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Sample records for acoustic cavitation bubbles

  1. Acoustic Shielding by Cavitation Bubbles in Shock Wave Lithotripsy (SWL)

    NASA Astrophysics Data System (ADS)

    Pishchalnikov, Yuri A.; McAteer, James A.; Bailey, Michael R.; Pishchalnikova, Irina V.; Williams, James C.; Evan, Andrew P.

    2006-05-01

    Lithotripter pulses (˜7-10 μs) initiate the growth of cavitation bubbles, which collapse hundreds of microseconds later. Since the bubble growth-collapse cycle trails passage of the pulse, and is ˜1000 times shorter than the pulse interval at clinically relevant firing rates, it is not expected that cavitation will affect pulse propagation. However, pressure measurements with a fiber-optic hydrophone (FOPH-500) indicate that bubbles generated by a pulse can, indeed, shield the propagation of the negative tail. Shielding was detected within 1 μs of arrival of the negative wave, contemporaneous with the first observation of expanding bubbles by high-speed camera. Reduced negative pressure was observed at 2 Hz compared to 0.5 Hz firing rate, and in water with a higher content of dissolved gas. We propose that shielding of the negative tail can be attributed to loss of acoustic energy into the expansion of cavitation bubbles.

  2. Controlled permeation of cell membrane by single bubble acoustic cavitation.

    PubMed

    Zhou, Y; Yang, K; Cui, J; Ye, J Y; Deng, C X

    2012-01-10

    Sonoporation is the membrane disruption generated by ultrasound and has been exploited as a non-viral strategy for drug and gene delivery. Acoustic cavitation of microbubbles has been recognized to play an important role in sonoporation. However, due to the lack of adequate techniques for precise control of cavitation activities and real-time assessment of the resulting sub-micron process of sonoporation, limited knowledge has been available regarding the detail processes and correlation of cavitation with membrane disruption at the single cell level. In the current study, we developed a combined approach including optical, acoustical, and electrophysiological techniques to enable synchronized manipulation, imaging, and measurement of cavitation of single bubbles and the resulting cell membrane disruption in real-time. Using a self-focused femtosecond laser and high frequency ultrasound (7.44MHz) pulses, a single microbubble was generated and positioned at a desired distance from the membrane of a Xenopus oocyte. Cavitation of the bubble was achieved by applying a low frequency (1.5MHz) ultrasound pulse (duration 13.3 or 40μs) to induce bubble collapse. Disruption of the cell membrane was assessed by the increase in the transmembrane current (TMC) of the cell under voltage clamp. Simultaneous high-speed bright field imaging of cavitation and measurements of the TMC were obtained to correlate the ultrasound-generated bubble activities with the cell membrane poration. The change in membrane permeability was directly associated with the formation of a sub-micrometer pore from a local membrane rupture generated by bubble collapse or bubble compression depending on ultrasound amplitude and duration. The impact of the bubble collapse on membrane permeation decreased rapidly with increasing distance (D) between the bubble (diameter d) and the cell membrane. The effective range of cavitation impact on membrane poration was determined to be D/d=0.75. The maximum mean

  3. Evidence for liquid phase reactions during single bubble acoustic cavitation.

    PubMed

    Troia, A; Madonna Ripa, D; Lago, S; Spagnolo, R

    2004-07-01

    We extended the recent experiment by Lepoint et al. [Sonochemistry and Sonoluminescence, NATO ASI Series, Series C 524, Kluwer Academic Publishers, Dordrecht/Boston/London, 1999, p. 285], involving a so-called single bubble sonochemistry process, to a three-phase system. We have found experimental evidence that a single cavitating bubble can activate the oxidation of I- ions after the injection of a CCl4 liquid drop in the bubble trapping apparatus. The solvent drop (CCl4 is almost water insoluble) is pushed towards the bubble position and forms a thin film on the bubble surface. When the acoustic pressure drive is increased above 100 kPa, the three-phase system gives rise to a dark filament, indicating the complexation reaction between starch (added to the water phase) and I2. I2 species is the product of surface reactions involving bubble-induced decomposition of CCl4. Further increase of the acoustic drive causes the thin CCl4 film to separate from the bubble and stops I2 production. The study of the chemical activity of this three-phase system could give new advances on dynamics of the bubble collapse. PMID:15157862

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

    PubMed Central

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Cavitation bubbles initiated by focused ultrasound waves are investigated through experiments and modeling. Pulses of focused ultrasound with a frequency of 335 kHz and a peak negative pressure of 8 MPa is generated in a water tank by a piezoelectric transducer to initiate cavitation. The pressure field is modeled by solving the Euler equations and used to simulate single bubble oscillation. The characteristics of cavitation bubbles observed by highspeed photography qualitatively agree with the simulation results. Finally, bubble clouds are captured using acoustic B-mode imaging that works synchronized with high-speed photography.

  6. Quantification of optison bubble size and lifetime during sonication dominant role of secondary cavitation bubbles causing acoustic bioeffects.

    PubMed

    Kamaev, Pavel P; Hutcheson, Joshua D; Wilson, Michelle L; Prausnitz, Mark R

    2004-04-01

    Acoustic cavitation has been shown to deliver molecules into viable cells, which is of interest for drug and gene delivery applications. To address mechanisms of these acoustic bioeffects, this work measured the lifetime of albumin-stabilized cavitation bubbles (Optison) and correlated it with desirable (intracellular uptake of molecules) and undesirable (loss of cell viability) bioeffects. Optison was exposed to 500 kHz ultrasound (acoustic pressures of 0.6-3.0 MPa and energy exposures of 0.2-200 J/cm2) either with or without the presence of DU145 prostate cancer cells (10(6) cells/ml) bathed in calcein, a cell-impermeant tracer molecule. Bubble lifetime was determined using a Coulter counter and flow cytometer, while bioeffects were evaluated by flow cytometry. The lifetime of Optison cavitation nuclei was found to decrease and bioeffects (molecular uptake and loss of cell viability) were found to increase with increasing acoustic energy exposure. These bioeffects correlated well with the disappearance of bubbles, suggesting that contrast agent destruction either directly or indirectly affected cells, probably involving unstabilized cavitation nuclei created upon the destruction of Optison. Because Optison solutions presonicated to destroy all detectable bubbles also caused significant bioeffects, the indirect mechanism involving secondary cavitation bubbles is more likely. PMID:15101659

  7. Effect of static pressure on acoustic energy radiated by cavitation bubbles in viscous liquids under ultrasound.

    PubMed

    Yasui, Kyuichi; Towata, Atsuya; Tuziuti, Toru; Kozuka, Teruyuki; Kato, Kazumi

    2011-11-01

    The effect of static pressure on acoustic emissions including shock-wave emissions from cavitation bubbles in viscous liquids under ultrasound has been studied by numerical simulations in order to investigate the effect of static pressure on dispersion of nano-particles in liquids by ultrasound. The results of the numerical simulations for bubbles of 5 μm in equilibrium radius at 20 kHz have indicated that the optimal static pressure which maximizes the energy of acoustic waves radiated by a bubble per acoustic cycle increases as the acoustic pressure amplitude increases or the viscosity of the solution decreases. It qualitatively agrees with the experimental results by Sauter et al. [Ultrason. Sonochem. 15, 517 (2008)]. In liquids with relatively high viscosity (∼200 mPa s), a bubble collapses more violently than in pure water when the acoustic pressure amplitude is relatively large (∼20 bar). In a mixture of bubbles of different equilibrium radius (3 and 5 μm), the acoustic energy radiated by a 5 μm bubble is much larger than that by a 3 μm bubble due to the interaction with bubbles of different equilibrium radius. The acoustic energy radiated by a 5 μm bubble is substantially increased by the interaction with 3 μm bubbles. PMID:22087995

  8. The penetration of acoustic cavitation bubbles into micrometer-scale cavities.

    PubMed

    Vaidya, Haresh Anant; Ertunç, Özgür; Lichtenegger, Thomas; Delgado, Antonio; Skupin, Andreas

    2016-04-01

    The penetration of acoustically induced cavitation bubbles in micrometer-scale cavities is investigated experimentally by means of high-speed photography and acoustic measurements. Micrometer-scale cavities of different dimensions (width=40 μm, 80 μm, 10 mm and depth=50 μm) are designed to replicate the cross section of microvias in a PCB. The aim here is to present a method for enhancing mass transfer due to the penetration of bubbles in such narrow geometries under the action of ultrasound. The micrometer-scale cavities are placed in a test-cell filled with water and subjected to an ultrasound excitation at 75 kHz. A cavitation bubble cluster is generated at the mouth of the cavity which acts as a continuous source of bubbles that penetrate into the cavity. The radial oscillation characteristics and translation of these bubbles are investigated in detail here. It is observed that the bubbles arrange themselves into streamer-like structures inside the cavity. Parameters such as bubble population and size distribution and their correlation with the phase of the incident ultrasound radiation are investigated in detail here. This provides a valuable insight into the dynamics of bubbles in narrow confined spaces. Mass transfer investigations show that fresh liquid can be continuously introduced in the cavities under the action of ultrasound. Our findings may have important consequences in optimizing the filling processes for microvias with high aspect ratios. PMID:26763751

  9. Transcranial ultrasonic therapy based on time reversal of acoustically induced cavitation bubble signature

    PubMed Central

    Gâteau, Jérôme; Marsac, Laurent; Pernot, Mathieu; Aubry, Jean-Francois; Tanter, Mickaël; Fink, Mathias

    2010-01-01

    Brain treatment through the skull with High Intensity Focused Ultrasound (HIFU) can be achieved with multichannel arrays and adaptive focusing techniques such as time-reversal. This method requires a reference signal to be either emitted by a real source embedded in brain tissues or computed from a virtual source, using the acoustic properties of the skull derived from CT images. This non-invasive computational method focuses with precision, but suffers from modeling and repositioning errors that reduce the accessible acoustic pressure at the focus in comparison with fully experimental time-reversal using an implanted hydrophone. In this paper, this simulation-based targeting has been used experimentally as a first step for focusing through an ex vivo human skull at a single location. It has enabled the creation of a cavitation bubble at focus that spontaneously emitted an ultrasonic wave received by the array. This active source signal has allowed 97%±1.1% of the reference pressure (hydrophone-based) to be restored at the geometrical focus. To target points around the focus with an optimal pressure level, conventional electronic steering from the initial focus has been combined with bubble generation. Thanks to step by step bubble generation, the electronic steering capabilities of the array through the skull were improved. PMID:19770084

  10. Observation of Microhollows Produced by Bubble Cloud Cavitation

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Miwa, Takashi

    2012-07-01

    When an ultrasonic wave with sound pressure less than the threshold level of bubble destruction irradiates microbubbles, the microbubbles aggregate by an acoustic radiation force and form bubble clouds. The cavitation of bubble clouds produces a large number of microhollows (microdips) on the flow channel wall. In this study, microhollow production by bubble cloud cavitation is evaluated using a blood vessel phantom made of N-isopropylacrylamide (NIPA) gel. Microbubble dynamics in bubble cloud cavitation is observed by a microscope with a short pulse light emitted diode (LED) light source. Microhollows produced on the flow channel wall are evaluated by a confocal laser microscope with a water immersion objective. It is observed that a mass of low-density bubbles (bubble mist) is formed by bubble cloud cavitation. The spatial correlation between the bubble mist and the microhollows shows the importance of the bubble mist in microhollow production by bubble cloud cavitation.

  11. Mechanics of collapsing cavitation bubbles.

    PubMed

    van Wijngaarden, Leen

    2016-03-01

    A brief survey is given of the dynamical phenomena accompanying the collapse of cavitation bubbles. The discussion includes shock waves, microjets and the various ways in which collapsing bubbles produce damage. PMID:25890856

  12. Discrete Bubble Modeling for Cavitation Bubbles

    NASA Astrophysics Data System (ADS)

    Choi, Jin-Keun; Chahine, Georges; Hsiao, Chao-Tsung

    2007-03-01

    Dynaflow, Inc. has conducted extensive studies on non-spherical bubble dynamics and interactions with solid and free boundaries, vortical flow structures, and other bubbles. From these studies, emerged a simplified Surface Averaged Pressure (SAP) spherical bubble dynamics model and a Lagrangian bubble tracking scheme. In this SAP scheme, the pressure and velocity of the surrounding flow field are averaged on the bubble surface, and then used for the bubble motion and volume dynamics calculations. This model is implemented using the Fluent User Defined Function (UDF) as Discrete Bubble Model (DBM). The Bubble dynamics portion can be solved using an incompressible liquid modified Rayleigh-Plesset equation or a compressible liquid modified Gilmore equation. The Discrete Bubble Model is a very suitable tool for the studies on cavitation inception of foils and turbo machinery, bubble nuclei effects, noise from the bubbles, and can be used in many practical problems in industrial and naval applications associated with flows in pipes, jets, pumps, propellers, ships, and the ocean. Applications to propeller cavitation, wake signatures of waterjet propelled ships, bubble-wake interactions, modeling of cavitating jets, and bubble entrainments around a ship will be presented.

  13. Acoustic cavitation bubbles in the kidney induced by focused shock waves in extracorporeal shock wave lithotripsy (ESWL)

    NASA Astrophysics Data System (ADS)

    Kuwahara, M.; Ioritani, N.; Kambe, K.; Taguchi, K.; Saito, T.; Igarashi, M.; Shirai, S.; Orikasa, S.; Takayama, K.

    1990-07-01

    On an ultrasonic imaging system a hyperechoic region was observed in a focal area of fucused shock waves in the dog kidney. This study was performed to learn whether cavitation bubbles are responsible for this hyperechoic region. The ultrasonic images in water of varying temperatures were not markedly different. In the flowing stream of distilled water, the stream was demonstrated as a hyperechoic region only with a mixture of air bubbles. Streams of 5%-50% glucose solutions were also demonstrated as a hyperechoic region. However, such concentration changes in living tissue, as well as thermal changes, are hardly thought to be induced. The holographic interferometry showed that the cavitation bubbles remained for more than 500 msec. in the focal area in water. This finding indicate that the bubble can remain for longer period than previously supposed. These results support the contentions that cavitation bubbles are responsible for the hyperechoic region in the kidney in situ.

  14. Theoretical model of ice nucleation induced by acoustic cavitation. Part 1: Pressure and temperature profiles around a single bubble.

    PubMed

    Cogné, C; Labouret, S; Peczalski, R; Louisnard, O; Baillon, F; Espitalier, F

    2016-03-01

    This paper deals with the inertial cavitation of a single gas bubble in a liquid submitted to an ultrasonic wave. The aim was to calculate accurately the pressure and temperature at the bubble wall and in the liquid adjacent to the wall just before and just after the collapse. Two different approaches were proposed for modeling the heat transfer between the ambient liquid and the gas: the simplified approach (A) with liquid acting as perfect heat sink, the rigorous approach (B) with liquid acting as a normal heat conducting medium. The time profiles of the bubble radius, gas temperature, interface temperature and pressure corresponding to the above models were compared and important differences were observed excepted for the bubble size. The exact pressure and temperature distributions in the liquid corresponding to the second model (B) were also presented. These profiles are necessary for the prediction of any physical phenomena occurring around the cavitation bubble, with possible applications to sono-crystallization. PMID:26044460

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

    PubMed

    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. PMID:16571378

  16. Robust acoustic wave manipulation of bubbly liquids

    NASA Astrophysics Data System (ADS)

    Gumerov, N. A.; Akhatov, I. S.; Ohl, C.-D.; Sametov, S. P.; Khazimullin, M. V.; Gonzalez-Avila, S. R.

    2016-03-01

    Experiments with water-air bubbly liquids when exposed to acoustic fields of frequency ˜100 kHz and intensity below the cavitation threshold demonstrate that bubbles ˜30 μm in diameter can be "pushed" away from acoustic sources by acoustic radiation independently from the direction of gravity. This manifests formation and propagation of acoustically induced transparency waves (waves of the bubble volume fraction). In fact, this is a collective effect of bubbles, which can be described by a mathematical model of bubble self-organization in acoustic fields that matches well with our experiments.

  17. Cavitation inception from bubble nuclei.

    PubMed

    Mørch, K A

    2015-10-01

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

  18. On thermonuclear processes in cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Nigmatulin, R. I.; Lahey, R. T., Jr.; Taleyarkhan, R. P.; West, C. D.; Block, R. C.

    2014-09-01

    The theoretical and experimental foundations of so-called bubble nuclear fusion are reviewed. In the nuclear fusion process, a spherical cavitation cluster ˜ 10-2 m in diameter is produced of spherical bubbles at the center of a cylindrical chamber filled with deuterated acetone using a focused acoustic field having a resonant frequency of about 20 kHz. The acoustically-forced bubbles effectuate volume oscillations with sharp collapses during the compression stage. At the final stages of collapse, the bubble cluster emits 2.5 MeV D-D fusion neutron pulses at a rate of ˜ 2000 per second. The neutron yield is ˜ 10^5 s -1. In parallel, tritium nuclei are produced at the same yield. It is shown numerically that, for bubbles having sufficient molecular mass, spherical shock waves develop in the center of the cluster and that these spherical shock waves (microshocks) produce converging shocks within the interior bubbles, which focus energy on the centers of the bubbles. When these shock waves reflect from the centers of the bubbles, extreme conditions of temperature ( ˜ 10^8 K) and density ( ˜ 10^4 kg m -3) arise in a (nano)spherical region ( ˜ 10-7 m in size) that last for ˜ 10-12 s, during which time about ten D-D fusion neutrons and tritium nuclei are produced in the region. A paradoxical result in our experiments is that it is bubble cluster (not streamer) cavitation and the sufficiently high molecular mass of (and hence the low sound speed in) D-acetone ( C3D6O) vapor (as compared, for example, to deuterated water D2O) which are necessary conditions for the formation of convergent spherical microshock waves in central cluster bubbles. It is these waves that allow the energy to be sufficiently focused in the nanospherical regions near the bubble centers for fusion events to occur. The criticism to which the concept of 'bubble fusion' has been subjected in the literature, in particular, most recently in Uspekhi Fizicheskikh Nauk (Physics - Uspekhi) journal, is

  19. Particle motion induced by bubble cavitation.

    PubMed

    Poulain, Stéphane; Guenoun, Gabriel; Gart, Sean; Crowe, William; Jung, Sunghwan

    2015-05-29

    Cavitation bubbles induce impulsive forces on surrounding substrates, particles, or surfaces. Even though cavitation is a traditional topic in fluid mechanics, current understanding and studies do not capture the effect of cavitation on suspended objects in fluids. In the present work, the dynamics of a spherical particle due to a cavitation bubble is experimentally characterized and compared with an analytical model. Three phases are observed: the growth of the bubble where the particle is pushed away, its collapse where the particle approaches the bubble, and a longer time scale postcollapse where the particle continues to move toward the collapsed bubble. The particle motion in the longer time scale presumably results from the asymmetric cavitation evolution at an earlier time. Our theory considering the asymmetric bubble dynamics shows that the particle velocity strongly depends on the distance from the bubble as an inverse-fourth-power law, which is in good agreement with our experimentation. This study sheds light on how small free particles respond to cavitation bubbles in fluids. PMID:26066438

  20. Numerical simulation of cavitation bubble dynamics induced by ultrasound waves in a high frequency reactor.

    PubMed

    Servant, G; Caltagirone, J P; Gérard, A; Laborde, J L; Hita, A

    2000-10-01

    The use of high frequency ultrasound in chemical systems is of major interest to optimize chemical procedures. Characterization of an open air 477 kHz ultrasound reactor shows that, because of the collapse of transient cavitation bubbles and pulsation of stable cavitation bubbles, chemical reactions are enhanced. Numerical modelling is undertaken to determine the spatio-temporal evolution of cavitation bubbles. The calculus of the emergence of cavitation bubbles due to the acoustic driving (by taking into account interactions between the sound field and bubbles' distribution) gives a cartography of bubbles' emergence within the reactor. Computation of their motion induced by the pressure gradients occurring in the reactor show that they migrate to the pressure nodes. Computed bubbles levitation sites gives a cartography of the chemical activity of ultrasound. Modelling of stable cavitation bubbles' motion induced by the motion of the liquid gives some insight on degassing phenomena. PMID:11062879

  1. Acoustic bubble removal method

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  2. Hysteresis of inertial cavitation activity induced by fluctuating bubble size distribution.

    PubMed

    Muleki Seya, Pauline; Desjouy, Cyril; Béra, Jean-Christophe; Inserra, Claude

    2015-11-01

    Amongst the variety of complex phenomena encountered in nonlinear physics, a hysteretic effect can be expected on ultrasound cavitation due to the intrinsic nonlinearity of bubble dynamics. When applying successive ultrasound shots for increasing and decreasing acoustic intensities, a hysteretic behaviour is experimentally observed on inertial cavitation activity, with a loop area sensitive to the inertial cavitation threshold. To get a better insight of the phenomena underlying this hysteretic effect, the evolution of the bubble size distribution is studied numerically by implementing rectified diffusion, fragmentation process, rising and dissolution of bubbles from an initial bubble size distribution. When applying increasing and decreasing acoustic intensities, the numerical distribution exhibits asymmetry in bubble number and distribution. The resulting inertial cavitation activity is assessed through the numerical broadband noise of the emitted acoustic radiation of the bubble cloud dynamics. This approach allows obtaining qualitatively the observed hysteretic effect and its interest in terms of control is discussed. PMID:26186844

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Quantitative assessment of reactive oxygen sonochemically generated by cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Yasuda, Jun; Miyashita, Takuya; Taguchi, Kei; Yoshizawa, Shin; Umemura, Shin-ichiro

    2015-07-01

    Acoustic cavitation bubbles can induce not only a thermal bioeffect but also a chemical bioeffect. When cavitation bubbles collapse and oscillate violently, they produce reactive oxygen species (ROS) that cause irreversible changes to the tissue. A sonosensitizer can promote such ROS generation. A treatment method using a sonosensitizer is called sonodynamic treatment. Rose bengal (RB) is one of the sonosensitizers whose in vivo and in vitro studies have been reported. In sonodynamic treatment, it is important to produce ROS at a high efficiency. For the efficient generation of ROS, a triggered high-intensity focused ultrasound (HIFU) sequence has been proposed. In this study, cavitation bubbles were generated in a chamber where RB solution was sealed, and a high-speed camera captured the behavior of these cavitation bubbles. The amount of ROS was also quantified by a potassium iodide (KI) method and compared with high-speed camera pictures to investigate the effectiveness of the triggered HIFU sequence. As a result, ROS could be obtained efficiently by this sequence.

  5. Acoustic methods for cavitation mapping in biomedical applications

    NASA Astrophysics Data System (ADS)

    Wan, M.; Xu, S.; Ding, T.; Hu, H.; Liu, R.; Bai, C.; Lu, S.

    2015-12-01

    In recent years, cavitation is increasingly utilized in a wide range of applications in biomedical field. Monitoring the spatial-temporal evolution of cavitation bubbles is of great significance for efficiency and safety in biomedical applications. In this paper, several acoustic methods for cavitation mapping proposed or modified on the basis of existing work will be presented. The proposed novel ultrasound line-by-line/plane-by-plane method can depict cavitation bubbles distribution with high spatial and temporal resolution and may be developed as a potential standard 2D/3D cavitation field mapping method. The modified ultrafast active cavitation mapping based upon plane wave transmission and reception as well as bubble wavelet and pulse inversion technique can apparently enhance the cavitation to tissue ratio in tissue and further assist in monitoring the cavitation mediated therapy with good spatial and temporal resolution. The methods presented in this paper will be a foundation to promote the research and development of cavitation imaging in non-transparent medium.

  6. Intensely oscillating cavitation bubble in microfluidics

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  7. Nucleus factory on cavitation bubble for amyloid β fibril

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  8. Nucleus factory on cavitation bubble for amyloid β fibril

    PubMed Central

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

    2016-01-01

    Structural evolution from monomer to fibril of amyloid β peptide is related to pathogenic mechanism of Alzheimer disease, and its acceleration is a long-running problem in drug development. This study reveals that ultrasonic cavitation bubbles behave as catalysts for nucleation of the peptide: The nucleation reaction is highly dependent on frequency and pressure of acoustic wave, and we discover an optimum acoustical condition, at which the reaction-rate constant for nucleation is increased by three-orders-of magnitudes. A theoretical model is proposed for explaining highly frequency and pressure dependent nucleation reaction, where monomers are captured on the bubble surface during its growth and highly condensed by subsequent bubble collapse, so that they are transiently exposed to high temperatures. Thus, the dual effects of local condensation and local heating contribute to dramatically enhance the nucleation reaction. Our model consistently reproduces the frequency and pressure dependences, supporting its essential applicability. PMID:26912021

  9. Nucleus factory on cavitation bubble for amyloid β fibril.

    PubMed

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

    2016-01-01

    Structural evolution from monomer to fibril of amyloid β peptide is related to pathogenic mechanism of Alzheimer disease, and its acceleration is a long-running problem in drug development. This study reveals that ultrasonic cavitation bubbles behave as catalysts for nucleation of the peptide: The nucleation reaction is highly dependent on frequency and pressure of acoustic wave, and we discover an optimum acoustical condition, at which the reaction-rate constant for nucleation is increased by three-orders-of magnitudes. A theoretical model is proposed for explaining highly frequency and pressure dependent nucleation reaction, where monomers are captured on the bubble surface during its growth and highly condensed by subsequent bubble collapse, so that they are transiently exposed to high temperatures. Thus, the dual effects of local condensation and local heating contribute to dramatically enhance the nucleation reaction. Our model consistently reproduces the frequency and pressure dependences, supporting its essential applicability. PMID:26912021

  10. A Study of Cavitation-Ignition Bubble Combustion

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet; Jacqmin, David A.

    2005-01-01

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

  11. Multiscale Modeling of Cavitating Bubbly Flows

    NASA Astrophysics Data System (ADS)

    Ma, J.; Hsiao, C.-T.; Chahine, G. L.

    2013-03-01

    Modeling of cavitating bubbly flows is challenging due to the wide range of characteristic lengths of the physics at play: from micrometers (e.g., bubble nuclei radius) to meters (e.g., propeller diameter or sheet cavity length). To address this, we present here a multiscale approach which integrates a Discrete Bubble Model for dispersed microbubbles and a level set N-S solver for macro cavities, along with a mesoscale transition model to bridge the two. This approach was implemented in 3DYNAFScopyright and used to simulate sheet-to-cloud cavitation over a hydrofoil. The hybrid model captures well the full cavitation process starting from free field nuclei and nucleation from solid surfaces. In low pressure region of the foil small nuclei are seen to grow large and eventually merge to form a large scale sheet cavity. A reentrant jet forms under the cavity, travels upstream, and breaks it, resulting in a bubble cloud of a large amount of microbubbles as the broken pockets shrink and travel downstream. This is in good agreement with experimental observations based of sheet lengths and frequency of lift force oscillation. DOE-SBIR, ONR (monitored by Dr. Ki-Han Kim)

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

    SciTech Connect

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

    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. Visualization of ultrasound induced cavitation bubbles using the synchrotron x-ray Analyzer Based Imaging technique

    NASA Astrophysics Data System (ADS)

    Izadifar, Zahra; Belev, George; Izadifar, Mohammad; Izadifar, Zohreh; Chapman, Dean

    2014-12-01

    Observing cavitation bubbles deep within tissue is very difficult. The development of a method for probing cavitation, irrespective of its location in tissues, would improve the efficiency and application of ultrasound in the clinic. A synchrotron x-ray imaging technique, which is capable of detecting cavitation bubbles induced in water by a sonochemistry system, is reported here; this could possibly be extended to the study of therapeutic ultrasound in tissues. The two different x-ray imaging techniques of Analyzer Based Imaging (ABI) and phase contrast imaging (PCI) were examined in order to detect ultrasound induced cavitation bubbles. Cavitation was not observed by PCI, however it was detectable with ABI. Acoustic cavitation was imaged at six different acoustic power levels and six different locations through the acoustic beam in water at a fixed power level. The results indicate the potential utility of this technique for cavitation studies in tissues, but it is time consuming. This may be improved by optimizing the imaging method.

  14. Cloud cavitation induced by shock-bubble interaction in a viscoelastic solid

    NASA Astrophysics Data System (ADS)

    Oguri, Ryota; Ando, Keita

    2015-12-01

    We experimentally study a shock-bubble interaction problem in a viscoelastic solid, which is relevant to shock wave lithotripsy. A gas bubble is produced by focusing an infrared laser pulse into gelatin. A spherical shock is then created, through rapid expansion of plasma that results from the laser focusing, in the vicinity of the gas bubble. The shock-bubble interaction is recorded by a CCD camera with flash illumination of a nanosecond green laser pulse. The observation captures cavitation inception in the gelatin under tension that results from acoustic impedance mismatching at the bubble wall. Namely, the shock reflects at the bubble interface as a rarefaction wave, which induces the nucleation of cavitation bubbles as a result of rupturing the gelatin.

  15. An experimental investigation of acoustic cavitation in gaseous liquids

    NASA Astrophysics Data System (ADS)

    Gaitan, Dario F.; Crum, Lawrence A.

    1990-11-01

    High amplitude radial pulsations of a single bubble in several glycerine and water mixtures were observed in an acoustic stationary wave system at acoustic pressure amplitudes on the order of 150 kPa at 21 to 25 kHz. Sonoluminescence, a phenomenon generally attributed to the high temperatures generated during the collapse of cavitation bubbles, was observed as short light pulses occurring once every acoustic period. These emissions could be seen to originate at the geometric center of the bubble when observed through a microscope. It was observed that the light emissions occurred simultaneously with the bubble collapse. Using a laser scattering technique, experimental radius-time curves were obtained which confirmed the absence of surface waves which are expected at pressure amplitudes above 100 kPa. From these radius-time curves, measurements of the pulsation amplitude, the timing of the major bubble collapse, and the number of rebounds were made and compared with several theories. The implications of this research on the current understanding of cavitation were discussed.

  16. A two-dimensional nonlinear model for the generation of stable cavitation bubbles.

    PubMed

    Vanhille, Christian

    2016-07-01

    Bubbles appear by acoustic cavitation in a liquid when rarefaction pressures attain a specific threshold value in a liquid. Once they are created, the stable cavitation bubbles oscillate nonlinearly and affect the ultrasonic field. Here we present a model developed for the study of bubble generation in a liquid contained in a two-dimensional cavity in which a standing ultrasonic field is established. The model considers dissipation and dispersion due to the bubbles. It also assumes that both the ultrasonic field and the bubble oscillations are nonlinear. The numerical experiments predict where the bubbles are generated from a population of nuclei distributed in the liquid and show how they affect the ultrasonic field. PMID:26964990

  17. Importance of the implosion of ESWL-induced cavitation bubbles.

    PubMed

    Delacrétaz, G; Rink, K; Pittomvils, G; Lafaut, J P; Vandeursen, H; Boving, R

    1995-01-01

    The damage induced by an extracorporeal shock wave lithotripter is observed with a fiber optic stress sensing technique. When a stone is placed in the focus, besides the expected stress induced by the incoming shock wave emitted by the ESWL apparatus, a second delayed stress is observed some hundreds of microseconds later. The second stress is induced by a shock wave generated at the collapse of a cavitation bubble. Partial reflection of the incoming shock wave at the stone boundary is at the origin of the large cavitation bubble formation. Sensing fiber fracture results always from the second shock wave due to the collapse of the cavitation bubble. Thus the largest stress is generated at the collapse. When no target is placed in the focus of the lithotripter, no large cavitation bubble is formed and no delayed shock wave is observed. Our results demonstrate unambiguously the decisive role of cavitation in ESWL procedures. PMID:7754583

  18. Cavitation Bubble Nucleation by Energetic Particles

    SciTech Connect

    West, C.D.

