603950 (Russian Federation)

    2015-10-28

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  3. Bubbles Outside the Plume During the LUMINY Wind-Wave Experiment

    NARCIS (Netherlands)

    Leeuw, G. de; Leifer, I.

    2002-01-01

    Since many bubble-mediated processes are size dependent, it is often necessary to characterize the bubble distribution over the full size spectrum. For example, in regards to bubble-mediated gas transfer, small bubbles are important for insoluble gases like helium, while large bubbles are important

  4. Bubbles with shock waves and ultrasound: a review.

    Science.gov (United States)

    Ohl, Siew-Wan; Klaseboer, Evert; Khoo, Boo Cheong

    2015-10-06

    The study of the interaction of bubbles with shock waves and ultrasound is sometimes termed 'acoustic cavitation'. It is of importance in many biomedical applications where sound waves are applied. The use of shock waves and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics-bubble interactions, with a focus on shock wave-bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the 'resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a shock wave complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving shock wave-bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead.

  5. GOATS 2011 Adaptive and Collaborative Exploitation of 3-Dimensional Environmental Acoustics in Distributed Undersea Networks

    Science.gov (United States)

    2013-09-30

    concept of a network of AUVs as an array of Virtual Sensors, based on fully integrated sensing, modeling and control , reducing the inter- platform...integrating high-fidelity acoustic modeling , platform dynamics and network communication and control . In regard to the environmental acoustic modeling ...static, passive and active sonar configurations for concurrent detection, classification and localization of subsea and bottom objects

  6. The coupled motions of bubbles in ultrasonic field

    Institute of Scientific and Technical Information of China (English)

    WANG Chenghui; LIN Shuyu

    2012-01-01

    The dynamic responses of bubbles in ultrasonic field include the radial vibration, translation, and their interactions. Based on the radial vibration modal where the secondary radiation of neighboring bubbles was considered, and interaction forces of bubbles, the coupled motions of two bubbles with different size in a plane ultrasonic field was simulated numerically. The results show that the radial vibration of a big bubble has natural properties and its translation velocity is rapid relatively. The behavior and distribution of bubbles was observed experimentally by using high speed photography. It is shown that the big bubbles translate rapidly in bubble clouds and vibrate radially with small-amplitude. On the other hand, the phenomena of attraction and coalescence among bubbles is observed, which may attribute to the effects of secondary radiation between neighboring bubbles.

  7. Effects of internal mass distribution and its isolation on the acoustic characteristics of a submerged hull

    Science.gov (United States)

    Peters, Herwig; Kinns, Roger; Kessissoglou, Nicole

    2014-03-01

    The primary aim of machinery isolation in marine vessels is to isolate structural vibration of the onboard machinery from the hull and to reduce far-field radiation of underwater noise. A substantial proportion of the total submarine mass is on flexible mounts that isolate supported masses from the hull at frequencies above the mounting system resonant frequency. This reduces the dynamically effective mass of the hull and affects the signature of the marine vessel due to propeller excitation. A fully coupled finite element/boundary element (FE/BE) model has been developed to investigate the effect of mass distribution and isolation in a submerged hull. The finite element model of the structure includes internal structures to represent the machinery and other flexibly mounted components. Changes in the radiated sound power demonstrate the effect of machinery isolation on the acoustic signature of the submerged hull due to the external propeller forces. Results are also presented to show how the arrangement of flexible mounts for a large internal structure can influence the radiation due to machinery forces.

  8. Novel cable coupling technique for improved shallow distributed acoustic sensor VSPs

    Science.gov (United States)

    Munn, Jonathan D.; Coleman, Thomas I.; Parker, Beth L.; Mondanos, Michael J.; Chalari, Athena

    2017-03-01

    Vertical seismic profiles (VSPs) collected using fiber optic distributed acoustic sensors (DAS) are becoming increasingly common; yet, ensuring good cable coupling with the borehole wall remains a persistent challenge. Traditional cable deployment techniques used in the petroleum industry are either not possible or do not provide data of sufficient quality for shallow applications. Additionally, no direct field comparison of coupling techniques in the same borehole exists to determine the impacts of poor coupling on DAS VSP data quality. This paper addresses these issues by: (1) presenting a novel cable coupling solution using a removable and relatively inexpensive FLUTe™ flexible borehole liner; and (2) presenting field examples of DAS VSPs under different coupling conditions. The proposed coupling technique is analogous to a fully cemented deployment in that the cable is continuously coupled directly to the formation. Field experiments conducted to assess and validate the technique demonstrate a marked improvement in VSP data quality when the cable is coupled with a flexible borehole liner. Without the liner, seismic profiles are dominated by a high-amplitude cable wave and the p-wave arrival is not observed; however, with cable coupling provided by a borehole liner inflated using hydrostatic pressure, the cable wave is suppressed and clear p-wave arrivals are visible. Additional tests examining the influence of fiber optic cable structure on seismic responses demonstrate that tight buffered fibers are more sensitive to dynamic strain than loose tube fibers making them potentially better suited for certain DAS applications.

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

    Science.gov (United States)

    Yasui, Kyuichi; Tuziuti, Toru; Iida, Yasuo

    2005-01-01

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

  10. A Correction of Random Incidence Absorption Coefficients for the Angular Distribution of Acoustic Energy under Measurement Conditions

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2009-01-01

    Most acoustic measurements are based on an assumption of ideal conditions. One such ideal condition is a diffuse and reverberant field. In practice, a perfectly diffuse sound field cannot be achieved in a reverberation chamber. Uneven incident energy density under measurement conditions can cause...... discrepancies between the measured value and the theoretical random incidence absorption coefficient. Therefore the angular distribution of the incident acoustic energy onto an absorber sample should be taken into account. The angular distribution of the incident energy density was simulated using the beam...... the theoretical absorption coefficient and the reverberation room measurement. The angle-weighted absorption coefficient, together with the size correction, agrees satisfactorily with the measured absorption data by the reverberation chamber method. At high frequencies and for large samples, the averaged...

  11. Acoustic characterization of void distributions across carbon-fiber composite layers

    Science.gov (United States)

    Tayong, Rostand B.; Smith, Robert A.; Pinfield, Valerie J.

    2016-02-01

    Carbon Fiber Reinforced Polymer (CFRP) composites are often used as aircraft structural components, mostly due to their superior mechanical properties. In order to improve the efficiency of these structures, it is important to detect and characterize any defects occurring during the manufacturing process, removing the need to mitigate the risk of defects through increased thicknesses of structure. Such defects include porosity, which is well-known to reduce the mechanical performance of composite structures, particularly the inter-laminar shear strength. Previous work by the authors has considered the determination of porosity distributions in a fiber-metal laminate structure [1]. This paper investigates the use of wave-propagation modeling to invert the ultrasonic response and characterize the void distribution within the plies of a CFRP structure. Finite Element (FE) simulations are used to simulate the ultrasonic response of a porous composite laminate to a typical transducer signal. This simulated response is then applied as input data to an inversion method to calculate the distribution of porosity across the layers. The inversion method is a multi-dimensional optimization utilizing an analytical model based on a normal-incidence plane-wave recursive method and appropriate mixture rules to estimate the acoustical properties of the structure, including the effects of plies and porosity. The effect of porosity is defined through an effective wave-number obtained from a scattering model description. Although a single-scattering approach is applied in this initial study, the limitations of the method in terms of the considered porous layer, percentage porosity and void radius are discussed in relation to single- and multiple-scattering methods. A comparison between the properties of the modeled structure and the void distribution obtained from the inversion is discussed. This work supports the general study of the use of ultrasound methods with inversion to

  12. Determination of the distribution of shallow-water seagrass and drift algae communities with acoustic seafloor discrimination

    OpenAIRE

    2016-01-01

    The spatial distribution of seagrass and algae communities can be difficult to determine in large, shallow lagoon systems where high turbidity prevents the use of optical methods like aerial photography or satellite imagery. Further complications can arise when algae are not permanently attached to the substratum and drift with tides and currents. A study using acoustic seafloor discrimination was conducted in the Indian River Lagoon (Florida, USA) to determine the extent of drift algae and s...

  13. Shock propagation in polydisperse bubbly flows

    OpenAIRE

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

    2009-01-01

    The effect of distributed bubble size on shock propagation in homogeneous bubbly liquids is computed using a continuum two-phase model. An ensemble-averaging technique is employed to derive the statistically averaged equations and a finite-volume method is used to solve the model equations. The bubble dynamics are incorporated using a Rayleigh-Plesset-type equation which includes the effects of heat transfer, liquid viscosity and compressibility. For the case of monodispe...

  14. Bat Acoustic Survey Report for ORNL: Bat Species Distribution on the Oak Ridge Reservation

    Energy Technology Data Exchange (ETDEWEB)

    McCracken, Kitty [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Giffen, Neil R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Haines, Angelina [XCEL Engineering Inc., Oak Ridge, TN (United States); Guge, B. J. [Tennessee Technological Univ., Cookeville, TN (United States); Evans, James W. [Tennessee Wildlife Resources Agency (TWRA), Nashville, TN (United States)

    2015-10-01

    This report summarizes results of a three-year acoustic survey of bat species on the US Department of Energy (DOE) Oak Ridge Reservation (ORR) in Oak Ridge, Tennessee. The survey was implemented through the Oak Ridge National Laboratory (ORNL) Natural Resources Management Program and included researchers from the ORNL Environmental Sciences Division and ORNL Facilities and Operations Directorate, Tennessee Wildlife Resources Agency’s ORR wildlife manager, a student from Tennessee Technological University, and a technician contracted through Excel Corp. One hundred and twenty-six sites were surveyed reservation-wide using Wildlife Acoustics SM2+ Acoustic Bat Detectors.

  15. Bubble interaction dynamics in Lagrangian and Hamiltonian mechanics.

    Science.gov (United States)

    Ilinskii, Yurii A; Hamilton, Mark F; Zabolotskaya, Evgenia A

    2007-02-01

    Two models of interacting bubble dynamics are presented, a coupled system of second-order differential equations based on Lagrangian mechanics, and a first-order system based on Hamiltonian mechanics. Both account for pulsation and translation of an arbitrary number of spherical bubbles. For large numbers of interacting bubbles, numerical solution of the Hamiltonian equations provides greater stability. The presence of external acoustic sources is taken into account explicitly in the derivation of both sets of equations. In addition to the acoustic pressure and its gradient, it is found that the particle velocity associated with external sources appears in the dynamical equations.

  16. Finite-amplitude vibration of a bubble and sonoluminescence

    Institute of Scientific and Technical Information of China (English)

    Qian Zu-Wen; Xiao Ling; Guo Liang-Hao

    2004-01-01

    Numerical solutions of the differential equation for a bubble performing finite-amplitude vibration are given in detail for a variety of situations. The results demonstrate that in lower acoustic pressure (maximum Mach number very low) its vibration has bounce. When acoustic pressure is in excess of 1.18atm and the instantaneous radius of the bubble approaches its equivalent Van der Waals radius, the maximum velocity and acceleration on the surface of a bubble have a huge increase in a very short period, which seems to favour the sonoluminescence. In vacuum environment (0.1atm),an intensive sonoluminescence could be generated.

  17. Surface Acoustic Wave (SAW) Technology For Clock Recovery In The Fiber Distributed Data Interface (FDDI)

    Science.gov (United States)

    Slawson, Michael R.

    1987-01-01

    This paper describes the use of Surface Acoustic Wave (SAW) technology for clock recovery, and the performance of this technology in the Fiber Distributed Data Interface (FDDI) draft standard. FDDI, because it operates at 125 MBd over the fiber optic media, requires tight control of the jitter accumulated in each point-to-point fiber link. The clock recovery function must be able to recover the clock and correctly sample the bit stream, given a relatively narrow "eye opening" at its input. Furthermore, the clock must be maintained during the FDDI "line states," which can have a very low transition density. This paper will first describe the particular implementation of SAW technology used for clock recovery, the SAW filter, and will define it purpose within the clock recovery function. Then, the jitter characteristics of the FDDI signal at the input to clock recovery, as well as the performance of the SAW-based clock recovery function under these input conditions, will be discussed. Experimental results obtained using a typical, Commercially available, SAW filter-based module will be presented. The various "detuning" sources of the SAW filter, which detract from the capability of the SAW-based module to perform accurate sampling, will be discussed. The performance of the module under FDDI line state conditions, particularly Master Line State (MLS) and Quit Line State (QLS), will be analyzed. The QLS, which indicated a disabled upstream transmitter or a cable break, contains no transitions and therefore no information for clock recovery. A circuit will be presented which uses the station's local oscillator and the "signal detect" function of the fiber optic receiver to derive the recovered clock in the event of QLS.

  18. Experimental study on interaction and coalescence of synchronized multiple bubbles

    Science.gov (United States)

    Cui, P.; Wang, Q. X.; Wang, S. P.; Zhang, A. M.

    2016-01-01

    Experiments are carried out on the interaction and coalescence of two, three, and four bubbles with approximately the same sizes, distributed evenly and symmetrically. The bubbles are generated simultaneously by electric discharges, using an in-house designed series circuit, and their interaction is captured using a high-speed camera. Particular attentions are paid to if/when coalescence of bubbles happens and the motion of the joined bubbles. Some new features are observed, which depend mainly on the dimensionless distance γbb = dbb/Rmax, where dbb is the inter-bubble distance and Rmax is the maximum bubble radius. For γbb > 2, a jet forms and penetrates each side bubble, directed to the center of the configuration, resulting in a protrusion. Towards the end of collapse, a large portion of bubble gases is compressed into the protrusion from the main part of the toroidal bubble. For γbb bubbles coalesce during expansion, and the part of the joined bubble's surface distal from the center of the configuration collapses faster than elsewhere. The experiments show that the oscillation period of multi-bubbles does not change appreciably without coalescence but increases significantly with coalescence. For three bubbles initiated at collinear positions with γbb > 2, the jets that form from the side bubbles are towards the middle, and the middle bubble splits into two parts, moving towards the two side bubbles. For γbb bubbles merge with the middle bubble during expansion, forming an ellipsoid bubble; the joined bubble collapses predominantly from two sides, where two inward jets form towards the end of collapse.

  19. Evolution of acoustically vaporized microdroplets in gas embolotherapy

    KAUST Repository

    Qamar, Adnan

    2012-01-01

    Acoustic vaporization dynamics of a superheated dodecafluoropentane (DDFP) microdroplet inside a microtube and the resulting bubble evolution is investigated in the present work. This work is motivated by a developmental gas embolotherapy technique that is intended to treat cancers by infarcting tumors using gas bubbles. A combined theoretical and computational approach is utilized and compared with the experiments to understand the evolution process and to estimate the resulting stress distribution associated with vaporization event. The transient bubble growth is first studied by ultra-high speed imaging and then theoretical and computational modeling is used to predict the entire bubble evolution process. The evolution process consists of three regimes: an initial linear rapid spherical growth followed by a linear compressed oval shaped growth and finally a slow asymptotic nonlinear spherical bubble growth. Although the droplets are small compared to the tube diameter, the bubble evolution is influenced by the tube wall. The final bubble radius is found to scale linearly with the initial droplet radius and is approximately five times the initial droplet radius. A short pressure pulse with amplitude almost twice as that of ambient conditions is observed. The width of this pressure pulse increases with increasing droplet size whereas the amplitude is weakly dependent. Although the rise in shear stress along the tube wall is found to be under peak physiological limits, the shear stress amplitude is found to be more prominently influenced by the initial droplet size. The role of viscous dissipation along the tube wall and ambient bulk fluid pressure is found to be significant in bubble evolution dynamics. © 2012 American Society of Mechanical Engineers.

  20. Evolution of acoustically vaporized microdroplets in gas embolotherapy.

    Science.gov (United States)

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

    2012-03-01

    Acoustic vaporization dynamics of a superheated dodecafluoropentane (DDFP) microdroplet inside a microtube and the resulting bubble evolution is investigated in the present work. This work is motivated by a developmental gas embolotherapy technique that is intended to treat cancers by infarcting tumors using gas bubbles. A combined theoretical and computational approach is utilized and compared with the experiments to understand the evolution process and to estimate the resulting stress distribution associated with vaporization event. The transient bubble growth is first studied by ultra-high speed imaging and then theoretical and computational modeling is used to predict the entire bubble evolution process. The evolution process consists of three regimes: an initial linear rapid spherical growth followed by a linear compressed oval shaped growth and finally a slow asymptotic nonlinear spherical bubble growth. Although the droplets are small compared to the tube diameter, the bubble evolution is influenced by the tube wall. The final bubble radius is found to scale linearly with the initial droplet radius and is approximately five times the initial droplet radius. A short pressure pulse with amplitude almost twice as that of ambient conditions is observed. The width of this pressure pulse increases with increasing droplet size whereas the amplitude is weakly dependent. Although the rise in shear stress along the tube wall is found to be under peak physiological limits, the shear stress amplitude is found to be more prominently influenced by the initial droplet size. The role of viscous dissipation along the tube wall and ambient bulk fluid pressure is found to be significant in bubble evolution dynamics.

  1. Jet formation in shock-heavy gas bubble interaction

    Institute of Scientific and Technical Information of China (English)

    Zhi-Gang Zhai; Ting Si; Li-Yong Zou; Xi-Sheng Luo

    2013-01-01

    The influences of the acoustic impedance and shock strength on the jet formation in shock-heavy gas bubble interaction are numerically studied in this work.The process of a shock interacting with a krypton or a SF6 bubble is studied by the numerical method VAS2D.As a validation,the experiments of a SF6 bubble accelerated by a planar shock were performed.The results indicate that,due to the mismatch of acoustic impedance,the way of jet formation in heavy gas bubble with different species is diversified under the same initial condition.With respect to the same bubble,the manner of jet formation is also distinctly different under different shock strengths.The disparities of the acoustic impedance result in different effects of shock focusing in the bubble,and different behaviors of shock wave inside and outside the bubble.The analyses of the wave pattern and the pressure variation indicate that the jet formation is closely associated with the pressure perturbation.Moreover,the analysis of the vorticity deposition,and comparisons of circulation and baroclinic torque show that the baroclinic vorticity also contributes to the jet formation.It is concluded that the pressure perturbation and baroclinic vorticity deposition are the two dominant factors for the jet formation in shock-heavy gas bubble interaction.

  2. Bubble nonlinear dynamics and stimulated scattering process

    Science.gov (United States)

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

    2016-02-01

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

  3. Ostwald Ripening in Multiple-Bubble Nuclei

    CERN Document Server

    Watanabe, Hiroshi; Inaoka, Hajime; Ito, Nobuyasu

    2014-01-01

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

  4. Ostwald ripening in multiple-bubble nuclei.

    Science.gov (United States)

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

    2014-12-21

    The Ostwald ripening of bubbles is studied by molecular dynamics simulations involving up to 679 × 10(6) Lennard-Jones particles. Many bubbles appear after depressurizing a system that is initially maintained in the pure-liquid phase, and the coarsening of bubbles follows. The self-similarity of the bubble-size distribution function predicted by Lifshitz-Slyozov-Wagner theory is directly confirmed. The total number of bubbles decreases asymptotically as t(-x) with scaling exponent x. As the initial temperature increases, the exponent changes from x = 3/2 to 1, which implies that the growth of bubbles changes from interface-limited (the t(1/2) law) to diffusion-limited (the t(1/3) law) growth.

  5. Fama on Bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    2016-01-01

    While Eugene Fama has repeatedly expressed his discontent with the notion of an “irrational bubble,” he has never publicly expressed his opinion on “rational bubbles.” On empirical grounds Fama rejects bubbles by referring to the lack of reliable evidence that price declines are predictable. Howe...... component in stock market valuation ratios, consistent with a rational bubble....

  6. Bubble Growth and Detachment from a Needle

    Science.gov (United States)

    Shusser, Michael; Rambod, Edmond; Gharib, Morteza

    1999-11-01

    The release of bubbles from an underwater nozzle or orifice occurs in large number of applications, such as perforated plate columns, blood oxygenators and various methods of water treatment. It is also a widely used method in laboratory research on multiphase flow and acoustics for generating small bubbles in a controlled fashion. We studied experimentally the growth and pinch-off of air bubbles released from a submerged needle into a quiescent liquid or a liquid flowing parallel to the needle. Micron-sized bubbles were generated by an air-liquid dispenser. High-speed imaging was performed to study the formation and detachment of bubbles from the tip of the needle. The impact of the needle diameter was investigated and the size and number of produced bubbles were assessed for different flow rates of air and for different velocities of the imposed upward liquid flow. The results were compared with available theoretical models and numerical computations. The existence of a critical gas flow rate and two regimes of bubble growth were verified.

  7. On thermonuclear processes in cavitation bubbles

    Science.gov (United States)

    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

  8. Lévy Stable Distribution and [0, 2] Power Law Dependence of Acoustic Absorption on Frequency in Various Lossy Media

    Institute of Scientific and Technical Information of China (English)

    CHEN Wen

    2005-01-01

    @@ Absorption of acoustic wave propagation in a large variety of lossy media is characterized by an empirical power law function of frequency, αo|ω|y. It has long been noted that the exponent y ranges from 0 to 2 for diverse media. Recently, the present author [J. Acoust. Soc. Am. 115 (2004) 1424] developed a fractional Laplacian wave equation to accurately model the power law dissipation, which can be further reduced to the fractional Laplacian diffusion equation. The latter is known underlying the Lévy stable distribution theory. Consequently,the parameters y is found to be the Lévy stability index, which is known to be bounded within 0 < y ≤ 2. This finding first provides a theoretical explanation of empirical observations y ∈ [0, 2]. Statistically, the frequencydependent absorption can thus be understood a Lévy stable process, where the parameter y describes the fractal nature of attenuative media.

  9. First Demonstration of a Scintillating Xenon Bubble Chamber for Dark Matter and CE$\

    Energy Technology Data Exchange (ETDEWEB)

    Baxter, D. [Fermilab; Chen, C. J. [Northwestern U.; Crisler, M. [PNL, Richland; Cwiok, T. [Northwestern U.; Dahl, C. E. [Fermilab; Grimsted, A. [Evanston Township High School; Gupta, J. [Northwestern U.; Jin, M. [Northwestern U.; Puig, R. [Northwestern U.; Temples, D. [Northwestern U; Zhang, J. [Northwestern U.

    2017-02-28

    A 30-gram xenon bubble chamber, operated at Northwestern University in June and November 2016, has for the first time observed simultaneous bubble nucleation and scintillation by nuclear recoils in liquid xenon. This chamber is instrumented with a CCD camera for near-IR bubble imaging, a solar-blind PMT to detect 175-nm xenon scintillation light, and a piezoelectric acoustic transducer to detect the ultrasonic emission from a growing bubble. The time-of-nucleation determined from the acoustic signal is used to correlate specific scintillation pulses with bubble-nucleating events. The observed single- and multiple-bubble rates when exposed to a $^{252}$Cf neutron source indicate that, for a thermodynamic "Seitz" threshold of 8.3 keV, the minimum nuclear recoil energy required to nucleate a bubble is between 11 and 25 keV. This is consistent with the observed scintillation spectrum for bubble-nucleating events. We see no evidence for bubble nucleation by gamma rays at the thresholds studied, setting a 90% CL upper limit of $6.3\\times10^{-7}$ bubbles per gamma interaction at a 4.2-keV thermodynamic threshold. This indicates stronger gamma discrimination than in CF$_3$I bubble chambers, supporting the hypothesis that scintillation production suppresses bubble nucleation by electron recoils, while nuclear recoils nucleate bubbles as usual. These measurements establish the noble-liquid bubble chamber as a promising new technology for WIMP and CE$\

  10. The role of acoustic screens in distribution of technogenic magnetic particles and chemical pollution in roadside soil

    Science.gov (United States)

    Wawer, Małgorzata; Magiera, Tadeusz; Szuszkiewicz, Marcin

    2015-04-01

    Roads constructed nowadays should by all means be functional for their motorized users but at the same time their effect on the environment ought to be limited to the minimum. Despite the existence of various methods for preventing from negative influence of roads on the environment, there is still lack of adequate techniques to monitor and reduce the spreading of roadside pollution in the air and soils. The aim of the study was to assess the influence of acoustic screens on spreading and deposition of solid pollutants deriving from car emissions, based on their quantitative and qualitative analysis. During this study, measurements of magnetic susceptibility and analyses of heavy metals as well as Pt and Rh contents in soil and plant samples (Taraxacum officinale, Plantago major, Parthenocissus quinquefolia) collected near different kinds of acoustic screens ("green walls", Plexiglass, sawdust concrete, steel panels and earth embankments) have been done. Previous investigations showed showed that most of traffic emission is deposited in the close vicinity of the roads (up to 10 m) and the level of contamination decreased with increasing distance from the road edge. However, the results of this project indicate that, in the area where the acoustic screens are located, this distribution is disturbed and the additional enrichment of heavy metals in soil about 10 - 15 m behind screens is observed. Spatial distribution of heavy metal contents in soil samples corresponds to its magnetic susceptibility values. High contents of Fe, Zn, Mn and Pb was observed next to acoustic screens made of sawdust concrete and steel panels. Additionally, concentration of Zn in soil samples collected close to these screens exceeded threshold value. Analyses of plants showed that the highest content of examined elements and highest values of magnetic susceptibility were recorded near road edge. What is more, samples of Parthenocissus quinquefolia collected at height 0.2 m were characterized

  11. Optimization of the Acoustic Pressure Distribution in a Resonant Photoacoustic Cell

    Institute of Scientific and Technical Information of China (English)

    陈柏; 陈兰荣; 范薇; 林尊琪

    2001-01-01

    The size of a cylindrical photoacoustic cell with suitable size was selected so that the resonant frequency of the first radial mode was equal to that of a longitudinal higher mode. By maintaining two thin coaxial tubes at each end, a enhanced photoacoustic cell was constructed with two tubes of 1/2 and 1/4 of the wavelength. In this enhanced photoacoustie cell, both the first radial resonance and the higher longitudinal resonance were excited adequately. Coupling of two acoustic modes makes the acoustic energy concentrating in the middle of the cell. The surface loss was decreased, the acoustic quality factor and pressure amplitude increased obviously as compared with conventional cylindrical cell.

  12. Direct laboratory observation of fluid distribution and its influence on acoustic properties of patchy saturated rocks

    Science.gov (United States)

    Lebedev, M.; Clennell, B.; Pervukhina, M.; Shulakova, V.; Mueller, T.; Gurevich, B.

    2009-04-01

    Porous rocks in hydrocarbon reservoirs are often saturated with a mixture of two or more fluids. Interpretation of exploration seismograms requires understanding of the relationship between distribution of the fluids patches and acoustic properties of rocks. The sizes of patches as well as their distribution affect significantly the seismic response. If the size of the fluid patch is smaller than the diffusion wavelength then pressure equilibration is achieved and the bulk modulus of the rock saturated with a mixture is defined by the Gassmann equations (Gassmann, 1951) with the saturation-weighted average of the fluid bulk modulus given by Wood's law (Wood, 1955, Mavko et al., 1998). If the fluid patch size is much larger than the diffusion wavelength then there is no pressure communication between different patches. In this case, fluid-flow effects can be neglected and the overall rock may be considered equivalent to an elastic composite material consisting of homogeneous parts whose properties are given by Gassmann theory with Hill's equation for the bulk modulus (Hill, 1963, Mavko et al., 1998). At intermediate values of fluid saturation the velocity-saturation relationship is significantly affected by the fluid patch distribution. In order to get an improved understanding of factors influencing the patch distribution and the resulting seismic wave response we performed simultaneous measurements of P-wave velocities and rock sample CT imaging. The CT imaging allows us to map the fluid distribution inside rock sample during saturation (water imbibition). We compare the experimental results with theoretical predictions. In this paper we will present results of simultaneous measurements of longitudinal wave velocities and imaging mapping of fluid distribution inside rock sample during sample saturation. We will report results of two kinds of experiments: "dynamic" and "quasi static" saturation. In both experiments Casino Cores Otway Basin sandstone, Australia core

  13. Comment on "Attenuation and dispersion of sound in dilute suspensions of spherical particles" [J. Acoust. Soc. Am. 108(1), 126-146 (2000)].

    Science.gov (United States)

    Shukla, Shiva Kant; Elvira, Luis

    2015-05-01

    Comment is made on an article by Temkin [J. Acoust. Soc. Am. 108(1), 126-146 (2000)]. This work illustrates the impact of particle size distribution on the dispersion and attenuation of sound waves propagating through particle suspensions. Temkin's propagation theory is extended for poly-disperse distributions of spherical particles, applicable to real suspensions. Significant changes in dispersion and attenuation appear near the particle resonance for both bubble and solid particle suspensions. Existing experimental data for bubble distributions also shows a good agreement with the poly-disperse modifications proposed.

  14. Adhesion of solid particles to gas bubbles. Part 2: Experimental

    NARCIS (Netherlands)

    Omota, Florin; Dimian, Alexandre C.; Bliek, Alfred

    2006-01-01

    In slurry bubble columns, the adhesion of solid catalyst particles to bubbles may significantly affect the G–L mass transfer and bubble size distribution. This feature may be exploited in design by modifying the hydrophilic or hydrophobic nature of the particles used. Previously we have proposed a g

  15. OptaSense distributed acoustic and seismic sensing using COTS fiber optic cables for infrastructure protection and counter terrorism

    Science.gov (United States)

    Duckworth, Gregory L.; Ku, Emery M.

    2013-06-01

    The OptaSense® Distributed Acoustic Sensing (DAS) technology can turn any cable with single-mode optical fiber into a very large and densely sampled acoustic/seismic sensor array—covering up to a 50 km aperture per system with "virtual" sensor separations as small as 1 meter on the unmodified cable. The system uses Rayleigh scattering from the imperfections in the fiber to return the optical signals measuring local fiber strain from seismic or air and water acoustic signals. The scalable system architecture can provide border monitoring and high-security perimeter and linear asset protection for a variety of industries—from nuclear facilities to oil and gas pipelines. This paper presents various application architectures and system performance examples for detection, localization, and classification of personnel footsteps, vehicles, digging and tunneling, gunshots, aircraft, and earthquakes. The DAS technology can provide a costeffective alternative to unattended ground sensors and geophone arrays, and a complement or alternative to imaging and radar sensors in many applications. The transduction, signal processing, and operator control and display technology will be described, and performance examples will be given from research and development testing and from operational systems on pipelines, critical infrastructure perimeters, railroads, and roadways. Potential new applications will be discussed that can take advantage of existing fiber-optic telecommunications infrastructure as "the sensor"—leading to low-cost and high-coverage systems.

  16. Effect of nonthermal ion distribution and dust temperature on nonlinear dust-acoustic solitary waves

    Indian Academy of Sciences (India)

    K Annou; R Annou

    2012-01-01

    Dust-acoustic solitary waves in unmagnetized dusty plasma whose constituents are inertial charged dust grains, Boltzmannian electrons and nonthermal ions have been investigated by taking into account finite dust temperature. The pseudopotential has been used to study solitary solution. The existence of solitary waves having negative potential is reported.

  17. Vertical distribution, composition and migratory patterns of acoustic scattering layers in the Canary Islands

    Science.gov (United States)

    Ariza, A.; Landeira, J. M.; Escánez, A.; Wienerroither, R.; Aguilar de Soto, N.; Røstad, A.; Kaartvedt, S.; Hernández-León, S.

    2016-05-01

    Diel vertical migration (DVM) facilitates biogeochemical exchanges between shallow waters and the deep ocean. An effective way of monitoring the migrant biota is by acoustic observations although the interpretation of the scattering layers poses challenges. Here we combine results from acoustic observations at 18 and 38 kHz with limited net sampling in order to unveil the origin of acoustic phenomena around the Canary Islands, subtropical northeast Atlantic Ocean. Trawling data revealed a high diversity of fishes, decapods and cephalopods (152 species), although few dominant species likely were responsible for most of the sound scattering in the region. We identified four different acoustic scattering layers in the mesopelagic realm: (1) at 400-500 m depth, a swimbladder resonance phenomenon at 18 kHz produced by gas-bearing migrant fish such as Vinciguerria spp. and Lobianchia dofleini, (2) at 500-600 m depth, a dense 38 kHz layer resulting primarily from the gas-bearing and non-migrant fish Cyclothone braueri, and to a lesser extent, from fluid-like migrant fauna also inhabiting these depths, (3) between 600 and 800 m depth, a weak signal at both 18 and 38 kHz ascribed either to migrant fish or decapods, and (4) below 800 m depth, a weak non-migrant layer at 18 kHz which was not sampled. All the dielly migrating layers reached the epipelagic zone at night, with the shorter-range migrations moving at 4.6 ± 2.6 cm s - 1 and the long-range ones at 11.5 ± 3.8 cm s - 1. This work reduces uncertainties interpreting standard frequencies in mesopelagic studies, while enhances the potential of acoustics for future research and monitoring of the deep pelagic fauna in the Canary Islands.

  18. Vertical distribution, composition and migratory patterns of acoustic scattering layers in the Canary Islands

    KAUST Repository

    Ariza, A.

    2016-01-21

    Diel vertical migration (DVM) facilitates biogeochemical exchanges between shallow waters and the deep ocean. An effective way of monitoring the migrant biota is by acoustic observations although the interpretation of the scattering layers poses challenges. Here we combine results from acoustic observations at 18 and 38 kHz with limited net sampling in order to unveil the origin of acoustic phenomena around the Canary Islands, subtropical northeast Atlantic Ocean. Trawling data revealed a high diversity of fishes, decapods and cephalopods (152 species), although few dominant species likely were responsible for most of the sound scattering in the region. We identified four different acoustic scattering layers in the mesopelagic realm: (1) at 400–500 m depth, a swimbladder resonance phenomenon at 18 kHz produced by gas-bearing migrant fish such as Vinciguerria spp. and Lobianchia dofleini, (2) at 500–600 m depth, a dense 38 kHz layer resulting primarily from the gas-bearing and non-migrant fish Cyclothone braueri, and to a lesser extent, from fluid-like migrant fauna also inhabiting these depths, (3) between 600 and 800 m depth, a weak signal at both 18 and 38 kHz ascribed either to migrant fish or decapods, and (4) below 800 m depth, a weak non-migrant layer at 18 kHz which was not sampled. All the dielly migrating layers reached the epipelagic zone at night, with the shorter-range migrations moving at 4.6 ± 2.6 cm s − 1 and the long-range ones at 11.5 ± 3.8 cm s − 1. This work reduces uncertainties interpreting standard frequencies in mesopelagic studies, while enhances the potential of acoustics for future research and monitoring of the deep pelagic fauna in the Canary Islands.

  19. Review of scattering and extinction cross-sections, damping factors, and resonance frequencies of a spherical gas bubble

    NARCIS (Netherlands)

    Ainslie, M.A.; Leighton, T.G.

    2011-01-01

    Perhaps the most familiar concepts when discussing acoustic scattering by bubbles are the resonance frequency for bubble pulsation, the bubbles' damping, and their scattering and extinction cross-sections, all of which are used routinely in oceanography, sonochemistry, and biomedicine. The apparent

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

    Science.gov (United States)

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

    2015-10-01

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

  1. Electron acoustic waves in a magnetized plasma with kappa distributed ions

    Energy Technology Data Exchange (ETDEWEB)

    Devanandhan, S.; Lakhina, G. S. [Indian Institute of Geomagnetism, Navi Mumbai (India); Singh, S. V. [Indian Institute of Geomagnetism, Navi Mumbai (India); School of Physics, University of Kwazulu-Natal, Durban (South Africa); Bharuthram, R. [University of the Western Cape, Bellville (South Africa)

    2012-08-15

    Electron acoustic solitary waves in a two component magnetized plasma consisting of fluid cold electrons and hot superthermal ions are considered. The linear dispersion relation for electron acoustic waves is derived. In the nonlinear regime, the energy integral is obtained by a Sagdeev pseudopotential analysis, which predicts negative solitary potential structures. The effects of superthermality, obliquity, temperature, and Mach number on solitary structures are studied in detail. The results show that the superthermal index {kappa} and electron to ion temperature ratio {sigma} alters the regime where solitary waves can exist. It is found that an increase in magnetic field value results in an enhancement of soliton electric field amplitude and a reduction in soliton width and pulse duration.

  2. Bubble Dynamics in a Two-Phase Medium

    CERN Document Server

    Jayaprakash, Arvind; Chahine, Georges

    2010-01-01

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

  3. Taming Acoustic Cavitation

    CERN Document Server

    Rivas, David Fernandez; Enriquez, Oscar R; Versluis, Michel; Prosperetti, Andrea; Gardeniers, Han; Lohse, Detlef

    2012-01-01

    In this fluid dynamics video we show acoustic cavitation occurring from pits etched on a silicon surface. By immersing the surface in a liquid, gas pockets are entrapped in the pits which upon ultrasonic insonation, are observed to shed cavitation bubbles. Modulating the driving pressure it is possible to induce different behaviours based on the force balance that determines the interaction among bubbles and the silicon surface. This system can be used for several applications like sonochemical water treatment, cleaning of surfaces with deposited materials such as biofilms.

  4. Modulational instability of ion-acoustic waves in plasma with a q-nonextensive nonthermal electron velocity distribution

    Energy Technology Data Exchange (ETDEWEB)

    Bouzit, Omar, E-mail: omar.bouzit@yahoo.fr; Tribeche, Mouloud, E-mail: mouloudtribeche@yahoo.fr, E-mail: mtribeche@usthb.dz [Plasma Physics Group (PPG), Theoretical Physics Laboratory (TPL), Faculty of Physics, University of Bab-Ezzouar, U.S.T.H.B, B.P. 32, El Alia, Algiers 16111 (Algeria); Bains, A. S., E-mail: bainsphysics@yahoo.co.in [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N5E2 (Canada)

    2015-08-15

    Modulation instability of ion-acoustic waves (IAWs) is investigated in a collisionless unmagnetized one dimensional plasma, containing positive ions and electrons following the mixed nonextensive nonthermal distribution [Tribeche et al., Phys. Rev. E 85, 037401 (2012)]. Using the reductive perturbation technique, a nonlinear Schrödinger equation which governs the modulation instability of the IAWs is obtained. Valid range of plasma parameters has been fixed and their effects on the modulational instability discussed in detail. We find that the plasma supports both bright and dark solutions. The valid domain for the wave number k where instabilities set in varies with both nonextensive parameter q as well as non thermal parameter α. Moreover, the analysis is extended for the rational solutions of IAWs in the instability regime. Present study is useful for the understanding of IAWs in the region where such mixed distribution may exist.

  5. Filling the gaps: Predicting the distribution of temperate reef biota using high resolution biological and acoustic data

    Science.gov (United States)

    Hill, Nicole A.; Lucieer, Vanessa; Barrett, Neville S.; Anderson, Tara J.; Williams, Stefan B.

    2014-06-01

    Management of the marine environment is often hampered by a lack of comprehensive spatial information on the distribution of diversity and the bio-physical processes structuring regional ecosystems. This is particularly true in temperate reef systems beyond depths easily accessible to divers. Yet these systems harbor a diversity of sessile life that provide essential ecosystem services, sustain fisheries and, as with shallower ecosystems, are also increasingly vulnerable to anthropogenic impacts and environmental change. Here we use cutting-edge tools (Autonomous Underwater Vehicles and ship-borne acoustics) and analytical approaches (predictive modelling) to quantify and map these highly productive ecosystems. We find the occurrence of key temperate-reef biota can be explained and predicted using standard (depth) and novel (texture) surrogates derived from multibeam acoustic data, and geographic surrogates. This suggests that combinations of fine-scale processes, such as light limitation and habitat complexity, and broad-scale processes, such as regional currents and exposure regimes, are important in structuring these diverse deep-reef communities. While some dominant habitat forming biota, including canopy algae, were widely distributed, others, including gorgonians and sea whips, exhibited patchy and restricted distributions across the reef system. In addition to providing the first quantitative and full coverage maps of reef diversity for this area, our modelling revealed that offshore reefs represented a regional diversity hotspot that is of high ecological and conservation value. Regional reef systems should not, therefore, be considered homogenous units in conservation planning and management. Full-coverage maps of the predicted distribution of biota (and associated uncertainty) are likely to be increasingly valuable, not only for conservation planning, but in the ongoing management and monitoring of these less-accessible ecosystems.

  6. Fama on bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    Eugene Fama has repeatedly expressed his discontent with the notion of an irrational bubble. However, he has never publicly expressed his opinion on rational bubbles. This is peculiar since such bubbles build naturally from the rational efficient markets paradigm that Fama strongly adheres to...

  7. Beer tapping: dynamics of bubbles after impact

    Science.gov (United States)

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

    2015-12-01

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

  8. Distribution of small dispersive coal dust particles and absorbed radioactive chemical elements in conditions of forced acoustic resonance in iodine air filter at nuclear power plant

    CERN Document Server

    Ledenyov, Oleg P

    2013-01-01

    The physical features of distribution of the small dispersive coal dust particles and the adsorbed radioactive chemical elements and their isotopes in the absorber with the granular filtering medium with the cylindrical coal granules were researched in the case of the intensive air dust aerosol stream flow through the iodine air filter (IAF). It was shown that, at the certain aerodynamic conditions in the IAF, the generation of the acoustic oscillations is possible. It was found that the acoustic oscillations generation results in an appearance of the standing acoustic waves of the air pressure (density) in the IAF. In the case of the intensive blow of the air dust aerosol, it was demonstrated that the standing acoustic waves have some strong influences on both: 1) the dynamics of small dispersive coal dust particles movement and their accumulation in the IAF; 2) the oversaturation of the cylindrical coal granules by the adsorbed radioactive chemical elements and their isotopes in the regions, where the antin...

  9. Sonoluminescence and multi-bubble cavitation phenomena for selected research and industrial applications

    Science.gov (United States)

    Greenwood, Larry; Olsen, Khris; Good, Morris; Bond, Leonard; Posakony, Gerald; Peters, Timothy; Baldwin, David; Wester, Dennis; Ahmed, Salahuddin

    2003-04-01

    Single bubble sonoluminescence (SBSL), multi-bubble sonoluminescence (MBSL), multi-bubble sonochemiluminescence (MBSCL) and other high power ultrasound cavitation and noncavitating ultrasound process stream interaction phenomena are known to produce a wide range of both physical and chemical effects that depend upon the system and operating conditions employed. Three interacting regimes are under investigation (a) high power and high frequency (including noncavitating systems), (b) single bubble resonance/sonoluminescence and (c) multi-bubble high power sonochemical processing. In all cases these involve various reactors, including possible schemes for continuous material feeding and processing for selected chemical, nonaqueous fluids and biological research and industrial applications. High power sonochemical and noncavitating ultrasound processing applications and a review of literature pertaining to the potential of high power processing, including fusion are discussed. Work includes the investigation of acoustic fields in reactors, characterization of sonoluminescence spectra, the investigation of system parameters to control maximum bubble temperature and pressure, and acoustic energy partition into light and acoustic emission/shock waves. Effects of various chemical systems on multi-bubble luminescence are being investigated and will be reported. Work to date has emphasized the evaluation of both single and multi-bubble sonoluminescence, spectral measurements, acoustic emission measurements and the observation of a continuous bubble feed phenomenon.

  10. Global distribution of equatorial plasma bubbles in the premidnight sector during solar maximum as observed by KOMPSAT-1 and Defense Meteorological Satellite Program F15

    Science.gov (United States)

    Park, Jaeheung; Min, Kyoung Wook; Kim, Vitaly P.; Kil, Hyosub; Lee, Jae-Jin; Kim, Hee-Jun; Lee, Ensang; Lee, Dae Young

    2005-07-01

    We investigated the global distribution of equatorial plasma bubbles (EPBs) using in situ plasma density measurements from Korea Multipurpose Satellite-1 (KOMPSAT-1) and Defense Meteorological Satellite Program (DMSP) F15 during the solar maximum period from June 2000 to August 2001. The results were generally consistent with those of previous studies. EPBs were observed at all longitudes around the magnetic dip equator in the equinoctial seasons with the peak occurrence in the American-Atlantic-African regions. During the June solstice, EPBs occurred predominantly in the African sector, with enhancements in the magnetic north in the Indian and west Pacific regions, but were totally suppressed in the American-Atlantic sector. During the December solstice, EPBs occurred frequently in the American-Atlantic sector but were suppressed in the other longitude sectors, especially in the Pacific sector. The EPB occurrence probability was seen to be correlated with the observed topside plasma density and the model prereversal upward drift speed of ambient plasmas (Fejer et al., 1999), with their respective dominance dependent on the seasons. However, the peak EPB occurrence in the American-Atlantic sector during the December solstice was displaced somewhat from the region of peak density and upward drift, probably due to a strong solar terminator influence on the flux tube-integrated E region Pedersen conductivity and due to anomaly morphology. The peak EPB occurrence in the African sector during the June solstice is consistent only with the high ambient density in that region, for there was no coincidence with the maximum vertical drift or the minimum E region Pedersen conductivity.

  11. Gas Bubble Growth in Muddy Sediments

    Science.gov (United States)

    2016-06-07

    appropriate model for growth (i.e. non - Newtonian viscous vs. plastic (Bingham) vs. elastic vs. visco-elastic). The modelling research (Bernard Boudreau...Rev. 8-98) Prescribed by ANSI Std Z39-18 On the modelling front, we have a working model of a sediment as a Newtonian /Power-Law fluid , surrounding a... Newtonian model or approximated with a Power-Law fluid model. IMPACT/APPLICATIONS Bubbles seriously compromise acoustic sensing of sediments, e.g. locating

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

    Science.gov (United States)

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

    2012-11-01

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

  13. Shape measurement of bubble in a liquid metal

    Science.gov (United States)

    Saito, Y.; Shen, X.; Mishima, K.; Matsubayashi, M.

    2009-06-01

    Dynamic behavior of a two-phase bubble, i.e. a steam bubble containing a droplet evaporating in the bubble, in the molten alloy was clearly visualized using high-frame-rate neutron radiography. In relation to some direct contact heat exchanger design with molten lead-bismuth (Pb-Bi), experiments have been done at JRR-3M of JAEA (Japan Atomic Energy Agency) with water droplets evaporating in a stable thermally stratified Newton's alloy pool. The instantaneous shape and size of the bubble has been iteratively estimated from the void fraction distributions and total void volume by assuming a symmetrical bubble shape.

  14. The effect of nearby bubbles on array gain.

    Science.gov (United States)

    Culver, R Lee; Park, J Daniel; Leighton, Timothy G; Coles, David G H

    2011-12-01

    The coherent processing of signals from multiple hydrophones in an array offers improvements in angular resolution and signal-to-noise ratio. When the array is steered in a particular direction, the signals arriving from that direction are added in phase, and any signals arriving from other directions are not. Array gain (AG) is a measure of how much the signal arriving from the steering direction is amplified relative to signals arriving from all other directions. The subject of this paper is the manner in which the AG of an acoustic array operating in water that contains air bubbles is affected by scattering from nearby bubbles. The effects of bubbles on acoustic attenuation and dispersion are considered separately from their effects on AG. Acoustic measurements made in bubbly water using the AB Wood tank at the Institute of Sound and Vibration Research, University of Southampton, in June 2008 show that as bubble density increases, relative phase shifts in individual hydrophone signals increase and signal correlation among the hydrophones is reduced. A theory and numerical simulation linking bubble density at the hydrophone to the AG is in good agreement with the measurements up to the point where multiple scattering becomes important.

  15. Characteristic study of head-on collision of dust-ion acoustic solitons of opposite polarity with kappa distributed electrons

    Science.gov (United States)

    Parveen, Shahida; Mahmood, Shahzad; Adnan, Muhammad; Qamar, Anisa

    2016-09-01

    The head on collision between two dust ion acoustic (DIA) solitary waves, propagating in opposite directions, is studied in an unmagnetized plasma constituting adiabatic ions, static dust charged (positively/negatively) grains, and non-inertial kappa distributed electrons. In the linear limit, the dispersion relation of the dust ion acoustic (DIA) solitary wave is obtained using the Fourier analysis. For studying characteristic head-on collision of DIA solitons, the extended Poincaré-Lighthill-Kuo method is employed to obtain Korteweg-de Vries (KdV) equations with quadratic nonlinearities and investigated the phase shifts in their trajectories after the interaction. It is revealed that only compressive solitary waves can exist for the positive dust charged concentrations while for negative dust charge concentrations both the compressive and rarefactive solitons can propagate in such dusty plasma. It is found that for specific sets of plasma parameters, the coefficient of nonlinearity disappears in the KdV equation for the negative dust charged grains. Therefore, the modified Korteweg-de Vries (mKdV) equations with cubic nonlinearity coefficient, and their corresponding phase shift and trajectories, are also derived for negative dust charged grains plasma at critical composition. The effects of different plasma parameters such as superthermality, concentration of positively/negatively static dust charged grains, and ion to electron temperature ratio on the colliding soliton profiles and their corresponding phase shifts are parametrically examined.

  16. An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator

    Science.gov (United States)

    Salvado, José; Espírito-Santo, António; Calado, Maria

    2012-01-01

    This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications. PMID:22969364

  17. An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator

    Directory of Open Access Journals (Sweden)

    Maria Calado

    2012-06-01

    Full Text Available This paper proposes a distributed system for analysis and monitoring (DSAM of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs. The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications.

  18. An intelligent sensor array distributed system for vibration analysis and acoustic noise characterization of a linear switched reluctance actuator.

    Science.gov (United States)

    Salvado, José; Espírito-Santo, António; Calado, Maria

    2012-01-01

    This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications.

  19. Can airborne ultrasound monitor bubble size in chocolate?

    OpenAIRE

    Watson, N; Hazlehurst, T; Povey, M; Vieira, J.; Sundara, R; Sandoz, JP

    2014-01-01

    Aerated chocolate products consist of solid chocolate with the inclusion of bubbles and are a popular consumer product in many countries. The volume fraction and size distribution of the bubbles has an effect on their sensory properties and manufacturing cost. For these reasons it is important to have an online real time process monitoring system capable of measuring their bubble size distribution. As these products are eaten by consumers it is desirable that the monitoring system is non cont...

  20. 两种气泡混合的声空化∗%Cavitation of two kinds of bubble mixtures

    Institute of Scientific and Technical Information of China (English)

    苗博雅; 安宇

    2015-01-01

    By solving the nonlinear wave equation coupled with the modified Rayleigh-Plesset equation, the characteristics of the acoustic field and bubble motion in cavitation environment can be described. In general, the cavitation cloud consists of many kinds of bubbles with different ambient radii. For simplicity, in this work the cavitation process of the mixture of two kinds of bubbles with different ambient radii is numerically simulated, and the ratio of the mixture is adjustable. Suppose that the cavitation in water contained in a cylindrical container is stimulated by ultrasonic horn. The dissipative absorption of the container wall is taken into account, which plays an important role in forming the stationary standing wave field, otherwise, the beat signal of acoustic pressure will appear which is absent in the observation. Based on the stationary acoustic wave field, for the case of the mixed-bubble cavitation, the interactions between bubbles and acoustic field, bubbles and bubbles, as well as the spectrum of acoustic signal are analyzed. We choose the cases that the ratio of two kinds of bubble species is varying, but the total density of bubble number is fixed to be 1/mm3, and find that those results are very different. For the case that the ambient radii of two bubble species are both a few micron, revealing that the interaction between bubbles and acoustic field is usually weak. As the proportion of bigger bubble increases, the change of the acoustic pressure and the averaged radius of bubble behave regularly;for the case that the ambient radius of one of bubble specie is relatively big, for example, the ambient radius is about a few tens of microns, the interactions between bubbles and acoustic field become stronger, and the nonlinearity is more apparent. We can observe the similar trends from the frequency spectrum. For the bubble of a few microns in size, the base frequency is dominant;in contrast, for the bubble of a few tens of microns in size, the

  1. Nonlinear dust acoustic waves with polarization force effects in Kappa distribution plasma

    Science.gov (United States)

    Chen, Hui; Zhou, Suyun; Luo, Rongxiang; Liu, Sanqiu

    2017-01-01

    The propagation characteristics of dust acoustic solitary waves (DASWs) in dusty plasmas with the effects of polarization force and superthermal ions are studied. First, the polarization force induced by superthermal ions is obtained. It is shown that the superthermality of background ions affect the Debye screening of dust grains as well as the polarization force significantly. Then for small amplitude solitary waves, the KdV equation is obtained by applying the reductive perturbation technique. And for the arbitrary amplitude solitary waves, the Sagdeev potential method is employed and the Sagdeev potential is analyzed. In both case, the effects of the polarization force associated the ions’ superthermality on the characteristic of the DASWs are analyzed.

  2. Dust ion acoustic solitary structures in presence of nonthermally distributed electrons and positrons

    CERN Document Server

    Paul, Ashesh; Das, K P

    2016-01-01

    The purpose of this paper is to extend the recent work of Paul & Bandyopadhyay [Astrophys. Space Sci. 361, 172(2016)] on the existence of different dust ion acoustic solitary structures in an unmagnetized collisionless dusty plasma consisting of negatively charged static dust grains, adiabatic warm ions, nonthermal electrons and isothermal positrons in a more generalized form by considering nonthermal positrons instead of isothermal positrons. The present system supports both positive and negative potential double layers, coexistence of solitary waves of both polarities and positive potential supersolitons. The qualitative and the quantitative changes in existence domains of different solitary structures which occur for the presence of nonthermal positrons have been presented in comparison with the results of Paul & Bandyopadhyay [Astrophys. Space Sci. 361, 172(2016)]. The formation of supersoliton structures and their limitations have been analyzed with the help of phase portraits of the dynamical sy...

  3. Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble's dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Mahdi, M. [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Ebrahimi, R. [Faculty of Aerospace Engineering, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Shams, M., E-mail: shams@kntu.ac.ir [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Pardis St., Molla-Sadra Ave, Vanak. Sq., P.O. Box: 19395-1999, Tehran (Iran, Islamic Republic of)

    2011-06-13

    A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack. -- Highlights: → Heat transfer and ionization energy losses were analyzed in the cavitation bubble. → Radiation of hydrodynamic bubble was approximately equal to the black body. → Radiation heat transfer did not affect the bubble dynamic. → Conduction decreased the bubble pressure and increased the bubble temperature. → Ionization decreased the temperature and increased the pressure in the bubble.