    1998-12-01

    In the early sixties, experimental measurements using a bubble chamber confirmed quantitatively the thermal spike theory of bubble nucleation by energetic particles: the energy of the slow, heavy alpha decay recoils used in those experiments matched the calculated bubble nucleation energy to within a few percent. It was a triumph, but was soon to be followed by a puzzle. Within a couple of years, experiments on similar liquids, but well below their normal boiling points, placed under tensile stress showed that the calculated bubble nucleation energy was an order of magnitude less than the recoil energy. Why should the theory work so well in the one case and so badly in the other? How did the liquid, or the recoil particle, "know" the difference between the two experiments? Another mathematical model of the same physical process, introduced in 1967, showed qualitatively why different analyses would be needed for liquids with high and low vapor pressures under positive or negative pressures. But, the quantitative agreement between the calculated nucleation energy and the recoil energy was still poor--the former being smaller by a factor of two to three. In this report, the 1967 analysis is extended and refined: the qualitative understanding of the difference between positive and negative pressure nucleation, "boiling" and "cavitation" respectively, is retained, and agreement between the negative pressure calculated to be needed for nucleation and the energy calculated to be available is much improved. A plot of the calculated negative pressure needed to induce bubble formation against the measured value now has a slope of 1.0, although there is still considerable scatter in the individual points.

  19. Cavitation bubble generation and control for HIFU transcranial adaptive focusing

    NASA Astrophysics Data System (ADS)

    Gâteau, J.; Marsac, L.; Pernot, M.; Aubry, J.-F.; Tanter, M.; Fink, M.

    2009-04-01

    Brain treatment with High Intensity Focused Ultrasound (HIFU) can be achieved by multichannel arrays through the skull using time-reversal focusing. Such a method requires a reference signal either sent by a real source embedded in brain tissues or computed from a virtual source, using the acoustic properties of the skull deduced from CT images. This noninvasive computational method allows precise focusing, but is time consuming and suffers from unavoidable modeling errors which reduce the accessible acoustic pressure at the focus in comparison with real experimental time-reversal using an implanted hydrophone. Ex vivo simulations with a half skull immersed in a water tank allow us to reach at low amplitude levels a pressure ratio of 83% of the reference pressure (real time reversal) at 1MHz. Using this method to transcranially focus a pulse signal in an agar gel (model for in vivo bubble formation), we induced a cavitation bubble that generated an ultrasonic wave received by the array. Selecting the 1MHz component, the signal was time reversed and re-emitted, allowing 97%±1.1% of pressure ratio to be restored. To target points in the vicinity of the geometrical focus, electronic steering from the reference signal has been achieved. Skull aberrations severely degrade the accessible pressure while moving away from the focus ( ˜90% at 10mm in the focal plane). Nevertheless, inducing cavitation bubbles close to the limit of the primary accessible zone allowed us to acquire multiple references signal to increase the electronic steering area by 50%.

  20. A Experimental Investigation of Acoustic Cavitation in Gaseous Liquids

    NASA Astrophysics Data System (ADS)

    Gaitan, Dario Felipe

    1990-01-01

    High amplitude radial pulsations of a single gas bubble in several glycerine and water mixtures have been observed in an acoustic stationary wave system at acoustic pressure amplitudes as high as 1.5 bars. Using a laser scattering technique, radius-time curves have been obtained experimentally which confirm the absence of surface waves. Measurements of the pulsation amplitude, the timing of the major bubble collapse, and the number of rebounds have been made and compared with the theory. From these data, calculations of the internal gas temperature and pressure during the collapse have been performed. Values of at least 2,000 K and 2,000 bars have been obtained using a sophisticated model of spherically symmetric bubble dynamics. Simultaneously, sonoluminescence (SL), a phenomenon discovered in 1933 and attributed today to the high temperatures and pressures generated during the collapse of the bubbles, were observed as short light pulses occurring once every acoustic period. The light emissions can be seen to originate at the geometric center of the bubble when observed through a microscope. Also, the simultaneity of the light emissions and the collapse of the bubble has been confirmed with the aid of a photomultiplier tube. This is the first recorded observation of SL generated by a single bubble. Comparisons of the measured quantities have been made to those predicted by several models. In addition, the implications of this research on the current understanding of cavitation related phenomena such as rectified diffusion, surface wave excitation and sonoluminescence will be discussed. Some possible future experiments are suggested which could further increase our understanding of cavitation bubble dynamics.

  1. High Speed Imaging of Bubble Clouds Generated in Pulsed Ultrasound Cavitational Therapy—Histotripsy

    PubMed Central

    Xu, Zhen; Raghavan, Mekhala; Hall, Timothy L.; Chang, Ching-Wei; Mycek, Mary-Ann; Fowlkes, J. Brian; Cain, Charles A.

    2009-01-01

    Our recent studies have demonstrated that mechanical fractionation of tissue structure with sharply demarcated boundaries can be achieved using short (<20 μs), high intensity ultrasound pulses delivered at low duty cycles. We have called this technique histotripsy. Histotripsy has potential clinical applications where noninvasive tissue fractionation and/or tissue removal are desired. The primary mechanism of histotripsy is thought to be acoustic cavitation, which is supported by a temporally changing acoustic backscatter observed during the histotripsy process. In this paper, a fast-gated digital camera was used to image the hypothesized cavitating bubble cloud generated by histotripsy pulses. The bubble cloud was produced at a tissue-water interface and inside an optically transparent gelatin phantom which mimics bulk tissue. The imaging shows the following: 1) Initiation of a temporally changing acoustic backscatter was due to the formation of a bubble cloud; 2) The pressure threshold to generate a bubble cloud was lower at a tissue-fluid interface than inside bulk tissue; and 3) at higher pulse pressure, the bubble cloud lasted longer and grew larger. The results add further support to the hypothesis that the histotripsy process is due to a cavitating bubble cloud and may provide insight into the sharp boundaries of histotripsy lesions. PMID:18019247

  2. Dual pulses for cavitation control in lithotripsy: Shock wave-bubble interactions and bioeffects

    NASA Astrophysics Data System (ADS)

    Sokolov, Dahlia L.

    2002-08-01

    Cavitation, the growth and collapse of gas/vapor bubbles, appears to play an important role in both stone comminution and tissue injury during shock wave lithotripsy, the clinical treatment in which focused, high amplitude shock pulses are used to comminute kidney stones. The goal of this research was to characterize in vitro cavitation activity and stone and cell damage in a novel system that uses converging dual pulses, produced by two identical, confocal lithotripters, to modify the cavitation field. The cavitation bubble dynamics were numerically calculated, and experiments were performed in a research electrohydraulic shock wave lithotripter to determine bubble size, lifetime, and pit depth created in aluminum foils by cavitation collapse. Furthermore, damage to model stones and to red blood cells was measured for both single and dual-pulses. A single shock pulse creates a ˜15 x 100 mm cloud of bubbles in water. The greatest cavitation activity and stone damage from single-pulses was found to occur 2 cm proximal to the geometric focus, F2, where the stone is normally aligned. Therefore, a 2 cm shift in stone alignment may potentially improve stone comminution and reduce tissue injury in clinical treatment. The dual-pulse lithotripter, on the other hand, generates a localized and intensified cavitation field that increased stone comminution efficiency at F2 by at least three times the maximum values achieved by single-pulses. At F2, acoustic pressure approximately doubled, as did bubble size, collapse time, and pit depth on foils. A significant reduction in comminution of stones suspended in glycerol indicates that cavitation activity, not the doubling of acoustic pressure, explains the increased comminution. On either side of F2, the second delayed pulse mitigated bubble collapse, resulting in little or no pitting on foils and reduced hemolysis, even when compared with single pulses. Numerical calculations of radial dynamics agreed with experimental findings

  3. Acoustic and Cavitation Fields of Shock Wave Therapy Devices

    NASA Astrophysics Data System (ADS)

    Chitnis, Parag V.; Cleveland, Robin O.

    2006-05-01

    Extracorporeal shock wave therapy (ESWT) is considered a viable treatment modality for orthopedic ailments. Despite increasing clinical use, the mechanisms by which ESWT devices generate a therapeutic effect are not yet understood. The mechanistic differences in various devices and their efficacies might be dependent on their acoustic and cavitation outputs. We report acoustic and cavitation measurements of a number of different shock wave therapy devices. Two devices were electrohydraulic: one had a large reflector (HMT Ossatron) and the other was a hand-held source (HMT Evotron); the other device was a pneumatically driven device (EMS Swiss DolorClast Vet). Acoustic measurements were made using a fiber-optic probe hydrophone and a PVDF hydrophone. A dual passive cavitation detection system was used to monitor cavitation activity. Qualitative differences between these devices were also highlighted using a high-speed camera. We found that the Ossatron generated focused shock waves with a peak positive pressure around 40 MPa. The Evotron produced peak positive pressure around 20 MPa, however, its acoustic output appeared to be independent of the power setting of the device. The peak positive pressure from the DolorClast was about 5 MPa without a clear shock front. The DolorClast did not generate a focused acoustic field. Shadowgraph images show that the wave propagating from the DolorClast is planar and not focused in the vicinity of the hand-piece. All three devices produced measurable cavitation with a characteristic time (cavitation inception to bubble collapse) that varied between 95 and 209 μs for the Ossatron, between 59 and 283 μs for the Evotron, and between 195 and 431 μs for the DolorClast. The high-speed camera images show that the cavitation activity for the DolorClast is primarily restricted to the contact surface of the hand-piece. These data indicate that the devices studied here vary in acoustic and cavitation output, which may imply that the

  4. Processing of Microalgae: Acoustic Cavitation and Hydrothermal Conversion

    NASA Astrophysics Data System (ADS)

    Greenly, Justin Michael

    The production of energy dense fuels from renewable algal biomass feedstocks -- if sustainably developed at a sufficiently large scale -- may reduce the consumption of petroleum from fossil fuels and provide many environmental benefits. Achieving economic feasibility has several technical engineering challenges that arise from dilute concentration of growing algae in aqueous media, small cell sizes, and durable cell walls. For microalgae to be a sustainable source of biofuels and co-products, efficient fractionation and conversion of the cellular contents is necessary. Research was carried out to address two processing options for efficient microalgae biofuel production: 1. Ultrasonic cavitation for cell disruption and 2. Hydrothermal conversion of a model algal triglyceride. 1. Ultrasonic cell disruption, which relies on cavitating bubbles in the suspension to produce damaging shock waves, was investigated experimentally over a range of concentrations and species types. A few seconds of high intensity sonication at fixed frequency yielded significant cell disruption, even for the more durable cells. At longer exposure times, effectiveness was seen to decline and was attributed, using acoustic measurements, to ultrasonic power attenuation in the ensuing cloud of cavitating bubbles. Processing at higher cell concentrations slowed cell disintegration marginally, but increased the effectiveness of dissipating ultrasonic energy. A theoretical study effectively predicted optimal conditions for a variety of parameters that were inaccessible in this experimental investigation. In that study, single bubble collapse was modeled to identify operating conditions that would increase cavitation, and thus cell disruption. Simulations were conducted by varying frequency and pressure amplitude of the ultrasound wave, and initial bubble size. The simulation results indicated that low frequency, high sound wave amplitudes, and small initial bubble size generate the highest shock

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

    PubMed

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

    2016-07-01

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

  6. Effect of dilute polymer additives on the acoustic cavitation threshold of water

    SciTech Connect

    Crum, L.A.; Brosey, J.E.

    1984-02-01

    Measurements are presented of the variation of the acoustic cavitation threshold of water with concentration of the polymer additives polyethylene oxide and guar gum. It was found that small amounts of these additives could significantly increase the cavitation threshold. A theoretical model, based upon nucleation of a gas bubble from a Harvey-type crevice in a mote or solid particle, is developed that gives good agreement with the measurements. The applicability of this approach to an explanation of cavitation index reduction in flow-generated or confined jet cavitation, when polymer additives are introduced, is discussed.

  7. Bubble dynamics under acoustic excitation with multiple frequencies

    NASA Astrophysics Data System (ADS)

    Zhang, Y. N.; Zhang, Y. N.; Li, S. C.

    2015-01-01

    Because of its magnificent mechanical and chemical effects, acoustic cavitation plays an important role in a broad range of biomedical, chemical and mechanical engineering problems. Particularly, irradiation of the multiple frequency acoustic wave could enhance the effects of cavitation. The advantages of employment of multi-frequency ultrasonic field include decreasing the cavitation thresholds, promoting cavitation nuclei generation, increasing the mass transfer and improving energy efficiency. Therefore, multi-frequency ultrasonic systems are employed in a variety of applications, e.g., to enhance the intensity of sonoluminenscence, to increase efficiency of sonochemical reaction, to improve the accuracy of ultrasound imaging and the efficiency of tissue ablation. Compared to single-frequency systems, a lot of new features of bubble dynamics exist in multi-frequency systems, such as special properties of oscillating bubbles, unique resonances in the bubble response curves, and unusual chaotic behaviours. In present paper, the underlying mechanisms of the cavitation effects under multi-frequency acoustical excitation are also briefly introduced.

  8. Transient cavitation and acoustic emission produced by different laser lithotripters.

    PubMed

    Zhong, P; Tong, H L; Cocks, F H; Pearle, M S; Preminger, G M

    1998-08-01

    Transient cavitation and shockwave generation produced by pulsed-dye and holmium:YAG laser lithotripters were studied using high-speed photography and acoustic emission measurements. In addition, stone phantoms were used to compare the fragmentation efficiency of various laser and electrohydraulic lithotripters. The pulsed-dye laser, with a wavelength (504 nm) strongly absorbed by most stone materials but not by water, and a short pulse duration of approximately 1 microsec, induces plasma formation on the surface of the target calculi. Subsequently, the rapid expansion of the plasma forms a cavitation bubble, which expands spherically to a maximum size and then collapses violently, leading to strong shockwave generation and microjet impingement, which comprises the primary mechanism for stone fragmentation with short-pulse lasers. In contrast, the holmium laser, with a wavelength (2100 nm) most strongly absorbed by water as well as by all stone materials and a long pulse duration of 250 to 350 microsec, produces an elongated, pear-shaped cavitation bubble at the tip of the optical fiber that forms a vapor channel to conduct the ensuing laser energy to the target stone (Moss effect). The expansion and subsequent collapse of the elongated bubble is asymmetric, resulting in weak shockwave generation and microjet impingement. Thus, stone fragmentation in holmium laser lithotripsy is caused primarily by thermal ablation (drilling effect). PMID:9726407

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  10. Cavitation bubble dynamics in microfluidic gaps of variable height.

    PubMed

    Quinto-Su, Pedro A; Lim, Kang Y; Ohl, Claus-Dieter

    2009-10-01

    We study experimentally the dynamics of laser-induced cavitation bubbles created inside a narrow gap. The gap height, h , is varied from 15 to 400 microm and the resulting bubble dynamics is compared to a semiunbounded fluid. The cavitation bubbles are created with pulsed laser light at constant laser energy and are imaged with a high-speed camera. The bubble lifetime increases with decreasing gap height by up to 50% whereas the maximum projected bubble radius remains constant. Comparing the radial dynamics to potential flow models, we find that with smaller gaps, the bubble-induced flow becomes essentially planar, thus slower flows with reduced shear. These findings might have important consequences for microfluidic applications where it is desirable to tune the strength and range of the interactions such as in the case of cell lysis and cell membrane poration. PMID:19905487

  11. Ultrasonic emissions reveal individual cavitation bubbles in water-stressed wood

    PubMed Central

    Ponomarenko, A.; Vincent, O.; Pietriga, A.; Cochard, H.; Badel, É.; Marmottant, P.

    2014-01-01

    Under drought conditions, the xylem of trees that conducts ascending sap produces ultrasonic emissions whose exact origin is not clear. We introduce a new method to record simultaneously both acoustic events and optical observation of the xylem conduits within slices of wood that were embedded in a transparent material setting a hydric stress. In this article, we resolved the rapid development of all cavitation bubbles and demonstrated that each ultrasound emission was linked to the nucleation of one single bubble, whose acoustic energy is an increasing function of the size of the conduit where nucleation occurred and also of the hydric stress. We modelled these observations by the fact that water columns in conduits store elastic energy and release it into acoustic waves when they are broken by cavitation bubbles. Water columns are thus elastic, and not rigid, ‘wires of water’ set under tension by hydric stresses. Cavitation bubbles are at the origin of an embolism, whose development was followed in our experiments. Such an embolism of sap circulation can result in a fatal condition for living trees. These findings provide new insights for the non-destructive monitoring of embolisms within trees, and suggest a new approach to study porous media under hydric stress. PMID:25056212

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

    PubMed Central

    Fernandez Rivas, David; 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 cavities micromachined in a silicon surface, which, when vibrated ultrasonically at a frequency of 200 kHz, generate a stream of bubbles that travel to the layer deposited on an opposing glass slide. Depending on the pressure amplitude, the bubble clouds ejected from the micropits attain different shapes as a result of complex bubble interaction forces, leading to distinct shapes of the cleaned areas. We have determined the removal rates for several inorganic and organic materials and obtained an improved efficiency in cleaning when compared to conventional cleaning equipment. We also provide values of the force the bubbles are able to exert on an atomic force microscope tip. PMID:23964308

  13. A reduced-order, single-bubble cavitation model with applications to therapeutic ultrasound

    PubMed Central

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

    2011-01-01

    Cavitation often occurs in therapeutic applications of medical ultrasound such as shock-wave lithotripsy (SWL) and high-intensity focused ultrasound (HIFU). Because cavitation bubbles can affect an intended treatment, it is important to understand the dynamics of bubbles in this context. The relevant context includes very high acoustic pressures and frequencies as well as elevated temperatures. Relative to much of the prior research on cavitation and bubble dynamics, such conditions are unique. To address the relevant physics, a reduced-order model of a single, spherical bubble is proposed that incorporates phase change at the liquid-gas interface as well as heat and mass transport in both phases. Based on the energy lost during the inertial collapse and rebound of a millimeter-sized bubble, experimental observations were used to tune and test model predictions. In addition, benchmarks from the published literature were used to assess various aspects of model performance. Benchmark comparisons demonstrate that the model captures the basic physics of phase change and diffusive transport, while it is quantitatively sensitive to specific model assumptions and implementation details. Given its performance and numerical stability, the model can be used to explore bubble behaviors across a broad parameter space relevant to therapeutic ultrasound. PMID:22088026

  14. Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

    PubMed Central

    Pflieger, Rachel; Chave, Tony; Virot, Matthieu; Nikitenko, Sergey I.

    2014-01-01

    The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic cavitation: the nucleation, growth, and implosive collapse of microbubbles in liquids submitted to power ultrasound. The violent implosion of bubbles leads to the formation of chemically reactive species and to the emission of light, named sonoluminescence. In this manuscript, we describe the techniques allowing study of extreme intrabubble conditions and chemical reactivity of acoustic cavitation in solutions. The analysis of sonoluminescence spectra of water sparged with noble gases provides evidence for nonequilibrium plasma formation. The photons and the "hot" particles generated by cavitation bubbles enable to excite the non-volatile species in solutions increasing their chemical reactivity. For example the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions varies with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation contributes at higher uranium concentration. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble, but then diffuse into the liquid phase and react with solution precursors to form a variety of products. For instance, the sonochemical reduction of Pt(IV) in pure water provides an innovative synthetic route for monodispersed nanoparticles of metallic platinum without any templates or capping agents. Many studies reveal the advantages of ultrasound to activate the divided solids. In general, the mechanical effects of ultrasound strongly contribute in heterogeneous systems in addition to chemical effects. In particular, the sonolysis of PuO2 powder in pure water yields stable colloids of plutonium due to both effects. PMID:24747272

  15. Impact of acoustic cavitation on food emulsions.

    PubMed

    Krasulya, Olga; Bogush, Vladimir; Trishina, Victoria; Potoroko, Irina; Khmelev, Sergey; Sivashanmugam, Palani; Anandan, Sambandam

    2016-05-01

    The work explores the experimental and theoretical aspects of emulsification capability of ultrasound to deliver stable emulsions of sunflower oil in water and meat sausages. In order to determine optimal parameters for direct ultrasonic emulsification of food emulsions, a model was developed based on the stability of emulsion droplets in acoustic cavitation field. The study is further extended to investigate the ultrasound induced changes to the inherent properties of raw materials under the experimental conditions of sono-emulsification. PMID:26603612

  16. The recreation of a unique shrimp's mechanically induced cavitation bubble

    NASA Astrophysics Data System (ADS)

    Miller, Ryan; Dougherty, Christopher; Eliasson, Veronica; Khanolkar, Gauri

    2014-11-01

    The Alpheus heterochaelis, appropriately nicknamed the ``pistol shrimp,'' possesses an oversized claw that creates a cavitation bubble upon rapid closure. The implosion of this bubble results in a shock wave that can stun or even kill the shrimp's prey (Versluis et al., 2000). Additionally, the implosion is so violent that sonoluminescence may occur. This light implies extreme temperatures, which have been recorded to reach as high as 10,000 K (Roach, 2001). By developing an analogous mechanism to the oversized claw, the goal of this experiment is to verify that cavitation can be produced similar to that of the pistol shrimp in nature as well as to analyze the resulting shock wave and sonoluminescence. High-speed schlieren imaging was used to observe the shock dynamics. Furthermore, results on cavitation collapse and light emission will be presented. USC Provost Undergraduate Research Fellowship/Rose Hills Undergraduate Research Fellowship.

  17. Cavitation and bubble dynamics: the Kelvin impulse and its applications.

    PubMed

    Blake, John R; Leppinen, David M; Wang, Qianxi

    2015-10-01

    Cavitation and bubble dynamics have a wide range of practical applications in a range of disciplines, including hydraulic, mechanical and naval engineering, oil exploration, clinical medicine and sonochemistry. However, this paper focuses on how a fundamental concept, the Kelvin impulse, can provide practical insights into engineering and industrial design problems. The pathway is provided through physical insight, idealized experiments and enhancing the accuracy and interpretation of the computation. In 1966, Benjamin and Ellis made a number of important statements relating to the use of the Kelvin impulse in cavitation and bubble dynamics, one of these being 'One should always reason in terms of the Kelvin impulse, not in terms of the fluid momentum…'. We revisit part of this paper, developing the Kelvin impulse from first principles, using it, not only as a check on advanced computations (for which it was first used!), but also to provide greater physical insights into cavitation bubble dynamics near boundaries (rigid, potential free surface, two-fluid interface, flexible surface and axisymmetric stagnation point flow) and to provide predictions on different types of bubble collapse behaviour, later compared against experiments. The paper concludes with two recent studies involving (i) the direction of the jet formation in a cavitation bubble close to a rigid boundary in the presence of high-intensity ultrasound propagated parallel to the surface and (ii) the study of a 'paradigm bubble model' for the collapse of a translating spherical bubble, sometimes leading to a constant velocity high-speed jet, known as the Longuet-Higgins jet. PMID:26442141

  18. THE ROLE OF INERTIAL CAVITATION IN ACOUSTIC DROPLET VAPORIZATION

    PubMed Central

    Fabiilli, Mario L.; Haworth, Kevin J.; Fakhri, Nasir H.; Kripfgans, Oliver D.; Carson, Paul L.; Fowlkes, J. Brian

    2011-01-01

    The vaporization of a superheated droplet emulsion into gas bubbles using ultrasound – termed acoustic droplet vaporization (ADV) – has potential therapeutic applications in embolotherapy and drug delivery. The optimization of ADV for therapeutic applications can be enhanced by understanding the physical mechanisms underlying ADV, which are currently not clearly elucidated. Acoustic cavitation is one possible mechanism. This paper investigates the relationship between the ADV and inertial cavitation (IC) thresholds (measured as peak rarefactional pressures) by studying parameters that are known to influence the IC threshold. These parameters include bulk fluid properties such as gas saturation, temperature, viscosity, and surface tension; droplet parameters such as degree of superheat, surfactant type, and size; and acoustic properties such as pulse repetition frequency and pulse width. In all cases the ADV threshold occurred at a lower rarefactional pressure than the IC threshold indicating that the phase-transition occurs before IC events. The viscosity and temperature of the bulk fluid are shown to influence both thresholds directly and inversely, respectively. An inverse trend is observed between threshold and diameter for droplets in the 1 to 2.5 μ range. Based on a choice of experimental parameters, it is possible to achieve ADV with or without IC. PMID:19473917

  19. Interferometric studies of the pressures developed in a liquid during infrared-laser-induced cavitation-bubble oscillation

    NASA Astrophysics Data System (ADS)

    Ward, B.; Emmony, D. C.

    The study of the behaviour of cavitation bubbles close to rigid boundaries is of particular importance because of the associated phenomenon of cavitation erosion which arises from the resulting changes in pressure in the surrounding liquid. In this paper, we present four sequences of Mach-Zehnder interferograms and shadowgraphs of IR-laser-generated bubbles in water for two distinct positions relative to a solid perspex block. Direct optical measurements of the transient pressure distributions in the nearby liquid are made for the initial expansion of the bubbles and around each of their subsequent collapse phases. In addition to the generation of spherical acoustic waves, the pressures developed around the bubble prior to collapse and the formation of a high-speed liquid jet are precisely quantified. Furthermore, calculations of the changes in potential energy of the enclosed vapour are carried out and related to the magnitudes of the energy radiated via acoustic waves.

  20. Cavitation in confined water: ultra-fast bubble dynamics

    NASA Astrophysics Data System (ADS)

    Vincent, Olivier; Marmottant, Philippe

    2012-02-01

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

  1. An Acoustofluidic Micromixer via Bubble Inception and Cavitation from Microchannel Sidewalls

    PubMed Central

    2015-01-01

    During the deep reactive ion etching process, the sidewalls of a silicon mold feature rough wavy structures, which can be transferred onto a polydimethylsiloxane (PDMS) microchannel through the soft lithography technique. In this article, we utilized the wavy structures of PDMS microchannel sidewalls to initiate and cavitate bubbles in the presence of acoustic waves. Through bubble cavitation, this acoustofluidic approach demonstrates fast, effective mixing in microfluidics. We characterized its performance by using viscous fluids such as poly(ethylene glycol) (PEG). When two PEG solutions with a resultant viscosity 54.9 times higher than that of water were used, the mixing efficiency was found to be 0.92, indicating excellent, homogeneous mixing. The acoustofluidic micromixer presented here has the advantages of simple fabrication, easy integration, and capability to mix high-viscosity fluids (Reynolds number: ∼0.01) in less than 100 ms. PMID:24754496

  2. Single bubble perturbation in cavitation proximity of solid glass: hot spot versus distance.

    PubMed

    Radziuk, Darya; Möhwald, Helmuth; Suslick, Kenneth

    2014-02-28

    A systematic study of the energy loss of a cavitation bubble in a close proximity of a glass surface is introduced for the first time in a low acoustic field (1.2-2.4 bar). Single bubble sonoluminescence (SBSL) is used as a tool to predict the temperature and pressure decrease of bubble (μm) versus surface distance. A glass as a model system is used to imitate the boundary conditions relevant for nano- or micromaterials. SBSL preequilibrated with 5% argon is perturbed by a glass rod with the tip (Z-perturbation) and with the long axis (X-perturbation) at a defined distance. From 2 mm to 500 μm argon-SBSL lines monotonically narrow and the effective emission temperature decreases from 9000 K to 6800 K comparable to multiple bubbles. The electron density decreases by two orders of magnitude in Z-perturbation and is by a factor of two higher in X-perturbation than the unperturbed cavitating bubble. The perturbed single bubble sonoluminescence pressure decreases from 2700 atm to 1200 atm at 2.4 bar. In water new non-SBSL SiO molecular emission lines are observed and OH emission disappears. PMID:24068109

  3. Effect of supercritical water shell on cavitation bubble dynamics

    NASA Astrophysics Data System (ADS)

    Shao, Wei-Hang; Chen, Wei-Zhong

    2015-05-01

    Based on reported experimental data, a new model for single cavitation bubble dynamics is proposed considering a supercritical water (SCW) shell surrounding the bubble. Theoretical investigations show that the SCW shell apparently slows down the oscillation of the bubble and cools the gas temperature inside the collapsing bubble. Furthermore, the model is simplified to a Rayleigh-Plesset-like equation for a thin SCW shell. The dependence of the bubble dynamics on the thickness and density of the SCW shell is studied. The results show the bubble dynamics depends on the thickness but is insensitive to the density of the SCW shell. The thicker the SCW shell is, the smaller are the wall velocity and the gas temperature in the bubble. In the authors’ opinion, the SCW shell works as a buffering agent. In collapsing, it is compressed to absorb a good deal of the work transformed into the bubble internal energy during bubble collapse so that it weakens the bubble oscillations. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174145 and 11334005).

  4. Effects of Tissue Stiffness, Ultrasound Frequency, and Pressure on Histotripsy-induced Cavitation Bubble Behavior

    PubMed Central

    Vlaisavljevich, Eli; Lin, Kuang-Wei; Warnez, Matthew; Singh, Rahul; Mancia, Lauren; Putnam, Andrew J.; Johnsen, Eric; Cain, Charles; Xu, Zhen

    2015-01-01

    Histotripsy is an ultrasound ablation method that controls cavitation to fractionate soft tissue. In order to effectively fractionate tissue, histotripsy requires cavitation bubbles to rapidly expand from nanometer-sized initial nuclei into bubbles often larger than 50 microns. Using a negative pressure high enough to initiate a bubble cloud and expand bubbles to a sufficient size, histotripsy has been shown capable of completely fractionating soft tissue into acelluar debris resulting in effective tissue removal. Previous work has shown that the histotripsy process is affected by tissue mechanical properties with stiffer tissues showing increased resistance to histotripsy fractionation, which we hypothesize to be caused by impeded bubble expansion in stiffer tissues. In this study, the hypothesis that increases in tissue stiffness causes a reduction in bubble expansion was investigated both theoretically and experimentally. High speed optical imaging was used to capture a series of time delayed images of bubbles produced inside mechanically tunable agarose tissue phantoms using histotripsy pulses produced by 345 kHz, 500 kHz, 1.5 MHz, and 3 MHz histotripsy transducers. The results demonstrated a significant decrease in maximum bubble radius (Rmax) and collapse time (tc) with both increasing Young’s modulus and increasing frequency. Furthermore, results showed that Rmax was not increased by raising the pressure above the intrinsic threshold. Finally, this work demonstrated the potential of using a dual-frequency strategy to modulate the expansion of histotripsy bubbles. Overall, the results of this study improve our understanding of how tissue stiffness and ultrasound parameters affect histotripsy-induced bubble behavior and provide a rational basis to tailor acoustic parameters for treatment of the specific tissues of interest. PMID:25715732

  5. Effects of tissue stiffness, ultrasound frequency, and pressure on histotripsy-induced cavitation bubble behavior

    NASA Astrophysics Data System (ADS)

    Vlaisavljevich, Eli; Lin, Kuang-Wei; Warnez, Matthew T.; Singh, Rahul; Mancia, Lauren; Putnam, Andrew J.; Johnsen, Eric; Cain, Charles; Xu, Zhen

    2015-03-01

    Histotripsy is an ultrasound ablation method that controls cavitation to fractionate soft tissue. In order to effectively fractionate tissue, histotripsy requires cavitation bubbles to rapidly expand from nanometer-sized initial nuclei into bubbles often larger than 50 µm. Using a negative pressure high enough to initiate a bubble cloud and expand bubbles to a sufficient size, histotripsy has been shown capable of completely fractionating soft tissue into acelluar debris resulting in effective tissue removal. Previous work has shown that the histotripsy process is affected by tissue mechanical properties with stiffer tissues showing increased resistance to histotripsy fractionation, which we hypothesize to be caused by impeded bubble expansion in stiffer tissues. In this study, the hypothesis that increases in tissue stiffness cause a reduction in bubble expansion was investigated both theoretically and experimentally. High speed optical imaging was used to capture a series of time delayed images of bubbles produced inside mechanically tunable agarose tissue phantoms using histotripsy pulses produced by 345 kHz, 500 kHz, 1.5 MHz, and 3 MHz histotripsy transducers. The results demonstrated a significant decrease in maximum bubble radius (Rmax) and collapse time (tc) with both increasing Young’s modulus and increasing frequency. Furthermore, results showed that Rmax was not increased by raising the pressure above the intrinsic threshold. Finally, this work demonstrated the potential of using a dual-frequency strategy to modulate the expansion of histotripsy bubbles. Overall, the results of this study improve our understanding of how tissue stiffness and ultrasound parameters affect histotripsy-induced bubble behavior and provide a rational basis to tailor acoustic parameters for treatment of the specific tissues of interest.