  4. Acoustically enhanced heat transport

    Energy Technology Data Exchange (ETDEWEB)

    Ang, Kar M.; Hung, Yew Mun; Tan, Ming K., E-mail: tan.ming.kwang@monash.edu [School of Engineering, Monash University Malaysia, 47500 Bandar Sunway, Selangor (Malaysia); Yeo, Leslie Y. [Micro/Nanophysics Research Laboratory, RMIT University, Melbourne, VIC 3001 (Australia); Friend, James R. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, California 92093 (United States)

    2016-01-15

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

  5. Acoustically enhanced heat transport

    Science.gov (United States)

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

    2016-01-01

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

  6. Flow Structures Around Micro-bubbles During Subcooled Nucleate Boiling

    Institute of Scientific and Technical Information of China (English)

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

    2005-01-01

    The flow structures were investigated around micro bubbles on extremely thin wires during subcooled nucleate boiling. Jet flows emanating from the bubbles were observed visually with the fluid field measurement using high-speed photography and a PIV system. The jet flows induced a strong pumping effect around a bubble. The multi-jet structure was further observed experimentally, indicating the evolution of flow structure around micro bubbles. Numerical simulations explore that the jet flows were induced by a strong Marangoni effect due to high temperature gradients near the wire. The bubble interface with multi-jet structure has abnormal temperature distribution such that the coolest parts were observed at two sides of a bubble extending into the subcooled bulk liquid rather than at the top. Evaporation and condensation on the bubble interface play important roles not only in controlling the intensity of the jet flow, but also in bringing out the multi-jet structure.

  7. Can modelled harbour porpoise distribution based on satellite tracking be validated from static acoustic monitoring

    DEFF Research Database (Denmark)

    Mikkelsen, Lonnie; Riget, Frank Farsø; Sveegaard, Signe

    Species distribution models are increasingly being used to model habitat suitability from positioning records. Here we use satellite locations from 15 tagged harbour porpoises (Phocoena phocoena) in the western Baltic Sea to model suitable habitats using the species distribution model MaxEnt (Max...

  8. Localized removal of layers of metal, polymer, or biomaterial by ultrasound cavitation bubbles

    NARCIS (Netherlands)

    Rivas, David Fernandez; Verhaagen, Bram; Seddon, James R. T.; Zijlstra, Aaldert G.; Jiang, Lei-Meng; van der Sluis, Luc W. M.; Versluis, Michel; Lohse, Detlef; Gardeniers, Han J. G. E.

    2012-01-01

    We present an ultrasonic device with the ability to locally remove deposited layers from a glass slide in a controlled and rapid manner. The cleaning takes place as the result of cavitating bubbles near the deposited layers and not due to acoustic streaming. The bubbles are ejected from air-filled c

  9. Tribonucleation of bubbles

    CERN Document Server

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

    2016-01-01

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

  10. Bubble-sweeping mechanisms

    Institute of Scientific and Technical Information of China (English)

    WANG; Hao; (王; 昊); PENG; Xiaofeng; (彭晓峰); WANG; Buxuan; (王补宣); LEE; Duzhong; (李笃中)

    2003-01-01

    A series of subcooled boiling experiments was conducted on very small platinum wires having diameters of 0.1 and 0.025 mm. Vapor bubbles were visually observed to sweep back and forth along the wires in the experiments. The dynamic characteristics of bubble-sweeping phenomenon are described, and the induced bubble interaction and nonlinear growth are investigated to understand the boiling heat transfer mechanisms. An unsymmetrical temperature model is proposed to explain the physical mechanism.

  11. Bubbles and market crashes

    CERN Document Server

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

    1994-01-01

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

  12. Acoustic elliptical cylindrical cloaks

    Institute of Scientific and Technical Information of China (English)

    Ma Hua; Qu Shao-Bo; Xu Zhuo; Wang Jia-Fu

    2009-01-01

    By making a comparison between the acoustic equations and the 2-dimensional (2D) Maxwell equations, we obtain the material parameter equations (MPE) for acoustic elliptical cylindrical cloaks. Both the theoretical results and the numerical results indicate that an elliptical cylindrical cloak can realize perfect acoustic invisibility when the spatial distributions of mass density and bulk modulus are exactly configured according to the proposed equations. The present work is the meaningful exploration of designing acoustic cloaks that are neither sphere nor circular cylinder in shape, and opens up possibilities for making complex and multiplex acoustic cloaks with simple models such as spheres, circular or elliptic cylinders.

  13. Indoor acoustic gain design

    Science.gov (United States)

    Concha-Abarca, Justo Andres

    2002-11-01

    The design of sound reinforcement systems includes many variables and usually some of these variables are discussed. There are criteria to optimize the performance of the sound reinforcement systems under indoor conditions. The equivalent acoustic distance, the necessary acoustic gain, and the potential acoustic gain are parameters which must be adjusted with respect to the loudspeaker array, electric power and directionality of loudspeakers, the room acoustics conditions, the distance and distribution of the audience, and the type of the original sources. The design and installation of front of the house and monitoring systems have individual criteria. This article is about this criteria and it proposes general considerations for the indoor acoustic gain design.

  14. A detection of Baryon Acoustic Oscillations from the distribution of galaxy clusters

    CERN Document Server

    Hong, Tao; Wen, Z L

    2015-01-01

    We calculate the correlation function of 79,091 galaxy clusters in the redshift region of $0.05 \\leq z \\leq 0.5$ selected from the WH15 cluster catalog. With a weight of cluster mass, a significant baryon acoustic oscillation (BAO) peak is detected on the correlation function with a significance of $3.9 \\sigma$. By fitting the correlation function with a $\\Lambda$CDM model curve, we find $D_v(z = 0.331) r_d^{fid}/r_d = 1269.4 \\pm 58$ Mpc which is consistent with the Planck 2015 cosmology. We find that the correlation functions of the higher mass sub-samples show a higher amplitude at small scales of $r < 80~h^{-1}{\\rm Mpc}$, which is consistent with our precious result. We find a clear signal of the `Finger-of-God' effect on the 2D correlation function of the whole sample, which indicates the random peculiar motion of central bright galaxies in the gravitation potential well of clusters.

  15. Physics of bubble oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Lauterborn, Werner; Kurz, Thomas [Third Physical Institute, University of Goettingen (Germany)

    2010-10-01

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

  16. Bubble and drop interfaces

    CERN Document Server

    Miller

    2011-01-01

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

  17. INTRASPECIFIC VARIATION IN ACOUSTIC TRAITS AND BODY SIZE, AND NEW DISTRIBUTIONAL RECORDS FOR PSEUDOPALUDICOLA GIARETTAI CARVALHO, 2012 (ANURA, LEPTODACTYLIDAE, LEIUPERINAE: IMPLICATIONS FOR ITS CONGENERIC DIAGNOSIS

    Directory of Open Access Journals (Sweden)

    THIAGO RIBEIRO DE CARVALHO

    2015-01-01

    Full Text Available In this paper, we provide an updated diagnosis for Pseudopaludicola giarettai based on the morphometric and acoustic variation observed with the assessment of new populations, plus an expansion of its distribution range. Our results support that all acoustic variation observed might be attributed to intraspecific variation. The variation in body size and dorsal stripe patterns observed for Pseudopaludicola giarettai reinforces that the distinctive whistling advertisement call pattern is the most reliable evidence line to diagnose it from its congeners, whereas morphological (robust body, glandular dorsum and morphometric (body size features vary considerably within and among populations so that they should no longer be employed as diagnostic features of Pseudopaludicola giarettai.

  18. Investigation on bubble dynamics characteristics and power spectral variation in acoustic field%声波作用下的气泡非线性动力学特性影响因素及功率谱变化规律研究

    Institute of Scientific and Technical Information of China (English)

    杨德森; 时洁; 时胜国; 张昊阳; 江薇; 靳仕源

    2013-01-01

    Based on Keller-Miksis model, the influences of multiple control parameters, such as acoustic pressure amplitude, acoustic frequency and bubble radius at rest, on the complicated dynamics characteristics of nonlinear bubble oscillation driven by acoustic wave are discussed by utilizing a variety of numerical analysis methods, and the restrictive relationships among different parameters are analyzed. It is shown that chaotic state can occur only in the condition of all of the parameters in the suitable threshold, as the same time, chaotic state is the result of interaction of multiple control parameters. Furthermore, the power spectral expansion and energy conversion are existed in this nonlinear system. It is certified that the stronger acoustic pressure amplitude, the greater the sub-harmonic energy, besides, the energy attenuation of fundamental harmonic is also much greater.%为获取声波作用下的气泡非线性动力学特性影响因素及频谱变化规律,本文以描述声场作用下气泡动力学特性的Keller-Miksis模型为基础,综合利用多种数值分析方法,对激励声压幅值、激励频率以及气泡平衡半径等参数对气泡非线性动力学特性影响及参数控制下该非线性系统中多种运动状态下的频谱能量变化规律进行了研究.研究结果表明,只有当系统参数皆在一定阈值范围内时,系统才可能发生混沌,系统混沌运动状态的产生是各种因素相互制约和均衡的结果,且在该系统中蕴含着复杂的频谱展宽和能量转换过程.在实验中观察到次谐波的出现,并证明了随着激励强度的增大,产生次谐波的能量越大,同时基波能量衰减也越大.本文的研究工作可为引导外加声场的频谱结构发生改变所带来的潜在的噪声控制等应用提供一定的理论和实验基础.

  19. Prospects for bubble fusion

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-09-01

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

  20. Electrochemical 'bubble swarm' enhancement of ultrasonic surface cleaning.

    Science.gov (United States)

    Birkin, P R; Offin, D G; Vian, C J B; Leighton, T G

    2015-09-07

    An investigation of surface cleaning using a swarm of gas bubbles within an acoustically activated stream is presented. Electrolysis of water at Pt microwires (100 μm diameter) to produce both hydrogen and oxygen bubbles is shown to enhance the extent of ultrasonic surface cleaning in a free flowing water stream containing an electrolyte (0.1 M Na2SO4) and low surfactant concentration (2 mM SDS). The surfactant was employed to allow control of the average size of the bubble population within the swarm. The electrochemical bubble swarm (EBS) is shown to perturb acoustic transmission through the stream. To optimise the cleaning process both the ultrasonic field and the electrochemical current are pulsed and synchronized but with different duty cycles. Cleaning action is demonstrated on structured surfaces (porcine skin and finger mimics) loaded with fluorescent particles. This action is shown to be significantly enhanced compared to that found with an inherent bubble population produced by the flow and acoustic regime alone under the same conditions.

  1. Model for the dynamics of two interacting axisymmetric spherical bubbles undergoing small shape oscillations

    Science.gov (United States)

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

    2011-01-01

    Interaction between acoustically driven or laser-generated bubbles causes the bubble surfaces to deform. Dynamical equations describing the motion of two translating, nominally spherical bubbles undergoing small shape oscillations in a viscous liquid are derived using Lagrangian mechanics. Deformation of the bubble surfaces is taken into account by including quadrupole and octupole perturbations in the spherical-harmonic expansion of the boundary conditions on the bubbles. Quadratic terms in the quadrupole and octupole amplitudes are retained, and surface tension and shear viscosity are included in a consistent manner. A set of eight coupled second-order ordinary differential equations is obtained. Simulation results, obtained by numerical integration of the model equations, exhibit qualitative agreement with experimental observations by predicting the formation of liquid jets. Simulations also suggest that bubble-bubble interactions act to enhance surface mode instability. PMID:22088009

  2. Evaporation, Boiling and Bubbles

    Science.gov (United States)

    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…

  3. Turbulence, bubbles and drops

    NARCIS (Netherlands)

    Veen, van der Roeland Cornelis Adriaan

    2016-01-01

    In this thesis, several questions related to drop impact and Taylor-Couette turbulence are answered. The deformation of a drop just before impact can cause a bubble to be entrapped. For many applications, such as inkjet printing, it is crucial to control the size of this entrapped bubble. To study t

  4. Bubbles in graphene

    DEFF Research Database (Denmark)

    Settnes, Mikkel; Power, Stephen; Lin, Jun

    2015-01-01

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

  5. Nucleus factory on cavitation bubble for amyloid β fibril

    Science.gov (United States)

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

    2016-02-01

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

  6. Bubble collision with gravitation

    CERN Document Server

    Hwang, Dong-il; Lee, Wonwoo; Yeom, Dong-han

    2012-01-01

    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.

  7. SIMULATION AND EXPERIMENT OF BUBBLY FLOW INSIDE THROTTLING GROOVE

    Institute of Scientific and Technical Information of China (English)

    FU Xin; DU Xuewen; ZOU Jun; YANG Huayong; JI Hong

    2007-01-01

    The relationship between pressure distribution and cavitation (noise) inside throttling groove is investigated by numerical simulation and experimental method. A valve pocket with several transducers is performed to detect the pressure distributions inside the valve chamber, and the results fit quite well with the computational fluid dynamics(CFD) analysis. High-speed imaging techniques are employed to investigate the cavitation mechanisms, in particular bubble inception and cluster formation near the throttling groove. A spectrum analyzer is used to measure the sound pressure level of noise generated by the bubble flow. It is found that the pressure distributions inside the groove are sensitive to the valve port configuration and back pressure. The pressure distribution determines the bubble size and number passing through the valve grooves and the sound pressure level of noise induced by collapsing bubbles. The inlet pressure mainly affects the saturation degree of bubbly flow inside the groove and the intensity of sound pressure level accordingly.

  8. Seasonal Suspended Particles Distribution Patterns in Western South Yellow Sea Based on Acoustic Doppler Current Profiler Observation

    Institute of Scientific and Technical Information of China (English)

    LI Jianchao; LI Guangxue; XU Jishang; QIAO Lulu; DONG Ping; DING Dong; LIU Shidong

    2015-01-01

    An Acoustic Doppler Current Profiler (ADCP) observation site was set up in the Western South Yellow Sea from 2012 to 2013 to study the local suspended particle matters (SPM) distribution pattern. The SPM concentration could be semi-quantitatively represented by backscatter intensity (Sv), converted by the echo intensity (EI) of ADCP. Results show two types of SPM in the water column: the quasi-biological SPM and quasi-mineral SPM. The quasi-biological SPM mainly exists in summer half year and is con-centrated above the thermocline. It has periodically diurnal variations with high concentration at night and low concentration in the daytime. The quasi-mineral SPM is located in lower part of the water column, with similar relation to monthly tidal current variation all year round. However, the daily quasi-mineral SPM distribution patterns vary between summer and winter half year. The sunlight is thought to be the origin factor leading to the diurnally vertical motion of the biological features, which might cause the diurnalSv variation. Unlike in winter half year when tidal current is relatively single driving force of the monthly SPM pattern, the high speed current near the thermocline is also responsible for the concentration of quasi-mineral SPM in summer half year. The sediment input difference between summer and winter half year contribute to the varied daily variation of quasi-mineral SPM with re-suspended SPM in winter and sediments from Yellow Sea Mud Area (YSMA) in summer. The seasonal variations in hydrodynamics, water structure and heavy-wind incidents are the primary factors influencing the differential seasonal SPM distribution patterns.

  9. Bubble oscillations and motion under vibration

    CERN Document Server

    O'Hern, Tim; Torczynski, John

    2011-01-01

    Bubbles under vibration can behave in unusual ways, e.g., moving downward against the force of buoyancy. While the bubble downward motion due to the Bjerknes force is well known at acoustic frequencies close to the bubble resonant frequency, these experiments demonstrate that these effects can be observed at relatively low frequencies as well. Experiments were performed in a thin, quasi-two-dimensional rectangular acrylic box partially filled with 20-cSt PDMS silicone oil with overlying ambient air. The apparatus was subjected to sinusoidal axial vibration that produced breakup of the gas-liquid free surface, producing liquid jets into the air, droplets pinching off from these jets, gas cavities in the liquid from impacts of these droplets, and bubble transport below the interface. Vibration conditions for the attached videos are 280 Hz frequency, 15 g acceleration, and 94 micron peak-to-peak displacement. Behaviors shown in the videos include the following. 1. Free surface breakup into jets and droplets, and...

  10. Effect of bubble size on nanofiber diameter in bubble electrospinning

    Directory of Open Access Journals (Sweden)

    Ren Zhong-Fu

    2016-01-01

    Full Text Available Polymer bubbles are widely used for fabrication of nanofibers. Bubble size affects not only bubble's surface tension, but also fiber's morphology. A mathematical model is established to reveal the effect of bubble size on the spinning process, and the experiment verification shows the theoretical analysis is reliable.

  11. Modeling the dynamics of single-bubble sonoluminescence

    CERN Document Server

    Vignoli, Lucas L; Thomé, Roberto C A; Nogueira, A L M A; Paschoal, Ricardo C; Rodrigues, Hilario

    2014-01-01

    Sonoluminescence (SL) is the phenomenon in which acoustic energy is (partially) transformed into light. It may occur by means of many or just one bubble of gas inside a liquid medium, giving rise to the terms multi-bubble- and single-bubble sonoluminescence (MBSL and SBSL). In the last years some models have been proposed to explain this phenomenon, but there is still no complete theory for the light emission mechanism (especially in the case of SBSL). In this work, we will not address this more complicated particular issue, but only present a simple model describing the dynamical behaviour of the sonoluminescent bubble, in the SBSL case. Using simple numerical techniques within the software Matlab, we discuss solutions considering various possibilities for some of the parameters involved: liquid compressibility, superficial tension, viscosity, and type of gas. The model may be used as an introductory study of sonoluminescence in physics courses at undergraduate or graduate levels, as well as a quite clarifyi...

  12. Ion-Acoustic Vortices in Two-Electron-Temperature Magnetoplasma with Cairn's Distributed Electrons and in the Presence of Ion Shear Flow

    Science.gov (United States)

    Haque, Q.; Mirza, Arshad M.; Iqbal, Javed

    2016-04-01

    Linear and nonlinear characteristics of electrostatic waves in a multicomponent magnetoplasma comprising of Boltzmann distributed electrons, Cairn's distributed hot electrons, and cold dynamic ions are studied. It is found that the effect of superthermal electrons, ion-neutral collisions, and ion shear flow modifies the propagation of ion-acoustic and drift waves. The growth rate of the ion shear flow instability varies with the addition of Cairn's distributed hot electrons. It is also investigated that the behavior of different type of vortices changes with the inclusion of superthermal hot electrons. The relevance of this investigation in space plasmas such as in auroral region and geomagnetic tail is also pointed out.

  13. Ion-acoustic Gardner Solitons in electron-positron-ion plasma with two-electron temperature distributions

    Science.gov (United States)

    Rehman, Momin A.; Mishra, M. K.

    2016-01-01

    The ion-acoustic solitons in collisionless plasma consisting of warm adiabatic ions, isothermal positrons, and two temperature distribution of electrons have been studied. Using reductive perturbation method, Korteweg-de Vries (K-dV), the modified K-dV (m-KdV), and Gardner equations are derived for the system. The soliton solution of the Gardner equation is discussed in detail. It is found that for a given set of parameter values, there exists a critical value of β=Tc/Th, (ratio of cold to hot electron temperature) below which only rarefactive KdV solitons exist and above it compressive KdV solitons exist. At the critical value of β, both compressive and rarefactive m-KdV solitons co-exist. We have also investigated the soliton in the parametric regime where the KdV equation is not valid to study soliton solution. In this region, it is found that below the critical concentration the system supports rarefactive Gardner solitons and above it compressive Gardner solitons are found. The effects of temperature ratio of two-electron species, cold electron concentration, positron concentration on the characteristics of solitons are also discussed.

  14. Acoustic scattering from an infinitely long cylindrical shell with an internal mass attached by multiple axisymmetrically distributed stiffeners

    CERN Document Server

    Titovich, Alexey S

    2014-01-01

    A thin infinitely long elastic shell is stiffened by $J$ in number identical lengthwise ribs distributed uniformly around the circumference and joined to a rod in the center. The 2D model of the substructure is a rigid central mass supported by $J$ axisymmetrically placed linear springs. The response of the shell-spring-mass system is quite different from a fluid filled shell or that of a solid cylinder due to the discrete number of contact points which couple the displacement of the shell at different locations. Exterior acoustic scattering due to normal plane wave incidence is solved in closed form for arbitrary $J$. The scattering matrix associated with the normal mode solution displays a simple structure, composed of distinct sub-matrices which decouple the incident and scattered fields into $J$ families. The presence of a springs-mass substructure causes resonances which are shown to be related to the subsonic shell flexural waves, and an approximate analytic expression is derived for the quasi-flexural ...

  15. Voronoi analysis of bubbly flows via ultrafast X-ray tomographic imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Yuk Man; Mueller, Karolin; Azizi, Salar; Schubert, Markus [Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Fluid Dynamics, Dresden (Germany)

    2016-03-15

    Although clustering of bubbles plays a significant role in bubble column reactors regarding the heat and mass transfer due to bubble-bubble and flow field interactions, it has yet to be fully understood. Contrary to flows in bubble columns, most literature studies on clustering report numerical and experimental results on dilute or micro-bubbly flows. In this paper, clustering of bubbles in a cylindrical bubble column of 100 mm diameter is experimentally investigated. Ultrafast X-ray tomographic imaging is used to obtain the bubble positions within a hybrid Eulerian framework. By means of Voronoi analysis, the clustering behavior of bubbles is investigated. Experiments are performed with different superficial gas velocities, where Voronoi diagrams are constructed at several column heights. From the PDFs of the Voronoi diagrams, it is shown that the bubble structuring in terms of Voronoi cell volumes develops slower than the bubble size distribution. The latter reaches a steady state earlier with increasing column height. The measured PDFs are compared with the PDF of randomly distributed points, which showed that the amount of bubbles as part of clusters (Voronoi cells < V/ anti V{sub cluster}) as well as bubbles as part of voids (Voronoi cells > V/ anti V{sub void}) increases with the superficial gas velocity. It is found that all experiments have an approximate cluster limit V/ anti V{sub cluster} of 0.63, while the void limit V/ anti V{sub void} varies between 1.5 and 3.0. (orig.)

  16. A novel data adaptive detection scheme for distributed fiber optic acoustic sensing

    Science.gov (United States)

    Ölçer, Íbrahim; Öncü, Ahmet

    2016-05-01

    We introduce a new approach for distributed fiber optic sensing based on adaptive processing of phase sensitive optical time domain reflectometry (Φ-OTDR) signals. Instead of conventional methods which utilizes frame averaging of detected signal traces, our adaptive algorithm senses a set of noise parameters to enhance the signal-to-noise ratio (SNR) for improved detection performance. This data set is called the secondary data set from which a weight vector for the detection of a signal is computed. The signal presence is sought in the primary data set. This adaptive technique can be used for vibration detection of health monitoring of various civil structures as well as any other dynamic monitoring requirements such as pipeline and perimeter security applications.

  17. Application of analyzer based X-ray imaging technique for detection of ultrasound induced cavitation bubbles from a physical therapy unit

    OpenAIRE

    Izadifar, Zahra; Belev, George; Babyn, Paul; Chapman, Dean

    2015-01-01

    Background The observation of ultrasound generated cavitation bubbles deep in tissue is very difficult. The development of an imaging method capable of investigating cavitation bubbles in tissue would improve the efficiency and application of ultrasound in the clinic. Among the previous imaging modalities capable of detecting cavitation bubbles in vivo, the acoustic detection technique has the positive aspect of in vivo application. However the size of the initial cavitation bubble and the am...

  18. How does gas pass? Bubble transport through sediments

    Science.gov (United States)

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

    2009-12-01

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

  19. Dust-acoustic solitary and shock waves in a strongly coupled liquid state dusty plasma with a vortex-like ion distribution

    Energy Technology Data Exchange (ETDEWEB)

    Mamun, A.A. [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Eliasson, B. [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)]. E-mail: bengt@tp4.rub.de; Shukla, P.K. [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

    2004-11-22

    It is shown that the nonlinear propagation of dust-acoustic waves in a strongly coupled dusty plasma is governed by a modified Korteweg-de-Vries-Burgers (KdV-Burgers) equation. The latter is derived from a set of generalized hydrodynamic equations for strongly correlated dust grains in a liquid-like state, a Boltzmann electron distribution, and a non-isothermal vortex-like ion distribution. The numerical solutions of the modified KdV-Burgers equation are presented in order to provide some salient features of dust-acoustic solitary and shock structures that may exist in laboratory dusty plasmas where the dust grains are in a strongly coupled liquid phase.

  20. Assessing the Role of Small-Scale Bio-Optical and Bio-Acoustical Distributions in Upper Ocean Biological and Optical Processes

    Science.gov (United States)

    2016-06-14

    addressed that goal by examining specific scientific questions that relate the distribution and variability in sub-1m scale bio-optical properties with...dynamics, optical and acoustical signal propagation, and remote sensing. The collaborative work we have been conducting within this project is...TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Oregon State University,College of Oceanic and Atmospheric

  1. Linear oscillation of gas bubbles in a viscoelastic material under ultrasound irradiation

    Science.gov (United States)

    Hamaguchi, Fumiya; Ando, Keita

    2015-11-01

    Acoustically forced oscillation of spherical gas bubbles in a viscoelastic material is studied through comparisons between experiments and linear theory. An experimental setup has been designed to visualize bubble dynamics in gelatin gels using a high-speed camera. A spherical gas bubble is created by focusing an infrared laser pulse into (gas-supersaturated) gelatin gels. The bubble radius (up to 150 μm) under mechanical equilibrium is controlled by gradual mass transfer of gases across the bubble interface. The linearized bubble dynamics are studied from the observation of spherical bubble oscillation driven by low-intensity, planar ultrasound driven at 28 kHz. It follows from the experiment for an isolated bubble that the frequency response in its volumetric oscillation was shifted to the high frequency side and its peak was suppressed as the gelatin concentration increases. The measurement is fitted to the linearized Rayleigh-Plesset equation coupled with the Voigt constitutive equation that models the behavior of linear viscoelastic solids; the fitting yields good agreement by tuning unknown values of the viscosity and rigidity, indicating that more complex phenomena including shear thinning, stress relaxation, and retardation do not play an important role for the small-amplitude oscillations. Moreover, the cases for bubble-bubble and bubble-wall systems are studied. The observed interaction effect on the linearized dynamics can be explained as well by a set of the Rayleigh-Plesset equations coupled through acoustic radiation among these systems. This suggests that this experimental setup can be applied to validate the model of bubble dynamics with more complex configuration such as a cloud of bubbles in viscoelastic materials.

  2. Linear oscillation of gas bubbles in a viscoelastic material under ultrasound irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Hamaguchi, Fumiya; Ando, Keita, E-mail: kando@mech.keio.ac.jp [Department of Mechanical Engineering, Keio University, Yokohama 223-8522 (Japan)

    2015-11-15

    Acoustically forced oscillation of spherical gas bubbles in a viscoelastic material is studied through comparisons between experiments and linear theory. An experimental setup has been designed to visualize bubble dynamics in gelatin gels using a high-speed camera. A spherical gas bubble is created by focusing an infrared laser pulse into (gas-supersaturated) gelatin gels. The bubble radius (up to 150 μm) under mechanical equilibrium is controlled by gradual mass transfer of gases across the bubble interface. The linearized bubble dynamics are studied from the observation of spherical bubble oscillation driven by low-intensity, planar ultrasound driven at 28 kHz. It follows from the experiment for an isolated bubble that the frequency response in its volumetric oscillation was shifted to the high frequency side and its peak was suppressed as the gelatin concentration increases. The measurement is fitted to the linearized Rayleigh–Plesset equation coupled with the Voigt constitutive equation that models the behavior of linear viscoelastic solids; the fitting yields good agreement by tuning unknown values of the viscosity and rigidity, indicating that more complex phenomena including shear thinning, stress relaxation, and retardation do not play an important role for the small-amplitude oscillations. Moreover, the cases for bubble-bubble and bubble-wall systems are studied. The observed interaction effect on the linearized dynamics can be explained as well by a set of the Rayleigh–Plesset equations coupled through acoustic radiation among these systems. This suggests that this experimental setup can be applied to validate the model of bubble dynamics with more complex configuration such as a cloud of bubbles in viscoelastic materials.