  6. Dynamic features of a laser-induced cavitation bubble near a solid boundary.

    PubMed

    Yang, Yuan Xiang; Wang, Qian Xi; Keat, T S

    2013-07-01

    This paper deals with detailed features of bubble dynamics near a solid boundary. The cavitation bubble was created by using a Q-switched Nd: YAG laser pulse and observed using a high-speed camera (up to 100,000 frames per second). A hydrophone system was employed to monitor the acoustic signals generated by the transient pressure impulses and estimate the bubble oscillation periods. Experimental observations were carried out for bubbles with various maximum expanded radius Rmax (between 1.0mm and 1.6mm) and stand-off distances, ds (defined as the distance between the solid boundary and the bubble center at inception) of 0.4≤γ≤3.0, and γ=ds/Rmax. The existence of a solid boundary created asymmetry in the flow field and forced the bubble to collapse non-spherically, which finally brought forth the jet impact phenomenon. The dimensionless first and second oscillation periods were dependent on γ. A series of expansion and collapse of the bubble with cascading loss of energy were observed after the bubble had been generated. This study revealed that most bubbles lost about two-thirds of the total energy from the first maximum expansion to the second maximum expansion. PMID:23411165

  7. Detection of cavitation vortex in hydraulic turbines using acoustic techniques

    NASA Astrophysics Data System (ADS)

    Candel, I.; Bunea, F.; Dunca, G.; Bucur, D. M.; Ioana, C.; Reeb, B.; Ciocan, G. D.

    2014-03-01

    Cavitation phenomena are known for their destructive capacity in hydraulic machineries and are caused by the pressure decrease followed by an implosion when the cavitation bubbles find an adverse pressure gradient. A helical vortex appears in the turbine diffuser cone at partial flow rate operation and can be cavitating in its core. Cavity volumes and vortex frequencies vary with the under-pressure level. If the vortex frequency comes close to one of the eigen frequencies of the turbine, a resonance phenomenon may occur, the unsteady fluctuations can be amplified and lead to important turbine and hydraulic circuit damage. Conventional cavitation vortex detection techniques are based on passive devices (pressure sensors or accelerometers). Limited sensor bandwidths and low frequency response limit the vortex detection and characterization information provided by the passive techniques. In order to go beyond these techniques and develop a new active one that will remove these drawbacks, previous work in the field has shown that techniques based on acoustic signals using adapted signal content to a particular hydraulic situation, can be more robust and accurate. The cavitation vortex effects in the water flow profile downstream hydraulic turbines runner are responsible for signal content modifications. Basic signal techniques use narrow band signals traveling inside the flow from an emitting transducer to a receiving one (active sensors). Emissions of wide band signals in the flow during the apparition and development of the vortex embeds changes in the received signals. Signal processing methods are used to estimate the cavitation apparition and evolution. Tests done in a reduced scale facility showed that due to the increasing flow rate, the signal -- vortex interaction is seen as modifications on the received signal's high order statistics and bandwidth. Wide band acoustic transducers have a higher dynamic range over mechanical elements; the system's reaction time

  8. Modeling of surface cleaning by cavitation bubble dynamics and collapse.

    PubMed

    Chahine, Georges L; Kapahi, Anil; Choi, Jin-Keun; Hsiao, Chao-Tsung

    2016-03-01

    Surface cleaning using cavitation bubble dynamics is investigated numerically through modeling of bubble dynamics, dirt particle motion, and fluid material interaction. Three fluid dynamics models; a potential flow model, a viscous model, and a compressible model, are used to describe the flow field generated by the bubble all showing the strong effects bubble explosive growth and collapse have on a dirt particle and on a layer of material to remove. Bubble deformation and reentrant jet formation are seen to be responsible for generating concentrated pressures, shear, and lift forces on the dirt particle and high impulsive loads on a layer of material to remove. Bubble explosive growth is also an important mechanism for removal of dirt particles, since strong suction forces in addition to shear are generated around the explosively growing bubble and can exert strong forces lifting the particles from the surface to clean and sucking them toward the bubble. To model material failure and removal, a finite element structure code is used and enables simulation of full fluid-structure interaction and investigation of the effects of various parameters. High impulsive pressures are generated during bubble collapse due to the impact of the bubble reentrant jet on the material surface and the subsequent collapse of the resulting toroidal bubble. Pits and material removal develop on the material surface when the impulsive pressure is large enough to result in high equivalent stresses exceeding the material yield stress or its ultimate strain. Cleaning depends on parameters such as the relative size between the bubble at its maximum volume and the particle size, the bubble standoff distance from the particle and from the material wall, and the excitation pressure field driving the bubble dynamics. These effects are discussed in this contribution. PMID:25982895

  9. Cavitation bubble dynamics during thulium fiber laser lithotripsy

    NASA Astrophysics Data System (ADS)

    Hardy, Luke A.; Kennedy, Joshua D.; Wilson, Christopher R.; Irby, Pierce B.; Fried, Nathaniel M.

    2016-02-01

    The Thulium fiber laser (TFL) is being explored for lithotripsy. TFL parameters differ from standard Holmium:YAG laser in several ways, including smaller fiber delivery, more strongly absorbed wavelength, low pulse energy/high pulse rate operation, and more uniform temporal pulse structure. High speed imaging of cavitation bubbles was performed at 105,000 fps and 10 μm spatial resolution to determine influence of these laser parameters on bubble formation. TFL was operated at 1908 nm with pulse energies of 5-75 mJ, and pulse durations of 200-1000 μs, delivered through 100-μm-core fiber. Cavitation bubble dynamics using Holmium laser at 2100 nm with pulse energies of 200-1000 mJ and pulse duration of 350 μs was studied, for comparison. A single, 500 μs TFL pulse produced a bubble stream extending 1090 +/- 110 μm from fiber tip, and maximum bubble diameters averaged 590 +/- 20 μm (n=4). These observations are consistent with previous studies which reported TFL ablation stallout at working distances < 1.0 mm. TFL bubble dimensions were five times smaller than for Holmium laser due to lower pulse energy, higher water absorption coefficient, and smaller fiber diameter used.

  10. The role of acoustic cavitation in liquid pressurization in narrow tubes

    NASA Astrophysics Data System (ADS)

    Tamura, S.; Hatakeyama, M.

    2013-04-01

    The liquid pressurization mechanism in narrow tubes as a result of high intensity ultrasonic field along the irradiation direction is discussed, with a focus on the physical behavior of acoustic cavitation bubbles formed at the tube's open end. The acoustic energy dissipated at the surface of the bubbles results in radiation pressure with a second harmonic frequency (2f). We show here that during the phenomenon, which resembles the functioning an ultrasonic pump, cyclical pressure fluctuations with the second harmonic frequency 2f are observed using a high-response pressure transducer. The maximum value of accumulating pressure is equivalent to the positive peak of the sound pressure in the tube without acoustic cavitation. It can be thought that the cyclic collapse and expansion of acoustic cavitation bubbles at the tube's open end contribute to the control of the inrushing sound pressure. In particular, the transmission behavior of the received pressure in a viscous liquid containing gas bubbles with high number density near the tube's open end (a quantity that is related to the kinematic viscosity of the medium liquid) plays an important role in this pressure accumulation mechanism. A dynamic model of this pressurization phenomenon is also discussed.

  11. Real-Time Monitoring and Quantitative Evaluation of Cavitation Bubbles Induced by High Intensity Focused Ultrasound Using B-Mode Imaging

    NASA Astrophysics Data System (ADS)

    Yu, Jie; Chen, Chu-Yi; Chen, Gong; Guo, Xia-Sheng; Ma, Yong; Tu, Juan; Zhang, Dong

    2014-03-01

    A software-based method is proposed to eliminate the flooding interference strips in B-mode images, and to evaluate the cavitation bubbles generated during high intensity focused ultrasound (HIFU) exposures. In vitro tissue phantoms are exposed to 1.12 MHz HIFU pulses with a fixed 100 Hz pulse repetition frequency. HIFU-induced cavitation bubbles are detected as hyperechoic regions in B-mode images. The temporal evolution of cavitation bubbles, generated by HIFU pulses with varying driving amplitude and pulse length, is analyzed by measuring the time-varying area of the hyperechoic region. The results show that: first, it is feasible to monitor HIFU-induced cavitation bubble activity in real-time using B-mode imaging; second, more cavitation bubbles can be generated with higher acoustic energy delivered; third, the hyperechoic region is observed to shrink gradually after ceasing the HIFU pulses, which indicates the dissolution of cavitation bubbles. This work will be helpful for developing an effective tool to realize real-time monitoring and quantitative evaluation of HIFU-induced cavitation bubble activity using a current commercialized B-mode machine.

  12. Shock wave emission during the collapse of cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Garen, W.; Hegedűs, F.; Kai, Y.; Koch, S.; Meyerer, B.; Neu, W.; Teubner, U.

    2016-02-01

    Shock wave emission induced by intense laser pulses is investigated experimentally. The present work focuses on the conditions of shock wave emission in glycerine and distilled water during the first bubble collapse. Experimental investigations are carried out in liquids as a function of temperature and viscosity. Comparison is made with the theoretical work of Poritsky (Proc 1st US Natl Congress Appl Mech 813-821, 1952) and Brennen (Cavitation and bubble dynamics, Oxford University Press 1995). To the best knowledge of the authors, this is the first experimental verification of those theories.

  13. Reduction of Bubble Cavitation by Modifying the Diffraction Wave from a Lithotripter Aperture

    PubMed Central

    2012-01-01

    Abstract Purpose A new method was devised to suppress the bubble cavitation in the lithotripter focal zone to reduce the propensity of shockwave-induced renal injury. Materials and Methods An edge extender was designed and fabricated to fit on the outside of the ellipsoidal reflector of an electrohydraulic lithotripter to disturb the generation of diffraction wave at the aperture, but with little effect on the acoustic field inside the reflector. Results Although the peak negative pressures at the lithotripter focus using the edge extender at 20 kV were similar to that of the original configuration (-11.1±0.9 vs −10.6±0.7 MPa), the duration of the tensile wave was shortened significantly (3.2±0.54 vs 5.83±0.56 μs, P<0.01). There is no difference, however, in both the amplitude and duration of the compressive shockwaves between these two configurations as well as the −6 dB beam width in the focal plane. The significant suppression effect of bubble cavitation was confirmed by the measured bubble collapse time using passive cavitation detection. At the lithotripter focus, while only about 30 shocks were needed to rupture a blood vessel phantom using the original HM-3 reflector at 20 kV, no damage could be produced after 300 shocks using the edge extender. Meanwhile, the original HM-3 lithotripter at 20 kV can achieve a stone comminution efficiency of 50.4±2.0% on plaster-of-Paris stone phantom after 200 shocks, which is comparable to that of using the edge extender (46.8±4.1%, P=0.005). Conclusions Modifying the diffraction wave at the lithotripter aperture can suppress the shockwave-induced bubble cavitation with significant reduced damage potential on the vessel phantom but satisfactory stone comminution ability. PMID:22332839

  14. Drop fragmentation by laser-induced cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Gonzalez-A, S. Roberto; Kerssens, Pjotr; Ohl, Claus-Dieter

    2015-11-01

    The fragmentation of water droplets by a short laser pulse has received significant attention since the 70's. The fundamental understanding of droplet vaporization/fragmentation is of interest in laser beam propagation in the atmosphere, in situ analysis of combustion products -a great concern due to its ecological implications- and more recently driven by a better understanding of the drop shaping by a laser pulse which is of interest in the development of extreme ultraviolet (EUV) machines. In this presentation we discuss about the incipient events that lead to the fragmentation of a drop produced by a cavitation bubble. When the bubble expands, it stretches the drop into a thin liquid film; this liquid film is eventually ruptured and a shockwave and small droplets are ejected as fast as 4 times the speed of sound in air. Interestingly, we also observe bubbles on the surface of the stretched film. Numerical simulations of a shock wave propagating inside a droplet show that cavitation bubbles appear when counter propagating shock waves that rebound from the walls of the drop meet. We also show different fragmentation scenarios recorded with high-speed video, one of them being a jelly fish like liquid film that eventually fragments into smaller drops.

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

    NASA Astrophysics Data System (ADS)

    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).

  16. Bubbles in drops: from cavitation to exploding stars

    NASA Astrophysics Data System (ADS)

    Kobel, Philippe; Obreschkow, Danail; Dorsaz, Nicolas; de Bosset, Aurele; Tinguely, Marc; Farhat, Mohamed

    2011-11-01

    We performed an experiment to generate single cavitation bubbles inside centimetric quasi-spherical water drops. To produce such drops, our experiment was realized under microgravity conditions (42nd ESA parabolic flight campaign). The ultra-fast recording of the bubble collapse and ensuing dynamics revealed consequences of the unique geometry of the drop's free surface. We obtained the first visualizations of a jet pair escaping the drop after the collapse of eccentrically-placed bubbles. The high quality of the images also disclosed some features of the inner drop dynamics. Due to their confinement within the isolated drop volume, shock waves emitted at the bubble collapse bounce back and forth thereby exciting gas nuclei into sub-millimetric bubbles. When located beneath the free surface, the collapse of these bubbles gives rise to narrow ``hair-like'' jets on the surface. Here we briefly describe the physics underlying these observations while discussing possible analogies with various astrophysical processes from the Sun (spicules) to asymmetric supernovae.

  17. The inception of cavitation bubble clouds induced by high-intensity focused ultrasound.

    PubMed

    Chen, Hong; Li, Xiaojing; Wan, Mingxi

    2006-12-22

    In many therapeutic applications of high-intensity focused ultrasound (HIFU) the appearance of cavitation bubbles is unavoidable, whereas the dynamics of the bubbles induced by HIFU have not been clarified. The objective of the present work is to observe the inception process of cavitation bubble clouds generated by HIFU transducer in water using high-speed photography. Sequential images captured within 600 micros after the onset of ultrasound transmission show the dynamics of cavitation bubbles' generation, growth, deformation, expansion and collapse in the focal region. However, when the observation time is narrowed to the initial 145 micros, both the still and streak images reveal that the cavitation bubbles astonishingly stay stable in the focal region for at least 60 micros. The results imply that through adjusting the HIFU exposure time while other physical parameters are appropriately chosen, it might be possible to control the generation of stable cavitation bubbles locally in the focal region. PMID:16782158

  18. Physical and chemical effects of acoustic cavitation in selected ultrasonic cleaning applications.

    PubMed

    Yusof, Nor Saadah Mohd; Babgi, Bandar; Alghamdi, Yousef; Aksu, Mecit; Madhavan, Jagannathan; Ashokkumar, Muthupandian

    2016-03-01

    Acoustic cavitation in a liquid medium generates several physical and chemical effects. The oscillation and collapse of cavitation bubbles, driven at low ultrasonic frequencies (e.g., 20 kHz), can generate strong shear forces, microjets, microstreaming and shockwaves. Such strong physical forces have been used in cleaning and flux improvement of ultrafiltration processes. These physical effects have also been shown to deactivate pathogens. The efficiency of deactivation of pathogens is not only dependent on ultrasonic experimental parameters, but also on the properties of the pathogens themselves. Bacteria with thick shell wall are found to be resistant to ultrasonic deactivation process. Some evidence does suggest that the chemical effects (radicals) of acoustic cavitation are also effective in deactivating pathogens. Another aspect of cleaning, namely, purification of water contaminated with organic and inorganic pollutants, has also been discussed in detail. Strong oxidising agents produced within acoustic cavitation bubbles could be used to degrade organic pollutants and convert toxic inorganic pollutants to less harmful substances. The effect of ultrasonic frequency and surface activity of solutes on the sonochemical degradation efficiency has also been discussed in this overview. PMID:26142078

  19. Fluctuation dynamics and 1/ f spectra characterizing the acoustic cavitation of liquids

    NASA Astrophysics Data System (ADS)

    Skokov, V. N.; Reshetnikov, A. V.; Vinogradov, A. V.; Koverda, V. P.

    2007-04-01

    The dynamics of acoustic cavitation in water and glycerin is studied experimentally. The power spectra and distribution functions of fluctuations are determined. In transient regimes, bubble structures in the form of fractal clusters are formed near the ultrasonic radiator. The power spectra have the form 1/ f, and the distribution functions of local fluctuations differ from the Gaussian ones and exhibit the scale invariance property.

  20. Prediction of the acoustic and bubble fields in insonified freeze-drying vials.

    PubMed

    Louisnard, O; Cogné, C; Labouret, S; Montes-Quiroz, W; Peczalski, R; Baillon, F; Espitalier, F

    2015-09-01

    The acoustic field and the location of cavitation bubble are computed in vials used for freeze-drying, insonified from the bottom by a vibrating plate. The calculations rely on a nonlinear model of sound propagation in a cavitating liquid [Louisnard, Ultrason. Sonochem., 19, (2012) 56-65]. Both the vibration amplitude and the liquid level in the vial are parametrically varied. For low liquid levels, a threshold amplitude is required to form a cavitation zone at the bottom of the vial. For increasing vibration amplitudes, the bubble field slightly thickens but remains at the vial bottom, and the acoustic field saturates, which cannot be captured by linear acoustics. On the other hand, increasing the liquid level may promote the formation of a secondary bubble structure near the glass wall, a few centimeters below the free liquid surface. These predictions suggest that rather complex acoustic fields and bubble structures can arise even in such small volumes. As the acoustic and bubble fields govern ice nucleation during the freezing step, the final crystal's size distribution in the frozen product may crucially depend on the liquid level in the vial. PMID:25800984

  1. Experimental investigation on dynamic characteristics and strengthening mechanism of laser-induced cavitation bubbles.

    PubMed

    Ren, X D; He, H; Tong, Y Q; Ren, Y P; Yuan, S Q; Liu, R; Zuo, C Y; Wu, K; Sui, S; Wang, D S

    2016-09-01

    The dynamic features of nanosecond laser-induced cavitation bubbles near the light alloy boundary were investigated with the high-speed photography. The shock-waves and the dynamic characteristics of the cavitation bubbles generated by the laser were detected using the hydrophone. The dynamic features and strengthening mechanism of cavitation bubbles were studied. The strengthening mechanisms of cavitation bubble were discussed when the relative distance parameter γ was within the range of 0.5-2.5. It showed that the strengthening mechanisms caused by liquid jet or shock-waves depended on γ much. The research results provided a new strengthening method based on laser-induced cavitation shotless peening (CSP). PMID:27150764

  2. Bubble proliferation in the cavitation field of a shock wave lithotripter.

    PubMed

    Pishchalnikov, Yuri A; Williams, James C; McAteer, James A

    2011-08-01

    Lithotripter shock waves (SWs) generated in non-degassed water at 0.5 and 2 Hz pulse repetition frequency (PRF) were characterized using a fiber-optic hydrophone. High-speed imaging captured the inertial growth-collapse-rebound cycle of cavitation bubbles, and continuous recording with a 60 fps camcorder was used to track bubble proliferation over successive SWs. Microbubbles that seeded the generation of bubble clouds formed by the breakup of cavitation jets and by bubble collapse following rebound. Microbubbles that persisted long enough served as cavitation nuclei for subsequent SWs, as such bubble clouds were enhanced at fast PRF. Visual tracking suggests that bubble clouds can originate from single bubbles. PMID:21877776

  3. The Minnaert Bubble: An Acoustic Approach

    ERIC Educational Resources Information Center

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude; Leroy, Valentin

    2008-01-01

    We propose an "ab initio" introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian…

  4. Quantitative measurements of acoustic emissions from cavitation at the surface of a stone in response to a lithotripter shock wave.

    PubMed

    Chitnis, Parag V; Cleveland, Robin O

    2006-04-01

    Measurements are presented of acoustic emissions from cavitation collapses on the surface of a synthetic kidney stone in response to shock waves (SWs) from an electrohydraulic lithotripter. A fiber optic probe hydrophone was used for pressure measurements, and passive cavitation detection was used to identify acoustic emissions from bubble collapse. At a lithotripter charging voltage of 20 kV, the focused SW incident on the stone surface resulted in a peak pressure of 43 +/- 6 MPa compared to 23 +/- 4 MPa in the free field. The focused SW incident upon the stone appeared to be enhanced due to the acoustic emissions from the forced cavitation collapse of the preexisting bubbles. The peak pressure of the acoustic emission from a bubble collapse was 34 +/- 15 MPa, that is, the same magnitude as the SWs incident on the stone. These data indicate that stresses induced by focused SWs and cavitation collapses are similar in magnitude thus likely play a similar role in stone fragmentation. PMID:16642802

  5. Stress wave emission and cavitation bubble dynamics by nanosecond optical breakdown in a tissue phantom

    NASA Astrophysics Data System (ADS)

    Brujan, Emil-Alexandru; Vogel, Alfred

    2006-07-01

    Stress wave emission and cavitation bubble dynamics after optical breakdown in water and a tissue phantom with Nd: YAG laser pulses of 6 ns duration were investigated both experimentally and numerically to obtain a better understanding of the physical mechanisms involved in plasma-mediated laser surgery. Experimental tools were high-speed photography with 50000 frames s(-1) , and acoustic measurements. The tissue phantom consisted of a transparent polyacrylamide (PAA) gel, the elastic properties of which can be controlled by modifying the water content. Breakdown in water produced a purely compressive stress wave. By contrast, in stiff PAA samples and for sufficiently large pulse energies, the compression wave was followed by an intense tensile wave, similar to the behaviour previously observed in cornea. The elastic/plastic response of the medium led to a significant decrease of the maximum size of the cavitation bubble and to a shortening of its oscillation period which was found to be related to the generation of the tensile stress wave upon breakdown. For increasing elastic modulus of the PAA, both the amplitudes of the bubble oscillation and of the stress wave emitted during bubble collapse decreased until the bubble oscillation was so strongly damped that no collapse stress wave was emitted. Numerical simulations were performed using a spherical model of bubble dynamics which includes the compressibility and elastic/plastic behaviour of the medium, viscosity, density and surface tension. The calculations revealed that consideration of the elastic/plastic behaviour of the medium surrounding the bubble is essential to describe the experimentally observed bipolar shape of the stress wave emitted upon optical breakdown. Water is a poor tissue model because the shape of the emitted stress waves and the bubble dynamics differ strongly for both materials. The mechanical properties of PAA were also found to be quite different from those of tissues. Experimental and

  6. Hydrodynamics of an endothermic gas with application to bubble cavitation

    NASA Astrophysics Data System (ADS)

    Lutsko, James F.

    2006-10-01

    The hydrodynamics for a gas of hard spheres which sometimes experience inelastic collisions resulting in the loss of a fixed, velocity-independent, amount of energy Δ is investigated with the goal of understanding the coupling between hydrodynamics and endothermic chemistry. The homogeneous cooling state of a uniform system and the modified Navier-Stokes equations are discussed and explicit expressions given for the pressure, cooling rates, and all transport coefficients for D dimensions. The Navier-Stokes equations are solved numerically for the case of a two-dimensional gas subject to a circular piston so as to illustrate the effects of the enegy loss on the structure of shocks found in cavitating bubbles. It is found that the maximal temperature achieved is a sensitive function of Δ with a minimum occurring near the physically important value of Δ ˜12000K˜1eV.

  7. Shockwave and cavitation bubble dynamics of atmospheric air

    NASA Astrophysics Data System (ADS)

    Leela, Ch.; Bagchi, S.; Tewari, Surya P.; Kiran, P. Prem

    2013-11-01

    The generation and evolution of laser induced shock waves (SWs) and the hot core plasma (HCP) created by focusing 7 ns, 532 nm laser pulses in ambient air is studied using time resolved shadowgraphic imaging technique. The dynamics of rapidly expanding plasma releasing SWs into the ambient atmosphere were studied for time delays ranging from nanoseconds to milliseconds with ns temporal resolution. The SW is observed to get detached from expanding HCP at around 3μs. Though the SWs were found to expand spherically following the Sedov-Taylor theory, the rapidly expanding HCP shows asymmetric expansion during both the expansion and cooling phase similar to that of inertial cavitation bubble (CB) dynamics. The asymmetric expansion of HCP leads to oscillation of the plasma boundary, eventually leading to collapse by forming vortices formed by the interaction of ambient air.

  8. Relationship between thrombolysis efficiency induced by pulsed focused ultrasound and cavitation bubble size

    NASA Astrophysics Data System (ADS)

    Xu, S.; Liu, X.; Wang, S.; Wan, M.

    2015-12-01

    In this study, the relationship between the efficiency of pulsed focused ultrasound (FUS)-induced thrombolysis and the size distribution of cavitation bubbles has been studied. Firstly, the thrombolysis efficiency, evaluated by degree of mechanical fragmentation was investigated with varying duty cycle. Secondly, the size distribution of cavitation bubbles after the 1st, 103th and 105th pulse during experiments for various duty cycles was studied. It was revealed that the thrombolysis efficiency was highest when the cavitation bubble size distribution was centred around linear resonance radius of the emission frequency of the FUS transducer. Therefore, in cavitation enhanced therapeutic applications, the essential of using a pulsed FUS may be controlling the size distribution of cavitation nuclei within an active size range so as to increase the treatment efficiency.

  9. Acoustic Behavior of Vapor Bubbles

    NASA Technical Reports Server (NTRS)

    Prosperetti, Andrea; Oguz, Hasan N.

    1996-01-01

    In a microgravity environment vapor bubbles generated at a boiling surface tend to remain near it for a long time. This affects the boiling heat transfer and in particular promotes an early transition to the highly inefficient film boiling regime. This paper describes the physical basis underlying attempts to remove the bubbles by means of pressure radiation forces.

  10. Hollow nanoparticle generation on laser-induced cavitation bubbles via bubble interface pinning

    NASA Astrophysics Data System (ADS)

    Yan, Zijie; Bao, Ruqiang; Wright, Roger N.; Chrisey, Douglas B.

    2010-09-01

    We report the self-assembly of ZnOx (0≤x≤1) (and permalloy) nanoclusters into hollow nanoparticles using pulsed laser ablation of bulk Zn (or permalloy) in ethanol-water binary mixture. The self-assembly is due to the trapping of laser-produced nanoclusters by the interfaces of cavitation bubbles and the bonding of the nanoclusters by capillary attraction. It was found that the bubbles generated in the mixture have significantly longer lifetimes compared to water alone, which provide an increasing chance to absorb diffusive nanoclusters. The mixture could be adjusted by adding viscous surfactant that makes the pulsed laser ablation in liquid a promising method for the discovery and fabrication of other hollow geometries.

  11. Cavitation and bubble cloud dynamics in a high-intensity focused ultrasonic field

    NASA Astrophysics Data System (ADS)

    Lu, Yuan; Katz, Joseph; Prosperetti, Andrea

    2011-11-01

    We focus a high power (200 W max, 500 kHz) ultrasonic beam to generate cavitation in quiescent water, and observe the process using high-speed holography. The intense pressure fluctuations cause corresponding variations in water density and refractive index, generating diffraction patterns that are evident in the holograms. These enable us to map the instantaneous spatial structures of the pressure field, and resolve its mean features, such as pressure nodes in a partial standing wave. At low powers, we observe slow growth of bubbles and their migration to the nodes due to the primary Bjerknes force. At high powers, this process persists in the periphery of the focal zone, but bubble clouds grow explosively near the center of the beam. These clouds travel in the sound propagation direction at a velocity of up to 5 m/s, but slow down briefly at the pressure nodes, while growing and shrinking. The bubbles contain mostly vapor, as the clouds vanishes in <100 μ s when the sound is turned off. Likely causes for these phenomena include acoustic streaming, Bjerknes forces, and attenuation of sound in the clouds.

  12. Acceleration of lithotripsy using cavitation bubbles induced by second-harmonic superimposition

    NASA Astrophysics Data System (ADS)

    Osuga, Masamizu; Yasuda, Jun; Jimbo, Hayato; Yoshizawa, Shin; Umemura, Shin-ichiro

    2016-07-01

    Shock wave lithotripsy potentially produces residual stone fragments too large to pass through ureters and significant injury to the normal tissue surrounding the stone. Previous works have shown that the collapse of cavitation bubbles induced by high-intensity focused ultrasound can produce small stone fragments via cavitation erosion. However, the erosion rate is hypothesized to be reduced by ultrasound attenuation by excessively generated bubble clouds. If so, it is important to generate the bubbles only on the stone surface. The effects of peak-negative-enhanced (PNE) and peak-positive-enhanced (PPE) waves obtained by second-harmonic superimposition were investigated to control cavitation bubbles. With the PNE waves, the bubbles were generated only on the stone surface and the maximum erosion rate was 232 ± 32 mg/min. All the fragments were smaller than 2 mm, which makes them pass through ureters naturally. The proposed method shows the potential to significantly improve the speed of lithotripsy.

  13. Electromagnetic acoustic source (EMAS) for generating shock waves and cavitation in mercury

    NASA Astrophysics Data System (ADS)

    Wang, Qi

    In the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory a vessel of liquid mercury is subjected to a proton beam. The resulting nuclear interaction produces neutrons that can be used for materials research, among other things, but also launches acoustic waves with pressures in excess of 10 MPa. The acoustic waves have high enough tensile stress to generate cavitation in the mercury which results in erosion to the steel walls of the vessel. In order to study the cavitation erosion and develop mitigation schemes it would be convenient to have a way of generating similar pressures and cavitation in mercury, without the radiation concerns associated with a proton beam. Here an electromagnetic acoustic source (EMAS) has been developed which consisted of a coil placed close to a metal plate which is in turn is in contact with a fluid. The source is driven by discharging a capacitor through the coil and results in a repulsive force on the plate launching acoustic waves in the fluid. A theoretical model is presented to predict the acoustic field from the EMAS and compares favorably with measurements made in water. The pressure from the EMAS was reported as a function of capacitance, charging voltage, number of coils, mylar thickness, and properties of the plates. The properties that resulted in the highest pressure were employed for experiments in mercury and a maximum pressure recorded was 7.1 MPa. Cavitation was assessed in water and mercury by high speed camera and by detecting acoustic emissions. Bubble clouds with lifetimes on the order of 100 µs were observed in water and on the order of 600 µs in mercury. Based on acoustic emissions the bubble radius in mercury was estimated to be 0.98 mm. Experiments to produce damage to a stainless steel plate in mercury resulted in a minimal effect after 2000 shock waves at a rate of 0.33 Hz - likely because the pressure amplitude was not high enough. In order to replicate the conditions in the SNS it is

  14. Optical measurements of gas bubbles in oil behind a cavitating micro-orifice flow

    NASA Astrophysics Data System (ADS)

    Iben, Uwe; Wolf, Fabian; Freudigmann, Hans-Arndt; Fröhlich, Jochen; Heller, Winfried

    2015-06-01

    In hydraulic systems, it is common for air release to occur behind valves or throttles in the form of bubbles. These air bubbles can affect the behavior and the performance of these systems to a substantial extent. In the paper, gas release in a liquid flow behind an orifice is analyzed by optical methods for various operation points. The bubbles are observed with a digital camera, and a detection algorithm based on the Hough transformation is used to determine their number and size. The appearance of gas bubbles is very sensitive to the inlet and outlet pressure of the orifice. Gas bubbles are only observed if choking cavitation occurs. An empirical relationship between an adjusted cavitation number and the appearance of gas release is presented. It is assumed that the observed bubbles contain mostly air. With the applied pressure differences, up to 30 % of the dissolved air was degassed in the form of bubbles.

  15. Enhancing the aggressive intensity of hydrodynamic cavitation through a Venturi tube by increasing the pressure in the region where the bubbles collapse

    NASA Astrophysics Data System (ADS)

    Soyama, H.; Hoshino, J.