  3. Impact of chevron spacing and asymmetric distribution on supersonic jet acoustics and flow

    Science.gov (United States)

    Heeb, N.; Gutmark, E.; Kailasanath, K.

    2016-05-01

    An experimental investigation into the effect of chevron spacing and distribution on supersonic jets was performed. Cross-stream and streamwise particle imaging velocimetry measurements were used to relate flow field modification to sound field changes measured by far-field microphones in the overexpanded, ideally expanded, and underexpanded regimes. Drastic modification of the jet cross-section was achieved by the investigated configurations, with both elliptic and triangular shapes attained downstream. Consequently, screech was nearly eliminated with reductions in the range of 10-25 dB depending on the operating condition. Analysis of the streamwise velocity indicated that both the mean shock spacing and strength were reduced resulting in an increase in the broadband shock associated noise spectral peak frequency and a reduction in the amplitude, respectively. Maximum broadband shock associated noise amplitude reductions were in the 5-7 dB range. Chevron proximity was found to be the primary driver of peak vorticity production, though persistence followed the opposite trend. The integrated streamwise vorticity modulus was found to be correlated with peak large scale turbulent mixing noise reduction, though optimal overall sound pressure level reductions did not necessarily follow due to the shock/fine scale mixing noise sources. Optimal large scale mixing noise reductions were in the 5-6 dB range.

  4. Quantitative calculation of reaction performance in sonochemical reactor by bubble dynamics

    Science.gov (United States)

    Xu, Zheng; Yasuda, Keiji; Liu, Xiao-Jun

    2015-10-01

    In order to design a sonochemical reactor with high reaction efficiency, it is important to clarify the size and intensity of the sonochemical reaction field. In this study, the reaction field in a sonochemical reactor is estimated from the distribution of pressure above the threshold for cavitation. The quantitation of hydroxide radical in a sonochemical reactor is obtained from the calculation of bubble dynamics and reaction equations. The distribution of the reaction field of the numerical simulation is consistent with that of the sonochemical luminescence. The sound absorption coefficient of liquid in the sonochemical reactor is much larger than that attributed to classical contributions which are heat conduction and shear viscosity. Under the dual irradiation, the reaction field becomes extensive and intensive because the acoustic pressure amplitude is intensified by the interference of two ultrasonic waves. Project supported by the National Natural Science Foundation of China (Grant Nos. 11404245, 11204129, and 11211140039).

  5. Quantitative calculation of reaction performance in sonochemical reactor by bubble dynamics

    Institute of Scientific and Technical Information of China (English)

    徐峥; 安田启司; 刘晓峻

    2015-01-01

    In order to design a sonochemical reactor with high reaction efficiency, it is important to clarify the size and intensity of the sonochemical reaction field. In this study, the reaction field in a sonochemical reactor is estimated from the distribution of pressure above the threshold for cavitation. The quantitation of hydroxide radical in a sonochemical reactor is obtained from the calculation of bubble dynamics and reaction equations. The distribution of the reaction field of the numerical simulation is consistent with that of the sonochemical luminescence. The sound absorption coefficient of liquid in the sonochemical reactor is much larger than that attributed to classical contributions which are heat conduction and shear viscosity. Under the dual irradiation, the reaction field becomes extensive and intensive because the acoustic pressure amplitude is intensified by the interference of two ultrasonic waves.

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

    Science.gov (United States)

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

    2011-11-01

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

  7. Propagation of shock waves in dilute bubbly liquids. 4. Comparison between theory and experiment for a uniform bubbly mixture

    Energy Technology Data Exchange (ETDEWEB)

    Kameda, Masaharu; Shimaura, Naoto; Higashino, Fumio [Tokyo Univ. of Agriculture and Technology, Fuchu, Tokyo (Japan); Matsumoto, Yoichiro

    1997-07-01

    Transient shock wave phenomena in a liquid containing noncondensable gas bubbles are studied experimentally and numerically. In order to obtain a uniform spatial distribution of bubbles experimentally, an upwardly directed bubbly flow, whose initial gas volume fraction is 0.2%, is generated in a shock tube. The liquid used is silicone oil. Nitrogen, argon, and SF{sub 6} gas bubbles are tested to show the thermal effects of the bubble interior. The transient pressure profiles determined in the experiments for the upwardly bubbly flow agree well quantitatively with those obtained by numerical calculation using a uniform spatial distribution of bubbles. Since the thermal diffusivity of SF{sub 6} is much lower than that of nitrogen and argon, the damping on the radial oscillation of the SF{sub 6} bubble is mainly due to the compressibility of the liquid. Thus, the radial motion of the bubble should be estimated by solving an equation in which the liquid compressibility is taken into account. (author)

  8. Popping the Bubble

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Government adopts regulations to control real estate prices A mid concerns surrounding the presence of housing bubbles across China,the Chinese Government is taking action to secure and stabilize the real

  9. Chemistry in Soap Bubbles.

    Science.gov (United States)

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

    2002-01-01

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

  10. Bubbling Out of Control

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Jim Chanos,founder of the U.S. hedge fund Kynikos Associates,characterized the prop-erty bubble in China as "Dubai times 1,000-or worse." Many Chinese economists agree. Yi Xianrong,a senior researcher at the Institute of Finance and Banking under the Chinese Academy of Social Sciences,said the property bubble in China was far worse than the Dubai crisis in an interview with the Beijing-based International Herald Leader. Edited excerpts follow:

  11. Bubble chamber: antiproton annihilation

    CERN Multimedia

    1971-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-10-28

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

  13. 浆料系统内上升气泡周围微细颗粒浓度分布和附着效率的理论研究%Theoretical Approach to Concentration Distribution and Adhesion Efficiency of Fine Particles Around a Rising Bubble in Slurry Systems

    Institute of Scientific and Technical Information of China (English)

    蔡旺锋; 许春建; 周明

    2002-01-01

    Quantitative prediction of distribution function and adhesion efficiency of particles around a risingbubble in slurry systems is presented in this work. By solving the convection-diffusion equation (Fokker-Planckequation), the influence of Brownian diffusivity of fine particles on concentration distribution and adhesion efficiencyis demonstrated with the hydrodynamic force and van der Waals attractive potential between particles and bubbleconsidered. It is found that two kinds of mechanism dominate the adhesion process of particles on bubble accordingaddition, the viscosity ratio of bubble to the suspending fluid was found to have obvious influence on particleadhesion.

  14. Solids mixing in bubbling fluidized beds: CFD-based analysis of Bubble Dynamics and Time Scales

    Science.gov (United States)

    Bakshi, Akhilesh; Altantzis, Christos; Ghoniem, Ahmed

    2016-11-01

    In bubbling fluidized bed reactors, solids mixing is critical because it directly affects fuel segregation and residence time. However, there continues to be a lack of understanding because (a) most diagnostic techniques are only feasible in lab-scale setups and (b) the dynamics are sensitive to the operating conditions. Thus, quantitative estimates of mixing (e.g., dispersion coefficient, mixing indices) often span orders of magnitude although it is well accepted that the micro-mixing and gross circulation of solid particles is driven by bubble motion. To quantify this dependence, solids mixing is investigated using fine-grid 3D CFD simulations of a large 50 cm diameter fluidized bed. Detailed diagnostics of the computed flow-field data are performed using MS3DATA, a tool that we developed to detect and track bubbles, and the solids motion is correlated with the spatial and size distribution of bubbles. This study will be useful for quantifying mixing at commercial scales.

  15. Phase Velocity and Full-Waveform Analysis of Co-located Distributed Acoustic Sensing (DAS) Channels and Geophone Sensor

    Science.gov (United States)

    Parker, L.; Mellors, R. J.; Thurber, C. H.; Wang, H. F.; Zeng, X.

    2015-12-01

    A 762-meter Distributed Acoustic Sensing (DAS) array with a channel spacing of one meter was deployed at the Garner Valley Downhole Array in Southern California. The array was approximately rectangular with dimensions of 180 meters by 80 meters. The array also included two subdiagonals within the rectangle along which three-component geophones were co-located. Several active sources were deployed, including a 45-kN, swept-frequency, shear-mass shaker, which produced strong Rayleigh waves across the array. Both DAS and geophone traces were filtered in 2-Hz steps between 4 and 20 Hz to obtain phase velocities as a function of frequency from fitting the moveout of travel times over distances of 35 meters or longer. As an alternative to this traditional means of finding phase velocity, it is theoretically possible to find the Rayleigh-wave phase velocity at each point of co-location as the ratio of DAS and geophone responses, because DAS is sensitive to ground strain and geophones are sensitive to ground velocity, after suitable corrections for instrument response (Mikumo & Aki, 1964). The concept was tested in WPP, a seismic wave propagation program, by first validating and then using a 3D synthetic, full-waveform seismic model to simulate the effect of increased levels of noise and uncertainty as data go from ideal to more realistic. The results obtained from this study provide a better understanding of the DAS response and its potential for being combined with traditional seismometers for obtaining phase velocity at a single location. This analysis is part of the PoroTomo project (Poroelastic Tomography by Adjoint Inverse Modeling of Data from Seismology, Geodesy, and Hydrology, http://geoscience.wisc.edu/feigl/porotomo).

  16. Numerical investigation of interaction between rising bubbles in a viscous liquid

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Ik Roh [Korea Institute of Marine Science and Technology Promotion, Seoul (Korea, Republic of); Shin Seung Won [Hongik University, Seoul (Korea, Republic of)

    2016-07-15

    The rising behavior of bubbles undergoing bubble-bubble interaction in a viscous liquid is studied using a two-dimensional direct numerical simulation. Level contour reconstruction method (LCRM), one of the connectivity-free front tracking methods, is applied to describe a moving interface accurately under highly deformable conditions. This work focuses on the effects of bubble size on the interaction of two bubbles rising side-by-side in a stagnant liquid. Several characteristics of bubble-bubble interaction are analyzed quantitatively as supported by energy analysis. The results showed clear differences between small and large bubbles with respect to their interaction behavior in terms of lateral movement, vortex intensity, suppression of surface deformation, and viscous dissipation rate. Distributions of vorticity and viscous dissipation rate near the bubble interfaces also differed depending on the size of the bubbles. Strong vortices from large bubbles triggered oscillation in bubble-bubble interaction and played a dominant role in the interaction process as the size of bubbles increases.

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

    Science.gov (United States)

    Ogasawara, Toshiyuki

    2005-11-01

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

  18. Effects of nonthermal distribution of electrons and polarity of net dust-charge number density on nonplanar dust-ion-acoustic solitary waves.

    Science.gov (United States)

    Mamun, A A; Shukla, P K

    2009-09-01

    Effects of the nonthermal distribution of electrons as well as the polarity of the net dust-charge number density on nonplanar (viz. cylindrical and spherical) dust-ion-acoustic solitary waves (DIASWs) are investigated by employing the reductive perturbation method. It is found that the basic features of the DIASWs are significantly modified by the effects of nonthermal electron distribution, polarity of net dust-charge number density, and nonplanar geometry. The implications of our results in some space and laboratory dusty plasma environments are briefly discussed.

  19. Bubble migration in a compacting crystal-liquid mush

    Science.gov (United States)

    Boudreau, Alan

    2016-04-01

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

  20. Effects of surfactant on bubble hydrodynamic behavior under flotation-related conditions in wastewater.

    Science.gov (United States)

    Li, Yanpeng; Zhu, Tingting; Liu, Yanyan; Tian, Ye; Wang, Huanran

    2012-01-01

    Bubble behavior is fundamental to the performance of froth flotation operations used in wastewater treatment processes. To fully understand and characterize bubble behavior under flotation-related conditions in wastewater, the high-speed photographic method has been employed to examine the motion of single bubbles and size distribution of bubble swarms with intermediate sizes ranging from 1 to 4 mm in the presence of surfactants in a laboratory scale flotation column. Both distilled water and synthetic municipal wastewater have been used to make solutions as well as two types of common surfactants. The instantaneous bubble motion has been recorded by a high speed camera. Subsequently, bubble trajectory, dimensions, velocity and distribution have been determined from the recorded frames using the image analysis software. The experimental results show that the addition of surfactant into wastewater has similar effects on bubble hydrodynamic behavior as in pure water (e.g., improving trajectory stabilization, dampening bubble deformation, slowing down terminal velocity, reducing bubble size and increasing the specific surface area of bubble swarm) due to the Marangoni effect. However, it is interesting to note that surfactant effects on single bubble hydrodynamics in wastewater are slightly stronger than those in pure water while surfactant effects on size parameters of bubble swarms in wastewater are significantly stronger than those in pure water. This finding suggests that besides surfactant, inorganic salts present in synthetic wastewater have an important influence on bubble dispersion.

  1. Experimental study on subharmonic and ultraharmonic acoustic waves in water-saturated sandy sediment.

    Science.gov (United States)

    Kim, Byoung-Nam; Lee, Kang Il; Yoon, Suk Wang

    2007-04-01

    Experimental observations of the subharmonic and ultraharmonic acoustic waves in water-saturated sandy sediment are reported in this paper. Acoustic pressures of both nonlinear acoustic waves strongly depend on the driving acoustic pressure at a transducer. The first ultraharmonic wave reaches a saturation value as the driving acoustic pressure increases. The acoustic pressure levels of both nonlinear acoustic waves exhibit some fluctuations in comparison with that of the primary acoustic wave as the receiving distance of hydrophone increases in sediment. The subharmonic and the ultraharmonic phenomena in this study show close resemblance to those produced in bubbly water.

  2. Upward-propagating capillary waves on the surface of short Taylor bubbles

    Science.gov (United States)

    Liberzon, Dan; Shemer, Lev; Barnea, Dvora

    2006-04-01

    Upward-propagating capillary waves are observed on the surface of short Taylor air bubbles rising in vertical pipes. The wave length distribution along the bubble surface is measured for bubbles rising in pipes of different diameters in stagnant and up-flowing water by digital image processing. It is shown that the waves are generated by bubble bottom oscillations, and their length is determined by wave-current interaction along the liquid film.

  3. Quantifying Methane Flux from a Prominent Seafloor Crater with Water Column Imagery Filtering and Bubble Quantification Techniques

    Science.gov (United States)

    Mitchell, G. A.; Gharib, J. J.; Doolittle, D. F.

    2015-12-01

    Methane gas flux from the seafloor to atmosphere is an important variable for global carbon cycle and climate models, yet is poorly constrained. Methodologies used to estimate seafloor gas flux commonly employ a combination of acoustic and optical techniques. These techniques often use hull-mounted multibeam echosounders (MBES) to quickly ensonify large volumes of the water column for acoustic backscatter anomalies indicative of gas bubble plumes. Detection of these water column anomalies with a MBES provides information on the lateral distribution of the plumes, the midwater dimensions of the plumes, and their positions on the seafloor. Seafloor plume locations are targeted for visual investigations using a remotely operated vehicle (ROV) to determine bubble emission rates, venting behaviors, bubble sizes, and ascent velocities. Once these variables are measured in-situ, an extrapolation of gas flux is made over the survey area using the number of remotely-mapped flares. This methodology was applied to a geophysical survey conducted in 2013 over a large seafloor crater that developed in response to an oil well blowout in 1983 offshore Papua New Guinea. The site was investigated by multibeam and sidescan mapping, sub-bottom profiling, 2-D high-resolution multi-channel seismic reflection, and ROV video and coring operations. Numerous water column plumes were detected in the data suggesting vigorously active vents within and near the seafloor crater (Figure 1). This study uses dual-frequency MBES datasets (Reson 7125, 200/400 kHz) and ROV video imagery of the active hydrocarbon seeps to estimate total gas flux from the crater. Plumes of bubbles were extracted from the water column data using threshold filtering techniques. Analysis of video images of the seep emission sites within the crater provided estimates on bubble size, expulsion frequency, and ascent velocity. The average gas flux characteristics made from ROV video observations is extrapolated over the number

  4. Planar dust-acoustic waves in electron–positron–ion–dust plasmas with dust-size distribution under higher-order transverse perturbations

    Indian Academy of Sciences (India)

    Hong-Yan Wang; Kai-Biao Zhang

    2015-01-01

    Propagation of small but finite nonlinear dust-acoustic solitary waves are investigated in a planar unmagnetized dusty plasma, which consists of electrons, positrons, ions and negatively charged dust particles with different sizes and masses. A Kadomtsev–Petviashvili (KP) equation is obtained by using reductive perturbation method. The effect of positron density and positron–electron temperature ratio on dust-acoustic solitary structures are studied. Numerical results show that the increase in positron number density increases the amplitude of hump-like solitons but decreases the dip-like solitary waves. Furthermore, increase in the positron–electron temperature ratio results in the decrease of the amplitude of dip-like solitary waves. It seems that both the dipand hump-like solitary waves can exist in this system. Our results also suggest that the dust-size distribution has a significant role on the amplitude of the solitary waves.

  5. Effect of nonthermal distributed electrons and temperature on phase shifts during the collision of inward and outward ion-acoustic solitary waves in nonplanar geometry

    Indian Academy of Sciences (India)

    Uday Narayan Ghosh; Prasantha Chatterjee; Deb Kumar Ghosh

    2013-10-01

    Interaction of nonplanar ion-acoustic solitary waves is an important source of information for studying the nature and characteristics of ion-acoustic solitary waves (IASWs). The head-on collision between two cylindrical/spherical IASWs in un-magnetized plasmas comprising of nonthermal distributed electrons and warm ions is investigated using the extended version of Poincaré–Lighthill–Kuo (PLK) perturbation method. How the interactions are taking place in cylindrical and spherical geometries are shown numerically. Analytical phase shifts are derived for nonplanar geometry. The effects of the ion to electron temperature parameter and the nonthermal electrons parameter on the phase shift are studied. It is shown that the properties of the interaction of IASWs in different geometries are very different.

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

    Science.gov (United States)

    Denzel, Philipp; Diemand, Jürg; Angélil, Raymond

    2016-01-01

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

  7. On 3D reconstruction of bubbles in volcanic ash particles

    Science.gov (United States)

    Proussevitch, A.; Sahagian, D.; Mulukutla, G.; Kiely, C.

    2007-12-01

    Bubbles in volcanic ash particles are primarily represented by the remnants of films and plateau borders from disrupting foam. Without preservation of complete bubbles, measuring bubble size distributions a challenging task, but one for which we have taken a novel approach. Concavities in ash particles retain a record of bubble sizes in the curvature of their concave surfaces that resulted from bubble fragmentation and quenching during energetic magma eruptions. We have used two methods to measure bubble fragment curvature on the basis of 3D reconstruction of ash particle surfaces. One is based on High Resolution X-Ray Tomography (HRXRT) and the second one is based on stereo images from tilting Scattered Electron Microscopy (SEM). Both methods allow the creation of Digital Elevation Model (DEM) datasets of the ash particle surfaces which in turn are used to identify and measure vertical cross-sectional profiles of the individual bubble fragments ("craters"). Function fit analysis for circular or elliptical functions are applied to each bubble cross sectional profile in two orthogonal directions to reconstruct sizes of the original, complete bubbles. The method allows measurement of submicron (SEM; XUM), micron or larger (HRXRT) bubbles in ash particles. The bubble size distributions so obtained can provide valuable insights regarding magma dynamics and vesiculation that lead to explosive eruptions, as well as the processes of fragmentation in eruption columns. There are no previous systematic information/databases of vesiculation metrics for explosive silicic eruptions, but this new method can be used to produce these and thus provide better insights into prehistoric eruption styles for volcanic hazard assessment.

  8. Colliding with a crunching bubble

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-03-26

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

  9. Optical nucleation of bubble clouds in a high pressure spherical resonator.

    Science.gov (United States)

    Anderson, Phillip; Sampathkumar, A; Murray, Todd W; Gaitan, D Felipe; Glynn Holt, R

    2011-11-01

    An experimental setup for nucleating clouds of bubbles in a high-pressure spherical resonator is described. Using nanosecond laser pulses and multiple phase gratings, bubble clouds are optically nucleated in an acoustic field. Dynamics of the clouds are captured using a high-speed CCD camera. The images reveal cloud nucleation, growth, and collapse and the resulting emission of radially expanding shockwaves. These shockwaves are reflected at the interior surface of the resonator and then reconverge to the center of the resonator. As the shocks reconverge upon the center of the resonator, they renucleate and grow the bubble cloud. This process is repeated over many acoustic cycles and with each successive shock reconvergence, the bubble cloud becomes more organized and centralized so that subsequent collapses give rise to stronger, better defined shockwaves. After many acoustic cycles individual bubbles cannot be distinguished and the cloud is then referred to as a cluster. Sustainability of the process is ultimately limited by the detuning of the acoustic field inside the resonator. The nucleation parameter space is studied in terms of laser firing phase, laser energy, and acoustic power used.

  10. Investigation of bubble-bubble interaction effect during the collapse of multi-bubble system

    Science.gov (United States)

    Shao, Xueming; Zhang, Lingxin; Wang, Wenfeng

    2014-11-01

    Bubble collapse is not only an important subject among bubble dynamics, but also a key consequence of cavitation. It has been demonstrated that the structural damage is associated with the rapid change in flow fields during bubble collapse. How to model and simulate the behavior of the bubble collapse is now of great interest. In the present study, both theoretical analysis and a direct numerical simulation on the basis of VOF are performed to investigate the collapses of single bubble and bubble cluster. The effect of bubble-bubble interaction on the collapse of multi-bubble system is presented. The work was supported by the National Natural Science Foundation of China (11272284, 11332009).

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

    Institute of Scientific and Technical Information of China (English)

    QU Jian-wu; MURAI Yuichi; YAMAMOTO Fujio

    2005-01-01

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

  12. Berry curvature and dynamics of a magnetic bubble

    Science.gov (United States)

    Koshibae, Wataru; Nagaosa, Naoto

    2016-04-01

    Magnetic bubbles have been the subject of intensive studies aiming to investigate their applications to memory devices. A bubble can be regarded as the closed domain wall and is characterized by the winding number of the in-plane components or the skyrmion number N sk , which are related to the number of Bloch lines (BLs). For the magnetic bubbles without BLs, the Thiele equation assuming no internal distortion describes the center-of-mass motion of the bubbles very well. For the magnetic bubbles with BLs, on the other hand, their dynamics is affected seriously by that of BLs along the domain wall. Here we show theoretically, that the distribution of the Berry curvature b z , i.e., the solid angle formed by the magnetization vectors, in the bubble plays the key role in the dynamics of a bubble with {N}{sk}=0 in a dipolar magnet. In this case, the integral of b z over the space is zero, while the nonuniform distribution of b z and associated Magnus force induce several nontrivial coupled dynamics of the internal deformation and center-of-mass motion as explicitly demonstrated by numerical simulations of Landau-Lifshitz-Gilbert equation. These findings give an alternative view and will pave a new route to design the bubble dynamics.

  13. Power Laws in Real Estate Prices during Bubble Periods

    Science.gov (United States)

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

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

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

    Science.gov (United States)

    Di Fulvio, Angela; Huang, Jean; Staib, Lawrence; d'Errico, Francesco

    2015-06-01

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

  15. The Terminal Velocity of a Bubble in an Oscillating Flow

    Science.gov (United States)

    Romero, L. A.; Kraynik, A. M.; Torczynski, J. R.

    2010-11-01

    A bubble in an acoustic field experiences a net "Bjerknes" force from the nonlinear coupling of its radial oscillations with the oscillating buoyancy force. It is typically assumed that the bubble's net terminal velocity can be found by considering a spherical bubble with the imposed "Bjerknes stresses". We have analyzed the motion of such a bubble using a rigorous perturbation approach and found that one must include a term involving an effective mass flux through the bubble that arises from the time average of the second-order nonlinear terms in the kinematic boundary condition. The importance of this term is governed by the dimensionless parameter α=R^2φ / R^2φ ν . - ν, where R is the bubble radius, φ is the driving frequency, and ν is the liquid kinematic viscosity. If α is large, this term is unimportant, but if α is small, this term is the dominant factor in determining the terminal velocity. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  16. Bubble nuclei; Noyaux Bulles

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-07-22

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

  17. Ultralow frequency acoustic resonances and its potential for mitigating tsunami wave formation

    CERN Document Server

    Estrada, Hector

    2012-01-01

    Bubbles display astonishing acoustical properties since they are able to absorb and scatter large amounts of energy coming from waves whose wavelengths are two orders of magnitude larger than the bubble size. Thus, as the interaction distance between bubbles is much larger than the bubble size, clouds of bubbles exhibit collective oscillations which can scatter acoustic waves three orders magnitude larger than the bubble size. Here we propose bubble based systems which resonate at frequencies that match the time scale relevant for seismogenic tsunami wave generation and may mitigate the devastating effects of tsunami waves. Based on a linear approximation, our na\\"ive proposal may open new research paths towards the mitigation of tsunami waves generation.

  18. Dynamics and acoustics of a cavitating Venturi flow using a homogeneous air-propylene glycol mixture

    Science.gov (United States)

    Navarrete, M.; Naude, J.; Mendez, F.; Godínez, F. A.

    2015-12-01

    Dynamics and acoustics generated in a cavitating Venturi tube are followed up as a function of the input power of a centrifugal pump. The pump of 5 hp with a modified impeller to produce uniform bubbly flow, pumps 70 liters of propylene glycol in a closed loop (with a water cooling system), in which the Venturi is arranged. The goal was to obtain correlations among acoustical emission, dynamics of the shock waves and the light emission from cavitation bubbles. The instrumentation includes: two piezoelectric transducers, a digital camera, a high-speed video camera, and photomultipliers. As results, we show the cavitation patterns as function of the pump power, and a graphical template of the distribution of the Venturi conditions as a function of the cavitation parameter. Our observations show for the first time the sudden formation of bubble clouds in the straight portion of the pipe after the diverging section of the Venturi. We assume that this is due to pre-existing of nuclei-cloud structures which suddenly grow up by the tensile tails of propagating shock waves (producing a sudden drop in pressure).

  19. Experimantal Study on the Bubble Clustering in Bubbly Flows

    Science.gov (United States)

    Takagi, Shu; Fujiwara, Akiko; Ogasawara, Toshiyuki; Matsumoto, Yoichiro

    2003-11-01

    The statistical properties of bubbly flows and the near-wall bubble-clustering behaviors are investigated for upward flow in a rectangular channel. Bubble size, turbulent properties of liquid phase and the bubble clustering motion were measured using image-processing technique, Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV), respectively. Using 3-pentanol as a surfactant, the mono-dispersed 1mm-bubbles are generated. The mono-dispersed bubbles in upward flows accumulate near the wall and construct bubble clusters. These bubble clusters were investigated. Experimental observation showed that the size of bubble cluster can be much larger than that of the coherent structure in single phase turbulence. The clusters change their shape in time and space and these bubble motions accelerate the mean streamwise velocity near the wall due to the buoyancy effect. Thus the mean velocity profile of the liquid phase becomes flattened. It is suggested that the highly accumulated bubbles in the vicinity of the wall disturb the transport of turbulence energy produced in the wall shear layer from the central region of the channel flow. Furthermore, in the middle of channel, the fluctuations of the liquid phase are mainly generated by the bubble motions.