    2016-04-01

    In this paper, we used a Venturi tube for generating hydrodynamic cavitation, and in order to obtain the optimum conditions for this to be used in chemical processes, the relationship between the aggressive intensity of the cavitation and the downstream pressure where the cavitation bubbles collapse was investigated. The acoustic power and the luminescence induced by the bubbles collapsing were investigated under various cavitating conditions, and the relationships between these and the cavitation number, which depends on the upstream pressure, the downstream pressure at the throat of the tube and the vapor pressure of the test water, was found. It was shown that the optimum downstream pressure, i.e., the pressure in the region where the bubbles collapse, increased the aggressive intensity by a factor of about 100 compared to atmospheric pressure without the need to increase the input power. Although the optimum downstream pressure varied with the upstream pressure, the cavitation number giving the optimum conditions was constant for all upstream pressures.

  16. Holmium laser ablation of cartilage: effects of cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Asshauer, Thomas; Jansen, Thomas; Oberthur, Thorsten; Delacretaz, Guy P.; Gerber, Bruno E.

    1995-05-01

    The ablation of fresh harvested porcine femur patellar groove cartilage by a 2.12 micrometers Cr:Tm:Ho:YAG laser in clinically used irradiation conditions was studied. Laser pulses were delivered via a 600 micrometers diameter fiber in isotonic saline. Ablation was investigated as a function of the angle of incidence of the delivery fiber with respect to the cartilage surface (0-90 degrees) and of radiant exposure. Laser pulses with energies of 0.5, 1.0 and 1.5 J and a duration of 250 microseconds were used. A constant fiber tip-tissue distance of 1 mm was maintained for all experiments. The dynamics of the induced vapor bubble and of the ablation process was monitored by time resolved flash videography with a 1 microseconds illumination. Acoustic transients were measured with a piezoelectric PVDF needle probe hydrophone. Bubble attachment to the cartilage surface during the collapse phase, leading to the direct exposition of the cartilage surface to the maximal pressure generated, was observed in all investigated irradiation conditions. Maximal pressure transients of up to 200 bars (at 1 mm distance from the collapse center) were measured at the bubble collapse at irradiation angles >= 60 degrees. No significant pressure variation was observed in perpendicular irradiation conditions as a function of radiant exposure. A significant reduction of the induced pressure for irradiation angles

  17. Effects of ultrasound frequency and acoustic amplitude on the size of sonochemically active bubbles - Theoretical study.

    PubMed

    Merouani, Slimane; Hamdaoui, Oualid; Rezgui, Yacine; Guemini, Miloud

    2013-05-01

    Numerical simulation of chemical reactions inside an isolated spherical bubble of oxygen has been performed for various ambient bubble radii at different frequencies and acoustic amplitudes to study the effects of these two parameters on the range of ambient radius for an active bubble in sonochemical reactions. The employed model combines the dynamic of bubble collapse with the chemical kinetics of single cavitation bubble. Results from this model were compared with some experimental results presented in the literature and good apparent trends between them were observed. The numerical calculations of this study showed that there always exists an optimal ambient bubble radius at which the production of oxidizing species at the end of the bubble collapse attained their upper limit. It was shown that the range of ambient radius for an active bubble increased with increasing acoustic amplitude and decreased with increasing ultrasound frequency. The optimal ambient radius decreased with increasing frequency. Analysis of curves showing optimal ambient radius versus acoustic amplitude for different ultrasonic frequencies indicated that for 200 and 300kHz, the optimal ambient radius increased linearly with increasing acoustic amplitude up to 3atm. However, slight minima of optimal radius were observed for the curves obtained at 500 and 1000kHz. PMID:23187064

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

    PubMed

    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. PMID:26611813

  19. High-speed observation of cavitation bubble clouds near a tissue boundary in high-intensity focused ultrasound fields.

    PubMed

    Chen, Hong; Li, Xiaojing; Wan, Mingxi; Wang, Supin

    2009-03-01

    Cavitation bubble clouds generated near a tissue boundary by high-intensity focused ultrasound (HIFU) were studied using high-speed photography. In all, 171 image series were captured during the initial 100 ms of continuous HIFU exposure, which showed that cavitation bubble clouds at the tissue boundary organized into two structures - "cone-shape bubble cloud structure" recorded in 146 image series and "crown-shape bubble cloud structure" recorded in 18 image series. The remaining 7 image series showed the interchanging of these two structures. It was found that when cavitation bubbles first appeared at the tissue boundary, they developed to cone-shape bubble cloud. The cone-shape bubble cloud structure was characterized by a nearly fixed tip in front of the tissue boundary. When the cavitation bubbles initially appeared away from the tissue boundary they evolved into a crown-shape bubble cloud. Deformation of tissue boundary was shown in all the recorded image series. PMID:19041998

  20. High-contrast active cavitation imaging technique based on multiple bubble wavelet transform.

    PubMed

    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. PMID:27586732

  1. Cavitation damage prediction for spallation target vessels by assessment of acoustic vibration

    SciTech Connect

    Futakawa, Masatoshi; Kogawa, Hiroyuki; Hasegawa, Shoichi; Ikeda, Dr. Yujiro; Riemer, Bernie; Wendel, Mark W; Haines, John R; Bauer, Guenter; Naoe, Dr. Takashi; Okita, Dr. Kohei; Fujiwara, Dr. Akiko; Matsumoto, Dr. Yoichiro; Tanaka, Dr. Nobuatsu

    2008-01-01

    Liquid-mercury target systems for MW-class spallation neutron sources are being developed around the world. Proton beams are used to induce the spallation reaction. At the moment the proton beam hits the target, pressure waves are generated in the mercury because of the abrupt heat deposition. The pressure waves interact with the target vessel leading to negative pressure that may cause cavitation along the vessel wall. In order to estimate the cavitation erosion, i.e. the pitting damage formed by the collapse of cavitation bubbles, off-beam tests were performed by using an electric magnetic impact testing machine (MIMTM), which can impose equivalent pressure pulses in mercury. The damage potential was defined based on the relationship between the pitting damage and the time-integrated acoustic vibration induced by impact due to the bubble collapses. Additionally, the damage potential was measured in on-beam tests carried out by using the proton beam at WNR (Weapons Neutron Research) facility in Los Alamos Neutron Science Center (LANSCE). In this paper, the concept of the damage potential, the relationship between the pitting damage formation and the damage potential both in off-beam and on-beam tests is shown.

  2. A New Active Cavitation Mapping Technique for Pulsed HIFU Applications – Bubble Doppler

    PubMed Central

    Li, Tong; Khokhlova, Tatiana; Sapozhnikov, Oleg; Hwang, Joo Ha; Sapozhnikov, Oleg; O’Donnell, Matthew

    2015-01-01

    In this work, a new active cavitation mapping technique for pulsed high-intensity focused ultrasound (pHIFU) applications termed bubble Doppler is proposed and its feasibility tested in tissue-mimicking gel phantoms. pHIFU therapy uses short pulses, delivered at low pulse repetition frequency, to cause transient bubble activity that has been shown to enhance drug and gene delivery to tissues. The current gold standard for detecting and monitoring cavitation activity during pHIFU treatments is passive cavitation detection (PCD), which provides minimal information on the spatial distribution of the bubbles. B-mode imaging can detect hyperecho formation, but has very limited sensitivity, especially to small, transient microbubbles. The bubble Doppler method proposed here is based on a fusion of the adaptations of three Doppler techniques that had been previously developed for imaging of ultrasound contrast agents – color Doppler, pulse inversion Doppler, and decorrelation Doppler. Doppler ensemble pulses were interleaved with therapeutic pHIFU pulses using three different pulse sequences and standard Doppler processing was applied to the received echoes. The information yielded by each of the techniques on the distribution and characteristics of pHIFU-induced cavitation bubbles was evaluated separately, and found to be complementary. The unified approach - bubble Doppler – was then proposed to both spatially map the presence of transient bubbles and to estimate their sizes and the degree of nonlinearity. PMID:25265178

  3. Acoustic Bubble Removal from Boiling Surfaces

    NASA Technical Reports Server (NTRS)

    Prosperetti, Andrea

    2002-01-01

    The object of the study was the investigation of the forces generated by standing acoustic waves on vapor bubbles, both far and near boundaries. In order to accomplish this objective, in view of the scarcity of publications on the topic, it has been necessary to build an edifice of knowledge about vapor bubbles in sound and flow fields from the ground up, as it were. We have addressed problems of gradually greater difficulty as follows: 1. In the first place, the physics of an stationary isolated bubble subject to a sound field in an unbounded liquid was addressed; 2. The case of bubbles translating in a stationary pressure field was then considered; 3. This was followed by a study of the combined effects of sound and translation, 4. And of a neighboring boundary 5. Finally, a new method to deal with nonspherical bubbles was developed- In addition to the work on vapor bubbles, some studies on gas bubbles were conducted in view of NASA's interest in the phenomenon of sonoluminescence.

  4. Dynamics of shock waves and cavitation bubbles in bilinear elastic-plastic media, and the implications to short-pulsed laser surgery

    NASA Astrophysics Data System (ADS)

    Brujan, E.-A.

    2005-01-01

    The dynamics of shock waves and cavitation bubbles generated by short laser pulses in water and elastic-plastic media were investigated theoretically in order to get a better understanding of their role in short-pulsed laser surgery. Numerical simulations were performed using a spherical model of bubble dynamics which include the elastic-plastic behaviour of the medium surrounding the bubble, compressibility, viscosity, density and surface tension. Breakdown in water produces a monopolar acoustic signal characterized by a compressive wave. Breakdown in an elastic-plastic medium produces a bipolar acoustic signal, with a leading positive compression wave and a trailing negative tensile wave. The calculations revealed that consideration of the tissue elasticity is essential to describe the bipolar shape of the shock wave emitted during optical breakdown. The elastic-plastic response of the medium surrounding the bubble leads to a significant decrease of the maximum size of the cavitation bubble and pressure amplitude of the shock wave emitted during bubble collapse, and shortening of the oscillation period of the bubble. The results are discussed with respect to collateral damage in short-pulsed laser surgery.

  5. Nonlinear Bubble Interactions in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Barbat, Tiberiu; Ashgriz, Nasser; Liu, Ching-Shi

    1996-01-01

    The systems consisting of a two-phase mixture, as clouds of bubbles or drops, have shown many common features in their responses to different external force fields. One of particular interest is the effect of an unsteady pressure field applied to these systems, case in which the coupling of the vibrations induced in two neighboring components (two drops or two bubbles) may result in an interaction force between them. This behavior was explained by Bjerknes by postulating that every body that is moving in an accelerating fluid is subjected to a 'kinetic buoyancy' equal with the product of the acceleration of the fluid multiplied by the mass of the fluid displaced by the body. The external sound wave applied to a system of drops/bubbles triggers secondary sound waves from each component of the system. These secondary pressure fields integrated over the surface of the neighboring drop/bubble may result in a force additional to the effect of the primary sound wave on each component of the system. In certain conditions, the magnitude of these secondary forces may result in significant changes in the dynamics of each component, thus in the behavior of the entire system. In a system containing bubbles, the sound wave radiated by one bubble at the location of a neighboring one is dominated by the volume oscillation mode and its effects can be important for a large range of frequencies. The interaction forces in a system consisting of drops are much smaller than those consisting of bubbles. Therefore, as a first step towards the understanding of the drop-drop interaction subject to external pressure fluctuations, it is more convenient to study the bubble interactions. This paper presents experimental results and theoretical predictions concerning the interaction and the motion of two levitated air bubbles in water in the presence of an acoustic field at high frequencies (22-23 KHz).

  6. The Minnaert bubble: an acoustic approach

    NASA Astrophysics Data System (ADS)

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude; Leroy, Valentin

    2008-11-01

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

  7. Numerical simulation of cavitation erosion on a NACA0015 hydrofoil based on bubble collapse strength

    NASA Astrophysics Data System (ADS)

    Hidalgo, V.; Luo, X.; Escaler, X.; Huang, R.; Valencia, E.

    2015-12-01

    The prediction of erosion under unsteady cavitation is crucial to prevent damage in hydraulic machinery. The present investigation deals with the numerical simulation of erosive partial cavitation around a NACA0015 hydrofoil. The study presents the calculation of the bubble collapse strength, Sb, based on the bubble potential energy to identify the surface areas with highest risk of damage. The results are obtained with a numerical scheme assuming homogeneous mixture flow, implicit LES and Zwart cavitation model. The 3D unsteady flow simulation has been solved using OpenFOAM. Python language and OpenFOAM calculator (foamCalcEx) have been used to obtain and represent Sb. The obtained results clearly show the instants of erosive bubble collapse and the affected surface areas.

  8. The dynamic behavior and compliance of a stream of cavitating bubbles.

    NASA Technical Reports Server (NTRS)

    Brennen, C.

    1973-01-01

    Study of the dynamic response of streams of cavitating bubbles to imposed pressure fluctuations to determine the role played by turbopump cavitation in the POGO instability of liquid rockets. Both quasi-static and more general linearized dynamic analyses are made of the perturbations to a cavitating flow through a region of reduced pressure in which the bubbles first grow and then collapse. The results, when coupled with typical bubble number density distribution functions, yield compliances which compare favorably with the existing measurements. Since the fluids involved are frequently cryogenic, a careful examination was made of the thermal effects both on the mean flow and on the perturbations. As a result, the discrepancy between theory and experiment for particular engines could be qualitatively ascribed to reductions in the compliance caused either by these thermal effects or by relatively high reduced frequencies.

  9. The Role of Acoustic Cavitation in Ultrasound-triggered Drug Release from Echogenic Liposomes

    NASA Astrophysics Data System (ADS)

    Kopechek, Jonathan A.

    Cardiovascular disease (CVD) is the leading cause of death in the United States and globally. CVD-related mortality, including coronary heart disease, heart failure, or stroke, generally occurs due to atherosclerosis, a condition in which plaques build up within arterial walls, potentially causing blockage or rupture. Targeted therapies are needed to achieve more effective treatments. Echogenic liposomes (ELIP), which consist of a lipid membrane surrounding an aqueous core, have been developed to encapsulate a therapeutic agent and/or gas bubbles for targeted delivery and ultrasound image enhancement. Under certain conditions ultrasound can cause nonlinear bubble growth and collapse, known as "cavitation." Cavitation activity has been associated with enhanced drug delivery across cellular membranes. However, the mechanisms of ultrasound-mediated drug release from ELIP have not been previously investigated. Thus, the objective of this dissertation is to elucidate the role of acoustic cavitation in ultrasound-mediated drug release from ELIP. To determine the acoustic and physical properties of ELIP, the frequency-dependent attenuation and backscatter coefficients were measured between 3 and 30 MHz. The results were compared to a theoretical model by measuring the ELIP size distribution in order to determine properties of the lipid membrane. It was found that ELIP have a broad size distribution and can provide enhanced ultrasound image contrast across a broad range of clinically-relevant frequencies. Calcein, a hydrophilic fluorescent dye, and papaverine, a lipophilic vasodilator, were separately encapsulated in ELIP and exposed to color Doppler ultrasound pulses from a clinical diagnostic ultrasound scanner in a flow system. Spectrophotometric techniques (fluorescence and absorbance measurements) were used to detect calcein or papaverine release. As a positive control, Triton X-100 (a non-ionic detergent) was added to ELIP samples not exposed to ultrasound in order

  10. Optical observation of shock waves and cavitation bubbles in high intensity laser-induced shock processes

    SciTech Connect

    Marti-Lopez, L.; Ocana, R.; Porro, J. A.; Morales, M.; Ocana, J. L.

    2009-07-01

    We report an experimental study of the temporal and spatial dynamics of shock waves, cavitation bubbles, and sound waves generated in water during laser shock processing by single Nd:YAG laser pulses of nanosecond duration. A fast ICCD camera (2 ns gate time) was employed to record false schlieren photographs, schlieren photographs, and Mach-Zehnder interferograms of the zone surrounding the laser spot site on the target, an aluminum alloy sample. We recorded hemispherical shock fronts, cylindrical shock fronts, plane shock fronts, cavitation bubbles, and phase disturbance tracks.

  11. Robust Acoustic Transducers for Bubble Chambers

    NASA Astrophysics Data System (ADS)

    Wells, Jonathan

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Golykh, R. N.

    2016-06-01

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

  13. Measurement of Bubble Size Distribution Based on Acoustic Propagation in Bubbly Medium

    NASA Astrophysics Data System (ADS)

    Wu, Xiongjun; Hsiao, Chao-Tsung; Choi, Jin-Keun; Chahine, Georges

    2013-03-01

    Acoustic properties are strongly affected by bubble size distribution in a bubbly medium. Measurement of the acoustic transmission becomes increasingly difficulty as the void fraction of the bubbly medium increases due to strong attenuation, while acoustic reflection can be measured more easily with increasing void fraction. The ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright, an instrument for bubble size measurement that is under development tries to take full advantage of the properties of acoustic propagation in bubbly media to extract bubble size distribution. Properties of both acoustic transmission and reflection in the bubbly medium from a range of short single-frequency bursts of acoustic waves at different frequencies are measured in an effort to deduce the bubble size distribution. With the combination of both acoustic transmission and reflection, assisted with validations from photography, the ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright has the potential to measure bubble size distributions in a wider void fraction range. This work was sponsored by Department of Energy SBIR program

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

    PubMed

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

    2015-06-01

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

  15. Cavitation controlled acoustic probe for fabric spot cleaning and moisture monitoring

    DOEpatents

    Sheen, Shuh-Haw; Chien, Hual-Te; Raptis, Apostolos C.

    1997-01-01

    A method and apparatus are provided for monitoring a fabric. An acoustic probe generates acoustic waves relative to the fabric. An acoustic sensor, such as an accelerometer is coupled to the acoustic probe for generating a signal representative of cavitation activity in the fabric. The generated cavitation activity representative signal is processed to indicate moisture content of the fabric. A feature of the invention is a feedback control signal is generated responsive to the generated cavitation activity representative signal. The feedback control signal can be used to control the energy level of the generated acoustic waves and to control the application of a cleaning solution to the fabric.

  16. A simple model of ultrasound propagation in a cavitating liquid. Part II: Primary Bjerknes force and bubble structures.

    PubMed

    Louisnard, O

    2012-01-01

    In a companion paper, a reduced model for propagation of acoustic waves in a cloud of inertial cavitation bubbles was proposed. The wave attenuation was calculated directly from the energy dissipated by a single bubble, the latter being estimated directly from the fully nonlinear radial dynamics. The use of this model in a mono-dimensional configuration has shown that the attenuation near the vibrating emitter was much higher than predictions obtained from linear theory, and that this strong attenuation creates a large traveling wave contribution, even for closed domain where standing waves are normally expected. In this paper, we show that, owing to the appearance of traveling waves, the primary Bjerknes force near the emitter becomes very large and tends to expel the bubbles up to a stagnation point. Two-dimensional axi-symmetric computations of the acoustic field created by a large area immersed sonotrode are also performed, and the paths of the bubbles in the resulting Bjerknes force field are sketched. Cone bubble structures are recovered and compare reasonably well to reported experimental results. The underlying mechanisms yielding such structures is examined, and it is found that the conical structure is generic and results from the appearance a sound velocity gradient along the transducer area. Finally, a more complex system, similar to an ultrasonic bath, in which the sound field results from the flexural vibrations of a thin plate, is also simulated. The calculated bubble paths reveal the appearance of other commonly observed structures in such configurations, such as streamers and flare structures. PMID:21764349

  17. Analysis of Temperature Rise Induced by High-Intensity Focused Ultrasound in Tissue-Mimicking Gel Considering Cavitation Bubbles

    NASA Astrophysics Data System (ADS)

    Asai, Ayumu; Okano, Hiroki; Yoshizawa, Shin; Umemura, Shin-ichiro

    2013-07-01

    High-intensity focused ultrasound (HIFU) causes a selective temperature rise in tissue and is used as a noninvasive method for tumor treatment. However, there is a problem in that it typically takes several hours to treat a large tumor. The development of a highly efficient method is required to shorten the treatment time. It is known that cavitation bubbles generated by HIFU enhance HIFU heating. In this study, the enhancement of the heating effect by cavitation was estimated in a numerical simulation solving a bio-heat transfer equation (BHTE) by increasing the absorption coefficients in and out of the volume of cavitation bubbles. The absorption coefficients were obtained by a curve fitting the temperature rise near the focal point between experiment and simulation. The results show that cavitation bubbles caused the increase in ultrasonic absorption not only in but also near the volume of cavitation bubbles.

  18. Theoretical estimation of the temperature and pressure within collapsing acoustical bubbles.

    PubMed

    Merouani, Slimane; Hamdaoui, Oualid; Rezgui, Yacine; Guemini, Miloud

    2014-01-01

    Formation of highly reactive species such as OH, H, HO2 and H2O2 due to transient collapse of cavitation bubbles is the primary mechanism of sonochemical reaction. The crucial parameters influencing the formation of radicals are the temperature and pressure achieved in the bubble during the strong collapse. Experimental determinations estimated a temperature of about 5000 K and pressure of several hundreds of MPa within the collapsing bubble. In this theoretical investigation, computer simulations of chemical reactions occurring in an O2-bubble oscillating in water irradiated by an ultrasonic wave have been performed for diverse combinations of various parameters such as ultrasound frequency (20-1000 kHz), acoustic amplitude (up to 0.3 MPa), static pressure (0.03-0.3 MPa) and liquid temperature (283-333 K). The aim of this series of computations is to correlate the production of OH radicals to the temperature and pressure achieved in the bubble during the strong collapse. The employed model combines the dynamic of bubble collapse in acoustical field with the chemical kinetics of single bubble. The results of the numerical simulations revealed that the main oxidant created in an O2 bubble is OH radical. The computer simulations clearly showed the existence of an optimum bubble temperature of about 5200±200 K and pressure of about 250±20 MPa. The predicted value of the bubble temperature for the production of OH radicals is in excellent agreement with that furnished by the experiments. The existence of an optimum bubble temperature and pressure in collapsing bubbles results from the competitions between the reactions of production and those of consumption of OH radicals at high temperatures. PMID:23769748

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

    SciTech Connect

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

    2007-11-01

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

  20. Interaction of lithotripter shockwaves with single inertial cavitation bubbles

    PubMed Central

    Klaseboer, Evert; Fong, Siew Wan; Turangan, Cary K.; Khoo, Boo Cheong; Szeri, Andrew J.; Calvisi, Michael L.; Sankin, Georgy N.; Zhong, Pei

    2008-01-01

    The dynamic interaction of a shockwave (modelled as a pressure pulse) with an initially spherically oscillating bubble is investigated. Upon the shockwave impact, the bubble deforms non-spherically and the flow field surrounding the bubble is determined with potential flow theory using the boundary-element method (BEM). The primary advantage of this method is its computational efficiency. The simulation process is repeated until the two opposite sides of the bubble surface collide with each other (i.e. the formation of a jet along the shockwave propagation direction). The collapse time of the bubble, its shape and the velocity of the jet are calculated. Moreover, the impact pressure is estimated based on water-hammer pressure theory. The Kelvin impulse, kinetic energy and bubble displacement (all at the moment of jet impact) are also determined. Overall, the simulated results compare favourably with experimental observations of lithotripter shockwave interaction with single bubbles (using laser-induced bubbles at various oscillation stages). The simulations confirm the experimental observation that the most intense collapse, with the highest jet velocity and impact pressure, occurs for bubbles with intermediate size during the contraction phase when the collapse time of the bubble is approximately equal to the compressive pulse duration of the shock wave. Under this condition, the maximum amount of energy of the incident shockwave is transferred to the collapsing bubble. Further, the effect of the bubble contents (ideal gas with different initial pressures) and the initial conditions of the bubble (initially oscillating vs. non-oscillating) on the dynamics of the shockwave–bubble interaction are discussed. PMID:19018296

  1. Interaction of lithotripter shockwaves with single inertial cavitation bubbles.

    PubMed

    Klaseboer, Evert; Fong, Siew Wan; Turangan, Cary K; Khoo, Boo Cheong; Szeri, Andrew J; Calvisi, Michael L; Sankin, Georgy N; Zhong, Pei

    2007-01-01

    The dynamic interaction of a shockwave (modelled as a pressure pulse) with an initially spherically oscillating bubble is investigated. Upon the shockwave impact, the bubble deforms non-spherically and the flow field surrounding the bubble is determined with potential flow theory using the boundary-element method (BEM). The primary advantage of this method is its computational efficiency. The simulation process is repeated until the two opposite sides of the bubble surface collide with each other (i.e. the formation of a jet along the shockwave propagation direction). The collapse time of the bubble, its shape and the velocity of the jet are calculated. Moreover, the impact pressure is estimated based on water-hammer pressure theory. The Kelvin impulse, kinetic energy and bubble displacement (all at the moment of jet impact) are also determined. Overall, the simulated results compare favourably with experimental observations of lithotripter shockwave interaction with single bubbles (using laser-induced bubbles at various oscillation stages). The simulations confirm the experimental observation that the most intense collapse, with the highest jet velocity and impact pressure, occurs for bubbles with intermediate size during the contraction phase when the collapse time of the bubble is approximately equal to the compressive pulse duration of the shock wave. Under this condition, the maximum amount of energy of the incident shockwave is transferred to the collapsing bubble. Further, the effect of the bubble contents (ideal gas with different initial pressures) and the initial conditions of the bubble (initially oscillating vs. non-oscillating) on the dynamics of the shockwave-bubble interaction are discussed. PMID:19018296

  2. Using acoustic cavitation to enhance chemotherapy of DOX liposomes: experiment in vitro and in vivo.

    PubMed

    Zhao, Ying-Zheng; Dai, Dan-Dan; Lu, Cui-Tao; Lv, Hai-Feng; Zhang, Yan; Li, Xing; Li, Wen-Feng; Wu, Yan; Jiang, Lei; Li, Xiao-Kun; Huang, Pin-Tong; Chen, Li-Juan; Lin, Min

    2012-09-01

    Experiments in vitro and in vivo were designed to investigate tumor growth inhibition of chemotherapeutics-loaded liposomes enhanced by acoustic cavitation. Doxorubicin-loaded liposomes (DOX liposomes) were used in experiments to investigate acoustic cavitation mediated effects on cell viability and chemotherapeutic function. The influence of lingering sensitive period after acoustic cavitation on tumor inhibition was also investigated. Animal experiment was carried out to verify the practicability of this technique in vivo. From experiment results, blank phospholipid-based microbubbles (PBM) combined with ultrasound (US) at intensity below 0.3 W/cm² could produce acoustic cavitation which maintained cell viability at high level. Compared with DOX solution, DOX liposomes combined with acoustic cavitation exerted effective tumor inhibition in vitro and in vivo. The lingering sensitive period after acoustic cavitation could also enhance the susceptibility of tumor to chemotherapeutic drugs. DOX liposomes could also exert certain tumor inhibition under preliminary acoustic cavitation. Acoustic cavitation could enhance the absorption efficiency of DOX liposomes, which could be used to reduce DOX adverse effect on normal organs in clinical chemotherapy. PMID:22188116

  3. Probing Cell Deformability via Acoustically Actuated Bubbles.

    PubMed

    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. PMID:26715211

  4. Probing Cell Deformability via Acoustically Actuated Bubbles

    PubMed Central

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

    2016-01-01

    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. PMID:26715211

  5. Translational motion of two interacting bubbles in a strong acoustic field.

    PubMed

    Doinikov, A A

    2001-08-01

    Using the Lagrangian formalism, equations of radial and translational motions of two coupled spherical gas bubbles have been derived up to terms of third order in the inverse distance between the bubbles. The equations of radial pulsations were then modified, for the purpose of allowing for effects of liquid compressibility, using Keller-Miksis' approach, and the equations of translation were added by viscous forces in the form of the Levich drag. This model was then used in a numerical investigation of the translational motion of two small, driven well below resonance, bubbles in strong acoustic fields with pressure amplitudes exceeding 1 bar. It has been found that, if the forcing is strong enough, the bubbles form a bound pair with a steady spacing rather than collide and coalesce, as classical Bjerknes theory predicts. Moreover, the viscous forces cause skewness in the system, which results in self-propulsion of the bubble pair. The latter travels as a unit along the center line in a direction that is determined by the ratio of the initial bubble radii. The results obtained are of immediate interest for understanding and modeling collective bubble phenomena in strong fields, such as acoustic cavitation streamers. PMID:11497693

  6. The acoustic signatures of cavitation erosion on grade DH36 steel

    NASA Astrophysics Data System (ADS)

    Armakolas, I.; Carlton, J.; Vidakovic, M.; Sun, T.; Grattan, K. T. V.

    2015-12-01

    Cavitation can cause considerable erosion to adjacent materials. Erosion is accompanied by acoustic emissions, related to crack formation and propagation inside the material. In this study a piezoelectric acoustic sensor mounted on the back of a grade DH36 steel plate is used to identify the acoustic signatures of cavitation. Cavitation is induced near the plate by means of an ultrasonic transducer (sonotrode). Various ‘non-erosive’ and erosive test rig configurations are examined and an acoustic threshold value for the onset of cavitation erosion is identified and presented. The use of a fibre Bragg grating (FBG)-based acoustic sensor developed at City University London for acoustic monitoring purposes is also examined. Acoustic signals from both sensors are analysed, by means of a fast Fourier transform, showing a very good agreement in terms of captured frequencies.

  7. Additional evidence of nuclear emissions during acoustic cavitation.

    PubMed

    Taleyarkhan, R P; Cho, J S; West, C D; Lahey, R T; Nigmatulin, R I; Block, R C

    2004-03-01

    Time spectra of neutron and sonoluminescence emissions were measured in cavitation experiments with chilled deuterated acetone. Statistically significant neutron and gamma ray emissions were measured with a calibrated liquid-scintillation detector, and sonoluminescence emissions were measured with a photomultiplier tube. The neutron and sonoluminescence emissions were found to be time correlated over the time of significant bubble cluster dynamics. The neutron emission energy was less than 2.5 MeV and the neutron emission rate was up to approximately 4 x 10(5) n/s. Measurements of tritium production were also performed and these data implied a neutron emission rate due to D-D fusion which agreed with what was measured. In contrast, control experiments using normal acetone did not result in statistically significant tritium activity, or neutron or gamma ray emissions. PMID:15089363

  8. Acoustic cavitation-based monitoring of the reversibility and permeability of ultrasound-induced blood-brain barrier opening

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Samiotaki, Gesthimani; Wang, Shutao; Acosta, Camilo; Chen, Cherry C.; Konofagou, Elisa E.

    2015-12-01

    Cavitation events seeded by microbubbles have been previously reported to be associated with MR- or fluorescent-contrast enhancement after focused ultrasound (FUS)-induced blood-brain barrier (BBB) opening. However, it is still unknown whether bubble activity can be correlated with the reversibility (the duration of opening and the likelihood of safe reinstatement) and the permeability of opened BBB, which is critical for the clinical translation of using passive cavitation detection to monitor, predict and control the opening. In this study, the dependence of acoustic cavitation on the BBB opening duration, permeability coefficient and histological damage occurrence were thus investigated. Transcranial pulsed FUS at 1.5 MHz in the presence of systemically circulating microbubbles was applied in the mouse hippocampi (n  =  60). The stable and inertial cavitation activities were monitored during sonication. Contrast-enhanced MRI was performed immediately after sonication and every 24 h up to 6 d thereafter, to assess BBB opening, brain tissue permeability and potential edema. Histological evaluations were used to assess the occurrence of neurovascular damages. It was found that stable cavitation was well correlated with: (1) the duration of the BBB opening (r2  =  0.77) (2) the permeability of the opened BBB (r2  =  0.82) (3) the likelihood of safe opening (P  <  0.05, safe opening compared to cases of damage; P  <  0.0001, no opening compared to safe opening). The inertial cavitation dose was correlated with the resulting BBB permeability (r2  =  0.72). Stable cavitation was found to be more reliable than inertial cavitation at assessing the BBB opening within the pressure range used in this study. This study demonstrates that the stable cavitation response during BBB opening holds promise for predicting and controlling the restoration and pharmacokinetics of FUS-opened BBB. The stable cavitation response therefore

  9. Acoustic cavitation-based monitoring of the reversibility and permeability of ultrasound-induced blood-brain barrier opening.