  20. Re-solution of fission gas - A review: Part I. Intragranular bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Olander, D.R. [Department of Nuclear Engineering, University of California, Berkeley, CA 94720-1730 (United States)]. E-mail: fuelpr@nuc.berkeley.edu; Wongsawaeng, D. [Department of Nuclear Engineering, University of California, Berkeley, CA 94720-1730 (United States)

    2006-08-01

    Theories of fission-fragment-driven re-solution of fission-gas atoms from intragranular bubbles in irradiated UO{sub 2} nuclear fuel are reviewed. Two mechanisms of re-solution are generally accepted: the heterogeneous process destroys entire bubbles in the path of fission fragments and returns the gas to the solid as individual atoms; the homogeneous process re-solves fission-gas atoms singly by scattering collisions with fission fragments and uranium recoils whose paths intersect the bubbles. Coupling of these two re-solution models with the bubble nucleation analogs determines the size and number density of the intragranular bubble population. Two approaches are reviewed: the single-size theory, in which all bubbles are accorded one size, and the bubble distribution theory, which seeks to determine the variation of bubble number density with size.

  1. Development of a water leak detector system for LMFBR steam generator. Pt. 1; Sound attenuation due to bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Kumagai, Hiromichi; Yoshida, Kazuo (Central Research Inst. of Electric Power Industry, Komae, Tokyo (Japan). Komae Research Lab.)

    1994-03-01

    In the steam generators (SG) of LMFBR, it is necessary to detect the leakage of water from tubes of heat exchanger as soon as leakage is occurred. The active acoustic detection method has drawn general interests owing to its short response time and reduction of the influence of background noise. In this paper, in order to study the applicability of active acoustic method for detection of water leakage in the SG, the sound attenuation characteristics due to bubbles are investigated under various bubble conditions and emitted sound conditions. Furthermore, using SG sector model, sound attenuation characteristics due to injection of bubbles are studied. As a result, it is clarified that the sound attenuation due to bubbles varies dependent upon size of bubbles, void fraction and thickness of bubble layer, that the attenuation of sound reaches maximum when bubbles resonate with the emitted frequency. The sound attenuation due to bubbles in the SG model attenuates immediately upon injection of bubbles, and sound attenuation depends upon bubble size as well as void fraction. (author).

  2. Multivariate bubbles and antibubbles

    Science.gov (United States)

    Fry, John

    2014-08-01

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

  3. Helium nano-bubble evolution in aging metal tritides.

    Energy Technology Data Exchange (ETDEWEB)

    Cowgill, Donald F.

    2004-05-01

    A continuum-scale, evolutionary model of helium (He) nano-bubble nucleation, growth and He release for aging bulk metal tritides is presented which accounts for major features of the experimental database. Bubble nucleation, modeled as self-trapping of interstitially diffusing He atoms, is found to occur during the first few days following tritium introduction into the metal and is sensitive to the He diffusivity and pairing energy. An effective helium diffusivity of 0.3 x 10{sup -16} cm{sup 2}/s at 300 K is required to generate the average bubble density of 5x 1017 bubbles/cm3 observed by transmission electron microscopy (TEM). Early bubble growth by dislocation loop punching with a l/radius bubble pressure dependence produces good agreement with He atomic volumes and bubble pressures determined from swelling data, nuclear magnetic resonance (NMR) measurements, and hydride pressure-composition-temperature (PCT) shifts. The model predicts that later in life neighboring bubble interactions may first lower the loop punching pressure through cooperative stress effects, then raise the pressure by partial blocking of loops. It also accounts for the shape of the bubble spacing distribution obtained from NMR data. This distribution is found to remain fixed with age, justifying the separation of nucleation and growth phases, providing a sensitive test of the growth formulation, and indicating that further significant bubble nucleation does not occur throughout life. Helium generated within the escape depth of surfaces and surface-connected porosity produces the low-level early helium release. Accelerated or rapid release is modeled as inter-bubble fracture using an average ligament stress criterion. Good agreement is found between the predicted onset of fracture and the observed He-metal ratio (HeM) for rapid He release from bulk palladium tritide. An examination of how inter-bubble fracture varies over the bubble spacing distribution shows that the critical Hem will be

  4. Contactless measurement of phase and concentration distributions in bubble columns using positron emitting radionuclides; Beruehrungslose Messung von Phasen- und Konzentrationsverteilungen in Blasensaeulen mit positronenemittierenden Radionukliden

    Energy Technology Data Exchange (ETDEWEB)

    Zippe, C.; Hoppe, D.; Fietz, J.; Hampel, U.; Hensel, F.; Maeding, P.; Prasser, H.M.; Zippe, W.

    2003-09-01

    Positron emission tomography (PET) is a well-established method for studying metabolic processes in humans and in use as a medical diagnostic procedure (metabolism, blood perfusion, metastasis detection). The present project was dedicated to a nonmedical application of this imaging method, namely to the development and use of a PET tomograph for studying the behaviour of foam in bubble columns on the ''SchaumPET'' test stand. This paper deals in particular with the technical realisation of the project and the image acquisition methods used. The capacity of positron emission tomography to detect the accumulation of a surfactant in a foam layer is demonstrated for the example of sodium capronate. [German] Die Positronen-Emissions-Tomographie (PET) ist eine etablierte Untersuchungsmethode zur Untersuchung von Stoffwechselvorgaengen im Menschen und wird als medizinisches Diagnoseverfahren (Stoffwechsel, Durchblutung, Metastasenerkennung) eingesetzt. Dieses Projekt beschaeftigt sich mit einer nichtmedizinischen Anwendung dieses bildgebenden Verfahrens - dem Aufbau und der Anwendung eines PET-Tomographen zur Untersuchung des Verhaltens von Schaum in Blasensaeulen, dem Versuchsstand SchaumPET. Insbesondere wird auf die technische Realisierung des Projektes und die angewendeten Verfahren zur Bildgewinnung eingegangen. Am Beispiel von Natriumcapronat wird gezeigt, dass sich die Anreicherung eines Tensids in einer Schaumschicht mit der Positronen-Emissions-Tomographie nachweisen laesst. (orig.)

  5. Tensor Effect on Bubble Nuclei

    Institute of Scientific and Technical Information of China (English)

    WANG Yan-Zhao; GU Jian-Zhong; ZHANG Xi-Zhen; DONG Jian-Min

    2011-01-01

    In the framework of the Hartree-Fock-Bogoliubov (HFB) approach with Skyrme interactions SLy5+T, SLy5+Tw and several sets of TIJ parametrizations, I.e. The Skyrme interaction parametrizations including the tensor terms, the proton density distribution in 34Si and 46Ar nuclei is calculated with and without the tensor force. It is shown that the bubble effect in 34Si does not depend a great deal on the Skyrme parametrization and the proton density distribution in 34Si is hardly influenced by the tensor force. As to 46Ar, the SLy5+Tw parametrization favors the formation of the bubble structure due to the inversion between the 2s1/2 and 1d3/2 orbits (2s1/2-ld3/2 inversion). The inversion mechanism induced by the SLy5+Tw interaction is analyzed based on the proton single-particle spectra obtained from the SLy5 and SLy5+Tw interactions as well as the wave functions of the 2s1/2 and 1d3/2 states.%In the framework of the Hartree-Fock-Bogoliubov (HFB) approach with Skyrme interactions SLy5+ T,SLy5+ Tω and several sets of TIJ parametrizations,i.e.the Skyrme interaction pararmetrizations including the tensor terms,the proton density distribution in 34Si and 46 Ar nuclei is calculated with and without the tensor force.It is shown that the bubble effect in 34Si does not depend a great deal on the Skyrme parametrization and the proton density distribution in 34Si is hardly influenced by the tensor force.As to 46Ar,the SLy5+ Tω parametrization favors the formation of the bubble structure due to the inversion between the 2s1/2 and 1d3/2 orbits (2s1/2-1d3/2 inversion).The inversion mechanism induced by the SLy5+ Tω interaction is analyzed based on the proton single-particle spectra obtained from the SLy5 and SLy5+ Tω interactions as well as the wave functions of the 2s1/2 and 1d3/2 states.The study of exotic nuclear structures has been a hot topic in nuclear physics.[1-4] Exotic nuclei are unstabile,superheavy nuclei,halo nuclei and so forth,whose structures are quite different

  6. Prediction of acoustic radiation from axisymmetric surfaces with arbitrary boundary conditions using the boundary element method on a distributed computing system.

    Science.gov (United States)

    Wright, Louise; Robinson, Stephen P; Humphrey, Victor F

    2009-03-01

    This paper presents a computational technique using the boundary element method for prediction of radiated acoustic waves from axisymmetric surfaces with nonaxisymmetric boundary conditions. The aim is to predict the far-field behavior of underwater acoustic transducers based on their measured behavior in the near-field. The technique is valid for all wavenumbers and uses a volume integral method to calculate the singular integrals required by the boundary element formulation. The technique has been implemented on a distributed computing system to take advantage of its parallel nature, which has led to significant reductions in the time required to generate results. Measurement data generated by a pair of free-flooding underwater acoustic transducers encapsulated in a polyurethane polymer have been used to validate the technique against experiment. The dimensions of the outer surface of the transducers (including the polymer coating) were an outer diameter of 98 mm with an 18 mm wall thickness and a length of 92 mm. The transducers were mounted coaxially, giving an overall length of 185 mm. The cylinders had resonance frequencies at 13.9 and 27.5 kHz, and the data were gathered at these frequencies.

  7. Concepts and Development of Bio-Inspired Distributed Embedded Wired/Wireless Sensor Array Architectures for Acoustic Wave Sensing in Integrated Aerospace Vehicles

    Science.gov (United States)

    Ghoshal, Anindya; Prosser, William H.; Kirikera, Goutham; Schulz, Mark J.; Hughes, Derke J.; Orisamolu, Wally

    2003-01-01

    This paper discusses the modeling of acoustic emissions in plate structures and their sensing by embedded or surface bonded piezoelectric sensor arrays. Three different modeling efforts for acoustic emission (AE) wave generation and propagation are discussed briefly along with their advantages and disadvantages. Continuous sensors placed at right angles on a plate are being discussed as a new approach to measure and locate the source of acoustic waves. Evolutionary novel signal processing algorithms and bio-inspired distributed sensor array systems are used on large structures and integrated aerospace vehicles for AE source localization and preliminary results are presented. These systems allow for a great reduction in the amount of data that needs to be processed and also reduce the chances of false alarms from ambient noises. It is envisioned that these biomimetic sensor arrays and signal processing techniques will be useful for both wireless and wired sensor arrays for real time health monitoring of large integrated aerospace vehicles and earth fixed civil structures. The sensor array architectures can also be used with other types of sensors and for other applications.

  8. DIRECT NUMERICAL SIMUIATION OF BUBBLE-CLUSTER'S DYNAMIC CHARACTERISTICS

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A Direct Numerical Simulation (DNS) for understanding the dynamic response of bubble cluster to pulses of pressure perturbations has been studied by using a front-tracking method. The results show that owing to high nonlinearity, the bubble shape and volume oscillations caused by passing by pressure wave will be transformed into an in-phase volumetric oscillation of whole bubble cluster at a particular low-frequency. The value of the frequency is independent of the pulse excitations but the characteristics of the bubble cluster such as its bubble size, bulk void fraction and its spacial distribution etc. It is believed that this study provides important information for us to understand the coupling mechanism of cavitation cloud involved in cavitation resonance, a phenomenon noticed by one of the authors more than two decades ago.

  9. Laser Doppler velocimetry measurement of turbulent bubbly channel flow

    Energy Technology Data Exchange (ETDEWEB)

    So, S.; Takagi, S.; Matsumoto, Y. [Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 (Japan); Morikita, H. [Morikita Shuppan Co. Ltd, 1-4-11,Fujimi Chiyoda-ku, Tokyo 102-0071 (Japan)

    2002-07-01

    Measurements of the turbulence properties of gas-liquid bubbly flows with mono-dispersed 1-mm-diameter bubbles are reported for upward flow in a rectangular channel. Bubble size and liquid-phase velocity were measured using image-processing and laser Doppler velocimetry (LDV), respectively. A description is given of the special arrangements for two-dimensional LDV needed to obtain reliable bubbly flow data, in particular the configuration of the optical system, the distinction of signals from the bubbles and liquid phase. To create the mono-dispersed bubbles, a small amount of surfactant (3-pentanol of 20 ppm) was added to the flow. Whilst this caused a drastic change in bubble size distribution and flow field, it did not affect the turbulence properties of the single-phase flow. In this study, experiments with three different bulk Reynolds numbers (1,350, 4,100, 8,200) were conducted with void fractions less than 1.2%. In all three cases, there was a very high accumulation of bubbles near the wall with bubble slip at the wall. The mean velocity profile of the liquid phase was steeper near the wall owing to the driving force of buoyant bubbles, and the streamwise turbulent intensity in the vicinity of the wall was enhanced. Furthermore the mean velocity profiles of the liquid phase were flattened in the wide region around the channel center. This region was lifted up by the bubble sheet near the wall, giving it a plug-like flow structure. In addition, the turbulent fluctuation and Reynolds stress in the liquid phase are very much suppressed in this region. This strong preferential accumulation near the wall produces the dramatic change of the whole flow structure. (orig.)

  10. Laser Doppler velocimetry measurement of turbulent bubbly channel flow

    Science.gov (United States)

    So, S.; Morikita, H.; Takagi, S.; Matsumoto, Y.

    2002-05-01

    Measurements of the turbulence properties of gas-liquid bubbly flows with mono-dispersed 1-mm-diameter bubbles are reported for upward flow in a rectangular channel. Bubble size and liquid-phase velocity were measured using image-processing and laser Doppler velocimetry (LDV), respectively. A description is given of the special arrangements for two-dimensional LDV needed to obtain reliable bubbly flow data, in particular the configuration of the optical system, the distinction of signals from the bubbles and liquid phase. To create the mono-dispersed bubbles, a small amount of surfactant (3-pentanol of 20 ppm) was added to the flow. Whilst this caused a drastic change in bubble size distribution and flow field, it did not affect the turbulence properties of the single-phase flow. In this study, experiments with three different bulk Reynolds numbers (1,350, 4,100, 8,200) were conducted with void fractions less than 1.2%. In all three cases, there was a very high accumulation of bubbles near the wall with bubble slip at the wall. The mean velocity profile of the liquid phase was steeper near the wall owing to the driving force of buoyant bubbles, and the streamwise turbulent intensity in the vicinity of the wall was enhanced. Furthermore the mean velocity profiles of the liquid phase were flattened in the wide region around the channel center. This region was lifted up by the bubble sheet near the wall, giving it a plug-like flow structure. In addition, the turbulent fluctuation and Reynolds stress in the liquid phase are very much suppressed in this region. This strong preferential accumulation near the wall produces the dramatic change of the whole flow structure.

  11. Dark Matter Search Results from the PICO-2L C$_3$F$_8$ Bubble Chamber

    CERN Document Server

    Amole, C; Asner, D M; Baxter, D; Behnke, E; Bhattacharjee, P; Borsodi, H; Bou-Cabo, M; Brice, S J; Broemmelsiek, D; Clark, K; Collar, J I; Cooper, P S; Crisler, M; Dahl, C E; Daley, S; Das, M; Debris, F; Dhungana, N; Farine, J; Felis, I; Filgas, R; Fines-Neuschild, M; Girard, F; Giroux, G; Hai, M; Hall, J; Harris, O; Jackson, C M; Jin, M; Krauss, C B; Lafrenière, M; Laurin, M; Lawson, I; Levine, I; Lippincott, W H; Mann, E; Martin, J P; Maurya, D; Mitra, P; Neilson, R; Noble, A J; Plante, A; Podviianiuk, R B; Priya, S; Robinson, A E; Ruschman, M; Scallon, O; Seth, S; Sonnenschein, A; Starinski, N; Štekl, I; Vàzquez-Jaùregui, E; Wells, J; Wichoski, U; Zacek, V; Zhang, J

    2015-01-01

    New data are reported from the operation of a 2-liter C$_3$F$_8$ bubble chamber in the 2100 meter deep SNOLAB underground laboratory, with a total exposure of 211.5 kg-days at four different recoil energy thresholds ranging from 3.2 keV to 8.1 keV. These data show that C3F8 provides excellent electron recoil and alpha rejection capabilities at very low thresholds, including the first observation of a dependence of acoustic signal on alpha energy. Twelve single nuclear recoil event candidates were observed during the run. The candidate events exhibit timing characteristics that are not consistent with the hypothesis of a uniform time distribution, and no evidence for a dark matter signal is claimed. These data provide the most sensitive direct detection constraints on WIMP-proton spin-dependent scattering to date, with significant sensitivity at low WIMP masses for spin-independent WIMP-nucleon scattering.

  12. Dark Matter Search Results from the PICO-2L C3F8 Bubble Chamber

    Energy Technology Data Exchange (ETDEWEB)

    Amole, C.; Ardid, M.; Asner, David M.; Baxter, D.; Behnke, E.; Bhattacharjee, P. S.; Borsodi, H.; Bou-Cabo, M.; Brice, S. J.; Broemmelsiek, D.; Clark, K.; Collar, J. I.; Cooper, P. S.; Crisler, M.; Dahl, C. E.; Daley, S.; Das, Madhusmita; Debris, F.; Dhungana, N.; Farine, J.; Felis, I.; Filgas, R.; Fines-Neuschild, M.; Girard, Francoise; Giroux, G.; Hai, M.; Hall, Jeter C.; Harris, O.; Jackson, C. M.; Jin, M.; Krauss, C. B.; Lafreniere, M.; Laurin, M.; Lawson, I.; Levine, I.; Lippincott, W. H.; Mann, E.; Martin, J. P.; Maurya, D.; Mitra, Pitam; Neilson, R.; Noble, A. J.; Plante, A.; Podviianiuk, R. B.; Priya, S.; Robinson, A. E.; Ruschman, M.; Scallon, O.; Seth, S.; Sonnenschein, Andrew; Starinski, N.; Stekl, I.; Vazquez-Jauregui, E.; Wells, J.; Wichoski, U.; Zacek, V.; Zhang, J.

    2015-06-12

    New data are reported from the operation of a 2-liter C3F8 bubble chamber in the 2100 meter deep SNOLAB underground laboratory, with a total exposure of 211.5 kg-days at four different recoil energy thresholds ranging from 3.2 keV to 8.1 keV. These data show that C3F8 provides excellent electron recoil and alpha rejection capabilities at very low thresholds, including the rst observation of a dependence of acoustic signal on alpha energy. Twelve single nuclear recoil event candidates were observed during the run. The candidate events exhibit timing characteristics that are not consistent with the hypothesis of a uniform time distribution, and no evidence for a dark matter signal is claimed. These data provide the most sensitive direct detection constraints on WIMP-proton spin-dependent scattering to date, with signicant sensitivity at low WIMP masses for spin-independent WIMP-nucleon scattering.

  13. A general derivation of the subharmonic threshold for non-linear bubble oscillations.

    Science.gov (United States)

    Prosperetti, Andrea

    2013-06-01

    The paper describes an approximate but rather general derivation of the acoustic threshold for a subharmonic component to be possible in the sound scattered by an insonified gas bubble. The general result is illustrated with several specific models for the mechanical behavior of the surface coating of bubbles used as acoustic contrast agents. The approximate results are found to be in satisfactory agreement with fully non-linear numerical results in the literature. The amplitude of the first harmonic is also found by the same method. A fundamental feature identified by the analysis is that the subharmonic threshold can be considerably lowered with respect to that of an uncoated free bubble if the mechanical response of the coating varies rapidly in the neighborhood of certain specific values of the bubble radius, e.g., because of buckling.

  14. The Early Years: Blowing Bubbles

    Science.gov (United States)

    Ashbrook, Peggy

    2016-01-01

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

  15. On the acoustic properties of vaporized submicron perfluorocarbon droplets.

    Science.gov (United States)

    Reznik, Nikita; Lajoinie, Guillaume; Shpak, Oleksandr; Gelderblom, Erik C; Williams, Ross; de Jong, Nico; Versluis, Michel; Burns, Peter N

    2014-06-01

    The acoustic characteristics of microbubbles created from vaporized submicron perfluorocarbon droplets with fluorosurfactant coating are examined. Utilizing ultra-high-speed optical imaging, the acoustic response of individual microbubbles to low-intensity diagnostic ultrasound was observed on clinically relevant time scales of hundreds of milliseconds after vaporization. It was found that the vaporized droplets oscillate non-linearly and exhibit a resonant bubble size shift and increased damping relative to uncoated gas bubbles due to the presence of coating material. Unlike the commercially available lipid-coated ultrasound contrast agents, which may exhibit compression-only behavior, vaporized droplets may exhibit expansion-dominated oscillations. It was further observed that the non-linearity of the acoustic response of the bubbles was comparable to that of SonoVue microbubbles. These results suggest that vaporized submicron perfluorocarbon droplets possess the acoustic characteristics necessary for their potential use as ultrasound contrast agents in clinical practice.

  16. Effect of dust size distribution and dust charge fluctuation on dust ion-acoustic shock waves in a multi-ion dusty plasma

    Indian Academy of Sciences (India)

    WANG HONGYAN; ZHANG KAIBIAO

    2016-07-01

    The effects of dust size distribution and dust charge fluctuation of dust grains on the small but finite amplitude nonlinear dust ion-acoustic shock waves, in an unmagnetized multi-ion dusty plasma which contains negative ions, positive ions and electrons, are studied in this paper. A Burgers equation and its stationary solutions are obtained by using the reductive perturbation method. The analytical and numerical results show that the height with polynomial dust size distribution is larger than that of the monosized dusty plasmas with the same dustgrains, but the thickness in the case of different dust grains is smaller than that of the monosized dusty plasmas. Furthermore, the moving speed of the shock waves also depend on different dust size distributions.

  17. Bubble reconstruction method for wire-mesh sensors measurements

    Science.gov (United States)

    Mukin, Roman V.

    2016-08-01

    A new algorithm is presented for post-processing of void fraction measurements with wire-mesh sensors, particularly for identifying and reconstructing bubble surfaces in a two-phase flow. This method is a combination of the bubble recognition algorithm presented in Prasser (Nuclear Eng Des 237(15):1608, 2007) and Poisson surface reconstruction algorithm developed in Kazhdan et al. (Poisson surface reconstruction. In: Proceedings of the fourth eurographics symposium on geometry processing 7, 2006). To verify the proposed technique, a comparison was done of the reconstructed individual bubble shapes with those obtained numerically in Sato and Ničeno (Int J Numer Methods Fluids 70(4):441, 2012). Using the difference between reconstructed and referenced bubble shapes, the accuracy of the proposed algorithm was estimated. At the next step, the algorithm was applied to void fraction measurements performed in Ylönen (High-resolution flow structure measurements in a rod bundle (Diss., Eidgenössische Technische Hochschule ETH Zürich, Nr. 20961, 2013) by means of wire-mesh sensors in a rod bundle geometry. The reconstructed bubble shape yields bubble surface area and volume, hence its Sauter diameter d_{32} as well. Sauter diameter is proved to be more suitable for bubbles size characterization compared to volumetric diameter d_{30}, proved capable to capture the bi-disperse bubble size distribution in the flow. The effect of a spacer grid was studied as well: For the given spacer grid and considered flow rates, bubble size frequency distribution is obtained almost at the same position for all cases, approximately at d_{32} = 3.5 mm. This finding can be related to the specific geometry of the spacer grid or the air injection device applied in the experiments, or even to more fundamental properties of the bubble breakup and coagulation processes. In addition, an application of the new algorithm for reconstruction of a large air-water interface in a tube bundle is

  18. The Liberal Arts Bubble

    Science.gov (United States)

    Agresto, John

    2011-01-01

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

  19. Popping the Bubble

    Institute of Scientific and Technical Information of China (English)

    LAN XINZHEN

    2010-01-01

    @@ Amid concerns surrounding the presence of housing bubbles across China,the Chinese Government is taking action to secure and stabilize the real estate market.In the past month,the government launched a series of regulatory policies aimed at cooling the overheated market.

  20. Scanning bubble chamber pictures

    CERN Multimedia

    1974-01-01

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

  1. BEBC bubble chamber

    CERN Multimedia

    1972-01-01

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

  2. Understanding the bubbles

    DEFF Research Database (Denmark)

    Turcan, Romeo V.

    that are identified to exist between the Internet and housing market bubbles: uncertainty and sentiments. The iteration between uncertainty and sentiments leads to the emergence of the third commonality: residue. The residue is the difference between the actors’ overall sentiment about exaggerated future prospects...

  3. Heavy liquid bubble chamber

    CERN Multimedia

    1965-01-01

    The CERN Heavy liquid bubble chamber being installed in the north experimental hall at the PS. On the left, the 1180 litre body; in the centre the magnet, which can produce a field of 26 800 gauss; on the right the expansion mechanism.

  4. Microfluidic "blinking" bubble pump

    NARCIS (Netherlands)

    Yin, Zhizhong; Prosperetti, Andrea

    2005-01-01

    The paper reports data obtained on a simple micropump, suitable for electrolytes, based on the periodic growth and collapse of a single vapor bubble in a microchannel. With a channel diameter of the order of 100 µm, pumping rates of several tens of µl/min and pressure differences of several kPa are

  5. Notes on radial oscillations of gas bubbles in liquids: thermal effects.

    Science.gov (United States)

    Zhang, Yuning; Li, S C

    2010-11-01

    For oscillations of gas bubbles in liquids, the polytropic exponent and thermal damping constant for the high frequency region have been re-evaluated based on the framework by Prosperetti [J. Acoust. Soc. Am. 61, 17-27 (2007)]. It is seen that the approximation of G(1)≪ 1 in Prosperetti (1977) should be dropped for G(1)≥ 10(-2). The ratios of bubble radii to wavelengths are the paramount parameters categorizing the behavior into three different regions.

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

    Science.gov (United States)

    Lee, Joohyoung; Park, Hyungmin

    2016-11-01

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

  7. Bubble properties of heterogeneous bubbly flows in a square bubble column: draft

    NARCIS (Netherlands)

    Bai, Wei; Deen, Niels G.; Kuipers, J.A.M.

    2009-01-01

    The present work focuses on the measurements of bubble properties in heterogeneous bubbly flows in a square bubble column. A four-point optical fibre probe was used for this purpose. The accuracy and intrusive effect of the optical probe was investigated first. The results show that the optical prob

  8. Propagation of Ion Acoustic Perturbations

    DEFF Research Database (Denmark)

    Pécseli, Hans

    1975-01-01

    Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered.......Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered....

  9. A model of bubble growth leading to xylem conduit embolism.

    Science.gov (United States)

    Hölttä, T; Vesala, T; Nikinmaa, E

    2007-11-01

    The dynamics of a gas bubble inside a water conduit after a cavitation event was modeled. A distinction was made between a typical angiosperm conduit with a homogeneous pit membrane and a typical gymnosperm conduit with a torus-margo pit membrane structure. For conduits with torus-margo type pits pit membrane deflection was also modeled and pit aspiration, the displacement of the pit membrane to the low pressure side of the pit chamber, was found to be possible while the emboli was still small. Concurrent with pit aspiration, the high resistance to water flow out of the conduit through the cell walls or aspirated pits will make the embolism process slow. In case of no pit aspiration and always for conduits with homogeneous pit membranes, embolism growth is more rapid but still much slower than bubble growth in bulk water under similar water tension. The time needed for the embolism to fill a whole conduit was found to be dependent on pit and cell wall conductance, conduit radius, xylem water tension, pressure rise in adjacent conduits due to water freed from the embolising conduit, and the rigidity and structure of the pits in the case of margo-torus type pit membrane. The water pressure in the conduit hosting the bubble was found to occur almost immediately after bubble induction inside a conduit, creating a sudden tension release in the conduit, which can be detected by acoustic and ultra-acoustic monitoring of xylem cavitation.

  10. Acoustic micronektonic distribution is structured by macroscale oceanographic processes across 20-50°S latitudes in the South-Western Indian Ocean

    Science.gov (United States)

    Béhagle, Nolwenn; Cotté, Cédric; Ryan, Tim E.; Gauthier, Olivier; Roudaut, Gildas; Brehmer, Patrice; Josse, Erwan; Cherel, Yves

    2016-04-01

    Micronekton constitutes the largest unexploited marine biomass worldwide. It is one of the most conspicuous and ecologically important components of the still poorly known mesopelagic ecosystem. Acoustic data were collected from both fishing and research vessels along 18 transects for a total of 47 682 linear kilometers to investigate large-scale distribution of micronekton over a long latitudinal gradient (20-50°S) and two contrasted seasons (summer and winter) in the South-Western Indian Ocean. Acoustic backscatter at 38 kHz was used as a proxy of mid-water organisms' abundance (0-800 m depth). Two consistent features were diel vertical migration of backscatters and vertical distribution of micronekton in three distinct layers, namely the surface (SL), intermediate (IL) and deep (DL) layers. Satellite remote sensing data was used to position oceanic fronts, and hence define water masses, from the tropical to low Antarctic zones. A key finding of this study was the significant correlation observed between abundance and distribution of acoustic backscatter and position relative to these front and water masses. Total backscatter peaked in the subtropical zone, with low abundances in the colder Polar Frontal Zone. The high overall abundances in subtropical waters resulted mainly from high backscatters in the IL and DL that contrasted with low SL values, especially during the day (2-11%). The warmer the waters, the higher SL backscatter was, with the highest absolute and relative (38-51% of the total abundance) values observed at night in the Tropical Zone and the lowest abundance in the Antarctic Zone. No significant seasonal pattern was found, but SL backscatters were very low in winter compared to summer in the Polar Frontal Zone. Moreover, the Northern winter shift of the fronts induced a Northern latitudinal shift of the peak in abundance from summer to winter. The present study highlights the value of building large acoustic databases collected from both

  11. Noise reduction as affected by the extent and distribution of acoustic treatment in a turbofan engine inlet

    Science.gov (United States)

    Minner, G. L.; Homyak, L.

    1976-01-01

    An inlet noise suppressor for a TF-34 engine designed to have three acoustically treated rings was tested with several different ring arrangements. The configurations included: all three rings; two outer rings; single outer ring; single intermediate ring, and finally no rings. It was expected that as rings were removed, the acoustic performance would be degraded considerably. While a degradation occurred, it was not as large as predictions indicated. In fact, the prediction showed good agreement with the data only for the full-ring inlet configuration. The under-predictions which occurred with ring removal were believed a result of ignoring the presence of spinning modes which are known to damp more rapidly in cylindrical ducts than would be predicted by least attenuated mode or plane wave analysis.

  12. Communication Acoustics

    DEFF Research Database (Denmark)

    Blauert, Jens

    Communication Acoustics deals with the fundamentals of those areas of acoustics which are related to modern communication technologies. Due to the advent of digital signal processing and recording in acoustics, these areas have enjoyed an enormous upswing during the last 4 decades. The book...... the book a source of valuable information for those who want to improve or refresh their knowledge in the field of communication acoustics - and to work their way deeper into it. Due to its interdisciplinary character Communication Acoustics is bound to attract readers from many different areas, such as......: acoustics, cognitive science, speech science, and communication technology....

  13. Bubble Dynamics and Shock Waves

    CERN Document Server

    2013-01-01

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

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

    Science.gov (United States)

    Strybulevych, A.; Leroy, V.; Shum, A. L.; Koksel, H. F.; Scanlon, M. G.; Page, J. H.

    2012-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-07-01

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

  16. Calculation of reactivity changes due to bubble collapse. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, T.J.; Petrie, L.M.

    1977-01-01

    Calculations based on Behrens' method indicate that a substantial increase in reactivity may accompany the collapse of a large number of small bubbles in an LMFBR core. More sophisticated transport approaches to this problem have encountered several difficulties: the large number of bubbles requires many mesh points; the desired effect can easily be masked by the movement of fuel to regions of greater (or lesser) importance; the reactivity is desired for a random distribution of spherical bubbles. This paper describes a transport approach to this problem which avoids the above difficulties by using the ''sub-group'' or ''probability table'' method.

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

    Science.gov (United States)

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

    2005-10-01

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

  18. Bubble and boundary layer behaviour in subcooled flow boiling

    Energy Technology Data Exchange (ETDEWEB)

    Maurus, Reinhold; Sattelmayer, Thomas [Lehrstuhl fuer Thermodynamik, Technische Universitaet Muenchen, 85747 Garching (Germany)

    2006-03-15

    Subcooled flow boiling is a commonly applied technique for achieving efficient heat transfer. In the study, an experimental investigation in the nucleate boiling regime was performed for water circulating in a closed loop at atmospheric pressure. The horizontal orientated test-section consists of a rectangular channel with a one side heated copper strip and good optical access. Various optical observation techniques were applied to study the bubble behaviour and the characteristics of the fluid phase. The bubble behaviour was recorded by the high-speed cinematography and by a digital high resolution camera. Automated image processing and analysis algorithms developed by the authors were applied for a wide range of mass flow rates and heat fluxes in order to extract characteristic length and time scales of the bubbly layer during the boiling process. Using this methodology, the bubbles were automatically analysed and the bubble size, bubble lifetime, waiting time between two cycles were evaluated. Due to the huge number of observed bubbles a statistical analysis was performed and distribution functions were derived. Using a two-dimensional cross-correlation algorithm, the averaged axial phase boundary velocity profile could be extracted. In addition, the fluid phase velocity profile was characterised by means of the particle image velocimetry (PIV) for the single phase flow as well as under subcooled flow boiling conditions. The results indicate that the bubbles increase the flow resistance. The impact on the flow exceeds by far the bubbly region and it depends on the magnitude of the boiling activity. Finally, the ratio of the averaged phase boundary velocity and of the averaged fluid velocity was evaluated for the bubbly region. (authors)

  19. Acoustic telemetry

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — To determine movements of green turtles in the nearshore foraging areas, we deployed acoustic tags and determined their movements through active and passive acoustic...

  20. Direct visualization of microalgae rupture by ultrasound-driven bubbles

    Science.gov (United States)

    Pommella, Angelo; Harun, Irina; Pouliopoulos, Antonis; Choi, James J.; Hellgardt, Klaus; Garbin, Valeria

    2015-11-01

    Cell rupture induced by ultrasound is central to applications in biotechnology. For instance, cell disruption is required in the production of biofuels from microalgae (unicellular species of algae). Ultrasound-induced cavitation, bubble collapse and jetting are exploited to induce sufficiently large viscous stresses to cause rupture of the cell membranes. It has recently been shown that seeding the flow with bubbles that act as cavitation nuclei significantly reduces the energy cost for cell processing. However, a fundamental understanding of the conditions for rupture of microalgae in the complex flow fields generated by ultrasound-driven bubbles is currently lacking. We perform high-speed video microscopy to visualize the miscroscale details of the interaction of Chlamydomonas reinhardtii , microalgae of about 10 μm in size, with ultrasound-driven microbubbles of 2-200 μm in diameter. We investigate the efficiency of cell rupture depending on ultrasound frequency and pressure amplitude (from 10 kPa up to 1 MPa), and the resulting bubble dynamics regimes. In particular we compare the efficiency of membrane rupture in the acoustic microstreaming flow induced by linear oscillations, with the case of violent bubble collapse and jetting. V.G. acknowledges partial support from the European Commission (FP7-PEOPLE-2013-CIG), Grant No. 618333.

  1. CRISIS FOCUS Blowing Bubbles

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

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

  2. Slurry bubble column hydrodynamics

    Science.gov (United States)

    Rados, Novica

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

  3. Argonne Bubble Experiment Thermal Model Development II

    Energy Technology Data Exchange (ETDEWEB)

    Buechler, Cynthia Eileen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-07-01

    This report describes the continuation of the work reported in “Argonne Bubble Experiment Thermal Model Development”. The experiment was performed at Argonne National Laboratory (ANL) in 2014. A rastered 35 MeV electron beam deposited power in a solution of uranyl sulfate, generating heat and radiolytic gas bubbles. Irradiations were performed at three beam power levels, 6, 12 and 15 kW. Solution temperatures were measured by thermocouples, and gas bubble behavior was observed. This report will describe the Computational Fluid Dynamics (CFD) model that was developed to calculate the temperatures and gas volume fractions in the solution vessel during the irradiations. The previous report described an initial analysis performed on a geometry that had not been updated to reflect the as-built solution vessel. Here, the as-built geometry is used. Monte-Carlo N-Particle (MCNP) calculations were performed on the updated geometry, and these results were used to define the power deposition profile for the CFD analyses, which were performed using Fluent, Ver. 16.2. CFD analyses were performed for the 12 and 15 kW irradiations, and further improvements to the model were incorporated, including the consideration of power deposition in nearby vessel components, gas mixture composition, and bubble size distribution. The temperature results of the CFD calculations are compared to experimental measurements.

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

    Science.gov (United States)

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

    2008-02-05

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

  5. The influence of polymeric membrane gas spargers on hydrodynamics and mass transfer in bubble column bioreactors

    DEFF Research Database (Denmark)

    Tirunehe, Gossay; Norddahl, B.

    2016-01-01

    Gas sparging performances of a flat sheet and tubular polymeric membranes were investigated in 3.1 m bubble column bioreactor operated in a semi batch mode. Air–water and air–CMC (Carboxymethyl cellulose) solutions of 0.5, 0.75 and 1.0 % w/w were used as interacting gas–liquid mediums. CMC...... solutions were employed in the study to simulate rheological properties of bioreactor broth. Gas holdup, bubble size distribution, interfacial area and gas–liquid mass transfer were studied in the homogeneous bubbly flow hydrodynamic regime with superficial gas velocity (UG) range of 0.0004–0.0025 m....../s. The study indicated that the tubular membrane sparger produced the highest gas holdup and densely populated fine bubbles with narrow size distribution. An increase in liquid viscosity promoted a shift in bubble size distribution to large stable bubbles and smaller specific interfacial area. The tubular...

  6. Modeling fish egg production and spatial distribution from acoustic data: a step forward into the analysis of recruitment.

    Directory of Open Access Journals (Sweden)

    Andrés Ospina-Álvarez

    Full Text Available To date, there are numerous transport simulation studies demonstrating the relevance of the hydrodynamics for the advection, dispersion and recruitment of early stages of marine organisms. However, the lack of data has conditioned the use of realistic locations for the model setup and configuration in transport studies. This work (I demonstrates the key role played by the use of the realistic initial position of the eggs of small pelagic fishes in the analysis of late-larval recruitment in coastal nursery areas and (II provides a general solution for deriving future egg positions and abundances from adult biomass obtained from acoustic surveys and available fecundity data. Using European anchovy in the NW Mediterranean as a case study, we first analyzed the impact of the initial location, timing, egg buoyancy and diel vertical migration of larvae on the potential late-larval recruitment to coastal areas. The results suggested that prior knowledge of the initial spawning grounds may substantially affect the estimates of potential recruitment. We then integrated biological and acoustics-derived data (the biomass and size structure, sex ratio, a weight-batch fecundity model, mean weight, number of fish and mean spawning to build a predictive model for interannual egg production. This model was satisfactorily contrasted with field data for two years obtained with the Daily Egg Production Method (DEPM. We discuss our results in the context of the fluctuations of European anchovy egg abundance from 2003 through 2010 in the NW Mediterranean and in terms of the potential applicability of the acoustics-based spatial predictive egg production model.

  7. Controlled Acoustic Bass System (CABS) A Method to Achieve Uniform Sound Field Distribution at Low Frequencies in Rectangular Rooms

    DEFF Research Database (Denmark)

    Celestinos, Adrian; Nielsen, Sofus Birkedal

    2008-01-01

    The sound field produced by loudspeakers at low frequencies in small- and medium-size rectangular listening rooms is highly nonuniform due to the multiple reflections and diffractions of sound on the walls and different objects in the room. A new method, called controlled acoustic bass system (CABS......), is introduced. The system utilizes front loudspeakers and extra loudspeakers on the opposite wall of the room processed to cancel out the rear-wall reflections, which effectively conveys a more uniform sound field. The system works in the time domain and presents good performance over the loudspeaker low...

  8. Specific and rapid effects of acoustic stimulation on the tonotopic distribution of Kv3.1b potassium channels in the adult rat.

    Science.gov (United States)

    Strumbos, J G; Polley, D B; Kaczmarek, L K

    2010-05-19

    Recent studies have demonstrated that total cellular levels of voltage-gated potassium channel subunits can change on a time scale of minutes in acute slices and cultured neurons, raising the possibility that rapid changes in the abundance of channel proteins contribute to experience-dependent plasticity in vivo. In order to investigate this possibility, we took advantage of the medial nucleus of the trapezoid body (MNTB) sound localization circuit, which contains neurons that precisely phase-lock their action potentials to rapid temporal fluctuations in the acoustic waveform. Previous work has demonstrated that the ability of these neurons to follow high-frequency stimuli depends critically upon whether they express adequate amounts of the potassium channel subunit Kv3.1. To test the hypothesis that net amounts of Kv3.1 protein would be rapidly upregulated when animals are exposed to sounds that require high frequency firing for accurate encoding, we briefly exposed adult rats to acoustic environments that varied according to carrier frequency and amplitude modulation (AM) rate. Using an antibody directed at the cytoplasmic C-terminus of Kv3.1b (the adult splice isoform of Kv3.1), we found that total cellular levels of Kv3.1b protein-as well as the tonotopic distribution of Kv3.1b-labeled cells-was significantly altered following 30 min of exposure to rapidly modulated (400 Hz) sounds relative to slowly modulated (0-40 Hz, 60 Hz) sounds. These results provide direct evidence that net amounts of Kv3.1b protein can change on a time scale of minutes in response to stimulus-driven synaptic activity, permitting auditory neurons to actively adapt their complement of ion channels to changes in the acoustic environment.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Novel Epoxy Resin/SiO2 Nanocomposites Preparation Method Based on Diminutive Bubbles Explosion

    Institute of Scientific and Technical Information of China (English)

    NIE Peng; ZHAO Xue-zeng; CHEN Fang; WANG Wei-jie; BAI Yong-ping

    2006-01-01

    To obtain suspended dispersion of nano-particles in liquid without any dispersant, a novel epoxy resin/SiO2 nanocomposites preparation method based on diminutive bubbles explosion is presented. And, corresponding nanocomposites preparation system was designed. The preparation system applies compressed gas as transmission medium to carry nanomaterials into epoxy resin solution. The compressed gas with nanomaterials turns into diminutive bubbles distributing in epoxy resin/SiO2. The great pressure difference between inner and outer-bubbles led to bubbles inflation and explosion. During the bubble inflation, bubble oscillation may generate. The stretching rate may reach 106 s-1, which favors more homogeneous dispersion of nanoparticles. During the bubbles explosion the released energy and the explosion shock waves disperse the nanoparticles into epoxy resin solution. By using the preparation system, epoxy resin/SiO2 nanocomposites were prepared. The SiO2 dispersed into epoxy as the configuration of 15 nm - 30 nm particles.

  11. Electrowetting of a soap bubble

    CERN Document Server

    Arscott, Steve

    2013-01-01

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

  12. Acoustic performance of low pressure axial fan rotors with different blade chord length and radial load distribution

    Science.gov (United States)

    Carolus, Thomas

    The paper examines the acoustic and aerodynamic performance of low-pressure axial fan rotors with a hub/tip ratio of 0.45. Six rotors were designed for the same working point by means of the well-known airfoil theory. The condition of an equilibrium between the static pressure gradient and the centrifugal forces is maintained. All rotors have unequally spaced blades to diminish tonal noise. The rotors are tested in a short cylindrical housing without guide vanes. All rotors show very similar flux-pressure difference characteristics. The peak efficiency and the noise performance is considerably influenced by the chosen blade design. The aerodynamically and acoustically optimal rotor is the one with the reduced load at the hub and increased load in the tip region under satisfied equilibrium conditions. It runs at the highest aerodynamic efficiency, and its noise spectrum is fairly smooth. The overall sound pressure level of this rotor is up to 8 dB (A) lower compared to the other rotors under consideration.

  13. Intraluminal bubble dynamics induced by lithotripsy shock wave

    Science.gov (United States)

    Song, Jie; Bai, Jiaming; Zhou, Yufeng

    2016-12-01

    Extracorporeal shock wave lithotripsy (ESWL) has been the first option in the treatment of calculi in the upper urinary tract since its introduction. ESWL-induced renal injury is also found after treatment and is assumed to associate with intraluminal bubble dynamics. To further understand the interaction of bubble expansion and collapse with the vessel wall, the finite element method (FEM) was used to simulate intraluminal bubble dynamics and calculate the distribution of stress in the vessel wall and surrounding soft tissue during cavitation. The effects of peak pressure, vessel size, and stiffness of soft tissue were investigated. Significant dilation on the vessel wall occurs after contacting with rapid and large bubble expansion, and then vessel deformation propagates in the axial direction. During bubble collapse, large shear stress is found to be applied to the vessel wall at a clinical lithotripter setting (i.e. 40 MPa peak pressure), which may be the mechanism of ESWL-induced vessel rupture. The decrease of vessel size and viscosity of soft tissue would enhance vessel deformation and, consequently, increase the generated shear stress and normal stresses. Meanwhile, a significantly asymmetric bubble boundary is also found due to faster axial bubble expansion and shrinkage than in radial direction, and deformation of the vessel wall may result in the formation of microjets in the axial direction. Therefore, this numerical work would illustrate the mechanism of ESWL-induced tissue injury in order to develop appropriate counteractive strategies for reduced adverse effects.

  14. Artificial neural network for bubbles pattern recognition on the images

    Science.gov (United States)

    Poletaev, I. E.; Pervunin, K. S.; Tokarev, M. P.

    2016-10-01

    Two-phase bubble flows have been used in many technological and energy processes as processing oil, chemical and nuclear reactors. This explains large interest to experimental and numerical studies of such flows last several decades. Exploiting of optical diagnostics for analysis of the bubble flows allows researchers obtaining of instantaneous velocity fields and gaseous phase distribution with the high spatial resolution non-intrusively. Behavior of light rays exhibits an intricate manner when they cross interphase boundaries of gaseous bubbles hence the identification of the bubbles images is a complicated problem. This work presents a method of bubbles images identification based on a modern technology of deep learning called convolutional neural networks (CNN). Neural networks are able to determine overlapping, blurred, and non-spherical bubble images. They can increase accuracy of the bubble image recognition, reduce the number of outliers, lower data processing time, and significantly decrease the number of settings for the identification in comparison with standard recognition methods developed before. In addition, usage of GPUs speeds up the learning process of CNN owning to the modern adaptive subgradient optimization techniques.

  15. Vortex Simulation of the Bubbly Flow around a Hydrofoil

    Directory of Open Access Journals (Sweden)

    Tomomi Uchiyama

    2007-01-01

    Full Text Available This study is concerned with the two-dimensional simulation for an air-water bubbly flow around a hydrofoil. The vortex method, proposed by the authors for gas-liquid two-phase free turbulent flow in a prior paper, is applied for the simulation. The liquid vorticity field is discrerized by vortex elements, and the behavior of vortex element and the bubble motion are simultaneously computed by the Lagrangian approach. The effect of bubble motion on the liquid flow is taken into account through the change in the strength of vortex element. The bubbly flow around a hydrofoil of NACA4412 with a chord length 100 mm is simulated. The Reynolds number is 2.5×105, the bubble diameter is 1 mm, and the volumetric flow ratio of bubble to whole fluid is 0.048. It is confirmed that the simulated distributions of air volume fraction and pressure agree well with the trend of the measurement and that the effect of angle of attack on the flow is favorably analyzed. These demonstrate that the vortex method is applicable to the bubbly flow analysis around a hydrofoil.

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

    Science.gov (United States)

    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

  17. Patterns of distribution of sound-scattering zooplankton in warm- and cold-core eddies in the Gulf of Mexico, from a narrowband acoustic Doppler current profiler survey

    Science.gov (United States)

    Zimmerman, Robert A.; Biggs, Douglas C.

    1999-03-01

    The acoustic backscatter intensity (ABI) reflected from epipelagic zooplankton communities in the central Gulf of Mexico was measured during June 1995 with a vessel-mounted, narrowband-153-kHz acoustic Doppler current profiler (ADCP). Horizontal and vertical variations in ABI were documented in three kinds of mesoscale hydrographic features commonly found in the Gulf of Mexico: the warm-core Loop Current (LC), a warm-core Loop Current eddy (LCE), and a cold-core region that separated the two warm-core features. Since new nitrogen domes close to surface waters in cold-core features whereas surface waters of warm-core features are nutrient depleted, the cold-core region was expected to have higher biological stocks as a result of locally higher primary production. Both ABI and net tow data confirmed that the cold-core region was in fact a zone of local aggregation of zooplankton and micronekton. During both day and night, ABI when integrated for the upper 50 and 100 m in the cold-core region was significantly greater than in the LC or in the LCE, and ABI was positively correlated with standing stock biomass taken by the net tows. Further investigations into the biological differences between Gulf of Mexico divergence and convergence regimes are warranted, and the ADCP will be a useful tool for examination of the distribution of sound scatterers in such features.

  18. Characterization of Bioeffects on Endothelial Cells under Acoustic Droplet Vaporization.

    Science.gov (United States)

    Seda, Robinson; Li, David S; Fowlkes, J Brian; Bull, Joseph L

    2015-12-01

    Gas embolotherapy is achieved by locally vaporizing microdroplets through acoustic droplet vaporization, which results in bubbles that are large enough to occlude blood flow directed to tumors. Endothelial cells, lining blood vessels, can be affected by these vaporization events, resulting in cell injury and cell death. An idealized monolayer of endothelial cells was subjected to acoustic droplet vaporization using a 3.5-MHz transducer and dodecafluoropentane droplets. Treatments included insonation pressures that varied from 2 to 8 MPa (rarefactional) and pulse lengths that varied from 4 to 16 input cycles. The bubble cloud generated was directly dependent on pressure, but not on pulse length. Cellular damage increased with increasing bubble cloud size, but was limited to the bubble cloud area. These results suggest that vaporization near the endothelium may impact the vessel wall, an effect that could be either deleterious or beneficial depending on the intended overall therapeutic application.

  19. Droplets, Bubbles and Ultrasound Interactions.

    Science.gov (United States)

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

    2016-01-01

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

  20. Passive broadband acoustic thermometry

    Science.gov (United States)

    Anosov, A. A.; Belyaev, R. V.; Klin'shov, V. V.; Mansfel'd, A. D.; Subochev, P. V.

    2016-04-01

    The 1D internal (core) temperature profiles for the model object (plasticine) and the human hand are reconstructed using the passive acoustothermometric broadband probing data. Thermal acoustic radiation is detected by a broadband (0.8-3.5 MHz) acoustic radiometer. The temperature distribution is reconstructed using a priori information corresponding to the experimental conditions. The temperature distribution for the heated model object is assumed to be monotonic. For the hand, we assume that the temperature distribution satisfies the heat-conduction equation taking into account the blood flow. The average error of reconstruction determined for plasticine from the results of independent temperature measurements is 0.6 K for a measuring time of 25 s. The reconstructed value of the core temperature of the hand (36°C) generally corresponds to physiological data. The obtained results make it possible to use passive broadband acoustic probing for measuring the core temperatures in medical procedures associated with heating of human organism tissues.

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

    Science.gov (United States)

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

    2014-05-01

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

  2. Simultaneous High-Speed Recording of Sonoluminescence and Bubble Dynamics in Multibubble Fields

    Science.gov (United States)

    Cairós, Carlos; Mettin, Robert

    2017-02-01

    Multibubble sonoluminescence (MBSL) is the emission of light from imploding cavitation bubbles in dense ensembles or clouds. We demonstrate a technique of high-speed recording that allows imaging of bubble oscillations and motion together with emitted light flashes in a nonstationary multibubble environment. Hereby a definite experimental identification of light emitting individual bubbles, as well as details of their collapse dynamics can be obtained. For the extremely bright MBSL of acoustic cavitation in xenon saturated phosphoric acid, we are able to explore effects of bubble translation, deformation, and interaction on MBSL activity. The recordings with up to 0.5 million frames per second show that few and only the largest bubbles in the fields are flashing brightly, and that emission often occurs repetitively. Bubble collisions can lead to coalescence and the start or intensification of the emission, but also to its termination via instabilities and splitting. Bubbles that develop a liquid jet during collapse can flash intensely, but stronger jetting gradually reduces the emissions. Estimates of MBSL collapse temperature peaks are possible by numerical fits of transient bubble dynamics, in one case yielding 38 000 K.

  3. Correlation of acoustic emissions associated with effects from diagnostic and therapeutic ultrasound

    Science.gov (United States)

    Samuel, Stanley

    2007-12-01

    This research has investigated the correlation of acoustic emissions with associated contrast-mediated ultrasound bio-effects. The hypothesis that motivated this study was that during exposure with ultrasound, the cavitation occurring in tissue emits acoustical signals, which if correlated with specific bio-effects, could provide a way to monitor the potential bio-effects of exposure. A good bio-effects indicator would find immediate use in research on drug and gene delivery, and could have clinical application in avoiding bio-effects in diagnosis. Studies conducted to test the hypothesis involved investigation of (i) the influence of pulse repetition frequency (PRF) and number of exposures on cell damage, (ii) the effect of total exposure duration and pulse-to-pulse bubble distribution on acoustic emissions and corresponding cell damage, and (iii) the translation of in vitro effects to an in situ environment. Exposures were primarily conducted at a peak rarefactional pressure of 2 MPa, 2.25 MHz insonating frequency and pulse length of 46 cycles. PRFs of 1-, 10-, 100-, 500-, and 1000 Hz were compared. High speed photography (2000 fps) was employed for the investigation of pulse-to-pulse bubble distribution while intravital microscopy was used for in situ studies. A strong correlation was observed between acoustic emissions and bio-effects with the availability of bubbles of resonant size serving as a key link between the two. It was observed that total exposure duration may play an important role in cell damage. Damage increased with increasing total exposure duration from 0 ms to 100 ms with a plateau at above 100 ms. These results were consistent for all studies. There is, therefore, an implication that manipulating these parameters may allow for measurement and control of the extent of bioeffects. Moreover, the correlation of acoustic emission and extravasation observed in in situ studies reveals that cumulative function of the relative integrated power spectrum

  4. Simulation of the spatial distribution of the acoustic pressure in sonochemical reactors with numerical methods: a review.