    PubMed

    Sun, Tao; Samiotaki, Gesthimani; Wang, Shutao; Acosta, Camilo; Chen, Cherry C; Konofagou, Elisa E

    2015-12-01

    Cavitation events seeded by microbubbles have been previously reported to be associated with MR- or fluorescent-contrast enhancement after focused ultrasound (FUS)-induced blood-brain barrier (BBB) opening. However, it is still unknown whether bubble activity can be correlated with the reversibility (the duration of opening and the likelihood of safe reinstatement) and the permeability of opened BBB, which is critical for the clinical translation of using passive cavitation detection to monitor, predict and control the opening. In this study, the dependence of acoustic cavitation on the BBB opening duration, permeability coefficient and histological damage occurrence were thus investigated. Transcranial pulsed FUS at 1.5 MHz in the presence of systemically circulating microbubbles was applied in the mouse hippocampi (n  =  60). The stable and inertial cavitation activities were monitored during sonication. Contrast-enhanced MRI was performed immediately after sonication and every 24 h up to 6 d thereafter, to assess BBB opening, brain tissue permeability and potential edema. Histological evaluations were used to assess the occurrence of neurovascular damages. It was found that stable cavitation was well correlated with: (1) the duration of the BBB opening (r(2)  =  0.77); (2) the permeability of the opened BBB (r(2)  =  0.82); (3) the likelihood of safe opening (P  <  0.05, safe opening compared to cases of damage; P  <  0.0001, no opening compared to safe opening). The inertial cavitation dose was correlated with the resulting BBB permeability (r(2)  =  0.72). Stable cavitation was found to be more reliable than inertial cavitation at assessing the BBB opening within the pressure range used in this study. This study demonstrates that the stable cavitation response during BBB opening holds promise for predicting and controlling the restoration and pharmacokinetics of FUS-opened BBB. The stable cavitation response

  10. Interaction dynamics of temporal and spatial separated cavitation bubbles in water

    NASA Astrophysics Data System (ADS)

    Tinne, N.; Ripken, T.; Lubatschowski, H.

    2010-02-01

    The LASIK procedure is a well established laser based treatment in ophthalmology. Nowadays it includes a cutting of the corneal tissue bases on ultra short pulses which are focused below the tissue surface to create an optical breakdown and hence a dissection of the tissue. The energy of the laser pulse is absorbed by non-linear processes that result in an expansion of a cavitation bubble and rupturing of the tissue. Due to a reduction of the duration of treatment the current development of ultra short laser systems points to higher repetition rates. This in turn results in a probable interaction between different cavitation bubbles of adjacent optical breakdowns. While the interaction of one single laser pulse with biological tissue is analyzed reasonably well experimentally and theoretically, the interaction of several spatial and temporal following pulses is scarcely determined yet. We present a high-speed photography analysis of cavitation bubble interaction for two spatial separated laser-induced optical breakdowns varying the laser pulse energy as well as the spatial distance. Depending on a change of these parameters different kinds of interactions such as a flattening and deformation of bubble shape, asymmetric water streams and jet formation were observed. The results of this research can be used to comprehend and optimize the cutting effect of ultra short pulse laser systems with high repetition rates (> 1 MHz).

  11. Effects of cavitation bubble interaction with temporally separated fs-laser pulses.

    PubMed

    Tinne, Nadine; Knoop, Gesche; Kallweit, Nicole; Veith, Sonja; Bleeker, Sebastian; Lubatschowski, Holger; Krüger, Alexander; Ripken, Tammo

    2014-04-01

    We present a time-resolved photographic analysis of the pulse-to-pulse interaction. In particular, we studied the influence of the cavitation bubble induced by a fs-pulse on the optical focusing of the consecutive pulse and its cavitation bubble dynamics in dependence on temporal pulse separation in water. As a first result, by decreasing the temporal separation of laser pulses, there is a diminishment of the laser-induced optical breakdown (LIOB) efficiency in terms of energy conversion, caused by disturbed focusing into persisting gas bubbles at the focal volume. A LIOB at the focal spot is finally suppressed by impinging the expanding or collapsing cavitation bubble of the preceding pulse. These results could be additionally confirmed in porcine gelatin solution with various concentrations. Hence, the interaction between the laser and transparent ophthalmic tissue may be accompanied by a raised central laser energy transmission, which could be observed in case of a temporal pulse overlap. In conclusion, our experimental results are of particular importance for the optimization of the prospective ophthalmic surgical process with future generation fs-lasers. PMID:24781592

  12. Dynamic and interaction of fs-laser induced cavitation bubbles for analyzing the cutting effect

    NASA Astrophysics Data System (ADS)

    Tinne, N.; Schumacher, S.; Nuzzo, V.; Ripken, T.; Lubatschowski, H.

    2009-07-01

    A prominent laser based treatment in ophthalmology is the LASIK procedure which nowadays includes a cutting of the corneal tissue based on ultra short pulses. Focusing an ultra short laser pulse below the surface of biological tissue an optical breakdown is caused and hence a dissection is obtained. The laser energy of the laser pulses is absorbed by nonlinear processes. As a result a cavitation bubble expands and ruptures the tissue. Hence positioning of several optical breakdowns side by side generates an incision. Due to a reduction of the duration of the treatment the current development of ultra short laser systems points to higher repetition rates in the range of hundreds of KHz or even MHz instead of tens of kHz. This in turn results in a probable occurrence of interaction between different optical breakdowns and respectively cavitation bubbles of adjacent optical breakdowns. While the interaction of one single laser pulse with biological tissue is analyzed reasonably well experimentally and theoretically, the interaction of several spatial and temporal following pulses is scarcely determined yet. Thus the aim of this study is to analyse the dynamic and interaction of two cavitation bubbles by using high speed photography. The applied laser pulse energy, the energy ratio and the spot distance between different cavitation bubbles were varied. Depending on a change of these parameters different kinds of interactions such as a flattening and deformation of bubble shape or jet formation are observed. Based on these results a further research seems to be inevitable to comprehend and optimize the cutting effect of ultra short pulse laser systems with high (> 1 MHz) repetition rates.

  13. Cavitation bubbles induced by Erbium lasers: implications for dentistry

    NASA Astrophysics Data System (ADS)

    Verleng, Marja; Verdaasdonk, Rudolf; van der Veen, Albert; Lemberg, Vladimir; Boutoussov, Dmitri

    2014-02-01

    With new fiber systems available for 3 μm, Erbium lasers become more interesting for precise tissue ablation in a water environment enabling new application in e.g. dentistry. The dynamics of explosive bubble formation was investigated at 2.78 μm (Er,Cr;YSGG) and 2.94 μm (Er:YAG), in relation to energy (10-50 mJ), pulse length (20-150 μs) and fiber tip shape (flat or taper). The dynamics of exploding and imploding vapor bubbles were captured with high speed imaging (10 - 300 μs range). Increasing the pulse length and energy, the vapor bubble became more elongated with an opaque surface for flat tip fibers. Tapered fibers produced spherical vapor bubbles with an optically transparent surface expected to be more forceful for creating mechanical effects in both hard and soft tissues. There was no significant difference between bubbles formed at 2.78 μm (Er,Cr;YSGG) and 2.94 μm (Er:YAG).

  14. System for Manipulating Drops and Bubbles Using Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    1999-01-01

    The manipulation and control of drops of liquid and gas bubbles is achieved using high intensity acoustics in the form of and/or acoustic radiation pressure and acoustic streaming. generated by a controlled wave emission from a transducer. Acoustic radiation pressure is used to deploy or dispense drops into a liquid or a gas or bubbles into a liquid at zero or near zero velocity from the discharge end of a needle such as a syringe needle. Acoustic streaming is useful in manipulating the drop or bubble during or after deployment. Deployment and discharge is achieved by focusing the acoustic radiation pressure on the discharge end of the needle, and passing the acoustic waves through the fluid in the needle. through the needle will itself, or coaxially through the fluid medium surrounding the needle. Alternatively, the acoustic waves can be counter-deployed by focusing on the discharge end of the needle from a transducer axially aligned with the needle, but at a position opposite the needle, to prevent premature deployment of the drop or bubble. The acoustic radiation pressure can also be used for detecting the presence or absence of a drop or a bubble at the tip of a needle or for sensing various physical characteristics of the drop or bubble such as size or density.

  15. Cavitation in medicine.

    PubMed

    Brennen, Christopher Earls

    2015-10-01

    We generally think of bubbles as benign and harmless and yet they can manifest the most remarkable range of physical effects. Some of those effects are the stuff of our everyday experience as in the tinkling of a brook or the sounds of breaking waves at the beach. But even these mundane effects are examples of the ability of bubbles to gather, focus and radiate energy (acoustic energy in the above examples). In other contexts that focusing of energy can lead to serious technological problems as when cavitation bubbles eat great holes through ships' propeller blades or cause a threat to the integrity of the spillways at the Hoover Dam. In liquid-propelled rocket engines, bubbles pose a danger to the stability of the propulsion system, and in artificial heart valves they can cause serious damage to the red blood cells. In perhaps the most extraordinary example of energy focusing, collapsing cavitation bubbles can emit not only sound, but also light with black body radiation temperatures equal to that of the sun (Brennen 1995 Cavitation and bubble dynamics). But, harnessed carefully, this almost unique ability to focus energy can also be put to remarkably constructive use. Cavitation bubbles are now used in a remarkable range of surgical and medical procedures, for example to emulsify tissue (most commonly in cataract surgery or in lithotripsy procedures for the reduction of kidney and gall stones) or to manipulate the DNA in individual cells. By creating cavitation bubbles non-invasively thereby depositing and focusing energy non-intrusively, one can generate minute incisions or target cancer cells. This paper will begin by briefly reviewing the history of cavitation phenomena and will end with a vision of the new horizons for the amazing cavitation bubble. PMID:26442145

  16. Analytical and experimental study of the acoustics and the flow field characteristics of cavitating self-resonating water jets

    SciTech Connect

    Chahine, G.L.; Genoux, P.F.; Johnson, V.E. Jr.; Frederick, G.S.

    1984-09-01

    Waterjet nozzles (STRATOJETS) have been developed which achieve passive structuring of cavitating submerged jets into discrete ring vortices, and which possess cavitation incipient numbers six times higher than obtained with conventional cavitating jet nozzles. In this study we developed analytical and numerical techniques and conducted experimental work to gain an understanding of the basic phenomena involved. The achievements are: (1) a thorough analysis of the acoustic dynamics of the feed pipe to the nozzle; (2) a theory for bubble ring growth and collapse; (3) a numerical model for jet simulation; (4) an experimental observation and analysis of candidate second-generation low-sigma STRATOJETS. From this study we can conclude that intensification of bubble ring collapse and design of highly resonant feed tubes can lead to improved drilling rates. The models here described are excellent tools to analyze the various parameters needed for STRATOJET optimizations. Further analysis is needed to introduce such important factors as viscosity, nozzle-jet interaction, and ring-target interaction, and to develop the jet simulation model to describe the important fine details of the flow field at the nozzle exit.

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

    PubMed

    Zhou, Yufeng; Gao, Xiaobin Wilson

    2013-08-01

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

  18. Wavelet-transform-based active imaging of cavitation bubbles in tissues induced by high intensity focused ultrasound.

    PubMed

    Liu, Runna; Xu, Shanshan; Hu, Hong; Huo, Rui; Wang, Supin; Wan, Mingxi

    2016-08-01

    Cavitation detection and imaging are essential for monitoring high-intensity focused ultrasound (HIFU) therapies. In this paper, an active cavitation imaging method based on wavelet transform is proposed to enhance the contrast between the cavitation bubbles and surrounding tissues. The Yang-Church model, which is a combination of the Keller-Miksis equation with the Kelvin-Voigt equation for the pulsations of gas bubbles in simple linear viscoelastic solids, is utilized to construct the bubble wavelet. Experiments with porcine muscles demonstrate that image quality is associated with the initial radius of the bubble wavelet and the scale. Moreover, the Yang-Church model achieves a somewhat better performance compared with the Rayleigh-Plesset-Noltingk-Neppiras-Poritsky model. Furthermore, the pulse inversion (PI) technique is combined with bubble wavelet transform to achieve further improvement. The cavitation-to-tissue ratio (CTR) of the best tissue bubble wavelet transform (TBWT) mode image is improved by 5.1 dB compared with that of the B-mode image, while the CTR of the best PI-based TBWT mode image is improved by 7.9 dB compared with that of the PI-based B-mode image. This work will be useful for better monitoring of cavitation in HIFU-induced therapies. PMID:27586712

  19. Realization of cavitation fields based on the acoustic resonance modes in an immersion-type sonochemical reactor.

    PubMed

    Wang, Yi-Chun; Yao, Ming-Chung

    2013-01-01

    Different modes of cavitation zones in an immersion-type sonochemical reactor have been realized based on the concept of acoustic resonance fields. The reactor contains three main components, namely a Langevin-type piezoelectric transducer (20 kHz), a metal horn, and a circular cylindrical sonicated cell filled with tap water. In order to diminish the generation of cavitation bubbles near the horn-tip, an enlarged cone-shaped horn is designed to reduce the ultrasonic intensity at the irradiating surface and to get better distribution of energy in the sonicated cell. It is demonstrated both numerically and experimentally that the cell geometry and the horn position have prominent effects on the pressure distribution of the ultrasound in the cell. With appropriate choices of these parameters, the whole reactor works at a resonant state. Several acoustic resonance modes observed in the simulation are realized experimentally to generate a large volume of cavitation zones using a very low ultrasonic power. PMID:22959558

  20. Characterization of the shock pulse-induced cavitation bubble activities recorded by an optical fiber hydrophone.

    PubMed

    Kang, Gwansuk; Cho, Sung Chan; Coleman, Andrew John; Choi, Min Joo

    2014-03-01

    A shock pressure pulse used in an extracorporeal shock wave treatment has a large negative pressure (<-5 MPa) which can produce cavitation. Cavitation cannot be measured easily, but may have known therapeutic effects. This study considers the signal recorded for several hundred microseconds using an optical hydrophone submerged in water at the focus of shock pressure field. The signal is characterized by shock pulse followed by a long tail after several microseconds; this signal is regarded as a cavitation-related signal (CRS). An experimental investigation of the CRS was conducted in the shock pressure field produced in water using an optical hydrophone (FOPH2000, RP Acoustics, Germany). The CRS was found to contain characteristic information about the shock pulse-induced cavitation. The first and second collapse times (t1 and t2) were identified in the CRS. The collapse time delay (tc = t2 - t1) increased with the driving shock pressures. The signal amplitude integrated for time from t1 to t2 was highly correlated with tc (adjusted R(2) = 0.990). This finding suggests that a single optical hydrophone can be used to measure shock pulse and to characterize shock pulse-induced cavitation. PMID:24606257

  1. Bubble-induced sheet cavitation inception on an isolated roughness element

    NASA Astrophysics Data System (ADS)

    van Rijsbergen, Martijn; Slot, Jesse

    2015-12-01

    The nucleation process on an isolated roughness element, located at the point of minimum pressure of a NACA 0015 hydrofoil was studied experimentally and computationally. The objective of this study was to investigate the working mechanism of bubble-induced sheet cavitation inception. High-speed micro-scale observations show the generation of a streak of cavitation—attached to the roughness element—in the wake of the bubble. Below its critical diameter, the bubble can detach from the streak cavity and travel on while the streak cavity remains. The solutions of a Rayleigh-Plesset equation along a streamline extracted from a RANS calculation show strong similarities with the experimental observations, but a factor 5 to 10 higher frame rate is needed to validate the calculations.

  2. Sonoporation at Small and Large Length Scales: Effect of Cavitation Bubble Collapse on Membranes.

    PubMed

    Fu, Haohao; Comer, Jeffrey; Cai, Wensheng; Chipot, Christophe

    2015-02-01

    Ultrasound has emerged as a promising means to effect controlled delivery of therapeutic agents through cell membranes. One possible mechanism that explains the enhanced permeability of lipid bilayers is the fast contraction of cavitation bubbles produced on the membrane surface, thereby generating large impulses, which, in turn, enhance the permeability of the bilayer to small molecules. In the present contribution, we investigate the collapse of bubbles of different diameters, using atomistic and coarse-grained molecular dynamics simulations to calculate the force exerted on the membrane. The total impulse can be computed rigorously in numerical simulations, revealing a superlinear dependence of the impulse on the radius of the bubble. The collapse affects the structure of a nearby immobilized membrane, and leads to partial membrane invagination and increased water permeation. The results of the present study are envisioned to help optimize the use of ultrasound, notably for the delivery of drugs. PMID:26261957

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

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

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

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

    SciTech Connect

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

    2009-03-10

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

  5. Orbital motions of bubbles in an acoustic field

    NASA Astrophysics Data System (ADS)

    Shirota, Minori; Yamashita, Ko; Inamura, Takao

    2012-09-01

    This experimental study aims to clarify the mechanism of orbital motion of two oscillating bubbles in an acoustic field. Trajectory of the orbital motion on the wall of a spherical levitator was observed using a high-speed video camera. Because of a good repeatability in volume oscillation of bubbles, we were also able to observe the radial motion driven at 24 kHz by stroboscopic like imaging technique. The orbital motions of bubbles raging from 0.13 to 0.18 mm were examined with different forcing amplitude and in different viscous oils. As a result, we found that pairs of bubbles revolve along an elliptic orbit around the center of mass of the bubbles. We also found that the two bubbles perform anti-phase radial oscillation. Although this radial oscillation should result in a repulsive secondary Bjerknes force, the bubbles kept a constant separate distance of about 1 mm, which indicates the existence of centripetal primary Bjerknes force.

  6. Water Treatment using Discharge Generated in Cavitation Field with Micro Bubble Cloud

    NASA Astrophysics Data System (ADS)

    Ihara, Satoshi; Hirohata, Taiki; Kominato, Yuichi; Yamabe, Chobei; Ike, Hideaki; Hakiai, Kazunori; Hirabayashi, Kazuya; Tamagawa, Masaaki

    New method of water treatment for wastewater using discharge in water cavitation field, in which numerous micro bubbles were generated by high-speed water flow, was proposed in this paper. Indigo carmine solution, which is a type of dye, with a concentration of 9mg/Liter was used as a specimen for demonstration of water treatment. The total volume of solution and average speed of solution in the cavitation field was 20 Liter and about 7.4 m/s, respectively. A reduction ratio of absorbance of 96% was obtained in 50 min of treatment time at an electrode distance of 2 mm and a discharge power of 16 W. Also it was found that the efficiency of decolorization was improved by changing the electrode location.

  7. Interaction Mechanisms of Cavitation Bubbles Induced by Spatially and Temporally Separated fs-Laser Pulses

    PubMed Central

    Tinne, Nadine; Kaune, Brigitte; Krüger, Alexander; Ripken, Tammo

    2014-01-01

    The emerging use of femtosecond lasers with high repetition rates in the MHz regime together with limited scan speed implies possible mutual optical and dynamical interaction effects of the individual cutting spots. In order to get more insight into the dynamics a time-resolved photographic analysis of the interaction of cavitation bubbles is presented. Particularly, we investigated the influence of fs-laser pulses and their resulting bubble dynamics with various spatial as well as temporal separations. Different time courses of characteristic interaction effects between the cavitation bubbles were observed depending on pulse energy and spatio-temporal pulse separation. These ranged from merely no interaction to the phenomena of strong water jet formation. Afterwards, the mechanisms are discussed regarding their impact on the medical application of effective tissue cutting lateral to the laser beam direction with best possible axial precision: the mechanical forces of photodisruption as well as the occurring water jet should have low axial extend and a preferably lateral priority. Furthermore, the overall efficiency of energy conversion into controlled mechanical impact should be maximized compared to the transmitted pulse energy and unwanted long range mechanical side effects, e.g. shock waves, axial jet components. In conclusion, these experimental results are of great importance for the prospective optimization of the ophthalmic surgical process with high-repetition rate fs-lasers. PMID:25502697

  8. Onset of particle trapping and release via acoustic bubbles.

    PubMed

    Chen, Yun; Fang, Zecong; Merritt, Brett; Strack, Dillon; Xu, Jie; Lee, Sungyon

    2016-08-01

    Trapping and sorting of micro-sized objects is one important application of lab on a chip devices, with the use of acoustic bubbles emerging as an effective, non-contact method. Acoustically actuated bubbles are known to exert a secondary radiation force (FSR) on micro-particles and stabilize them on the bubble surface, when this radiation force exceeds the external hydrodynamic forces that act to keep the particles in motion. While the theoretical expression of FSR has been derived by Nyborg decades ago, no direct experimental validation of this force has been performed, and the relationship between FSR and the bubble's ability to trap particles in a given lab on a chip device remains largely empirical. In order to quantify the connection between the bubble oscillation and the resultant FSR, we experimentally measure the amplitude of bubble oscillations that give rise to FSR and observe the trapping and release of a single microsphere in the presence of the mean flow at the corresponding acoustic parameters using an acoustofluidic device. By combining well-developed theories that connect bubble oscillations to the acoustic actuation, we derive the expression for the critical input voltage that leads to particle release into the flow, in good agreement with the experiments. PMID:26805706

  9. Ultrasonic cavitation erosion of Ti in 0.35% NaCl solution with bubbling oxygen and nitrogen.

    PubMed

    Li, D G; Wang, J D; Chen, D R; Liang, P

    2015-09-01

    The influences of oxygen and nitrogen on the ultrasonic cavitation erosion of Ti in 0.35%NaCl solution at room temperature, were investigated using a magnetostrictive-induced ultrasonic cavitation erosion (CE) facility and scanning electron microscopy (SEM). The roles of oxygen and nitrogen in the composition and the electronic property of the passive film on Ti, were studied by Mott-Schottky plot and X-ray photoelectron spectroscopy (XPS). The results showed that the mass loss of Ti in 0.35%NaCl solution increased with increasing cavitation time. Bubbling oxygen can evidently increase the resistance of ultrasonic cavitation erosion comparing with bubbling nitrogen. XPS results showed that the thickness of the passive film on Ti in 0.35%NaCl solution in the case of bubbling oxygen for 3 weeks, was about 7 nm, and the passive film was mainly composed of TiO2 with an anatase structure. While TiO2 with a rutile structure was found to be the major component of the passive film on Ti in 0.35%NaCl solution in the case of bubbling nitrogen for 3 weeks, and the film thickness was 5 nm. The results extracted from Mott-Schottky plot showed that the passive film on Ti in the case of bubbling oxygen had more donor density than the passive film on Ti in the case of bubbling nitrogen. PMID:25818362

  10. Study on the spatial distribution of the liquid temperature near a cavitation bubble wall.

    PubMed

    Shen, Yang; Yasui, Kyuichi; Sun, Zhicheng; Mei, Bin; You, Meiyan; Zhu, Tong

    2016-03-01

    A simple new model of the spatial distribution of the liquid temperature near a cavitation bubble wall (Tli) is employed to numerically calculate Tli. The result shows that Tli is almost same with the ambient liquid temperature (T0) during the bubble oscillations except at strong collapse. At strong collapse, Tli can increase to about 1510 K, the same order of magnitude with that of the maximum temperature inside the bubble, which means that the chemical reactions occur not only in gas-phase inside the collapsing bubble but also in liquid-phase just outside the collapsing bubble. Four factors (ultrasonic vibration amplitude, ultrasonic frequency, the surface tension and the viscosity) are considered to study their effects for the thin liquid layer. The results show that for the thin layer, the thickness and the temperature increase as the ultrasonic vibration amplitude rise; conversely, the thickness and the temperature decrease with the increase of the ultrasonic frequency, the surface tension or the viscosity. PMID:26585020

  11. Enhanced Condensation of Vapor Bubbles by Acoustic Actuation

    NASA Astrophysics Data System (ADS)

    Boziuk, Thomas; Smith, Marc; Glezer, Ari

    2014-11-01

    The effects of acoustic actuation on enhancement of the condensation rate of vapor bubbles in a liquid pool are investigated experimentally. Vapor bubbles are formed by direct injection into quiescent liquid in a sealed tank under controlled ambient pressure that varies from atmospheric to partial vacuum. The bubbles are injected vertically from a pressurized steam reservoir through nozzles of varying characteristic diameters, and the actuation is applied during different stages of the bubbles formation and advection. It is shown that kHz range acoustic actuation leads to excitation of high-amplitude surface capillary (Faraday) waves at the vapor-liquid interface that significantly increases the condensation rate. The concomitant controlled changes in bubble volume and in the structure of the vapor interface strongly affect bubble advection in the liquid pool. The increase in condensation rate is affected by the surface waves that increase the mixing in the thermal boundary layer surrounding the bubble, and on the advection of the bubble within the pool. High-speed image processing is used to quantitatively measure the scale of the capillary waves and their effect on vapor bubble dynamics at several ambient pressures that affect the global condensation rate.

  12. Applications of Acoustics and Cavitation to Noninvasive Therapy and Drug Delivery

    NASA Astrophysics Data System (ADS)

    Coussios, Constantin C.; Roy, Ronald A.

    2008-01-01

    Biomedical acoustics is rapidly evolving from a diagnostic modality into a therapeutic tool, and acoustic cavitation is often the common denominator in a wide range of new therapeutic applications. High-intensity focused ultrasound (HIFU) waves generated outside the body can be used to deposit heat deep within the body. Through a quantitative analysis of heat deposition by ultrasound, it is shown that inertial cavitation can help address some of the major challenges of HIFU therapy by providing a means of enhancing and monitoring treatment noninvasively. In the context of drug delivery, both inertial and stable cavitation play roles in enhancing drug activity and uptake. In particular, shape oscillations arising during stable cavitation provide an effective micropumping mechanism for enhanced mass transport across inaccessible interfaces.

  13. The acoustic environment of a sonoluminescing bubble

    NASA Astrophysics Data System (ADS)

    Holzfuss, Joachim; Rüggeberg, Matthias; Holt, R. Glynn

    2000-07-01

    A bubble is levitated in water in a cylindrical resonator which is driven by ultrasound. It has been shown that in a certain region of parameter space the bubble is emitting light pulses (sonoluminescence). One of the properties observed is the enormous spatial stability leaving the bubble "pinned" in space allowing it to emit light with a timing of picosecond accuracy. We argue that the observed stability is due to interactions of the bubble with the resonator. A shock wave emitted at collapse time together with a self generated complex sound field, which is experimentally mapped with high resolution, is responsible for the observed effects.

  14. An acoustical bubble counter for superheated drop detectors.

    PubMed

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

    2006-01-01

    A new bubble counter has been developed based on the well-established approach of detecting vaporization events acoustically in superheated drop detectors (SDDs). This counter is called the Framework Scientific ABC 1260, and it represents a major improvement over prior versions of this technology. By utilizing advanced acoustic pattern recognition software, the bubble formation event can be differentiated from ambient background noise, as well as from other acoustic signatures. Additional structural design enhancements include a relocation of the electronic components to the bottom of the device; thus allowing for greater stability, easier access to vial SDDs without exposure to system electronics. Upgrades in the electronics permit an increase in the speed of bubble detection by almost 50%, compared with earlier versions of the counters. By positioning the vial on top of the device, temperature and sound insulation can be accommodated for extreme environments. Lead shells can also be utilized for an enhanced response to high-energy neutrons. PMID:16891351

  15. Identification of cavitation signatures using both optical and PZT acoustic sensors

    NASA Astrophysics Data System (ADS)

    Vidakovic, M.; Armakolas, I.; Sun, T.; Carlton, J.; Grattan, K. T. V.

    2015-09-01

    This paper presents the results obtained from monitoring a simulated material cavitation process using both a fibre Bragg grating (FBG)-based acoustic sensor system developed at City University London and a commercial PZT (Piezoelectric Transducer) acoustic sensor, with an aim to identify the cavitation signatures. In the experiment, a sample metal plate with its back surface being instrumented with both sensors is positioned very close to an excitation sonotrode with a standard frequency of 19.5kHz. The data obtained from both sensors are recorded and analyzed, showing a very good agreement.

  16. The dynamics of cavitation bubble clouds in high-intensity focused ultrasound field observed by high-speed photography

    NASA Astrophysics Data System (ADS)

    Li, Xiaojing; Chen, Hong; Wan, Mingxi

    2007-01-01

    High-speed photography is being considered as an effective technique to record the transient phenomena in medical field. This presentation summarizes our previous work of using high-speed photography in the observation of cavitation bubble clouds generated in high-intensity focused ultrasound (HIFU) field, aiming at the better understanding of the cavitation mechanism during the medical application of HIFU. A high-speed photography system synchronized with HIFU emission facilities was built up, and using this system we have investigated the dynamics of cavitation bubble clouds (i) in the whole HIFU free field; (ii) in the focal region of HIFU free field; and (iii) near the tissue surface in HIFU field. The spatial-temporal evolution of the bubble cloud and the characteristics of bubble cloud structures as well as the possible explanations to the recorded phenomena are reviewed. All the results we got elucidated that the highspeed camera is a potent tool to detect the cavitation phenomena in HIFU field.

  17. Investigation of acoustic cavitation energy in a large-scale sonoreactor.

    PubMed

    Son, Younggyu; Lim, Myunghee; Khim, Jeehyeong

    2009-04-01

    Acoustic cavitation energy distributions were investigated for various frequencies such as 35, 72, 110 and 170 kHz in a large-scale sonoreactor. The energy analyses were conducted in three-dimensions and the highest and most stable cavitation energy distribution was obtained not in 35 kHz but in 72 kHz. However, the half-cavitation-energy distance was larger in the case of 35 kHz ultrasound than in the case of 72 kHz, demonstrating that cavitation energy for one cycle was higher for a lower frequency. This discrepancy was due to the large surface area of the cavitation-energy-meter probe. In addition, 110 and 170 kHz ultrasound showed a very low and poor cavitation energy distribution. Therefore larger input power was required to optimize the use of higher frequency ultrasound in the sonoreactor with long-irradiation distance. The relationship between cavitation energy and sonochemical efficiency using potassium iodide (KI) dosimetry was best fitted quadratically. From 7.77 x 10(-10) to 4.42 x 10(-9)mol/J of sonochemical efficiency was evaluated for the cavitation energy from 31.76 to 103. 67 W. In addition, the cavitation energy attenuation was estimated under the assumption that cavitation energy measured in this study would be equivalent to sound intensity, resulting in 0.10, 0.18 and 2.44 m(-1) of the attenuation coefficient (alpha) for 35, 72 and 110 kHz, respectively. Furthermore, alpha/(frequency)(2) was not constant, as some previous studies have suggested. PMID:19144557

  18. Nuclear Emissions During Self-Nucleated Acoustic Cavitation

    SciTech Connect

    Taleyarkhan, R.P.; Xu, Y.; West, C.D.; Lahey, R.T. Jr.; Block, R.C.; Nigmatulin, R.I.

    2006-01-27

    A unique, new stand-alone acoustic inertial confinement nuclear fusion test device was successfully tested. Experiments using four different liquid types were conducted in which bubbles were self-nucleated without the use of external neutrons. Four independent detection systems were used (i.e., a neutron track plastic detector to provide unambiguous visible records for fast neutrons, a BF{sub 3} detector, a NE-113-type liquid scintillation detector, and a NaI {gamma} ray detector). Statistically significant nuclear emissions were observed for deuterated benzene and acetone mixtures but not for heavy water. The measured neutron energy was {<=}2.45 MeV, which is indicative of deuterium-deuterium (D-D) fusion. Neutron emission rates were in the range {approx}5x10{sup 3} n/s to {approx}10{sup 4} n/s and followed the inverse law dependence with distance. Control experiments did not result in statistically significant neutron or {gamma} ray emissions.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Bubble-induced acoustic mixing in a microfluidic device

    NASA Astrophysics Data System (ADS)

    Chen, Huaying; Petkovic-Duran, Karolina; Best, Michael; Zhu, Yonggang

    2015-12-01

    Homogeneous and fast mixing of samples at microscale is a critical requirement for successful applications of microfluidics in biochemical analysis, chemical synthesis, drug delivery and nanomaterial synthesis. This paper reports the optimisation of bubble-induced mixing in a microfluidic device in terms of voltage, driving frequency, piezo transducer position and PDMS thickness. The microfluidic device consists of a microwell (with the diameter of 1mm and volume of ~95 nL) with two rectangular bubble traps (400×400μm) on both sides of the well. After the injection of liquid, air bubbles were spontaneously trapped in two rectangular traps. When the frequency of a piezo was equal to the resonance frequency of air bubbles, strong liquid recirculation formed (so called acoustic microstreaming) in the vicinity of the interface of air bubbles and water. The acoustic induced flow of microbeads and mixing of water and fluorescence dye were imaged to study the mixing efficiency. For a given voltage and PDMS thickness, when the piezo was placed on top of the well, the mixing was most vigorous. For a given frequency, the mixing efficiency was directly proportional to the voltage (4-20V) and inversely proportional to the PDMS thickness (0.3-2mm). When the frequency driving the piezo was approaching the resonance frequency of air bubbles, the mixing efficiency was maximal, while when it was far away from the resonance frequency of air bubbles, the mixing efficiency was much lower. This work provides guidance to the design and the application of bubble-induced acoustic mixing in microfluidics.

  1. Influence of the vibro-acoustic sensor position on cavitation detection in a Kaplan turbine

    NASA Astrophysics Data System (ADS)

    Schmidt, H.; Kirschner, O.; Riedelbauch, S.; Necker, J.; Kopf, E.; Rieg, M.; Arantes, G.; Wessiak, M.; Mayrhuber, J.

    2014-03-01

    Hydraulic turbines can be operated close to the limits of the operating range to meet the demand of the grid. When operated close to the limits, the risk increases that cavitation phenomena may occur at the runner and / or at the guide vanes of the turbine. Cavitation in a hydraulic turbine can cause material erosion on the runner and other turbine parts and reduce the durability of the machine leading to required outage time and related repair costs. Therefore it is important to get reliable information about the appearance of cavitation during prototype operation. In this experimental investigation the high frequency acoustic emissions and vibrations were measured at 20 operating points with different cavitation behaviour at different positions in a large prototype Kaplan turbine. The main goal was a comparison of the measured signals at different sensor positions to identify the sensitivity of the location for cavitation detection. The measured signals were analysed statistically and specific values were derived. Based on the measured signals, it is possible to confirm the cavitation limit of the examined turbine. The result of the investigation shows that the position of the sensors has a significant influence on the detection of cavitation.

  2. Micropropulsion by an acoustic bubble for navigating microfluidic spaces.

    PubMed

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

    2015-03-21

    This paper describes an underwater micropropulsion principle where a gaseous bubble trapped in a suspended microchannel and oscillated by external acoustic excitation generates a propelling force. The propelling swimmer is designed and microfabricated from parylene on the microscale (the equivalent diameter of the cylindrical bubble is around 60 μm) using microphotolithography. The propulsion mechanism is studied and verified by computational fluid dynamics (CFD) simulations as well as experiments. The acoustically excited and thus periodically oscillating bubble generates alternating flows of intake and discharge through an opening of the microchannel. As the Reynolds number of oscillating flow increases, the difference between the intake and discharge flows becomes significant enough to generate a net flow (microstreaming flow) and a propulsion force against the channel. As the size of the device is reduced, however, the Reynolds number is also reduced. To maintain the Reynolds number in a certain range and thus generate a strong propulsion force in the fabricated device, the oscillation amplitude of the bubble is maximized (resonated) and the oscillation frequency is set high (over 10 kHz). Propelling motions by a single bubble as well as an array of bubbles are achieved on the microscale. In addition, the microswimmer demonstrates payload carrying. This propulsion mechanism may be applied to microswimmers that navigate microfluidic environments and possibly narrow passages in human bodies to perform biosensing, drug delivery, imaging, and microsurgery. PMID:25650274

  3. Acoustic Sensor Design for Dark Matter Bubble Chamber Detectors

    PubMed Central

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

    2016-01-01

    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). PMID:27294937

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

    PubMed

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

    2016-01-01

    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). PMID:27294937

  5. Spectrum of laser light scattered by nanoparticles in an ablation-induced cavitation bubble

    NASA Astrophysics Data System (ADS)

    Takeuchi, Masato; Sasaki, Koichi

    2016-04-01

    The spectrum of the laser light scattered by nanoparticles in a cavitation bubble, which was induced by laser ablation of a titanium target in water, was measured using a triple-grating spectrograph. The scattered laser light observed at 100 \\upmu s after laser ablation had no wavelength-shifted component, suggesting that nanoparticles at this delay time were metallic. The wavelength-shifted component was observed in the spectrum at a delay time of 200 \\upmu s, suggesting the formation of oxidized nanoparticles. However, we observed no peaks in the spectrum of the scattered laser light in the present in situ laser-light scattering experiment. On the other hand, we observed clear peaks in the Raman spectrum of synthesized nanoparticles. The experimental results suggest slow crystallization of nanoparticles in liquid in liquid-phase laser ablation.

  6. Electromagnetically actuated micromanipulator using an acoustically oscillating bubble

    NASA Astrophysics Data System (ADS)

    Kwon, J. O.; Yang, J. S.; Lee, S. J.; Rhee, K.; Chung, S. K.

    2011-11-01

    A novel non-invasive micromanipulation technique has been developed where a microrobot swimming in an aqueous medium manipulates micro-objects, through electromagnetic actuation using an acoustically oscillating bubble attached to the microrobot as a grasping tool. This micromanipulation concept was experimentally verified; an investigation of electromagnetic actuation and acoustic excitation was also performed. Two-dimensional propulsion of a magnetic piece was demonstrated through electromagnetic actuation, using three pairs of electric coils surrounding the water chamber, and confirming that the propulsion speed of the magnetic piece was linearly proportional to the applied current intensity. Micro-object manipulation was separately demonstrated using an air bubble with glass beads (80 µm diameter) and a steel ball (800 µm diameter) in an aqueous medium. Upon acoustic excitation of the bubble by a piezo-actuator around its resonant frequency, the generated radiation force attracted and captured the neighboring glass beads and steel ball. The grasping force was indirectly measured by exposing the glass beads captured by the oscillating bubble to a stream generated by an auto-syringe pump in a mini-channel. By measuring the maximum speed of the streaming flow when the glass beads detached from the oscillating bubble and flowed downstream, the grasping force was calculated as 50 nN, based on Stokes' drag approximation. Finally, a fish egg was successfully manipulated with the integration of electromagnetic actuation and acoustic excitation, using a mini-robot consisting of a millimeter-sized magnetic piece with a bubble attached to its bottom. This novel micromanipulation may be an efficient tool for both micro device assembly and single-cell manipulation.

  7. A novel sensor for monitoring acoustic cavitation. Part I: Concept, theory, and prototype development.

    PubMed

    Zeqiri, Bajram; Gélat, Pierre N; Hodnett, Mark; Lee, Nigel D

    2003-10-01

    This paper describes a new concept for an ultrasonic cavitation sensor designed specifically for monitoring acoustic emissions generated by small microbubbles when driven by an applied acoustic field. Its novel features include a hollow, open-ended, cylindrical shape, with the sensor being a right circular cylinder of height 32 mm and external diameter 38 mm. The internal diameter of the sensor is 30 mm; its inner surface is fabricated from a 110-microm layer of piezoelectrically active film whose measurement bandwidth is sufficient to enable acoustic emissions up to and beyond 10 MHz to be monitored. When in use, the sensor is immersed within the liquid test medium and high frequency (megahertz) acoustic emissions occurring within the hollow body of the sensor are monitored. In order to shield the sensor response from events occurring outside the cylinder, the outer surface of the sensor cylinder is encapsulated within a special 4-mm thick polyurethane-based cavitation shield with acoustic properties specifically developed to be minimally perturbing to the 40 kHz applied acoustic field but attenuating to ultrasound generated at megahertz frequencies (plane-wave transmission loss > 30 dB at 1 MHz). This paper introduces the rationale behind the new sensor, describing details of its construction and the materials formulation program undertaken to develop the cavitation shield. PMID:14609074

  8. Exploitation of acoustic cavitation-induced microstreaming to enhance molecular transport.

    PubMed

    Bhatnagar, Sunali; Schiffter, Heiko; Coussios, Constantin-C

    2014-06-01

    Ultrasound (US) exposure of soft tissues, such as the skin, has been shown to increase permeability, enhancing the passage of drug molecules via passive processes such as diffusion. However, US regimes have not been exploited to enhance active convective transport of drug molecules from a donor layer, such as a gel, into another medium. A layered tissue-mimicking material (TMM) was used as a model for a drug donor layer and underlying soft tissue to test penetration of agents in response to a range of US parameters. Influence of agent molecular mass (3-2000 kDa), US frequency (0.256/1.1 MHz) and US pressure (0-10 MPa) on transport was characterised. Agents of four different molecular sizes were embedded within the TMM with or without cavitation nuclei (CN) and US applied to achieve inertial cavitation. Post-insonation, samples were analysed to determine the concentration and penetration distance of agent transported. US exposure substantially enhanced transport. At both US frequencies, enhancement of transport was significantly higher (p < 0.05) above the cavitation threshold, and CN reduced the pressure at which cavitation, and therefore transport, was achieved. Acoustic cavitation activity and related phenomena was the predominant transport mechanism, and addition of CN significantly enhanced transport within a range of clinically applicable acoustic pressures. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci. PMID:24719277

  9. Comment on "Acoustical observation of bubble oscillations induced by bubble popping"

    NASA Astrophysics Data System (ADS)

    Blanc, É.; Ollivier, F.; Antkowiak, A.; Wunenburger, R.

    2015-03-01

    We have reproduced the experiment of acoustic monitoring of spontaneous popping of single soap bubbles standing in air reported by Ding et al. [2aa Phys. Rev. E 75, 041601 (2007), 10.1103/PhysRevE.75.041601]. By using a single microphone and two different signal acquisition systems recording in parallel the signal at the microphone output, among them the system used by Ding et al., we have experimentally evidenced that the acoustic precursors of bubble popping events detected by Ding et al. actually result from an acausal artifact of the signal processing performed by their acquisition system which lies outside of its prescribed working frequency range. No acoustic precursor of popping could be evidenced with the microphone used in these experiments, whose sensitivity is 1 V Pa-1 and frequency range is 500 Hz-100 kHz.

  10. Blowing Polymer Bubbles in an Acoustic Levitator

    NASA Technical Reports Server (NTRS)

    Lee, M. C.

    1985-01-01

    In new manufacturing process, small gas-filled polymer shells made by injecting gas directly into acoustically levitated prepolymer drops. New process allows sufficient time for precise control of shell geometry. Applications foreseen in fabrication of deuterium/tritium-filled fusion targets and in pharmaceutical coatings. New process also useful in glass blowing and blow molding.

  11. Changes in cell morphology due to plasma membrane wounding by acoustic cavitation

    PubMed Central

    Schlicher, Robyn K.; Hutcheson, Joshua D.; Radhakrishna, Harish; Apkarian, Robert P.; Prausnitz, Mark R.

    2010-01-01

    Acoustic cavitation-mediated wounding (i.e., sonoporation) has great potential to improve medical and laboratory applications requiring intracellular uptake of exogenous molecules; however, the field lacks detailed understanding of cavitation-induced morphological changes in cells and their relative importance. Here, we present an in-depth study of the effects of acoustic cavitation on cells using electron and confocal microscopy coupled with quantitative flow cytometry. High resolution images of treated cells show that morphologically different types of blebs can occur after wounding conditions caused by ultrasound exposure as well as by mechanical shear and strong laser ablation. In addition, these treatments caused wound-induced non-lytic necrotic death resulting in cell bodies we call wound-derived perikarya (WD-P). However, only cells exposed to acoustic cavitation experienced ejection of intact nuclei and nearly instant lytic necrosis. Quantitative analysis by flow cytometry indicates that wound-derived perikarya are the dominant morphology of nonviable cells, except at the strongest wounding conditions, where nuclear ejection accounts for a significant portion of cell death after ultrasound exposure. PMID:20350691

  12. Impact of shock wave pattern and cavitation bubble size on tissue damage during ureteroscopic electrohydraulic lithotripsy.

    PubMed

    Vorreuther, R; Corleis, R; Klotz, T; Bernards, P; Engelmann, U

    1995-03-01

    It is known that electrohydraulic lithotripsy (EHL) during ureteroscopy may cause ureteral damage. To evaluate this trauma potential, find its mechanism and make it possible to avoid it, our research employed photographic evaluation, tissue studies, shock wave measurements and disintegration tests. The setup included a 3.3 F probe attached to an experimental generator with adjustable voltages and capacities providing energies from 25 mJ. to 1300 mJ. per pulse. In general, we distinguish between two traumatic mechanisms: (1) After placing the probe directly on the mucosa the rapid initial plasma penetrates the tissue resulting in a small, nonthermal, punched-like defect, whose depth depends on the energy applied. This trauma has minor clinical implications and is avoided by maintaining a minimum safety distance of 1 mm.; (2) According to physics, each plasma is followed by a cavitation bubble. The maximum size of this bubble depends on the energy applied and ranges from 3 mm. (25 mJ) to > 15 mm. (1300 mJ). In proportion to the bubble size, the ureteral wall may be distended or disrupted, even when the probe is not in direct contact with the mucosa. Therefore, the goal should be to obtain a low energy pressure pulse with high disintegration efficacy. Our evaluation of the pressure waves revealed that the selection of a high voltage and a low capacity leads to short and steep "laser-like" pulses. These pulses have a significant higher impact on stone disintegration than the broader pulses of the same energy provided by currently available generators. PMID:7861549

  13. Contribution of stress wave and cavitation bubble in evaluation of cell-cell adhesion by femtosecond laser-induced impulse

    NASA Astrophysics Data System (ADS)

    Iino, Takanori; Li, Po-Lin; Wang, Wen-Zhe; Deng, Jia-Huei; Lu, Yun-Chang; Kao, Fu-Jen; Hosokawa, Yoichiroh

    2014-10-01

    When an intense femtosecond laser is focused in a cell culture medium, shock wave, stress wave, and cavitation bubble are generated at the laser focal point. Cell-cell adhesion can be broken at the cellular level by the impacts of these factors. We have applied this breaking of the adhesion to an estimation of the cell-cell adhesion strength. In this application, it is important to identify which of these factors is the dominant factor that breaks the adhesion. Here we investigated this issue using streptavidin-coated microbeads adhering to a biotin-coated substrate as a mimic of the cell-cell adhesion. The results indicated that the break was induced mainly by the stress wave, not by the impact of the cavitation bubble.

  14. Efficient Generation of Cavitation Bubbles in Gel Phantom by Ultrasound Exposure with Negative-Followed by Positive-Peak-Pressure-Emphasized Waves

    NASA Astrophysics Data System (ADS)

    Yasuda, Jun; Asai, Ayumu; Yoshizawa, Shin; Umemura, Shin-ichiro

    2013-07-01

    Cavitation bubbles have much potential for emphasizing therapeutic treatments such as high-intensity focused ultrasound (HIFU) treatment, histotripsy, and sonodynamic therapy. Their highly efficient as well as controlled generation is important to utilize them effectively as well as safely. However, producing negative pressure over the cavitation threshold by focused ultrasound is difficult because of the nonlinear propagation combined with the focal phase shift. We have suggested a dual-frequency ultrasound exposure method, in which N- and P-waves emphasizing either the peak negative or positive pressure, respectively, are synthesized by superimposing the second harmonic onto the fundamental frequency. In this study, high-speed camera observation demonstrated that the exposure with N-waves immediately followed by P-waves could generate cavitation bubbles most efficiently in gel phantom. Furthermore, the measured negative and positive pressure distributions of the N- and P-wave fields, respectively, agreed well with the optically observed distributions of cavitation inception and cavitation cloud growth.

  15. The Dynamics of Vapor Bubbles in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Hao, Y.; Prosperetti, A.

    1999-01-01

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

  16. Energy analysis during acoustic bubble oscillations: relationship between bubble energy and sonochemical parameters.

    PubMed

    Merouani, Slimane; Hamdaoui, Oualid; Rezgui, Yacine; Guemini, Miloud

    2014-01-01

    In this work, energy analysis of an oscillating isolated spherical bubble in water irradiated by an ultrasonic wave has been theoretically studied for various conditions of acoustic amplitude, ultrasound frequency, static pressure and liquid temperature in order to explain the effects of these key parameters on both sonochemistry and sonoluminescence. The Keller-Miksis equation for the temporal variation of the bubble radius in compressible and viscous medium has been employed as a dynamics model. The numerical calculations showed that the rate of energy accumulation, dE/dt, increased linearly with increasing acoustic amplitude in the range of 1.5-3.0 atm and decreased sharply with increasing frequency in the range 200-1000 kHz. There exists an optimal static pressure at which the power w is highest. This optimum shifts toward a higher value as the acoustic amplitude increases. The energy of the bubble slightly increases with the increase in liquid temperature from 10 to 60 °C. The results of this study should be a helpful means to explain a variety of experimental observations conducted in the field of sonochemistry and sonoluminescence concerning the effects of operational parameters. PMID:23683796

  17. Detecting cavitation in mercury exposed to a high-energy pulsed proton beam.

    PubMed

    Manzi, Nicholas J; Chitnis, Parag V; Holt, R Glynn; Roy, Ronald A; Cleveland, Robin O; Riemer, Bernie; Wendel, Mark

    2010-04-01

    The Oak Ridge National Laboratory Spallation Neutron Source employs a high-energy pulsed proton beam incident on a mercury target to generate short bursts of neutrons. Absorption of the proton beam produces rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent collapse of these cavitation bubbles promote erosion of the steel target walls. Preliminary measurements using two passive cavitation detectors (megahertz-frequency focused and unfocused piezoelectric transducers) installed in a mercury test target to monitor cavitation generated by proton beams with charges ranging from 0.041 to 4.1 muC will be reported on. Cavitation was initially detected for a beam charge of 0.082 muC by the presence of an acoustic emission approximately 250 mus after arrival of the incident proton beam. This emission was consistent with an inertial cavitation collapse of a bubble with an estimated maximum bubble radius of 0.19 mm, based on collapse time. The peak pressure in the mercury for the initiation of cavitation was predicted to be 0.6 MPa. For a beam charge of 0.41 muC and higher, the lifetimes of the bubbles exceeded the reverberation time of the chamber ( approximately 300 mus), and distinct windows of cavitation activity were detected, a phenomenon that likely resulted from the interaction of the reverberation in the chamber and the cavitation bubbles. PMID:20370004

  18. Detecting cavitation in mercury exposed to a high-energy pulsed proton beam

    SciTech Connect

    Manzi, Nicholas J; Chitnis, Parag V; Holt, Ray G; Roy, Ronald A; Cleveland, Robin O; Riemer, Bernie; Wendel, Mark W

    2010-01-01

    The Oak Ridge National Laboratory Spallation Neutron Source employs a high-energy pulsed proton beam incident on a mercury target to generate short bursts of neutrons. Absorption of the proton beam produces rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent collapse of these cavitation bubbles promote erosion of the steel target walls. Preliminary measurements using two passive cavitation detectors (megahertz-frequency focused and unfocused piezoelectric transducers) installed in a mercury test target to monitor cavitation generated by proton beams with charges ranging from 0.041 to 4.1 C will be reported on. Cavitation was initially detected for a beam charge of 0.082 C by the presence of an acoustic emission approximately 250 s after arrival of the incident proton beam. This emission was consistent with an inertial cavitation collapse of a bubble with an estimated maximum bubble radius of 0.19 mm, based on collapse time. The peak pressure in the mercury for the initiation of cavitation was predicted to be 0.6 MPa. For a beam charge of 0.41 C and higher, the lifetimes of the bubbles exceeded the reverberation time of the chamber (~300 s), and distinct windows of cavitation activity were detected, a phenomenon that likely resulted from the interaction of the reverberation in the chamber and the cavitation bubbles.

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

    PubMed

    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. PMID:25164271

  20. High-speed observation of cavitation bubble cloud structures in the focal region of a 1.2 MHz high-intensity focused ultrasound transducer.

    PubMed

    Chen, Hong; Li, Xiaojing; Wan, Mingxi; Wang, Supin

    2007-03-01

    Cavitation bubble clouds in the focal region of HIFU play important roles in therapeutic applications of HIFU. Temporal evolution and spatial distribution of cavitation bubble clouds generated in the focal region of a 1.2 MHz single element concave HIFU transducer in water are investigated by high-speed photography. It is found that during the initial 600 micro s insonation cavitation bubble clouds organize to the "screw-like structure" or "cap-like structure". The screw-like structure is characterized by a nearly fixed tip at the geometrical focus of the HIFU transducer, and the cap-like structure is marked by a dent formed in the direction of ultrasound transmission. After 600 micro s, another two structures are recorded - "streamer structure" and "cluster structure". The streamer structure is also featured by a nearly fixed bottom position at the focus, while the cluster structure is distinguished by agglomerations of bubbles around the focus. PMID:17071124

  1. Cavitation-induced fragmentation of an acoustically-levitated droplet

    NASA Astrophysics Data System (ADS)

    Gonzalez Avila, Silvestre Roberto; Ohl, Claus-Dieter

    2015-12-01

    In this paper we investigate the initial sequence of events that lead to the fragmentation of a millimetre sized water droplets when interacting with a focused ns-laser pulse. The experimental results show complex processes that result from the reflection of an initial shock wave from plasma generation with the soft boundary of the levitating droplet; furthermore, when the reflected waves from the walls of the droplet refocus they leave behind a trail of microbubbles that later act as cavitation inception regions. Numerical simulations of a shock wave impacting and reflecting from a soft boundary are also reported; the simulated results show that the lowest pressure inside the droplet occurs at the equatorial plane. The results of the numerical model display good agreement with the experimental results both in time and in space.

  2. Passive acoustic mapping of magnetic microbubbles for cavitation enhancement and localization

    NASA Astrophysics Data System (ADS)

    Crake, Calum; de Saint Victor, Marie; Owen, Joshua; Coviello, Christian; Collin, Jamie; Coussios, Constantin-C.; Stride, Eleanor

    2015-01-01

    Magnetic targeting of microbubbles functionalized with superparamagnetic nanoparticles has been demonstrated previously for diagnostic (B-mode) ultrasound imaging and shown to enhance gene delivery in vitro and in vivo. In the present work, passive acoustic mapping (PAM) was used to investigate the potential of magnetic microbubbles for localizing and enhancing cavitation activity under focused ultrasound. Suspensions of magnetic microbubbles consisting of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), air and 10 nm diameter iron oxide nanoparticles were injected into a tissue mimicking phantom at different flow velocities (from 0 to 50 mm s-1) with or without an applied magnetic field. Microbubbles were excited using a 500 kHz single element focused transducer at peak negative focal pressures of 0.1-1.0 MPa, while a 64 channel imaging array passively recorded their acoustic emissions. Magnetic localization of microbubble-induced cavitation activity was successfully achieved and could be resolved using PAM as a shift in the spatial distribution and increases in the intensity and sustainability of cavitation activity under the influence of a magnetic field. Under flow conditions at shear rates of up to 100 s-1 targeting efficacy was maintained. Application of a magnetic field was shown to consistently increase the energy of cavitation emissions by a factor of 2-5 times over the duration of exposures compared to the case without targeting, which was approximately equivalent to doubling the injected microbubble dose. These results suggest that magnetic targeting could be used to localize and increase the concentration of microbubbles and hence cavitation activity for a given systemic dose of microbubbles or ultrasound intensity.

  3. Towards a reference cavitating vessel Part III—design and acoustic pressure characterization of a multi-frequency sonoreactor

    NASA Astrophysics Data System (ADS)

    Wang, Lian; Memoli, Gianluca; Hodnett, Mark; Butterworth, Ian; Sarno, Dan; Zeqiri, Bajram

    2015-08-01

    A multi-frequency cavitation vessel (RV-multi) has been commissioned at the National Physical Laboratory (NPL, UK), with the aim of establishing a standard source of acoustic cavitation in water, with reference to which details of the cavitation process can be studied and cavitation measurement techniques evaluated. The vessel is a cylindrical cavity with a maximum capacity up to 17 L, and is designed to work at six frequency ranges, from 21 kHz to 136 kHz, under controlled temperature conditions. This paper discusses the design of RV-multi and reports experiments carried out to establish the reproducibility of the acoustic pressure field established within the vessel and its operating envelope, including sensitivity to aspects such as water depth and temperature. The acoustic field distribution was determined along the radial and depth directions within the vessel using a miniature hydrophone, for two input voltage levels under low power transducer excitation conditions (e.g. below the cavitation threshold). Particular care was taken in determining peak acoustic pressure locations, as these are critical for accompanying cavitation studies. Perturbations of the vessel by the measuring hydrophone were also monitored with a bottom-mounted pressure sensor.

  4. Cavitation-induced damage of soft materials by focused ultrasound bursts: A fracture-based bubble dynamics model.

    PubMed

    Movahed, Pooya; Kreider, Wayne; Maxwell, Adam D; Hutchens, Shelby B; Freund, Jonathan B

    2016-08-01

    A generalized Rayleigh-Plesset-type bubble dynamics model with a damage mechanism is developed for cavitation and damage of soft materials by focused ultrasound bursts. This study is linked to recent experimental observations in tissue-mimicking polyacrylamide and agar gel phantoms subjected to bursts of a kind being considered specifically for lithotripsy. These show bubble activation at multiple sites during the initial pulses. More cavities appear continuously through the course of the observations, similar to what is deduced in pig kidney tissues in shock-wave lithotripsy. Two different material models are used to represent the distinct properties of the two gel materials. The polyacrylamide gel is represented with a neo-Hookean elastic model and damaged based upon a maximum-strain criterion; the agar gel is represented with a strain-hardening Fung model and damaged according to the strain-energy-based Griffith's fracture criterion. Estimates based upon independently determined elasticity and viscosity of the two gel materials suggest that bubble confinement should be sufficient to prevent damage in the gels, and presumably injury in some tissues. Damage accumulation is therefore proposed to occur via a material fatigue, which is shown to be consistent with observed delays in widespread cavitation activity. PMID:27586763

  5. Chromatically encoded high-speed photography of cavitation bubble dynamics inside inhomogeneous ophthalmic tissue

    NASA Astrophysics Data System (ADS)

    Tinne, N.; Matthias, B.; Kranert, F.; Wetzel, C.; Krüger, A.; Ripken, T.

    2016-03-01

    The interaction effect of photodisruption, which is used for dissection of biological tissue with fs-laser pulses, has been intensively studied inside water as prevalent sample medium. In this case, the single effect is highly reproducible and, hence, the method of time-resolved photography is sufficiently applicable. In contrast, the reproducibility significantly decreases analyzing more solid and anisotropic media like biological tissue. Therefore, a high-speed photographic approach is necessary in this case. The presented study introduces a novel technique for high-speed photography based on the principle of chromatic encoding. For illumination of the region of interest within the sample medium, the light paths of up to 12 LEDs with various emission wavelengths are overlaid via optical filters. Here, MOSFET-electronics provide a LED flash with a duration <100 ns; the diodes are externally triggered with a distinct delay for every LED. Furthermore, the different illumination wavelengths are chromatically separated again for detection via camera chip. Thus, the experimental setup enables the generation of a time-sequence of <= 12 images of a single cavitation bubble dynamics. In comparison to conventional time-resolved photography, images in sample media like water and HEMA show the significant advantages of this novel illumination technique. In conclusion, the results of this study are of great importance for the fundamental evaluation of the laser-tissue interaction inside anisotropic biological tissue and for the optimization of the surgical process with high-repetition rate fs-lasers. Additionally, this application is also suitable for the investigation of other microscopic, ultra-fast events in transparent inhomogeneous materials.

  6. Target geometry and rigidity determines laser-induced cavitation bubble transport and nanoparticle productivity - a high-speed videography study.

    PubMed

    Kohsakowski, Sebastian; Gökce, Bilal; Tanabe, Rie; Wagener, Philipp; Plech, Anton; Ito, Yoshiro; Barcikowski, Stephan

    2016-06-28

    Laser-induced cavitation has mostly been studied in bulk liquid or at a two-dimensional wall, although target shapes for the particle synthesis may strongly affect bubble dynamics and interfere with particle productivity. We investigated the dynamics of the cavitation bubble induced by pulsed-laser ablation in liquid for different target geometries with high-speed laser microsecond videography and focus on the collapse behaviour. This method enables us observations in a high time resolution (intervals of 1 μs) and single-pulse experiments. Further, we analyzed the nanoparticle productivity, the sizes of the synthesized nanoparticles and the evolution of the bubble volume for each different target shape and geometry. For the ablation of metal (Ag, Cu, Ni) wire tips a springboard-like behaviour after the first collapse is observed which can be correlated with vertical projectile motion. Its turbulent friction in the liquid causes a very efficient transport and movement of the bubble and ablated material into the bulk liquid and prevents particle redeposition. This effect is influenced by the degree of freedom of the wire as well as the material properties and dimensions, especially the Young's modulus. The most efficient and largest bubble movement away from the wire was observed for a thin (500 μm) silver wire with velocities up to 19.8 m s(-1) and for materials with a small Young's modulus and flexural rigidity. We suggest that these observations may contribute to upscaling strategies and increase of particle yield towards large synthesis of colloids based on targets that may continuously be fed. PMID:27273693

  7. Cavitation bubble-driven cell and particle behavior in an ultrasound standing wave.

    PubMed

    Kuznetsova, Larisa A; Khanna, Sanjay; Amso, Nazar N; Coakley, W Terence; Doinikov, Alexander A

    2005-01-01

    The behavior of human erythrocytes and 1-microm-diameter fluorescent latex beads in the presence of Optison contrast agent in a single half-wavelength (lambda/2) ultrasound standing wave (USSW) resonator has been studied. The particle movements were observed with an epi-fluorescent microscope and the velocity of the particles and cells was measured by particle image velocimetry (PIV). Acoustic emissions were monitored with a microphone and a spectrum analyzer. Optison contrast agent disintegrated immediately on exposure to ultrasound of 0.98-MPa acoustic pressure amplitude or higher in a chamber driven at its resonance frequency of 1.56 MHz. A discrete cloud of active microbubbles, detected at the pressure node plane, disappeared gradually and was completely lost within 15 s. The microscopy showed three-dimensional regions of circulation of both 1-microm tracer particles and erythrocytes in planes perpendicular to the pressure node plane. A numerical simulation showed that, for parameters that conform to the experimental conditions, a bubble of a subresonance size moves towards and translates about a pressure node plane. This result is in agreement with the experimental observation that the particle and cell circulation is induced by the presence and/or translational motion of microbubbles at the pressure node plane. PMID:15704403

  8. Extremely Efficient Liquid Exfoliation and Dispersion of Layered Materials by Unusual Acoustic Cavitation

    PubMed Central

    Han, Joong Tark; Jang, Jeong In; Kim, Haena; Hwang, Jun Yeon; Yoo, Hyung Keun; Woo, Jong Seok; Choi, Sua; Kim, Ho Young; Jeong, Hee Jin; Jeong, Seung Yol; Baeg, Kang-Jun; Cho, Kilwon; Lee, Geon-Woong

    2014-01-01

    Layered materials must be exfoliated and dispersed in solvents for diverse applications. Usually, highly energetic probe sonication may be considered to be an unfavourable method for the less defective exfoliation and dispersion of layered materials. Here we show that judicious use of ultrasonic cavitation can produce exfoliated transition metal dichalcogenide nanosheets extraordinarily dispersed in non-toxic solvent by minimising the sonolysis of solvent molecules. Our method can also lead to produce less defective, large graphene oxide nanosheets from graphite oxide in a short time (within 10 min), which show high electrical conductivity (>20,000 S m−1) of the printed film. This was achieved by adjusting the ultrasonic probe depth to the liquid surface to generate less energetic cavitation (delivered power ~6 W), while maintaining sufficient acoustic shearing (0.73 m s−1) and generating additional microbubbling by aeration at the liquid surface. PMID:24875584

  9. Extremely Efficient Liquid Exfoliation and Dispersion of Layered Materials by Unusual Acoustic Cavitation

    NASA Astrophysics Data System (ADS)

    Han, Joong Tark; Jang, Jeong In; Kim, Haena; Hwang, Jun Yeon; Yoo, Hyung Keun; Woo, Jong Seok; Choi, Sua; Kim, Ho Young; Jeong, Hee Jin; Jeong, Seung Yol; Baeg, Kang-Jun; Cho, Kilwon; Lee, Geon-Woong

    2014-05-01

    Layered materials must be exfoliated and dispersed in solvents for diverse applications. Usually, highly energetic probe sonication may be considered to be an unfavourable method for the less defective exfoliation and dispersion of layered materials. Here we show that judicious use of ultrasonic cavitation can produce exfoliated transition metal dichalcogenide nanosheets extraordinarily dispersed in non-toxic solvent by minimising the sonolysis of solvent molecules. Our method can also lead to produce less defective, large graphene oxide nanosheets from graphite oxide in a short time (within 10 min), which show high electrical conductivity (>20,000 S m-1) of the printed film. This was achieved by adjusting the ultrasonic probe depth to the liquid surface to generate less energetic cavitation (delivered power ~6 W), while maintaining sufficient acoustic shearing (0.73 m s-1) and generating additional microbubbling by aeration at the liquid surface.