    Science.gov (United States)

    Tudela, Ignacio; Sáez, Verónica; Esclapez, María Deseada; Díez-García, María Isabel; Bonete, Pedro; González-García, José

    2014-05-01

    Numerical methods for the calculation of the acoustic field inside sonoreactors have rapidly emerged in the last 15 years. This paper summarizes some of the most important works on this topic presented in the past, along with the diverse numerical works that have been published since then, reviewing the state of the art from a qualitative point of view. In this sense, we illustrate and discuss some of the models recently developed by the scientific community to deal with some of the complex events that take place in a sonochemical reactor such as the vibration of the reactor walls and the nonlinear phenomena inherent to the presence of ultrasonic cavitation. In addition, we point out some of the upcoming challenges that must be addressed in order to develop a reliable tool for the proper designing of efficient sonoreactors and the scale-up of sonochemical processes.

  5. Bioeffects due to acoustic droplet vaporization

    Science.gov (United States)

    Bull, Joseph

    2015-11-01

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

  6. Dynamic Bubble Behaviour during Microscale Subcooled Boiling

    Institute of Scientific and Technical Information of China (English)

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

    2005-01-01

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

  7. Micro-bubble morphologies following drop impacts onto a pool surface

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2012-10-01

    When a drop impacts at low velocity onto a pool surface, a hemispheric air layer cushions and can delay direct contact. Herein we use ultra-high-speed video to study the rupture of this layer, to explain the resulting variety of observed distribution of bubbles. The size and distribution of micro-bubbles is determined by the number and location of the primary punctures. Isolated holes lead to the formation of bubble necklaces when the edges of two growing holes meet, whereas bubble nets are produced by regular shedding of micro-bubbles from a sawtooth edge instability. For the most viscous liquids the air film contracts more rapidly than the capillary-viscous velocity through repeated spontaneous ruptures of the edge. From the speed of hole opening and the total volume of micro-bubbles we conclude that the air sheet ruptures when its thickness approaches ?100.

  8. Hydrogen bubble flotation of fine minerals containing calcium

    Institute of Scientific and Technical Information of China (English)

    Sun Wei; Ma Liang; Hu Yuehua; Dong Yanhong; Zhang Gang

    2011-01-01

    One characteristic of electro-flotation is the presence of micro bubbles that are well known for improving the flotation performance of fine particles.An electro-flotation method was studied with fine scheelite and fluorite particles sized into three different fractions.Experiments were performed in a modified Hallimond tube.We investigated the effects of gas holdup,particle size,and different mesh electrode apertures on mineral recovery.Flotation results show that two size fractions show increased flotation recovery as the gas holdup increases.For the sized scheelite and fluorite,the flotation effect is diverse for different sizes of the cathode aperture.Pictures of the bubbles taken by a high speed CCD were used to determine the hydrogen bubble size distribution generated as a function of collector,current density,and electrode size.The diameters of the hydrogen bubbles ranged from 12 to 117 μm in alkaline conditions.

  9. Acoustical Imaging

    CERN Document Server

    Litniewski, Jerzy; Kujawska, Tamara; 31st International Symposium on Acoustical Imaging

    2012-01-01

    The International Symposium on Acoustical Imaging is a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. This interdisciplinary Symposium has been taking place continuously since 1968. In the course of the years the proceedings volumes in the Acoustical Imaging Series have become a reference for cutting-edge research in the field. In 2011 the 31st International Symposium on Acoustical Imaging was held in Warsaw, Poland, April 10-13. Offering both a broad perspective on the state-of-the-art as well as  in-depth research contributions by the specialists in the field, this Volume 31 in the Series contains an excellent collection of papers in six major categories: Biological and Medical Imaging Physics and Mathematics of Acoustical Imaging Acoustic Microscopy Transducers and Arrays Nondestructive Evaluation and Industrial Applications Underwater Imaging

  10. Triangular bubble spline surfaces.

    Science.gov (United States)

    Kapl, Mario; Byrtus, Marek; Jüttler, Bert

    2011-11-01

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

  11. Acoustic cavitation movies

    Science.gov (United States)

    Crum, Lawrence A.

    2003-04-01

    Acoustic cavitation is a phenomenon that occurs on microsecond time scales and micron length scales, yet, it has many macroscopic manifestations. Accordingly, it is often difficult, at least for the author, to form realistic physical descriptions of the specific mechanisms through which it expresses itself in our macroscopic world. For example, there are still many who believe that cavitation erosion is due to the shock wave that is emitted by bubble implosion, rather than the liquid jet created on asymmetric collapse...and they may be right. Over the years, the author has accumulated a number of movies and high-speed photographs of cavitation activity, which he uses to form his own visual references. In the time allotted, he will show a number of these movies and photographs and discuss their relevance to existing technological problems. A limited number of CDs containing the presented materials will be available to interested individuals. [Work supported in part by the NIH, USAMRMC, and the ONR.

  12. Bubble chamber: colour enhanced tracks

    CERN Multimedia

    1998-01-01

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

  13. Explosive micro-bubble actuator

    NARCIS (Netherlands)

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

    2008-01-01

    Explosive evaporation occurs when a liquid is exposed to extremely high heat-fluxes. Within a few microseconds a bubble in the form vapour film is generated, followed by rapid growth due to the pressure impulse and finally the bubbles collapse. This effect, which already has proven its use in curren

  14. A general derivation of the subharmonic threshold for non-linear bubble oscillations

    NARCIS (Netherlands)

    Prosperetti, A.

    2013-01-01

    The paper describes an approximate but rather general derivation of the acoustic threshold for a subharmonic component to be possible in the sound scattered by an insonified gas bubble. The general result is illustrated with several specific models for the mechanical behavior of the surface coating

  15. Acoustic textiles

    CERN Document Server

    Nayak, Rajkishore

    2016-01-01

    This book highlights the manufacturing and applications of acoustic textiles in various industries. It also includes examples from different industries in which acoustic textiles can be used to absorb noise and help reduce the impact of noise at the workplace. Given the importance of noise reduction in the working environment in several industries, the book offers a valuable guide for companies, educators and researchers involved with acoustic materials.

  16. Acoustic biosensors

    OpenAIRE

    Fogel, Ronen; Limson, Janice; Seshia, Ashwin A.

    2016-01-01

    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of ...

  17. Bubbling behaviors induced by gas-liquid mixture permeating through a porous medium

    Science.gov (United States)

    Hu, Liang; Li, Mingbo; Chen, Wenyu; Xie, Haibo; Fu, Xin

    2016-08-01

    This paper investigates the bubbling behaviors induced by gas-liquid mixture permeating through porous medium (PM), which was observed in developing immersion lithography system and was found having great differences with traditional bubbling behaviors injected with only gas phase through the PM. An experimental setup was built up to investigate the bubbling characteristics affected by the mixed liquid phase. Both the flow regimes of gas-liquid mixture in micro-channel (upstream of the PM) and the bubbling flow regimes in water tank (downstream of the PM) were recorded synchronously by high-speed camera. The transitions between the flow regimes are governed by gas and liquid Weber numbers. Based on the image analysis, the characteristic parameters of bubbling region, including the diameter of bubbling area on PM surface, gas-phase volume flux, and dispersion angle of bubbles in suspending liquid, were studied under different proportions of gas and liquid flow rate. Corresponding empirical correlations were developed to describe and predict these parameters. Then, the pertinent bubble characteristics in different bubbling flow regimes were systematically investigated. Specifically, the bubble size distribution and the Sauter mean diameter affected by increasing liquid flow rate were studied, and the corresponding analysis was given based on the hydrodynamics of bubble-bubble and bubble-liquid interactions. According to dimensionless analysis, the general prediction equation of Sauter mean diameter under different operating conditions was proposed and confirmed by experimental data. The study of this paper is helpful to improve the collection performance of immersion lithography and aims to reveal the differences between the bubbling behaviors on PM caused by only gas flow and gas-liquid mixture flow, respectively, for the researches of fluid flow.

  18. Dark matter limits froma 15 kg windowless bubble chamber

    Energy Technology Data Exchange (ETDEWEB)

    Szydagis, Matthew Mark [Univ. of Chicago, IL (United States)

    2011-03-01

    The COUPP collaboration has successfully used bubble chambers, a technology previously applied only to high-energy physics experiments, as direct dark matter detectors. It has produced the world's most stringent spin-dependent WIMP limits, and increasingly competitive spin-independent limits. These limits were achieved by capitalizing on an intrinsic rejection of the gamma background that all other direct detection experiments must address through high-density shielding and empirically-determined data cuts. The history of COUPP, including its earliest prototypes and latest results, is briefly discussed in this thesis. The feasibility of a new, windowless bubble chamber concept simpler and more inexpensive in design is discussed here as well. The dark matter limits achieved with a 15 kg windowless chamber, larger than any previous COUPP chamber (2 kg, 4 kg), are presented. Evidence of the greater radiopurity of synthetic quartz compared to natural is presented using the data from this 15 kg device, the first chamber to be made from synthetic quartz. The effective reconstruction of the three-dimensional positions of bubbles in a highly distorted optical field, with ninety-degree bottom lighting similar to cloud chamber lighting, is demonstrated. Another innovation described in this thesis is the use of the sound produced by bubbles recorded by an array of piezoelectric sensors as the primary means of bubble detection. In other COUPP chambers, cameras have been used as the primary trigger. Previous work on bubble acoustic signature differentiation using piezos is built upon in order to further demonstrate the ability to discriminate between alpha- and neutron-induced events.

  19. Growing bubbles rising in line

    Directory of Open Access Journals (Sweden)

    John F. Harper

    2001-01-01

    Full Text Available Over many years the author and others have given theories for bubbles rising in line in a liquid. Theory has usually suggested that the bubbles will tend towards a stable distance apart, but experiments have often showed them pairing off and sometimes coalescing. However, existing theory seems not to deal adequately with the case of bubbles growing as they rise, which they do if the liquid is boiling, or is a supersaturated solution of a gas, or simply because the pressure decreases with height. That omission is now addressed, for spherical bubbles rising at high Reynolds numbers. As the flow is then nearly irrotational, Lagrange's equations can be used with Rayleigh's dissipation function. The theory also works for bubbles shrinking as they rise because they dissolve.

  20. Empirical relationships of homogeneous bubble nucleation, growth and coalescence in rhyolitic melt

    Science.gov (United States)

    Giachetti, T.; Gonnermann, H. M.; Gardner, J. E.; Truong, N.; Toledo, P.; Hajimirza, S.

    2015-12-01

    Decompression experiments of homogeneous nucleation, growth and coalescence of bubbles in rhyolitic melt provide new data for an empirical formulation to predict bubble number density and size from controlled experimental conditions. Samples were hydrated at 200-250 MPa and 850 °C to water contents of 5.4-6.0 wt%, followed by decompression at rates of 60-150 MPa.s-1. Samples were held at final pressures for 6-90 s, allowing for bubble growth and coalescence after decompression and nucleation. Scanning electron microscopic (SEM) images and computed tomography (CT) scans of the decompressed glasses were analyzed for size distributions of both isolated and coalesced bubbles separately. Sample porosities vary from 4% to 63%, and connected porosity is positively correlated with total porosity for samples where it is greater than approximately 35%. A steep increase in the proportion of connected bubbles is observed once the average bubble wall thickness becomes lower than approximately 2 μm. In combination with SEM, CT and bubble size distributions these results indicate that bubble coalescence is independent of bubble size. Bubble number density varies from 8.9×1011 m-3 to 4.4×1016 m-3 (melt-referenced), and is positively correlated with the degree of supersaturation (130-210 MPa), as well as initial water content. For most experiments, we do not observe any increase in bubble number density after 10-20 s, suggesting that bubble nucleation has stopped. The bubble number density does not show a systematic correlation with decompression rate.

  1. Absorption boundary conditions for geomertical acoustics

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2012-01-01

    Defining accurate acoustical boundary conditions is of crucial importance for room acoustic simulations. In predicting sound fields using phased geometrical acoustics methods, the absorption coefficients or surface impedances of the boundary surfaces can be used, but no guideline has been developed...... solutions. Two rectangular rooms with uniform and non-uniform absorption distributions are tested. It is concluded that the impedance and random incidence absorption boundary conditions produce reasonable results with some exceptions at low frequencies for acoustically soft materials....

  2. A Study of Bubble and Slug Gas-Liquid Flow in a Microgravity Environment

    Science.gov (United States)

    McQuillen, J.

    2000-01-01

    surfactant), to identify clusters that promote coalescence and transition the void fraction distribution in bubbly and slug flow,to measure the wall friction in bubbly flow. These experiments will consist of multiple bubbles type flows and will utilize hot wire and film anemometers to measure liquid velocity and wall shear stress respectively and double fiber optic probes to measure bubble size and velocity as a function of tube radius and axial location.

  3. Using novel acoustic and visual mapping tools to predict the small-scale spatial distribution of live biogenic reef framework in cold-water coral habitats

    Science.gov (United States)

    De Clippele, L. H.; Gafeira, J.; Robert, K.; Hennige, S.; Lavaleye, M. S.; Duineveld, G. C. A.; Huvenne, V. A. I.; Roberts, J. M.

    2017-03-01

    Cold-water corals form substantial biogenic habitats on continental shelves and in deep-sea areas with topographic highs, such as banks and seamounts. In the Atlantic, many reef and mound complexes are engineered by Lophelia pertusa, the dominant framework-forming coral. In this study, a variety of mapping approaches were used at a range of scales to map the distribution of both cold-water coral habitats and individual coral colonies at the Mingulay Reef Complex (west Scotland). The new ArcGIS-based British Geological Survey (BGS) seabed mapping toolbox semi-automatically delineated over 500 Lophelia reef `mini-mounds' from bathymetry data with 2-m resolution. The morphometric and acoustic characteristics of the mini-mounds were also automatically quantified and captured using this toolbox. Coral presence data were derived from high-definition remotely operated vehicle (ROV) records and high-resolution microbathymetry collected by a ROV-mounted multibeam echosounder. With a resolution of 0.35 × 0.35 m, the microbathymetry covers 0.6 km2 in the centre of the study area and allowed identification of individual live coral colonies in acoustic data for the first time. Maximum water depth, maximum rugosity, mean rugosity, bathymetric positioning index and maximum current speed were identified as the environmental variables that contributed most to the prediction of live coral presence. These variables were used to create a predictive map of the likelihood of presence of live cold-water coral colonies in the area of the Mingulay Reef Complex covered by the 2-m resolution data set. Predictive maps of live corals across the reef will be especially valuable for future long-term monitoring surveys, including those needed to understand the impacts of global climate change. This is the first study using the newly developed BGS seabed mapping toolbox and an ROV-based microbathymetric grid to explore the environmental variables that control coral growth on cold-water coral

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

    Science.gov (United States)

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

    2017-02-01

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

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

    Science.gov (United States)

    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 directions in the body-centered cubic U matrix causes the gas bubble alignment along 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.

  6. Helium bubble linkage and the transition to rapid He release in aging Pd tritide.

    Energy Technology Data Exchange (ETDEWEB)

    Cowgill, Donald F.

    2006-02-01

    A model is presented for the linking of helium bubbles growing in aging metal tritides. Stresses created by neighboring bubbles are found to produce bubble growth toward coalescence. This process is interrupted by the fracture of ligaments between bubble arrays. The condition for ligament fracture percolates through the material to reach external surfaces, leading to material micro-cracking and the release of helium within the linked-bubble cluster. A comparison of pure coalescence and pure fracture mechanisms shows the critical HeM concentration for bubble linkage is not strongly dependent on details of the linkage process. The combined stress-directed growth and fracture process produces predictions for the onset of rapid He release and the He emission rate. Transition to this rapid release state is determined from the physical size of the linked-bubble clusters, which is calculated from dimensional invariants in classical percolation theory. The result is a transition that depends on material dimensions. The onset of bubble linkage and rapid He release are found to be quite sensitive to the bubble spacing distribution, which is log-normal for bubbles nucleated by self-trapping.

  7. Bubble size measurement in three-phase system using photograph technology

    Institute of Scientific and Technical Information of China (English)

    SUN Wei; HU Yue-hua; LIU Run-qing

    2005-01-01

    A special experiment setup was designed to observe the interaction between bubbles and particle in flotation cell and to analyze the bubble characteristics such as bubble size, distribution and bubble-loading efficiency. Bubbles in water-gas system and three-phase system were measured. The results indicate that with the current setup the bubbles as small as 10 μm can be easily distinguished. The average size of the bubbles generated under the given conditions in two-phase system is 410 μm at frother concentration of 0.004%, which is in good correspondence with the results of other works. The effect of frother on bubble size was probed. Increasing frother concentration from 0 to 0.004% causes a reduction of bubble size from 700 to 400 μm. The bubble loading efficiency was reported. The result indicates that the fine particle is more easily entrapped than the coarse particle. Some factors, which have effect on measurement accuracy were discussed. The aeration speed has a significant effect on the accuracy of results, if it surpasses 30 mL/s, and the image becomes unclear due to the entrapment of fine particle. Another factor, which can affect observing results, is the sampling position. At a wrong sampling position, the images become unclear.

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

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Shenyang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Burkes, Douglas E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Senor, David J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Setyawan, Wahyu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Xu, Zhijie [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-07-08

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

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

    Science.gov (United States)

    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.

  10. Interaction of reactive oily bubble in flotation of bastnaesite

    Institute of Scientific and Technical Information of China (English)

    周芳; 王娄翔; 徐政和; 刘青侠; 池汝安

    2014-01-01

    To understand the flotation mechanism of bastnaesite using reactive oily bubble, the interaction between bastnaesite parti-cles and reactive oily bubbles was investigated by electro-kinetic studies, induction time measurements and small-scale flotation ex-periments. The bastnaesite flotation could be seen as a hetero-coagulation between bastnaesite particles and reactive oily bubbles which was confirmed by the zeta potential distribution and induction time measurements from pH 4.8 to pH 9.0. The small-scale flo-tation tests were consistent with the hetero-coagulation results, and showed a better flotation of reactive oily bubble than air bubble among all pH range. The interaction force between bastnaesite particles and reactive oily bubbles was evaluated by the classical DLVO theory. It indicated that the attachment could be predicted well by the DLVO theory only in a restricted pH range due to the absence of hydrophilic interaction repulsion force and chemical interaction force.

  11. Energy spectra in bubbly turbulence

    CERN Document Server

    Prakash, Vivek N; Ramos, Fabio Ernesto Mancilla; Tagawa, Yoshiyuki; Lohse, Detlef; Sun, Chao

    2013-01-01

    We conduct experiments in a turbulent bubbly flow to study the unknown nature of the transition between the classical -5/3 energy spectrum scaling for a single-phase turbulent flow and the -3 scaling for a swarm of bubbles rising in a quiescent liquid and of bubble-dominated turbulence. The bubblance parameter, b, which measures the ratio of the bubble-induced kinetic energy to the kinetic energy induced by the turbulent liquid fluctuations before bubble injection, is used to characterise the bubbly flow. We vary b from $b = \\infty$ (pseudo-turbulence) to b = 0 (single-phase flow) over 2-3 orders of magnitude: ~O(0.01, 0.1, 5) to study its effect on the turbulent energy spectrum and liquid velocity fluctuations. The experiments are conducted in a multi-phase turbulent water tunnel with air bubbles of diameters 2-4 mm and 3-5 mm. An active-grid is used to generate nearly homogeneous and isotropic turbulence in the liquid flow. The liquid speeds and gas void fractions are varied to achieve the above mentioned b...

  12. Doughnut-shaped soap bubbles

    Science.gov (United States)

    Préve, Deison; Saa, Alberto

    2015-10-01

    Soap bubbles are thin liquid films enclosing a fixed volume of air. Since the surface tension is typically assumed to be the only factor responsible for conforming the soap bubble shape, the realized bubble surfaces are always minimal area ones. Here, we consider the problem of finding the axisymmetric minimal area surface enclosing a fixed volume V and with a fixed equatorial perimeter L . It is well known that the sphere is the solution for V =L3/6 π2 , and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for V <α L3/6 π2 , with α ≈0.21 , such a surface cannot be the usual lens-shaped surface formed by the juxtaposition of two spherical caps, but is rather a toroidal surface. Practically, a doughnut-shaped bubble is known to be ultimately unstable and, hence, it will eventually lose its axisymmetry by breaking apart in smaller bubbles. Indisputably, however, the topological transition from spherical to toroidal surfaces is mandatory here for obtaining the global solution for this axisymmetric isoperimetric problem. Our result suggests that deformed bubbles with V <α L3/6 π2 cannot be stable and should not exist in foams, for instance.

  13. Radiation acoustics

    CERN Document Server

    Lyamshev, Leonid M

    2004-01-01

    Radiation acoustics is a developing field lying at the intersection of acoustics, high-energy physics, nuclear physics, and condensed matter physics. Radiation Acoustics is among the first books to address this promising field of study, and the first to collect all of the most significant results achieved since research in this area began in earnest in the 1970s.The book begins by reviewing the data on elementary particles, absorption of penetrating radiation in a substance, and the mechanisms of acoustic radiation excitation. The next seven chapters present a theoretical treatment of thermoradiation sound generation in condensed media under the action of modulated penetrating radiation and radiation pulses. The author explores particular features of the acoustic fields of moving thermoradiation sound sources, sound excitation by single high-energy particles, and the efficiency and optimal conditions of thermoradiation sound generation. Experimental results follow the theoretical discussions, and these clearl...

  14. 3D shock-bubble interaction

    Science.gov (United States)

    Hejazialhosseini, Babak; Rossinelli, Diego; Koumoutsakos, Petros

    2013-09-01

    We present a simulation for the interactions of shockwaves with light spherical density inhomogeneities. Euler equations for two-phase compressible flows are solved in a 3D uniform resolution finite volume based solver using 5th order WENO reconstructions of the primitive quantities, HLL-type numerical fluxes and 3rd order TVD time stepping scheme. In this study, a normal Mach 3 shockwave in air is directed at a helium bubble with an interface Atwood number of -0.76. We employ 4 billion cells on a supercomputing cluster and demonstrate the development of this flow until relatively late times. Shock passage compresses the bubble and deposits baroclinic vorticity on the interface. Initial distribution of the vorticity and compressions lead to the formation of an air jet, interface roll-ups and the formation of a long lasting vortical core, the white core. Compressed upstream of the bubble turns into a mixing zone and as the vortex ring distances from this mixing zone, a plume-shaped region is formed and sustained. Close observations have been reported in previous experimental works. The visualization is presented in a fluid dynamics video.

  15. Acoustic Source Localization via Time Difference of Arrival Estimation for Distributed Sensor Networks using Tera-scale Optical-Core Devices

    Energy Technology Data Exchange (ETDEWEB)

    Imam, Neena [ORNL; Barhen, Jacob [ORNL

    2009-01-01

    For real-time acoustic source localization applications, one of the primary challenges is the considerable growth in computational complexity associated with the emergence of ever larger, active or passive, distributed sensor networks. These sensors rely heavily on battery-operated system components to achieve highly functional automation in signal and information processing. In order to keep communication requirements minimal, it is desirable to perform as much processing on the receiver platforms as possible. However, the complexity of the calculations needed to achieve accurate source localization increases dramatically with the size of sensor arrays, resulting in substantial growth of computational requirements that cannot be readily met with standard hardware. One option to meet this challenge builds upon the emergence of digital optical-core devices. The objective of this work was to explore the implementation of key building block algorithms used in underwater source localization on the optical-core digital processing platform recently introduced by Lenslet Inc. This demonstration of considerably faster signal processing capability should be of substantial significance to the design and innovation of future generations of distributed sensor networks.

  16. Local Measurement of Gas-Liquid Bubbly Flow with a Double-Sensor Probe

    Institute of Scientific and Technical Information of China (English)

    孙科霞; 张鸣远; 陈学俊

    2000-01-01

    A double-sensor probe was used to measure local interfacial parameters of a gas-liquid bubbly flow in a horizontal tube. The parameters included void fraction, interfacial concentration, bubble size distribution, bubble frequency and bubble interface velocity. The authors paid special attention to the probe design and construction for minimizing measurement errors. Measures were also taken in the design of sensor ends for preventing corrosions in the flow. This is an effort to improve the current double-sensor probe technique to meet the ever-increasing needs to local varameter measurements in gas-liquid two-phase flows.

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

    Institute of Scientific and Technical Information of China (English)

    Buxuan Wang; Chunhui Li; Xiaofeng Peng

    2005-01-01

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

  18. The Fermi Bubbles: Gamma-ray, Microwave, and Polarization Signatures of Leptonic AGN Jets

    CERN Document Server

    Yang, H -Y K; Zweibel, E

    2013-01-01

    The origin of the Fermi bubbles and the microwave haze is yet to be determined. To disentangle different models requires detailed comparisons between theoretical predictions and multi-wavelength observations. Our previous simulations have demonstrated that the primary features of the Fermi bubbles could be successfully reproduced by recent jet activity from the central active galactic nucleus (AGN). In this work, we generate gamma-ray and microwave maps and spectra based on the simulated properties of cosmic rays (CRs) and magnetic fields in order to examine whether the observed bubble and haze emission could be explained by leptons contained in the AGN jets. We also investigate the model predictions of the polarization properties of the Fermi bubbles. We find that: (1) The same population of leptons can simultaneously explain the bubble and haze emission given that the magnetic fields within the bubbles are very close to the exponentially distributed ambient field, which can be explained by mixing in of the ...

  19. Near-critical-angle scattering for the characterization of clouds of bubbles: particular effects.

    Science.gov (United States)

    Onofri, Fabrice R A; Krzysiek, Mariusz A; Barbosa, Séverine; Messager, Valérie; Ren, Kuan-Fang; Mroczka, Janusz

    2011-10-20

    We report experimental investigations on the influence of various optical effects on the far-field scattering pattern produced by a cloud of optical bubbles near the critical scattering angle. Among the effects considered, there is the change of the relative refractive index of the bubbles (gas bubbles or some liquid-liquid droplets), the influence of intensity gradients induced by the laser beam intensity profile and by the spatial filtering of the collection optics, the coherent and multiple scattering effects occurring for densely packed bubbles, and the tilt angle of spheroidal optical bubbles. The results obtained herein are thought to be fundamental for the development of future works to model these effects and for the extension of the range of applicability of an inverse technique (referenced herein as the critical angle refractometry and sizing technique), which is used to determine the size distribution and composition of bubbly flows.

  20. Partial coalescence of soap bubbles

    Science.gov (United States)

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

    2015-11-01

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

  1. Bubble Growth in Lunar Basalts

    Science.gov (United States)

    Zhang, Y.

    2009-05-01

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

  2. Thermal Phase in Bubbling Geometries

    Institute of Scientific and Technical Information of China (English)

    LIU Chang-Yong

    2008-01-01

    We use matrix model to study thermal phase in bubbling half-BPS type IIB geometries with SO(4)×SO(4) symmetry.Near the horizon limit,we find that thermal vacua of bubbling geometries have disjoint parts,and each part is one kind of phase of the thermal system.We connect the thermal dynamics of bubbling geometries with one-dimensional fermions thermal system.Finally,we try to give a new possible way to resolve information loss puzzle.