  10. Understanding acoustic cavitation for sonolytic degradation of p-cresol as a model contaminant.

    PubMed

    Balachandran, Rajesh; Patterson, Zach; Deymier, Pierre; Snyder, Shane A; Keswani, Manish

    2016-03-01

    Many modern techniques exist for the degradation of organic pollutants in water. Numerous treatment processes which utilize the formation of hydroxyl radicals for oxidation of pollutants have been studied thoroughly. In this study, a three pronged approach has been used to characterize and understand the effect of two distinct acoustic frequencies (37 kHz and 1 MHz) on cavitation behavior. Correlation of this behavior with sonolysis of a target phenol pollutant is described. Hydroxyl radical capture, hydrophone, and microelectrode studies in this work show that megasonic frequencies are more effective for generation of hydroxyl radicals and stable cavitation events than ultrasonic frequencies. UV absorption and fluorescence measurements confirm that the combination of ultrasonic sonolysis with a Fenton reagent achieved complete degradation of p-cresol at 50 mg/L in about 30 min. Cost estimates have been made for different sonication processes and compared with traditional advanced oxidation processes. PMID:26761597

  11. Cavitations induced by plasmas, plasmas induced by cavitations, and plasmas produced in cavitations

    NASA Astrophysics Data System (ADS)

    Sasaki, Koichi

    2015-11-01

    Cavitation bubbles are not static bubbles but have dynamics of expansion, shrinkage, and collapse. Since the collapse of a cavitation bubble is roughly an adiabatic process, the inside of the bubble at the collapse has a high temperature and a high pressure, resulting in the production of a plasma. This talk will be focused on cavitation-related plasma phenomena and the role of the cavitation bubble in the synthesis of nanoparticles. A method for inducing a cavitation bubble is laser ablation in liquid. After the disappearance of laser-produced plasma with optical emission, we have observed the formation of a cavitation bubble. We have found that the inside of the cavitation bubble is the reaction field for the synthesis of nanoparticles. The atomic and molecular species ejected from the ablation target toward the liquid are transported into the cavitation bubble, and they condense into nanoparticles inside it. It is important to note that nanoparticles are stored inside the cavitation bubble until its collapse. We have shown that the size and the structure of nanoparticles are controlled by controlling the dynamics of the cavitation bubbles. Another method for inducing cavitation bubbles is to use ultrasonic power. We have found a simple method for the efficient production of standing cavitation bubbles. The method is just inserting a punching metal plate into water irradiated by ultrasonic wave. The depth of water and the position of the punching plate should be tuned precisely. We have proposed the mechanism of the efficient production of cavitation bubbles by this method. Currently, we try to have electric discharges in cavitation bubbles with the intention of realizing nonequilibrium sonochemistry. In particular, the electric discharge in a laser-induced cavitation bubble shows interesting distortion of the bubble shape, which suggests the electrostatic characteristics of the cavitation bubble.

  12. Air emission into a water shear layer through porous media. Part 2: Cavitation induced pressure attenuation

    SciTech Connect

    Myer, E.C.; Marboe, R.C.

    1994-12-31

    Cavitation near the casing of a hydroturbine can lead to damage through both cavitation erosion and mechanical vibration of the casing and the associated piping. Cavitation erosion results from the collapse of cavitation bubbles on or near a surface such as the casing wall. Mechanical vibrations transmitted to the casing directly through the collapse of bubbles on the casing wall indirectly through a coupling of the acoustic pressure pulse due to a nearby collapse on the turbine blade. Air emission along the casing can reduce the intensity of the tip vortex and the gap cavitation through ventilation of the cavity. Reduction in the machinery vibration is obtained by reduction of the intensity of cavitation bubble collapse and attenuation and scattering of the radiated acoustic pressure. This requires a bubble layer which may be introduced in the vicinity of the turbine blade tips. This layer remains for some distance downstream of the blades and is effective for attenuation of tip vortex induced noise and blade surface cavitation noise. For the purpose of characterizing this bubble layer within a water pipe, the authors spanned a pipe with a two dimensional hydrofoil and emitted air through porous media (20 and 100 micron porosity sintered stainless steel) into the shear flow over the hydrofoil. This paper is limited to an investigation of the attenuation of acoustic pressure propagating to the casing rather than the reduction in acoustic source level due to collapse cushioning effects.

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

    PubMed

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

    2014-03-01

    This study investigated the manipulation of bubbles generated by acoustic droplet vaporization (ADV) under clinically relevant flow conditions. Optical microscopy and high-frequency ultrasound imaging were used to observe bubbles generated by 2-MHz ultrasound pulses at different time points after the onset of ADV. The dependence of the bubble population on droplet concentration, flow velocity, fluid viscosity and acoustic parameters, including acoustic pressure, pulse duration and pulse repetition frequency, was investigated. The results indicated that post-ADV bubble growth spontaneously driven by air permeation markedly affected the bubble population after insonation. The bubbles can grow to a stable equilibrium diameter as great as twice the original diameter in 0.5-1 s, as predicted by the theoretical calculation. The growth trend is independent of flow velocity, but dependent on fluid viscosity and droplet concentration, which directly influence the rate of gas uptake by bubbles and the rate of gas exchange across the wall of the semipermeable tube containing the bubbles and, hence, the gas content of the host medium. Varying the acoustic pressure does not markedly change the formation of bubbles as long as the ADV thresholds of most droplets are reached. Varying pulse duration and pulse repetition frequency markedly reduces the number of bubbles. Lengthening pulse duration favors the production of large bubbles, but reduces the total number of bubbles. Increasing the PRF interestingly provides superior performance in bubble disruption. These results also suggest that an ADV bubble population cannot be assessed simply on the basis of initial droplet size or enhancement of imaging contrast by the bubbles. Determining the optimal acoustic parameters requires careful consideration of their impact on the bubble population produced for different application scenarios. PMID:24433748

  14. The dynamics of histotripsy bubbles

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  15. Development of anticavitation hydrophone using a titanium front plate: Effect of the titanium front plate in high-intensity acoustic field with generation of acoustic cavitation

    NASA Astrophysics Data System (ADS)

    Shiiba, Michihisa; Okada, Nagaya; Kurosawa, Minoru; Takeuchi, Shinichi

    2016-07-01

    Novel anticavitation hydrophones were fabricated by depositing a hydrothermally synthesized lead zirconate titanate polycrystalline film at the back of a titanium front plate. These anticavitation hydrophones were not damaged by the measurement of the acoustic field formed by a high-intensity focused ultrasound (HIFU) device. Their sensitivity was improved by approximately 20 dB over that of the conventional anticavitation hydrophone by modifying their basic structure and materials. The durability of the anticavitation hydrophone that we fabricated was compared by exposing it to a high-intensity acoustic field at the focal point of the HIFU field and in the water tank of an ultrasound cleaner. Therefore, the effect of the surface of the titanium front plate on acoustic cavitation was investigated by exposing such a surface to the high-intensity acoustic field. We found that the fabricated anticavitation hydrophone was robust and was not damaged easily, even in the focused acoustic field where acoustic cavitation occurs.

  16. Effect of picosecond laser induced cavitation bubbles generated on Au targets in a nanoparticle production set-up

    NASA Astrophysics Data System (ADS)

    Tiberi, M.; Simonelli, A.; Cristoforetti, G.; Marsili, P.; Giammanco, F.; Giorgetti, E.

    2013-03-01

    This work is aimed at an analysis of the influence on the efficiency of nanoparticle production of a cavitation bubble (CB), which forms during the laser ablation process in high-fluence regime. The CB is produced on an Au metal target immersed in water by 1064 nm ps Nd:YAG laser pulses at different fluences. Its time-space evolution is monitored by a shadowgraphic set-up, while the Au nanoparticles production rate is tagged by the growth of the plasmon resonance, which is detected by measuring shot-by-shot the UV-Vis absorbance. We analyze the dependence of bubble size on the experimental parameters. Our results appear of interest to enhance the nanoparticle production efficiency in a liquid medium.

  17. Small Gas Bubble Experiment for Mitigation of Cavitation Damage and Pressure Waves in Short-pulse Mercury Spallation Targets

    SciTech Connect

    Wendel, Mark W; Felde, David K; Sangrey, Robert L; Abdou, Ashraf A; West, David L; Shea, Thomas J; Hasegawa, Shoichi; Kogawa, Hiroyuki; Naoe, Dr. Takashi; Farny, Dr. Caleb H.; Kaminsky, Andrew L

    2014-01-01

    Populations of small helium gas bubbles were introduced into a flowing mercury experiment test loop to evaluate mitigation of beam-pulse induced cavitation damage and pressure waves. The test loop was developed and thoroughly tested at the Spallation Neutron Source (SNS) prior to irradiations at the Los Alamos Neutron Science Center - Weapons Neutron Research Center (LANSCE-WNR) facility. Twelve candidate bubblers were evaluated over a range of mercury flow and gas injection rates by use of a novel optical measurement technique that accurately assessed the generated bubble size distributions. Final selection for irradiation testing included two variations of a swirl bubbler provided by Japan Proton Accelerator Research Complex (J-PARC) collaborators and one orifice bubbler developed at SNS. Bubble populations of interest consisted of sizes up to 150 m in radius with achieved gas void fractions in the 10^-5 to 10^-4 range. The nominal WNR beam pulse used for the experiment created energy deposition in the mercury comparable to SNS pulses operating at 2.5 MW. Nineteen test conditions were completed each with 100 pulses, including variations on mercury flow, gas injection and protons per pulse. The principal measure of cavitation damage mitigation was surface damage assessment on test specimens that were manually replaced for each test condition. Damage assessment was done after radiation decay and decontamination by optical and laser profiling microscopy with damaged area fraction and maximum pit depth being the more valued results. Damage was reduced by flow alone; the best mitigation from bubble injection was between half and a quarter that of flow alone. Other data collected included surface motion tracking by three laser Doppler vibrometers (LDV), loop wall dynamic strain, beam diagnostics for charge and beam profile assessment, embedded hydrophones and pressure sensors, and sound measurement by a suite of conventional and contact microphones.

  18. Memory effect and redistribution of cavitation nuclei in a thin liquid layer.

    PubMed

    Bai, Lixin; Lin, Weijun; Wu, Pengfei; Deng, Jingjun; Li, Chao; Xu, Delong; Wang, Dong; Chen, Lishuo

    2016-09-01

    Temporal evolution and spatial distribution of acoustic cavitation structures in a thin liquid layer were investigated experimentally with high-speed photography. The inception and disappearance processes of cavitation bubble cloud revealed that the metastable cavitaton structures formed in the thin liquid layer caused a long-term "memory effect". A factor which weakens the memory effect was identified. The distribution of cavitation nuclei was investigated by changing the temporal decay of the memory effect. PMID:27150763

  19. Clustering reveals cavitation-related acoustic emission signals from dehydrating branches.

    PubMed

    Vergeynst, Lidewei L; Sause, Markus G R; De Baerdemaeker, Niels J F; De Roo, Linus; Steppe, Kathy

    2016-06-01

    The formation of air emboli in the xylem during drought is one of the key processes leading to plant mortality due to loss in hydraulic conductivity, and strongly fuels the interest in quantifying vulnerability to cavitation. The acoustic emission (AE) technique can be used to measure hydraulic conductivity losses and construct vulnerability curves. For years, it has been believed that all the AE signals are produced by the formation of gas emboli in the xylem sap under tension. More recent experiments, however, demonstrate that gas emboli formation cannot explain all the signals detected during drought, suggesting that different sources of AE exist. This complicates the use of the AE technique to measure emboli formation in plants. We therefore analysed AE waveforms measured on branches of grapevine (Vitis vinifera L. 'Chardonnay') during bench dehydration with broadband sensors, and applied an automated clustering algorithm in order to find natural clusters of AE signals. We used AE features and AE activity patterns during consecutive dehydration phases to identify the different AE sources. Based on the frequency spectrum of the signals, we distinguished three different types of AE signals, of which the frequency cluster with high 100-200 kHz frequency content was strongly correlated with cavitation. Our results indicate that cavitation-related AE signals can be filtered from other AE sources, which presents a promising avenue into quantifying xylem embolism in plants in laboratory and field conditions. PMID:27095256

  20. 2-D steering and propelling of acoustic bubble-powered microswimmers.

    PubMed

    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

  1. Transcranial Assessment and Visualization of Acoustic Cavitation: Modeling and Experimental Validation

    PubMed Central

    Clement, Gregory T.; McDannold, Nathan

    2015-01-01

    The interaction of ultrasonically-controlled microbubble oscillations (acoustic cavitation) with tissues and biological media has been shown to induce a wide range of bioeffects that may have significant impact to therapy and diagnosis of central nervous system diseases and disorders. However, the inherently non-linear microbubble oscillations combined with the micrometer and microsecond scales involved in these interactions and the limited methods to assess and visualize them transcranially hinder both their optimal use and translation to the clinics. To overcome these challenges, we present a noninvasive and clinically relevant framework that combines numerical simulations with multimodality imaging to assess and visualize the microbubble oscillations transcranially. In the present work, acoustic cavitation was studied with an integrated US and MR imaging guided clinical FUS system in non-human primates. This multimodality imaging system allowed us to concurrently induce and visualize acoustic cavitation transcranially. A high-resolution brain CT-scan that allowed us to determine the head acoustic properties (density, speed of sound, and absorption) was also co-registered to the US and MR images. The derived acoustic properties and the location of the targets that were determined by the 3D-CT scans and the post sonication MRI respectively were then used as inputs to two-and three-dimensional Finite Difference Time Domain (2D, 3D-FDTD) simulations that matched the experimental conditions and geometry. At the experimentally-determined target locations, synthetic point sources with pressure amplitude traces derived by either a Gaussian function or the output of a microbubble dynamics model were numerically excited and propagated through the skull towards a virtual US imaging array. Then, using passive acoustic mapping that was refined to incorporate variable speed of sound, we assessed the losses and aberrations induced by the skull as a function of the acoustic

  2. Numerical estimation of cavitation intensity

    NASA Astrophysics Data System (ADS)

    Krumenacker, L.; Fortes-Patella, R.; Archer, A.

    2014-03-01

    Cavitation may appear in turbomachinery and in hydraulic orifices, venturis or valves, leading to performance losses, vibrations and material erosion. This study propose a new method to predict the cavitation intensity of the flow, based on a post-processing of unsteady CFD calculations. The paper presents the analyses of cavitating structures' evolution at two different scales: • A macroscopic one in which the growth of cavitating structures is calculated using an URANS software based on a homogeneous model. Simulations of cavitating flows are computed using a barotropic law considering presence of air and interfacial tension, and Reboud's correction on the turbulence model. • Then a small one where a Rayleigh-Plesset software calculates the acoustic energy generated by the implosion of the vapor/gas bubbles with input parameters from macroscopic scale. The volume damage rate of the material during incubation time is supposed to be a part of the cumulated acoustic energy received by the solid wall. The proposed analysis method is applied to calculations on hydrofoil and orifice geometries. Comparisons between model results and experimental works concerning flow characteristic (size of cavity, pressure,velocity) as well as pitting (erosion area, relative cavitation intensity) are presented.

  3. Enhanced delivery of gold nanoparticles by acoustic cavitation for photoacoustic imaging and photothermal therapy

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Hsin; Liao, Ai-Ho; Lin, Jia-Yu; Lee, Cheng-Ru; Wu, Cheng-Ham; Liu, Tzu-Min; Wang, Churng-Ren; Li, Pai-Chi

    2013-03-01

    Gold-nanorods incorporated with microbubbles (AuMBs) were introduced as a photoacoustic/ultrasound dual- modality contrast agent in our previous study. The application can be extended to theragnosis purpose. With the unique physical characteristics of AuMBs, we propose an enhanced delivery method for the encapsulated particles. For example, laser thermotherapy mediated by plasmonic nanoparticles can be made more effective by using microbubbles as a targeted carrier and acoustic cavitation for enhanced sonoporation. The hypothesis was experimentally tested. Firts, these AuMBs first act as molecular probes with binding to specific ligands. The improved targeting efficacy was macroscopically observed by an ultrasound system. The extended retention of targeted AuMB was observed and recorded for 30 minutes in a CT-26 tumor bearing mouse. Secondly, cavitation induced by time-varying acoustic field was also applied to disrupt the microbubbles and cause increased transient cellular permeability (a.k.a., sonoporation). Multimodal optical microscope based on a Cr:forsterite laser was used to directly observe these effects. The microscope can acquired third-harmonic generation (THG) and two-photon fluorescent (2PF) signals produced by the AuMBs. In vitro examination shows approximately a 60% improvement in terms of fluorescence signals from the cellular uptake of gold nanoparticles after sonoporation treatment. Therefore, we conclude that the controlled release is feasible and can further improve the therapeutic effects of the nanoparticles.

  4. Acoustic Droplet Vaporization, Cavitation, and Therapeutic Properties of Copolymer-Stabilized Perfluorocarbon Nanoemulsions

    SciTech Connect

    Nam, Kweon-Ho; Christensen, Douglas A.; Rapoport, Natalya; Kennedy, Anne M.

    2009-04-14

    Acoustic and therapeutic properties of Doxorubicin (DOX) and paclitaxel (PTX)-loaded perfluorocarbon nanoemulsions have been investigated in a mouse model of ovarian cancer. The nanoemulsions were stabilized by two biodegradable amphiphilic block copolymers that differed in the structure of the hydrophobic block. Acoustic droplet vaporization (ADV) and cavitation parameters were measured as a function of ultrasound frequency, pressure, duty cycles, and temperature. The optimal parameters that induced ADV and inertial cavitation of the formed microbubbles were used in vivo in the experiments on the ultrasound-mediated chemotherapy of ovarian cancer. A combination tumor treatment by intravenous injections of drug-loaded perfluoropentane nanoemulsions and tumor-directed 1-MHz ultrasound resulted in a dramatic decrease of ovarian or breast carcinoma tumor volume and sometimes complete tumor resolution. However, tumors often recurred three to six weeks after the treatment indicating that some cancer cells survived the treatment. The recurrent tumors proved more aggressive and resistant to the repeated therapy than initial tumors suggesting selection for the resistant cells during the first treatment.

  5. Acoustic Droplet Vaporization, Cavitation, and Therapeutic Properties of Copolymer-Stabilized Perfluorocarbon Nanoemulsions

    NASA Astrophysics Data System (ADS)

    Nam, Kweon-Ho; Christensen, Douglas A.; Kennedy, Anne M.; Rapoport, Natalya

    2009-04-01

    Acoustic and therapeutic properties of Doxorubicin (DOX) and paclitaxel (PTX)-loaded perfluorocarbon nanoemulsions have been investigated in a mouse model of ovarian cancer. The nanoemulsions were stabilized by two biodegradable amphiphilic block copolymers that differed in the structure of the hydrophobic block. Acoustic droplet vaporization (ADV) and cavitation parameters were measured as a function of ultrasound frequency, pressure, duty cycles, and temperature. The optimal parameters that induced ADV and inertial cavitation of the formed microbubbles were used in vivo in the experiments on the ultrasound-mediated chemotherapy of ovarian cancer. A combination tumor treatment by intravenous injections of drug-loaded perfluoropentane nanoemulsions and tumor-directed 1-MHz ultrasound resulted in a dramatic decrease of ovarian or breast carcinoma tumor volume and sometimes complete tumor resolution. However, tumors often recurred three to six weeks after the treatment indicating that some cancer cells survived the treatment. The recurrent tumors proved more aggressive and resistant to the repeated therapy than initial tumors suggesting selection for the resistant cells during the first treatment.

  6. Acoustic bubble: Controlled and selective micropropulsion and chemical waveform generator

    NASA Astrophysics Data System (ADS)

    Ahmed, Daniel

    The physics governing swimming at the microscale---where viscous forces dominate over inertial---is distinctly different than that at the macroscale. Devices capable of finely controlled swimming at the microscale could enable bold ideas such as targeted drug delivery, non-invasive microsurgery, and precise materials assembly. Progress has already been made towards such artificial microswimmers using several means of actuation: chemical reactions and applied magnetic, electric or acoustic fields. However, the prevailing goal of selective actuation of a single microswimmer from within a group, the first step towards collaborative, guided action by a group of swimmers, has so far not been achieved. Here I present a new class of microswimmer that accomplishes for the first time selective actuation (Chapter 1). The swimmer design eschews the commonly-held design paradigm that microswimmers must use non-reciprocal motion to achieve propulsion; instead, the swimmer is propelled by oscillatory motion of an air bubble trapped within the swimmer's polymer body. This oscillatory motion is driven by a low-power biocompatible acoustic field to the ambient liquid, with meaningful swimmer propulsion occurring only at resonance frequencies of the bubble. This acoustically-powered microswimmer performs controllable rapid translational and rotational motion even in highly viscous liquid. By using a group of swimmers each with a different bubble size (and thus different resonance frequencies) selective actuation of a single swimmer from among the group can be readily achieved. Cellular response to chemical microenvironments depends on the spatiotemporal characteristics of the stimulus, which is central to many biological processes including gene expression, cell migration, differentiation, apoptosis, and intercellular signaling. To date, studies have been limited to digital (or step) chemical stimulation with little control over the temporal counterparts. Microfluidic approaches

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

    NASA Technical Reports Server (NTRS)

    Azuma, H.

    1993-01-01

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

  8. Acoustic wave propagation in air-bubble curtains in water. Part 1. History and theory

    SciTech Connect

    Domenico, S.N.

    1982-03-01

    Air bubbles in water increase the compressibility several orders of magnitude above that in bubble-free water, thereby greatly reducing the velocity and increasing attenuation of acoustic waves. Currently, air bubble curtains are used to prevent damage of submerged structures (e.g., dams) by shock waves from submarine explosives. Also, air-bubble curtains are used to reduce damage to water-filler tanks in which metals are formed by explosives. Published results of laboratory experiments confirm theoretic velocity and attenuation functions and demonstrate that these quantities are dependent principally upon frequency, bubble size, and fractional volume of air. 31 references.

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

    PubMed

    Wang, Meng; Yuan, Wenqiao

    2016-01-01

    Microalgal cell disruption induced by acoustic cavitation was simulated through solving the bubble dynamics in an acoustical field and their radial kinetics (chemical kinetics of radical species) occurring in the bubble during its oscillation, as well as calculating the bubble wall pressure at the collapse point. Modeling results indicated that increasing ultrasonic intensity led to a substantial increase in the number of bubbles formed during acoustic cavitation, however, the pressure generated when the bubbles collapsed decreased. Therefore, cumulative collapse pressure (CCP) of bubbles was used to quantify acoustic disruption of a freshwater alga, Scenedesmus dimorphus, and a marine alga, Nannochloropsis oculata and compare with experimental results. The strong correlations between CCP and the intracellular lipid fluorescence density, chlorophyll-a fluorescence density, and cell particle/debris concentration were found, which suggests that the developed models could accurately predict acoustic cell disruption, and can be utilized in the scale up and optimization of the process. PMID:26384877

  10. Acoustic studies for alpha background rejection in dark matter bubble chamber detectors

    SciTech Connect

    Bou-Cabo, M.; Felis, I.; Ardid, M.; Collaboration: COUPP Collaboration

    2013-08-08

    COUPP (Chicagoland Observatory for Underground Particle Physics) is an experiment with bubble chambers able to detect dark matter directly either with Spin-Dependent or with Spin-Independent interactions. The target material is a superheated liquid (usually CF3I) that can be bubble nucleated due to nuclear recoils produced by elastic collisions of dark matter particles. The bubble growth inside the chamber is accompanied with an acoustic signature. The acoustic technique has been successfully used to have a good alpha discrimination (about 99%). In this paper, we present different studies and results related with the characterization of the acoustic properties of the detector and the different phenomena involved in the acoustic measurements of the bubble growth, such as sound generation, sound transmission and optimization of piezoelectric transducers.

  11. An acoustic levitation technique for the study of nonlinear oscillations of gas bubbles in liquids

    NASA Astrophysics Data System (ADS)

    Young, D. A.; Crum, L. A.

    1983-08-01

    A technique of acoustic levitation was developed for the study of individual gas bubbles in a liquid. Isopropyl alcohol and a mixture of glycerine and water (33-1/3% glycerine by volume) were the two liquids used in this research. Bubbles were levitated near the acoustic pressure antinode of an acoustic wave in the range of 20-22 kHz. Measurements were made of the levitation number as a function of the normalized radius of the bubbles. The levitation number is the ratio of the hydrostatic pressure gradient to the acoustic pressure gradient. These values were then compared to a nonlinear theory. Results were very much in agreement except for the region near the n=2 harmonic. An explanation for the discrepancy between theory and experiment appears to lie in the polytropic exponent associated with the gas in the interior of the bubble.

  12. Efficient generation of cavitation bubbles and reactive oxygen species using triggered high-intensity focused ultrasound sequence for sonodynamic treatment

    NASA Astrophysics Data System (ADS)

    Yasuda, Jun; Yoshizawa, Shin; Umemura, Shin-ichiro

    2016-07-01

    Sonodynamic treatment is a method of treating cancer using reactive oxygen species (ROS) generated by cavitation bubbles in collaboration with a sonosensitizer at a target tissue. In this treatment method, both localized ROS generation and ROS generation with high efficiency are important. In this study, a triggered high-intensity focused ultrasound (HIFU) sequence, which consists of a short, extremely high intensity pulse immediately followed by a long, moderate-intensity burst, was employed for the efficient generation of ROS. In experiments, a solution sealed in a chamber was exposed to a triggered HIFU sequence. Then, the distribution of generated ROS was observed by the luminol reaction, and the amount of generated ROS was quantified using KI method. As a result, the localized ROS generation was demonstrated by light emission from the luminol reaction. Moreover, it was demonstrated that the triggered HIFU sequence has higher efficiency of ROS generation by both the KI method and the luminol reaction emission.

  13. A model of the interaction of bubbles and solid particles under acoustic excitation

    NASA Astrophysics Data System (ADS)

    Hay, Todd Allen

    The Lagrangian formalism utilized by Ilinskii, Hamilton and Zabolotskaya [J. Acoust. Soc. Am. 121, 786-795 (2007)] to derive equations for the radial and translational motion of interacting bubbles is extended here to obtain a model for the dynamics of interacting bubbles and elastic particles. The bubbles and particles are assumed to be spherical but are otherwise free to pulsate and translate. The model is accurate to fifth order in terms of a nondimensional expansion parameter R/d, where R is a characteristic radius and d is a characteristic distance between neighboring bubbles or particles. The bubbles and particles may be of nonuniform size, the particles elastic or rigid, and external acoustic sources are included to an order consistent with the accuracy of the model. Although the liquid is assumed initially to be incompressible, corrections accounting for finite liquid compressibility are developed to first order in the acoustic Mach number for a cluster of bubbles and particles, and to second order in the acoustic Mach number for a single bubble. For a bubble-particle pair consideration is also given to truncation of the model at fifth order in R/d via automated derivation of the model equations to arbitrary order. Numerical simulation results are presented to demonstrate the effects of key parameters such as particle density and size, liquid compressibility, particle elasticity and model order on the dynamics of single bubbles, pairs of bubbles, bubble-particle pairs and clusters of bubbles and particles under both free response conditions and sinusoidal or shock wave excitation.

  14. Observations of clustering inside oceanic bubble clouds and the effect on short-range acoustic propagation.

    PubMed

    Weber, Thomas C

    2008-11-01

    It has recently been shown [Weber, T. C. et al. (2007). "Acoustic propagation through clustered bubble clouds," IEEE J. Ocean. Eng. 32, 513-523] that gas bubble clustering plays a role in determining the acoustic field characteristics of bubbly fluids. In particular, it has been shown that clustering changes the bubble-induced attenuation as well as the ping-to-ping variability in the acoustic field. The degree to which bubble clustering exists in nature, however, is unknown. This paper describes a method for quantifying bubble clustering using a high frequency (400 kHz) multibeam sonar, and reports on observations of near-surface bubble clustering during a storm (14.6 m/s wind speed) in the Gulf of Maine. The multibeam sonar data are analyzed to estimate the pair correlation function, a measure of bubble clustering. In order to account for clustering in the mean acoustic field, a modification to the effective medium wave number is made. With this modification, the multibeam sonar observations are used to predict the effect of clustering on the attenuation of the mean field for short-range propagation (1 m) at frequencies between 10 and 350 kHz. Results for this specific case show that clustering can cause the attenuation to change by 20%-80% over this frequency range. PMID:19045766

  15. Aspherical bubble dynamics and oscillation times

    SciTech Connect

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

    1999-06-01

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

  16. Condition of resonant break-up of gas bubbles by an acoustic wave in liquid

    NASA Astrophysics Data System (ADS)

    Vanovskiy, V. V.; Petrov, A. G.

    2016-07-01

    The linear theory of damping of radial vibrations of a bubble in a liquid is constructed by taking into account the key dissipative mechanisms: thermal, viscous, and acoustic. The basic approximation of homobaricity made helps to obtain the results in a convenient and simple form. The results obtained for damping are used further in the description of the forced resonant oscillations of a bubble in an acoustic wave with the frequency equal to the eigenfrequency of the radial oscillation mode and twice as high as the frequency of the deformation oscillation mode (resonance 2:2:1). It is shown that the amplitude of deformation oscillations, which is reasonably large for breaking, is developed at a relatively small pressure amplitude of the exciting acoustic wave, and subharmonics arise in the acoustic-emission spectrum. The condition of bubble break-up is obtained for a fast and slow start of the acoustic wave.

  17. Exploiting flow to control the in vitro spatiotemporal distribution of microbubble-seeded acoustic cavitation activity in ultrasound therapy.