  3. Fluctuations of Broadband Acoustic Signals in Shallow Water

    Science.gov (United States)

    2015-09-30

    detailed 3D environment data required as input to the model has been constructed using temperature and radar image data. Improvement has been made with...bubbles, and water column variability on acoustic wave propagation have been investigated using Parabolic Equation (PE) model and multiple raytracing ...shipboard radar images and temperature data [3], are developed to study acoustic propagation scenario with vertical and horizontal array receivers in

  4. High-speed observation of bubble cloud generation near a rigid wall by second-harmonic superimposed ultrasound.

    Science.gov (United States)

    Yoshizawa, Shin; Yasuda, Jun; Umemura, Shin-ichiro

    2013-08-01

    Cavitation bubbles are known to accelerate therapeutic effects of ultrasound. Although negative acoustic pressure is the principle factor of cavitation, positive acoustic pressure has a role for bubble cloud formation at a high intensity of focused ultrasound when cavitation bubbles provide pressure release surfaces converting the pressure from highly positive to negative. In this study, the second-harmonic was superimposed onto the fundamental acoustic pressure to emphasize either peak positive or negative pressure. The peak negative and positive pressure emphasized waves were focused on a surface of an aluminum block. Cavitation bubbles induced near the block were observed with a high-speed camera by backlight and the size of the cavitation generation region was measured from the high-speed images. The negative pressure emphasized waves showed an advantage in cavitation inception over the positive pressure emphasized waves. In the sequence of the negative pressure emphasized waves immediately followed by the positive pressure emphasized waves, cavitation bubbles were generated on the block by the former waves and the cavitation region were expanded toward the transducer in the latter waves with high reproducibility. The sequence demonstrated its potential usefulness in enhancing the effects of therapeutic ultrasound at a high acoustic intensity.

  5. Acoustic Nonlinear Behaviour of Microbubble Contrast Agent

    Institute of Scientific and Technical Information of China (English)

    俞金飞; 陆荣荣; 龚秀芬; 石涛

    2002-01-01

    We have investigated the nonlinear characteristics of a microbubble contrast agent Sonazoid R (Nycomed,Norway), including the second, third, 1/2-order, 3/2-order and 5/2-order harmonics. We have measured the 1/2-order subharmonic response to different transmission sound pressures. We have found that subharmonic signals cannot be generated until the acoustic pressure reaches a certain value, which is the most different subharmonic from high harmonics. This result is favourable for the further study of the subharmonic in the bubbly liquid.The 3/2-order ultraharmonic response to acoustic pressure was also measured.

  6. Bubble stimulation efficiency of dinoflagellate bioluminescence.

    Science.gov (United States)

    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.

  7. Study of acoustic resonance of cascades

    Science.gov (United States)

    Honjo, M.; Tominaga, T.

    Discrete sounds and vibrations from guide vanes due to acoustic resonance in the vane flow path, are experimentally investigated. Other causes of pure sounds in stationary vanes are considered, such as direct radiation from wake shedding vortices, bubble vortices or leading edges, and radial or axial modes of air columns. Two-dimensional cascade tests are performed under various conditions, and the data are compared with theoretical results of flat plate cascades. Three-dimensional ducted guide vane model tests are carried out to apply prototype guide vanes, and to confirm the resonance of the two-dimensional tests. Results show that frequency is more sensitive to chord length than pitch length, and the ratio of the fluctuation frequency to fluid sound velocity/pitch length is independent of the scale. Bubble vortices on concave surfaces or leading edges are not exciting sources; and under the limit of solidity, no exciting energy can generate acoustic resonance in correspondence to the mode.

  8. Ultrasound induced bubble clusters and tunnels in tissue-mimicking agar phantoms

    Science.gov (United States)

    Movahed, Pooya; Kreider, Wayne; Maxwell, Adam D.; Bailey, Michael R.; Freund, Jonathan B.

    2016-11-01

    Soft tissue fractionation induced by acoustic cavitation is desired for non-invasive tissue removal in histotripsy, while being a potential injury mechanism in other therapeutic ultrasound treatments such as lithotripsy. In this work, we investigate the formation of bubble clusters and tunnels in tissue-mimicking agar phantoms by focused ultrasound bursts to inform a class of damage models. Agar phantoms of different stiffness were subjected to a series of multi-cycle ultrasound bursts, using a burst wave lithotripsy (BWL) protocol, and simultaneously imaged at 200 frames per second (1 image per ultrasound burst). Some bubbles become visible in images ( 200 microns) due to the negative pressure ( 7.5 MPa) in the initial bursts, and the number of visible bubbles increases continuously during the subsequent bursts. A Rayleigh-Plesset-type bubble dynamics model, which accounts for viscoelastic confinement of agar gels, is developed. Material fatigue leading to eventual irreversible fracture-like failure in this model is proposed to explain the key observations. In addition to isolated, approximately spherical bubbles, long tunnel-like features are observed, which are seemingly lines of joined bubbles along a possible fracture or defect. The geometry of these tunnel-like features is quantified, and a physical explanation for tunnel formation is proposed in terms of bubble expansion and unstable collapse. This work was supported by NIH NIDDK Grant P01-DK043881.

  9. Measuring and modeling the bubble population produced by an underwater explosion.

    Science.gov (United States)

    Holt, Fred D; Lee Culver, R

    2011-11-01

    Underwater explosions have been studied intensively in the United States since 1941 [e.g., R. H. Cole, Underwater Explosions (Princeton University Press, Princeton, NJ, 1945), pp. 3-13]. Research to date has primarily focused on the initial shock and subsequent pressure waves caused by the oscillations of the "gas-globe" resulting from charge detonation. These phenomena have relatively short timescales (typically less than 2 s). However, after the gas-globe rises through the water column and breaks the surface, there remains behind a cloud of bubbles and perhaps debris from the explosion container which has been markedly less studied. A recent experiment measured the spatial and temporal acoustic response of the bubble cloud resulting from a 13.6 kg PBXN-111 charge detonated at 15.2 m (50 ft) depth. A directional projector was used to propagate linear frequency-modulated (5-65 kHz) and 40 kHz tonal pulses through the bubble cloud. Two hydrophone arrays were positioned so as to measure the energy lost in propagating through the bubble cloud. Three methods have been utilized to invert measurements and estimate the bubble population. The bubble population estimates have been used to develop a model for the bubble population resulting from an underwater explosion.

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

    Science.gov (United States)

    1982-04-13

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

  11. High-contrast active cavitation imaging technique based on multiple bubble wavelet transform.

    Science.gov (United States)

    Lu, Shukuan; Xu, Shanshan; Liu, Runna; Hu, Hong; Wan, Mingxi

    2016-08-01

    In this study, a unique method that combines the ultrafast active cavitation imaging technique with multiple bubble wavelet transform (MBWT) for improving cavitation detection contrast was presented. The bubble wavelet was constructed by the modified Keller-Miksis equation that considered the mutual effect among bubbles. A three-dimensional spatial model was applied to simulate the spatial distribution of multiple bubbles. The effects of four parameters on the signal-to-noise ratio (SNR) of cavitation images were evaluated, including the following: initial radii of bubbles, scale factor in the wavelet transform, number of bubbles, and the minimum inter-bubble distance. And the other two spatial models and cavitation bubble size distributions were introduced in the MBWT method. The results suggested that in the free-field experiments, the averaged SNR of images acquired by the MBWT method was improved by 7.16 ± 0.09 dB and 3.14 ± 0.14 dB compared with the values of images acquired by the B-mode and single bubble wavelet transform (SBWT) methods. In addition, in the tissue experiments, the averaged cavitation-to-tissue ratio of cavitation images acquired by the MBWT method was improved by 4.69 ± 0.25 dB and 1.74± 0.29 dB compared with that of images acquired by B-mode and SBWT methods.

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

    Science.gov (United States)

    2016-06-07

    Bubbles & Turbulence in the Ocean Surface Layer & Topographic Interactions in Coastal Waters David Farmer Institute of Ocean Sciences 9860 West...ocean surface layer , and their relationship to wave breaking, turbulence and the effects of buoyancy, gas dissolution and advection by coherent...cases, bubble size distributions were measured, along with other characteristics of the surface layer . Our approach has involved determination of the

  13. Bubble-included chocolate: relating structure with sensory response.

    Science.gov (United States)

    Haedelt, J; Beckett, S T; Niranjan, K

    2007-04-01

    Bubbles impart a very unique texture, chew, and mouth-feel to foods. However, little is known about the relationship between structure of such products and consumer response in terms of mouth-feel and eating experience. The objective of this article is to investigate the sensory properties of 4 types of bubble-containing chocolates, produced by using different gases: carbon dioxide, nitrogen, nitrous oxide, and argon. The structure of these chocolates were characterized in terms of (1) gas hold-up values determined by density measurements and (2) bubble size distribution which was measured by undertaking an image analysis of X-ray microtomograph sections. Bubble size distributions were obtained by measuring bubble volumes after reconstructing 3D images from the tomographic sections. A sensory study was undertaken by a nonexpert panel of 20 panelists and their responses were analyzed using qualitative descriptive analysis (QDA). The results show that chocolates made from the 4 gases could be divided into 2 groups on the basis of bubble volume and gas hold-up: the samples produced using carbon dioxide and nitrous oxide had a distinctly higher gas hold-up containing larger bubbles in comparison with those produced using argon and nitrogen. The sensory study also demonstrated that chocolates made with the latter were perceived to be harder, less aerated, slow to melt in the mouth, and having a higher overall flavor intensity. These products were further found to be creamier than the chocolates made by using carbon dioxide and nitrous oxide; the latter sample also showed a higher intensity of cocoa flavor.

  14. Acoustic Droplet Vaporization in Biology and Medicine

    Directory of Open Access Journals (Sweden)

    Chung-Yin Lin

    2013-01-01

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

  15. The Housing Bubble Fact Sheet

    OpenAIRE

    Dean Baker

    2005-01-01

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

  16. Bubble bean bags in shampoo

    CERN Document Server

    Kundu, Anup; Das, Gargi; Harikrishnan, G

    2011-01-01

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

  17. Effects of a tropical cyclone on the distribution of hatchery-reared black-spot tuskfish Choerodon schoenleinii determined by acoustic telemetry.

    Science.gov (United States)

    Kawabata, Y; Okuyama, J; Asami, K; Okuzawa, K; Yoseda, K; Arai, N

    2010-08-01

    The effects of a tropical cyclone on the distribution of hatchery-reared black-spot tuskfish Choerodon schoenleinii were examined using acoustic telemetry. Nine fish were released in Urasoko Bay, Ishigaki Island, Japan, in September 2006, and another nine were released in June to July 2007, before a cyclone's passing through the area in September 2007. Data for the fish released in 2006 were used as the cyclone-inexperienced group to compare their distribution pattern to that of the 2007 cyclone-experienced group. Both groups of fish were monitored for up to 150 days. Of the nine fish in each group, four (44%) and two (22%) were monitored for over 150 days in the cyclone-inexperienced and the cyclone-experienced groups, respectively. Three of the five fish that had settled in the monitoring area left the area within a few days of the cyclone event. To estimate the time of disappearance of the fish, maximum wind speed during a period of 7 days (indicating the occurrence and intensity of the tropical cyclone), fish size and release year were evaluated as explanatory variables using a Cox proportional hazards model with Akaike's information criterion. The best predictive model included the effect of maximum wind speed. One fish that left the monitoring area displayed movement patterns related to strong winds, suggesting that wind-associated strong currents swept the fish away. No relationships were found between the movement patterns of the other two fish and any physical environmental data. The daily detection periods of one of the two fish gradually decreased after the cyclone hit, and this fish eventually left the monitoring area within 3 days, suggesting that it shifted to a habitat outside the monitoring area. These results indicate that tropical cyclones have both direct and indirect effects on the distribution of hatchery-reared C. schoenleinii.

  18. Acoustic network event classification using swarm optimization

    Science.gov (United States)

    Burman, Jerry

    2013-05-01

    Classifying acoustic signals detected by distributed sensor networks is a difficult problem due to the wide variations that can occur in the transmission of terrestrial, subterranean, seismic and aerial events. An acoustic event classifier was developed that uses particle swarm optimization to perform a flexible time correlation of a sensed acoustic signature to reference data. In order to mitigate the effects from interference such as multipath, the classifier fuses signatures from multiple sensors to form a composite sensed acoustic signature and then automatically matches the composite signature with reference data. The approach can classify all types of acoustic events but is particularly well suited to explosive events such as gun shots, mortar blasts and improvised explosive devices that produce an acoustic signature having a shock wave component that is aperiodic and non-linear. The classifier was applied to field data and yielded excellent results in terms of reconstructing degraded acoustic signatures from multiple sensors and in classifying disparate acoustic events.

  19. Mechanisms of single bubble cleaning.

    Science.gov (United States)

    Reuter, Fabian; Mettin, Robert

    2016-03-01

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

  20. Studies of a novel sensor for assessing the spatial distribution of cavitation activity within ultrasonic cleaning vessels.

    Science.gov (United States)

    Zeqiri, Bajram; Hodnett, Mark; Carroll, Anthony J

    2006-01-01

    This paper describes investigations of the spatial distribution of cavitation activity generated within an ultrasonic cleaning vessel, undertaken using a novel cavitation sensor concept. The new sensor monitors high frequency acoustic emissions (>1 MHz) generated by micron-sized bubbles driven into acoustic cavitation by the applied acoustic field. Novel design features of the sensor, including its hollow, cylindrical shape, provide the sensor with spatial resolution, enabling it to associate the megahertz acoustic emissions produced by the cavitating bubbles with specific regions of space within the vessel. The performance of the new sensor has been tested using a 40 kHz ultrasonic cleaner employing four transducers and operating at a nominal electrical power of 140 W under controlled conditions. The results demonstrate the ability of the sensors to identify 'hot-spots' and 'cold-spots' in cavitation activity within the vessel, and show good qualitative agreement with an assessment of the spatial distribution of cavitation determined through erosion monitoring of thin sheets of aluminium foil. The implications of the studies for the development of reliable methods of quantifying the performance of cleaning vessels are discussed in detail.

  1. Doughnut-shaped soap bubbles

    CERN Document Server

    Preve, Deison

    2015-01-01

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

  2. Linear Stability Analysis of an Acoustically Vaporized Droplet

    Science.gov (United States)

    Siddiqui, Junaid; Qamar, Adnan; Samtaney, Ravi

    2015-11-01

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

  3. Measuring online social bubbles

    Directory of Open Access Journals (Sweden)

    Dimitar Nikolov

    2015-12-01

    Full Text Available Social media have become a prevalent channel to access information, spread ideas, and influence opinions. However, it has been suggested that social and algorithmic filtering may cause exposure to less diverse points of view. Here we quantitatively measure this kind of social bias at the collective level by mining a massive datasets of web clicks. Our analysis shows that collectively, people access information from a significantly narrower spectrum of sources through social media and email, compared to a search baseline. The significance of this finding for individual exposure is revealed by investigating the relationship between the diversity of information sources experienced by users at both the collective and individual levels in two datasets where individual users can be analyzed—Twitter posts and search logs. There is a strong correlation between collective and individual diversity, supporting the notion that when we use social media we find ourselves inside “social bubbles.” Our results could lead to a deeper understanding of how technology biases our exposure to new information.

  4. Acoustical Imaging

    CERN Document Server

    Akiyama, Iwaki

    2009-01-01

    The 29th International Symposium on Acoustical Imaging was held in Shonan Village, Kanagawa, Japan, April 15-18, 2007. This interdisciplinary Symposium has been taking place every two years since 1968 and forms a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. In the course of the years the volumes in the Acoustical Imaging Series have developed and become well-known and appreciated reference works. Offering both a broad perspective on the state-of-the-art in the field as well as an in-depth look at its leading edge research, this Volume 29 in the Series contains again an excellent collection of seventy papers presented in nine major categories: Strain Imaging Biological and Medical Applications Acoustic Microscopy Non-Destructive Evaluation and Industrial Applications Components and Systems Geophysics and Underwater Imaging Physics and Mathematics Medical Image Analysis FDTD method and Other Numerical Simulations Audience Researcher...

  5. Battlefield acoustics

    CERN Document Server

    Damarla, Thyagaraju

    2015-01-01

    This book presents all aspects of situational awareness in a battlefield using acoustic signals. It starts by presenting the science behind understanding and interpretation of sound signals. The book then goes on to provide various signal processing techniques used in acoustics to find the direction of sound source, localize gunfire, track vehicles, and detect people. The necessary mathematical background and various classification and fusion techniques are presented. The book contains majority of the things one would need to process acoustic signals for all aspects of situational awareness in one location. The book also presents array theory, which is pivotal in finding the direction of arrival of acoustic signals. In addition, the book presents techniques to fuse the information from multiple homogeneous/heterogeneous sensors for better detection. MATLAB code is provided for majority of the real application, which is a valuable resource in not only understanding the theory but readers, can also use the code...

  6. Acoustics Research

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Fisheries acoustics data are collected from more than 200 sea-days each year aboard the FRV DELAWARE II and FRV ALBATROSS IV (decommissioned) and the FSV Henry B....

  7. Room Acoustics

    Science.gov (United States)

    Kuttruff, Heinrich; Mommertz, Eckard

    The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.

  8. Acoustic surveys for juvenile anchovy in the Bay of Biscay: Abundance estimate as an indicator of the next year's recruitment and spatial distribution patterns

    KAUST Repository

    Boyra, Guillermo

    2013-08-16

    A series of acoustic surveys (JUVENA) began in 2003 targeting juvenile anchovy (Engraulis encrasicolus) in the Bay of Biscay. A specific methodology was designed for mapping and estimating juvenile abundance annually, four months after the spawning season. After eight years of the survey, a consistent picture of the spatial pattern of the juvenile anchovy has emerged. Juveniles show a vertical and horizontal distribution pattern that depends on size. The younger individuals are found isolated from other species in waters closer to the surface, mainly off the shelf within the mid-southern region of the bay. The largest juveniles are usually found deeper and closer to the shore in the company of adult anchovy and other pelagic species. In these eight years, the survey has covered a wide range of juvenile abundances, and the estimates show a significant positive relationship between the juvenile biomasses and the one-year-old recruits of the following year. This demonstrates that the JUVENA index provides an early indication of the strength of next year\\'s recruitment to the fishery and can therefore be used to improve the management advice for the fishery of this short-lived species. © 2013 International Council for the Exploration of the Sea.

  9. A boundary element method for the simulation of non-spherical bubbles and their interactions near a free surface

    Institute of Scientific and Technical Information of China (English)

    Zhang-Rui Li; Lei Sun; Zhi Zong; Jing Dong

    2012-01-01

    The basic principle and numerical technique for simulating two three-dimensional bubbles near a free surface are studied in detail by using boundary element method.The singularities of influence coefficient matrix are eliminated using coordinate transformation and so-called 4π rule.The solid angle for the open surface is treated in direct method based on its definition.Several kinds of configurations for the bubbles and free surface have been investigated.The pressure contours during the evolution of bubbles are obtained in our model and can better illuminate the mechanism underlying the motions of bubbles and free surface.The bubble dynamics and their interactions have close relation with the standoff distances,buoyancy parameters and initial sizes of bubbles.Completely different bubble shapes,free surface motions,jetting patterns and pressure distributions under different parameters can be observed in our model,as demonstrated in our calculation results.

  10. FEASTING BLACK HOLE BLOWS BUBBLES

    Science.gov (United States)

    2002-01-01

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

  11. Acoustic Model of the Remnant Bubble Cloud from Underwater Explosion

    Science.gov (United States)

    2012-11-01

    oceanography, Sydney, Academic Press. Underwater Explosion Research 1950, Office of Naval Re- search, Washington, D.C., Vol. 2. Wilcox, DC 1994, Turbulence Modeling for CFD, DCW Industries, Inc., La Canada CA.

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

    Science.gov (United States)

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

    2012-01-01

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

  13. Experiments on turbulent diffusion of the gaseous phase in rectangular bubble column using image processing

    Energy Technology Data Exchange (ETDEWEB)

    Alexander Zaruba; Eckhard Krepper; Horst-Michael Prasser [Forschungszentrum Rossendorf e.V., P.O.Box 510119, 01314 Dresden (Germany)

    2005-07-01

    Full text of publication follows: The paper describes the application of high-speed video observation combined with digital image processing techniques to measure the turbulent diffusion coefficient of the gaseous phase in a bubble column. The test channel is a rectangular bubble column with a cross-section of 100 x 20 mm and a height of 1500 mm. Sequences of the images were taken at different heights of the column with a high-speed video system. A diffuse illumination from the backside of the column was found to produce bubble images with a characteristic bright spot in the center. This bright spot was used for a bubble tracking that tolerates some overlapping of the bubbles. This allows to enhance the applicability of the bubble tracking to higher gas fractions compared to the tracking of the entire bubble shadows. After the bubble trajectories were extracted from the image sequence, the lateral displacement of bubbles between two virtual horizontal measuring planes was calculated for each bubble that crosses both planes. This lateral displacement is caused by the turbulent fluctuations of the bubble velocity. It is analyzed statistically by constructing probability density functions of the lateral displacement, which can be well described by Gaussian standard distributions. The dispersion coefficient of the standard distributions that were fitted to the experimental data shows a linear dependency from the square-root of the vertical distance between the two control planes, which supports the assumption of a diffusion model for the lateral displacement. Deviations from the linear dependency were identified to be the result of deterministic oscillatory motions of the rising bubbles. This effect is typical for low-viscosity liquids, while the bubble oscillations are damped at higher viscosities. Results are presented for different gas flow rates (superficial gas velocity ranged from 0.5 to 4 mm/s), different primary bubble sizes produced by a variation of the

  14. Technical Note: Detection of gas bubble leakage via correlation of water column multibeam images

    Directory of Open Access Journals (Sweden)

    J. Schneider von Deimling

    2012-03-01

    Full Text Available Hydroacoustic detection of natural gas release from the seafloor has been conducted in the past by using singlebeam echosounders. In contrast, modern multibeam swath mapping systems allow much wider coverage, higher resolution, and offer 3-D spatial correlation. Up to the present, the extremely high data rate hampers water column backscatter investigations and more sophisticated visualization and processing techniques are needed. Here, we present water column backscatter data acquired with a 50 kHz prototype multibeam system over a period of 75 seconds. Display types are of swath-images as well as of a "re-sorted" singlebeam presentation. Thus, individual and/or groups of gas bubbles rising from the 24 m deep seafloor clearly emerge in the acoustic images, making it possible to estimate rise velocities. A sophisticated processing scheme is introduced to identify those rising gas bubbles in the hydroacoustic data. We apply a cross-correlation technique adapted from particle imaging velocimetry (PIV to the acoustic backscatter images. Temporal and spatial drift patterns of the bubbles are assessed and are shown to match very well to measured and theoretical rise patterns. The application of this processing to our field data gives clear results with respect to unambiguous bubble detection and remote bubble rise velocimetry. The method can identify and exclude the main source of misinterpretations, i.e. fish-mediated echoes. Although image-based cross-correlation techniques are well known in the field of fluid mechanics for high resolution and non-inversive current flow field analysis, we present the first application of this technique as an acoustic bubble detector.

  15. Acoustic characterization of single ultrasound contrast agent microbubbles

    NARCIS (Netherlands)

    Sijl, Jeroen; Gaud, Emmanuel; Frinking, Peter J.A.; Arditi, Marcel; Jong, de Nico; Lohse, Detlef; Versluis, Michel

    2008-01-01

    Individual ultrasound contrast agent microbubbles (BR14) were characterized acoustically. The bubbles were excited at a frequency of 2 MHz and at peak-negative pressure amplitudes of 60 and 100 kPa. By measuring the transmit and receive transfer functions of both the transmit and receive transduce

  16. Energy concentration and positional stability of sonoluminescent bubbles in sulfuric acid for different static pressures.

    Science.gov (United States)

    Rosselló, Juan Manuel; Dellavale, Damián; Bonetto, Fabián José

    2013-09-01

    In this study we report several experimental and numerical results on the influence of static pressure (P_{0}) over the main parameters in single bubble sonoluminescence (SBSL), using a sulfuric acid aqueous solution (SA) with low concentrations of argon gas dissolved. Bifrequency driving was used in the experiments to enhance spatial stability of the bubbles. The experimental results were compared with simulations provided by a numerical code that models the radial dynamics of the bubbles. The results showed that an increase on the static pressure of the system shifts the Bjerknes instability threshold, allowing the bubble to access higher acoustic pressures (P_{Ac}^{}). Furthermore, a decrease in the measured ambient radius R_{0} and the calculated relative gas concentration c_{∞}/c_{0} were observed. A notorious increment in the bubble collapse violence and energy focusing for P_{0} above 1 bar was achieved. These were mainly indicated by the growth of the bubble expansion ratio (R_{max}/R_{0}), the bubble mechanical energy density, and the maximum bubble wall velocity dR/dt. In agreement with the previous statement, the maximum temperature during the bubble collapse predicted by the model is augmented as well. The use of different harmonics in the ultrasound pressure field regarding energy focusing is also discussed. Finally, we analyzed the stability regions of the R_{0}-P_{Ac}^{} parameter space via numerical predictions for P_{0} above the measured, identifying the shape instabilities as the main limiting agent to obtain further energy concentration in SA systems at high static pressures.

  17. Study of air-liquid flow patterns in hydrocyclone enhanced by air bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Z.; Wang, H.; Tu, S.T. [School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai (China)

    2009-01-15

    In order to improve the oil-water separation efficiency of a hydrocyclone, a new process utilizing air bubbles has been developed to enhance separation performance. Using the two-component phase Doppler particle analyzer (PDPA) technique, the velocities of two phases, air and liquid, and air bubble diameter were measured in a hydrocyclone. The air-liquid mixing pump can produce 15 to 60 {mu}m-diameter air bubbles in water. There is an optimum air-liquid ratio for oil-water separation of a hydrocyclone enhanced by air bubbles. An air core occurs in the hydrocyclone when the air-liquid ratio is more than 1 %. The velocities of air bubbles have a similar flow pattern to the water phase. The axial and tangential velocity differences of the air bubbles at different air-liquid ratio are greater near the wall and near the core of the hydrocyclone. The measured results show that the size distribution of the air bubbles produced by the air-liquid mixing pump is beneficial to the process where air bubbles capture oil droplets in the hydrocyclone. These studies are helpful to understand the separation mechanism of a hydrocyclone enhanced by air bubbles. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  18. Bubble sorting in pinched microchannels for ultrasound contrast agent enrichment

    NARCIS (Netherlands)

    Kok, M.P.; Segers, T.J.; Versluis, M.

    2015-01-01

    Ultrasound contrast agent (UCA) suspensions contain encapsulated microbubbles with a wide size distribution, with radii between 1 and 10 μm. Medical transducers generally operate at a narrow frequency bandwidth, severely limiting the fraction of bubbles that resonates to the driving ultrasound. Thus

  19. On Collisionless Damping of Ion Acoustic Waves

    DEFF Research Database (Denmark)

    Jensen, Vagn Orla; Petersen, P.I.

    1973-01-01

    Exact theoretical treatments show that the damping of ion acoustic waves in collisionless plasmas does not vanish when the derivative of the undisturbed distribution function at the phase velocity equals zero.......Exact theoretical treatments show that the damping of ion acoustic waves in collisionless plasmas does not vanish when the derivative of the undisturbed distribution function at the phase velocity equals zero....

  20. The significance of multiple scattering in bubble measurements near the sea surface

    DEFF Research Database (Denmark)

    Jensen, Leif Bjørnø; Bjørnø, Irina K.

    1996-01-01

    improvement of the scattering theory [C. Feuillade, J. Acoust. Soc. Am. 98, 1178–1190 (1995)], predicts a downward frequency shift and a suppression of the attenuation peak. His results emphasize the importance of the still unsolved problem on proximity thresholds for influence of multiple scattering in terms...... of bubble plume qualities. Available, but still unconfirmed, experimental data show the significance of multiple scattering in bubble plumes having void fractions >~0.22%. This paper forms an attempt to illuminate and solve the proximity threshold question, forming the basis for the significance...