    PubMed

    Pouliopoulos, Antonios N; Bonaccorsi, Simone; Choi, James J

    2014-11-21

    Focused ultrasound and microbubbles have been extensively used to generate therapeutic bioeffects. Despite encouraging in vivo results, there remains poor control of the magnitude and spatial distribution of these bioeffects due to the limited ability of conventional pulse shapes and sequences to control cavitation dynamics. Thus current techniques are restricted by an efficacy-safety trade-off. The primary aim of the present study was to incorporate the presence of flow in the design of new short pulse sequences, which can more uniformly distribute the cavitation activity. Microbubbles flowing (fluid velocity: 10 mm s(-1)) through a 300 μm tube were sonicated with a focused 0.5 MHz transducer while acoustic emissions were captured with an inserted focused 7.5 MHz passive cavitation detector. The two foci were co-axially aligned and their focal points were overlapped. Whereas conventional sequences are composed of a long burst (>10,000 cycles) emitted at a low burst repetition frequency (<10 Hz), we decomposed this burst into short pulses by adding intervals to facilitate inter-pulse microbubble movement. To evaluate how this sequence influenced cavitation distribution, we emitted short pulses (peak-rarefactional pressure (PRP): 40-366 kPa, pulse length (PL): 5-25 cycles) at high pulse repetition frequencies (PRF: 0.625-10 kHz) for a burst length of 100 ms. Increased cavitation persistence, implied by the duration of the microbubble acoustic emissions, was a measure of improved distribution due to the presence of flow. Sonication at lower acoustic pressures, longer pulse intervals and lower PLs improved the spatial distribution of cavitation. Furthermore, spectral analysis of the microbubble emissions revealed that the improvement at low pressures is due to persisting stable cavitation. In conclusion, new short-pulse sequences were shown to improve spatiotemporal control of acoustic cavitation dynamics during physiologically relevant flow. This

  18. Bubble Combustion

    NASA Technical Reports Server (NTRS)

    Corrigan, Jackie

    2004-01-01

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

  19. Characterization of acoustic emissions resulting from particle collision with a stationary bubble.

    PubMed

    Zhang, Wen; Spencer, Steven J; Coghill, Peter

    2013-05-01

    The present work characterizes the acoustic emissions resulting from the collision of a particle driven under gravity with a captive bubble. Conventional methods to investigate the bubble particle collision interaction model measure a descriptive parameter known as the collision time. During such a collision, particle impact may cause a strong deformation and a following oscillation of the bubble-particle interface generates detectable passive acoustic emissions (AE). Experiments and models presented show that the AE frequency monotonically decreases with the particle radius and is independent of the impact velocity, whereas the AE amplitude has a more complicated relationship with impact parameters. PMID:23654360

  20. Shadowgraph Imaging and Numerical Simulation of Cavitation Bubbles Formed in Pulsed Laser Ablation Plasmas in the Vicinity of the Critical Point of CO2

    NASA Astrophysics Data System (ADS)

    Muneoka, Hitoshi; Himeno, Shohei; Urabe, Keiichiro; Stauss, Sven; Baba, Motoyoshi; Suemoto, Tohru; Terashima, Kazuo

    2015-09-01

    The characteristic behavior of cavitation bubbles formed in pulsed laser ablation plasmas in supercritical CO2 were investigated by shadowgraph imaging and numerical simulations. The time evolution of the cavitation bubbles could be divided into three phases near the critical point: Expansion, Double layer formation, and Contraction. The distribution of the refractive index was estimated from the variation of the direction of the refracted light in the shockwave in the expansion phase. It was suggested that the cause of the reduction of the transmitted light in the outer shell in the double-layer phase was not due to refraction, and the contributions of nanoparticles and clusters generated in supercritical fluids were implied. The characteristics in time evolution of the bubble size in the contraction phase, in particular almost constant position of the interface in a relatively long time, was proposed to be due to zero surface tension by numerical simulations. The results suggest that the properties and fluid structure peculiar to SCF affect the structure of cavitation bubbles.

  1. Enhancement and quenching of high-intensity focused ultrasound cavitation activity via short frequency sweep gaps.

    PubMed

    Hallez, Loïc; Lee, Judy; Touyeras, Francis; Nevers, Aymeric; Ashokkumar, Muthupandian; Hihn, Jean-Yves

    2016-03-01

    This letter reports on the use of frequency sweeps to probe acoustic cavitation activity generated by high-intensity focused ultrasound (HIFU). Unprecedented enhancement and quenching of HIFU cavitation activity were observed when short frequency sweep gaps were applied in negative and positive directions, respectively. It was revealed that irrespective of the frequency gap, it is the direction and frequency sweep rate that govern the cavitation activity. These effects are related to the response of bubbles generated by the starting frequency to the direction of the frequency sweep, and the influence of the sweep rate on growth and coalescence of bubbles, which in turn affects the active bubble population. These findings are relevant for the use of HIFU in chemical and therapeutic applications, where greater control of cavitation bubble population is critical. PMID:26584998

  2. Interaction dynamics of fs-laser induced cavitation bubbles and their impact on the laser-tissue-interaction of modern ophthalmic laser systems

    NASA Astrophysics Data System (ADS)

    Tinne, N.; Ripken, T.; Lubatschowski, H.; Heisterkamp, A.

    2011-07-01

    A today well-known laser based treatment in ophthalmology is the LASIK procedure which nowadays includes cutting of the corneal tissue with ultra-short laser pulses. Instead of disposing a microkeratome for cutting a corneal flap, a focused ultra-short laser pulse is scanned below the surface of biological tissue causing the effect of an optical breakdown and hence obtaining a dissection. Inside the tissue, the energy of the laser pulses is absorbed by non-linear processes; as a result a cavitation bubble expands and ruptures the tissue. Hence, positioning of several optical breakdowns side by side generates an incision. Due to a reduction of the amount of laser energy, with a moderate duration of treatment at the same time, the current development of ultra-short pulse laser systems points to higher repetition rates in the range of even Megahertz instead of tens or hundreds of Kilohertz. In turn, this results in a pulse overlap and therefor a probable occurrence of interaction between different optical breakdowns and respectively cavitation bubbles of adjacent optical breakdowns. While the interaction of one single laser pulse with biological tissue is analyzed reasonably well experimentally and theoretically, the interaction of several spatial and temporal following pulses is scarcely determined yet. Thus, the aim of this study is to analyse the dynamic and interaction of two cavitation bubbles by using high speed photography. The applied laser pulse energy, the energy ratio and the spot distance between different cavitation bubbles were varied. Depending on a change of these parameters different kinds of interactions such as a flattening and deformation of bubble shape or jet formation are observed. The effects will be discussed regarding the medical ophthalmic application of fs-lasers. Based on these results a further research seems to be inevitable to comprehend and optimize the cutting effect of ultra-short pulse laser systems with high (> 500 kHz) repetition

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

    PubMed

    Czerski, Helen; Deane, Grant B

    2010-11-01

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

  4. Oscillating bubble concentration and its size distribution using acoustic emission spectra.

    PubMed

    Avvaru, Balasubrahmanyam; Pandit, Aniruddha B

    2009-01-01

    New method has been proposed for the estimation of size and number density distribution of oscillating bubbles in a sonochemical reactor using acoustic emission spectra measurements. Bubble size distribution has been determined using Minnaert's equation [M. Minnaert, On musical air bubbles and sound of running water, Philanthr. Mag. 16 (1933) 235], i.e., size of oscillating bubble is inversely related to the frequency of its volume oscillations. Decomposition of the pressure signal measured by the hydrophone in frequency domain of FFT spectrum and then inverse FFT reconstruction of the signal at each frequency level has been carried out to get the information about each of the bubble/cavity oscillation event. The number mean radius of the bubble size is calculated to be in the range of 50-80 microm and it was not found to vary much with the spatial distribution of acoustic field strength of the ultrasound processor used in the work. However, the number density of the oscillating bubbles and the nature of the distribution were found to vary in different horizontal planes away from the driving transducer surface in the ultrasonic bath. A separate set of experiments on erosion assessment studies were carried out using a thin aluminium foil, revealing a phenomena of active region of oscillating bubbles at antinodal points of the stationary waves, identical to the information provided by the acoustic emission spectra at the same location in the ultrasonic bath. PMID:18752981

  5. Toward the development of erosion-free ultrasonic cavitation cleaning with gas-supersaturated water

    NASA Astrophysics Data System (ADS)

    Yamashita, Tatsuya; Ando, Keita

    2015-11-01

    In ultrasonic cleaning, contaminant particles attached at target surfaces are removed by liquid flow or acoustic waves that are induced by acoustic cavitation bubbles. However, the inertial collapse of such bubbles often involve strong shock emission or water hammer by re-entrant jets, thereby giving rise to material erosion. Here, we aim at developing an erosion-free ultrasonic cleaning technique with the aid of gas-supersaturated water. The key idea is that (gaseous) cavitation is triggered easily even with low-intensity sonication in water where gases are dissolved beyond Henry's saturation limit, allowing us to buffer violent bubble collapse. In this presentation, we report on observations of the removal of micron/submicron-sized particles attached at glass surfaces by the action of gaseous cavitation bubbles under low-intensity sonication.

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

    NASA Astrophysics Data System (ADS)

    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

  7. Probability of cavitation for single ultrasound pulses applied to tissues and tissue-mimicking materials

    PubMed Central

    Maxwell, Adam D.; Cain, Charles A.; Hall, Timothy L.; Fowlkes, J. Brian; Xu, Zhen

    2012-01-01

    In this article, the negative pressure values at which inertial cavitation consistently occurs in response to a single, 2-cycle, focused ultrasound pulse were measured in several media relevant to cavitation-based ultrasound therapy. The pulse was focused into a chamber containing one of the media, which included liquids, tissue-mimicking materials, and ex-vivo canine tissue. Focal waveforms were measured by two separate techniques using a fiber-optic hydrophone. Inertial cavitation was identified by high-speed photography in optically transparent media and an acoustic passive cavitation detector. The probability of cavitation (Pcav) for a single pulse as a function of peak negative pressure (p−) followed a sigmoid curve, with the probability approaching 1 when the pressure amplitude was sufficient. The statistical threshold (defined as Pcav = 0.5) was between p− = 26.0–30.0 MPa in all samples with a high water content, but varied between p− = 13.7 to > 36 MPa for other media. A model for radial cavitation bubble dynamics was employed to evaluate the behavior of cavitation nuclei at these pressure levels. A single bubble nucleus with an inertial cavitation threshold of p− = 28.2 MPa was estimated to have a 2.5 nm radius in distilled water. These data may be valuable for cavitation-based ultrasound therapy to predict the likelihood of cavitation at different pressure levels and dimensions of cavitation-induced lesions in tissue. PMID:23380152

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

    SciTech Connect

    Maksimov, Alexey

    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.

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

    PubMed

    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. PMID:12083190

  10. Acoustic chaos

    SciTech Connect

    Lauterborn, W.; Parlitz, U.; Holzfuss, J.; Billo, A.; Akhatov, I.

    1996-06-01

    Acoustic cavitation, a complex, spatio-temporal dynamical system, is investigated with respect to its chaotic properties. The sound output, the {open_quote}{open_quote}noise{close_quote}{close_quote}, is subjected to time series analysis. The spatial dynamics of the bubble filaments is captured by high speed holographic cinematography and subsequent digital picture processing from the holograms. Theoretical models are put forward for describing the pattern formation. {copyright} {ital 1996 American Institute of Physics.}

  11. EXPERIMENTS AND SIMULATIONS WITH LARGE GAS BUBBLES IN MERCURY TOWARDS ESTABLISHING A GAS LAYER TO MITIGATE CAVITATION DAMAGE

    SciTech Connect

    Wendel, Mark W; Riemer, Bernie; Felde, David K; Ruggles, Arthur; Karnowski, Thomas Paul

    2006-01-01

    One of several options that shows promise for protecting solid surfaces from cavitation damage in liquid metal spallation targets, involves introducing an interstitial gas layer between the liquid metal and the containment vessel wall. Several approaches toward establishing such a protective gas layer are being investigated at the Oak Ridge National Laboratory including large bubble injection, and methods that involve stabilization of the layer by surface modifications to enhance gas hold-up on the wall or by inserting a porous media. It has previously been reported that using a gas layer configuration in a test target showed an order-of-magnitude decrease in damage for an in-beam experiment. Video images that were taken of the successful gas/mercury flow configuration have been analyzed and correlated. The results show that the success was obtained under conditions where only 60% of the solid wall was covered with gas. Such a result implies that this mitigation scheme may have much more potential. Additional experiments with gas injection into water are underway. Multi-component flow simulations are also being used to provide direction for these new experiments. These simulations have been used to size the gas layer and position multiple inlet nozzles.

  12. Improvements to the methods used to measure bubble attenuation using an underwater acoustical resonator.

    PubMed

    Czerski, Helen; Vagle, Svein; Farmer, David M; Hall-Patch, Nick

    2011-11-01

    Active acoustic techniques are commonly used to measure oceanic bubble size distributions, by inverting the bulk acoustical properties of the water (usually the attenuation) to infer the bubble population. Acoustical resonators have previously been used to determine attenuation over a wide range of frequencies (10-200 kHz) in a single measurement, corresponding to the simultaneous measurement of a wide range of bubble sizes (20-300 μm radii). However, there is now also considerable interest in acquiring measurements of bubbles with radii smaller than 16 μm, since these are thought to be important for ocean optics and as tracers for near-surface flow. To extend the bubble population measurement to smaller radii, it is necessary to extend the attenuation measurements to higher frequencies. Although the principles of resonator operation do not change as the frequency increases, the assumptions previously made during the spectral analysis may no longer be valid. In order to improve the methods used to calculate attenuation from acoustical resonator outputs, a more complete analysis of the resonator operation is presented here than has been published previously. This approach allows for robust attenuation measurements over a much wider frequency range and enables accurate measurements from lower-quality spectral peaks. PMID:22088016

  13. Acoustic Cavitation: A Potential Remediation Technology for On-Site Elimination of Perfluorinated Contaminants

    NASA Astrophysics Data System (ADS)

    Vecitis, C. D.; Cheng, J.; Park, H.; Hoffmann, M. R.

    2006-12-01

    Perfluorinated chemicals are emerging as globally ubiquitous contaminants which are recalcitrant to the conventional remediation techniques of adsorption and chemical oxidation. The release of these chemicals to the environment occurs from specific sites such as manufacturing plants, fire-fighting foams at airports and contaminated landfills. Even though these compounds are widely recognized as potentially hazardous, disposal regulations have been limited due to the ineffectiveness of current pump and treat technologies towards these species. We have shown that ultrasonically induced acoustic cavitation can effectively mineralize aqueous perfluorinated acid and sulfonate species by in situ pyrolysis and chemical oxidation at the lab and pilot scale. Efficiency has been tested on a variety of matrices such as tap water, groundwater and landfill pump-out with VOC content being the major detriment towards remediation. Advanced oxidation by the simultaneously application of ozone and ultrasound seems to partially eliminate this barrier by enhancing the rate of VOC mineralization. Application of this technology to a contaminated field site and the obstacles of scaling to such a degree are discussed.

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

    PubMed

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

    2015-01-01

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

  15. Toward the optimization of double-pulse LIBS underwater: effects of experimental parameters on the reproducibility and dynamics of laser-induced cavitation bubble.

    PubMed

    Cristoforetti, Gabriele; Tiberi, Marco; Simonelli, Andrea; Marsili, Paolo; Giammanco, Francesco

    2012-03-01

    Double-pulse laser-induced breakdown spectroscopy (LIBS) was recently proposed for the analysis of underwater samples, since it overcomes the drawbacks of rapid plasma quenching and of large continuum emission, typical of single-pulse ablation. Despite the attractiveness of the method, this approach suffers nevertheless from a poor spectroscopic reproducibility, which is partially due to the scarce reproducibility of the cavitation bubble induced by the first laser pulse, since pressure and dimensions of the bubble strongly affect plasma emission. In this work, we investigated the reproducibility and the dynamics of the cavitation bubble induced on a solid target in water, and how they depend on pulse duration, energy, and wavelength, as well as on target composition. Results are discussed in terms of the effects on the laser ablation process produced by the crater formation and by the interaction of the laser pulse with floating particles and gas bubbles. This work, preliminary to the optimization of the spectroscopic signal, provides an insight of the phenomena occurring during laser ablation in water, together with useful information for the choice of the laser source to be used in the apparatus. PMID:22410923

  16. Validation of an approximate model for the thermal behavior in acoustically driven bubbles.

    PubMed

    Stricker, Laura; Prosperetti, Andrea; Lohse, Detlef

    2011-11-01

    The chemical production of radicals inside acoustically driven bubbles is determined by the local temperature inside the bubbles. Therefore, modeling of chemical reaction rates in bubbles requires an accurate evaluation of the temperature field and the heat exchange with the liquid. The aim of the present work is to compare a detailed partial differential equation model in which the temperature field is spatially resolved with an ordinary differential equation model in which the bubble contents are assumed to have a uniform average temperature and the heat exchanges are modeled by means of a boundary layer approximation. The two models show good agreement in the range of pressure amplitudes in which the bubble is spherically stable. PMID:22087996

  17. Detection of cavitation in hydraulic turbines

    NASA Astrophysics Data System (ADS)

    Escaler, Xavier; Egusquiza, Eduard; Farhat, Mohamed; Avellan, François; Coussirat, Miguel

    2006-05-01

    An experimental investigation has been carried out in order to evaluate the detection of cavitation in actual hydraulic turbines. The methodology is based on the analysis of structural vibrations, acoustic emissions and hydrodynamic pressures measured in the machine. The proposed techniques have been checked in real prototypes suffering from different types of cavitation. In particular, one Kaplan, two Francis and one Pump-Turbine have been investigated in the field. Additionally, one Francis located in a laboratory has also been tested. First, a brief description of the general features of cavitation phenomenon is given as well as of the main types of cavitation occurring in hydraulic turbines. The work presented here is focused on the most important ones which are the leading edge cavitation due to its erosive power, the bubble cavitation because it affects the machine performance and the draft tube swirl that limits the operation stability. Cavitation detection is based on the previous understanding of the cavity dynamics and its location inside the machine. This knowledge has been gained from flow visualisations and measurements in laboratory devices such as a high-speed cavitation tunnel and a reduced scale turbine test rig. The main techniques are the study of the high frequency spectral content of the signals and of their amplitude demodulation for a given frequency band. Moreover, low frequency spectral content can also be used in certain cases. The results obtained for the various types of cavitation found in the selected machines are presented and discussed in detail in the paper. Conclusions are drawn about the best sensor, measuring location, signal processing and analysis for each type of cavitation, which serve to validate and to improve the detection techniques.

  18. FOREWORD: International Symposium of Cavitation and Multiphase Flow (ISCM 2014)

    NASA Astrophysics Data System (ADS)

    Wu, Yulin

    2015-01-01

    multiphase flow detection Fluid-structure interaction induced by cavitation and multiphase flow Multi-scale modelling of cavitating flows and Multiphase Flow Cavitation nuclei: theory and experiments Supercavitation and its applications Synergetic effects of cavitation and silt-laden erosion Shock waves and microjets generated by cavitation Nonlinear oscillations of gas and vapour bubbles Fundamentals of physics of acoustic cavitation Sonochemistry and sonoluminescence Biomedical applications of cavitation effects Ultrasonic cavitation for molten metal treatment Cavitation for enhanced heat transfer The ISCM 2014 brought together 95 scientists, researchers and graduate students from 11 countries, affiliated with universities, technology centers and industrial firms to debate topics related to advanced technologies for cavitation and Multiphase Flow, which would enhance the sustainable development of cavitation and Multiphase Flow in interdisciplinary sciences and technology. The technical committee selected 54 technical papers on the following topics: (i) Hydrodynamic Cavitation, (ii) Super Cavitation, (iii) Pump Cavitation, (iv) Acoustic Cavitation, (v) Interdisciplinary Research of Cavitation and Multi-Phase Flows, and 13 invited plenary and invited forum lectures, which were presented at the symposium, to be included in the proceedings. All the papers of ISCM 2014, which are published in this Volume of IOP Conference Series: Materials Science and Engineering, had been peer reviewed through processes administered by the editors of the ISCM 2014, those are Yulin WU, Shouqi YUAN, Zhengwei WANG, Shuhong LIU, Xingqi LUO, Fujun WANG and Guoyu WANG. The papers published in this Volume include 54 technical papers and 3 full length texts of the invited lectures. We sincerely hope that the International Symposium on Cavitation and Multiphase Flow is a significant step forward in the world wide efforts to address the present challenges in the modern science and technology. Professor

  19. Orbital revolution of a pair of bubbles in an acoustic field

    NASA Astrophysics Data System (ADS)

    Shirota, Minori; Yamashita, Kou; Inamura, Takao

    2011-11-01

    This experimental study aims to clarify the mechanism of orbital motion of two oscillating bubbles in an acoustic field. Trajectory of the orbital motion was observed using a high-speed video camera. Because of a good repeatability in volume oscillation of bubbles, we were also able to observe the radial motion driven at 24 kHz by stroboscopic like imaging; the cyclic bubble oscillation was appeared to slow down by capturing images at the framing rate close to the forcing frequency. The orbital motions of bubbles raging from 0.13 to 0.18 mm were examined with different forcing amplitude and in different viscous oils. As a result, we found that pairs of bubbles revolve along a circular orbit around the center of mass of the orbiting two bubbles. We also found that the two bubbles perform anti-phase radial oscillation. Although this radial oscillation should result in a repulsive secondary Bjerknes force, the bubbles kept a constant separate distance of about 1 mm, which indicates the existence of centripetal primary Bjerknes force. The angular velocity of orbital revolution increases linearly with the increase in Bjerknes force.

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

    PubMed

    Simão, André G; Guimarães, Luiz G

    2016-01-01

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

  1. Quantum Analogies in the Interaction between Acoustic Waves and Bubble Clouds

    NASA Astrophysics Data System (ADS)

    Parrales, Miguel A.; Rodriguez-Rodriguez, Javier

    2014-11-01

    Analogies between quantum mechanical and acoustical propagation phenomena have a great interest in academic research due to their ability to shed light on some complex quantum effects, which are impossible to visualize directly in the macroscopic world. In this talk, we describe a number of these analogies concerning the acoustic behavior of bubble clouds. Firstly, we show that the structure of the collective oscillation modes of a spherical bubble cloud resembles that of the atomic orbitals of a hydrogen atom. Secondly, we present an analogy between some perturbation methods used in quantum-electrodynamics and the computation of the acoustic response of the randomly distributed bubble cloud by considering the contribution to the total scattered pressure of the multiple scattering paths that take place inside the clouds. As an application of this analogy, we obtain the scattering cross-section of a diluted cloud, which remarkably mimics the quantum scattering of an neutron wave when passing through an atomic nucleus. Finally, we numerically reproduce the behavior of an electron in a covalent bond between two hydrogen atoms by simulating the acoustic wave propagation through two neighboring spherical bubble assemblages. Funded by the Spanish Ministry of Economy and Competitiveness through Grants DPI2011-28356-C03-01 and DPI2011-28356-C03-02.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  3. A detector for monitoring the onset of cavitation during therapy-level measurements of ultrasonic power

    NASA Astrophysics Data System (ADS)

    Hodnett, M.; Zeqiri, B.

    2004-01-01

    Acoustic cavitation occurring in the water path between a transducer and the target of a radiation force balance can provide a significant source of error during measurements of ultrasonic power. These problems can be particularly acute at physiotherapy levels (>1 W), and low frequencies (leq 1 MHz). The cavitating bubbles can absorb and scatter incident ultrasound, leading to an underestimate in the measured power. For these reasons, International Specification standards demand the use of degassed water. This imposes requirements that may actually be difficult to meet, for example, in the case of hospitals. Also, initially degassed water will rapidly re-gas, increasing the likelihood of cavitation occurring. For these reasons, NPL has developed a device that monitors acoustic emissions generated by bubble activity, for detecting the onset of cavitation during power measurements. A commercially available needle hydrophone is used to detect these emissions. The acoustic signals are then monitored using a Cavitation Detector (CD) unit, comprising an analogue electrical filter that may be tuned to detect frequency components generated by cavitating bubbles, and which provides an indication of when the measured level exceeds a pre-defined threshold. This paper describes studies to establish a suitable detection scheme, the principles of operation of the CD unit, and the performance tests carried out with a range of propagation media.

  4. FOREWORD: International Symposium of Cavitation and Multiphase Flow (ISCM 2014)

    NASA Astrophysics Data System (ADS)

    Wu, Yulin

    2015-01-01

    multiphase flow detection Fluid-structure interaction induced by cavitation and multiphase flow Multi-scale modelling of cavitating flows and Multiphase Flow Cavitation nuclei: theory and experiments Supercavitation and its applications Synergetic effects of cavitation and silt-laden erosion Shock waves and microjets generated by cavitation Nonlinear oscillations of gas and vapour bubbles Fundamentals of physics of acoustic cavitation Sonochemistry and sonoluminescence Biomedical applications of cavitation effects Ultrasonic cavitation for molten metal treatment Cavitation for enhanced heat transfer The ISCM 2014 brought together 95 scientists, researchers and graduate students from 11 countries, affiliated with universities, technology centers and industrial firms to debate topics related to advanced technologies for cavitation and Multiphase Flow, which would enhance the sustainable development of cavitation and Multiphase Flow in interdisciplinary sciences and technology. The technical committee selected 54 technical papers on the following topics: (i) Hydrodynamic Cavitation, (ii) Super Cavitation, (iii) Pump Cavitation, (iv) Acoustic Cavitation, (v) Interdisciplinary Research of Cavitation and Multi-Phase Flows, and 13 invited plenary and invited forum lectures, which were presented at the symposium, to be included in the proceedings. All the papers of ISCM 2014, which are published in this Volume of IOP Conference Series: Materials Science and Engineering, had been peer reviewed through processes administered by the editors of the ISCM 2014, those are Yulin WU, Shouqi YUAN, Zhengwei WANG, Shuhong LIU, Xingqi LUO, Fujun WANG and Guoyu WANG. The papers published in this Volume include 54 technical papers and 3 full length texts of the invited lectures. We sincerely hope that the International Symposium on Cavitation and Multiphase Flow is a significant step forward in the world wide efforts to address the present challenges in the modern science and technology. Professor

  5. Sonochemistry and bubble dynamics.

    PubMed

    Mettin, Robert; Cairós, Carlos; Troia, Adriano

    2015-07-01

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

  6. Quantitative observations of cavitation activity in a viscoelastic medium.

    PubMed

    Collin, Jamie R T; Coussios, Constantin C

    2011-11-01

    Quantitative experimental observations of single-bubble cavitation in viscoelastic media that would enable validation of existing models are presently lacking. In the present work, single bubble cavitation is induced in an agar gel using a 1.15 MHz high intensity focused ultrasound transducer, and observed using a focused single-element passive cavitation detection (PCD) transducer. To enable quantitative observations, a full receive calibration is carried out of a spherically focused PCD system by a bistatic scattering substitution technique that uses an embedded spherical scatterer and a hydrophone. Adjusting the simulated pressure received by the PCD by the transfer function on receive and the frequency-dependent attenuation of agar gel enables direct comparison of the measured acoustic emissions with those predicted by numerical modeling of single-bubble cavitation using a modified Keller-Miksis approach that accounts for viscoelasticity of the surrounding medium. At an incident peak rarefactional pressure near the cavitation threshold, period multiplying is observed in both experiment and numerical model. By comparing the two sets of results, an estimate of the equilibrium bubble radius in the experimental observations can be made, with potential for extension to material parameter estimation. Use of these estimates yields good agreement between model and experiment. PMID:22088001

  7. Acoustic monitoring of gas emissions from the seafloor. Part I: quantifying the volumetric flow of bubbles

    NASA Astrophysics Data System (ADS)

    Leblond, Isabelle; Scalabrin, Carla; Berger, Laurent

    2014-09-01

    Three decades of continuous ocean exploration have led us to identify subsurface fluid related processes as a key phenomenon in marine earth science research. The number of seep areas located on the seafloor has been constantly increasing with the use of multi-scale imagery techniques. Due to recent advances in transducer technology and computer processing, multibeam echosounders are now commonly used to detect submarine gas seeps escaping from the seafloor into the water column. A growing number of en- route surveys shows that sites of gas emissions escaping from the seafloor are much more numerous than previously thought. Estimating the temporal variability of the gas flow rate and volumes escaping from the seafloor has thus become a challenge of relevant interest which could be addressed by sea-floor continuous acoustic monitoring. Here, we investigate the feasibility of estimating the volumetric flow rates of gas emissions from horizontal backscattered acoustic signals. Different models based on the acoustic backscattering theory of bubbles are presented. The forward volume backscattering strength and the inversion volumetric flow rate solutions were validated with acoustic measurements from artificial gas flow rates generated in controlled sea-water tank experiments. A sensitivity analysis was carried out to investigate the behavior of the 120-kHz forward solution with respect to model input parameters (horizontal distance between transducer and bubble stream, bubble size distribution and ascent rate). The most sensitive parameter was found to be the distance of the bubble stream which can affect the volume backscattering strength by 20 dB within the horizontal range of 0-200 m. Results were used to derive the detection probability of a bubble stream for a given volume backscattering strength threshold according to different bubble flow rates and horizontal distance.

  8. The cavitation induced Becquerel effect and the hot spot theory of sonoluminescence.

    PubMed

    Prevenslik, T V

    2003-06-01

    Over 150 years ago, Becquerel discovered the ultraviolet illumination of one of a pair of identical electrodes in liquid water produced an electric current, the phenomenon called the Becquerel effect. Recently, a similar effect was observed if the water surrounding one electrode is made to cavitate by focused acoustic radiation, which by similarity is referred to as the cavitation induced Becquerel effect. The current in the cavitation induced Becquerel effect was found to be semi-logarithmic with the standard electrode potential that is consistent with the oxidation of the electrode surface by the photo-decomposition theory of photoelectrochemistry. But oxidation of the electrode surface usually requires high temperatures, say as in cavitation. Absent high bubble temperatures, cavitation may produce vacuum ultraviolet (VUV) light that excites water molecules in the electrode film to higher H(2)O(*) energy states, the excited states oxidizing the electrode surface by chemical reaction. Solutions of the Rayleigh-Plesset equation during bubble collapse that include the condensation of water vapor show any increase in temperature or pressure of the water vapor by compression heating is compensated by the condensation of vapor to the bubble wall, the bubbles collapsing almost isothermally. Hence, the cavitation induced Becquerel effect is likely caused by cavitation induced VUV light at ambient temperature. PMID:12782265

  9. The Influence of Dissolved Carbon Dioxide on Cavitation Intensity in Ultrasound Cleaning Systems

    NASA Astrophysics Data System (ADS)

    Brems, Steven; Hauptmann, Marc; Camerotto, Elisabeth; Pacco, Antoine; Struyf, Herbert; Mertens, Paul; Gottschalk, Christiane; De Gendt, Stefan

    2013-06-01

    A study is made of the effect of dissolved CO2 on cavitation inception and activity in an ultrasound system with a sound frequency of 928 kHz. It is shown that measurable cavitation activity is completely absent at moderate acoustic power densities (≤1.7 W cm-2) when only CO2 is dissolved in ultra pure water. It is suggested that the enhanced stability of CO2 bubbles against coalescence might be the origin of the delayed cavitation inception when compared to other dissolved gases. A combination of dissolved O2 and CO2 can lead to a measurable cavitation activity at an acoustic power of 420 mW cm-2, but an increase of the dissolved CO2 level reduces, in general, the observed cavitation activity. In order to compare results with different dissolved gas concentrations, measurements are performed with acoustic pulses and the pulse off time is varied. An optimal pulse-off time exists, where a maximum of cavitation activity is observed. However, the pulse-off time interval with enhanced cavitation activity is narrowed with increasing dissolved CO2 concentrations. Again, a decrease in bubble coalescence might explain the narrowing of the “enhancement peak”.

  10. Dynamics of soap bubble bursting and its implications to volcano acoustics

    NASA Astrophysics Data System (ADS)

    Vidal, V.; Ripepe, M.; Divoux, T.; Legrand, D.; Géminard, J.-C.; Melo, F.

    2010-04-01

    In order to assess the physical mechanisms at stake when giant gas bubbles burst at the top of a magma conduit, laboratory experiments have been performed. An overpressurized gas cavity is initially closed by a thin liquid film, which suddenly bursts. The acoustic signal produced by the bursting is investigated. The key result is that the amplitude and energy of the acoustic signal strongly depend on the film rupture time. As the rupture time is uncontrolled in the experiments and in the field, the measurement of the acoustic excess pressure in the atmosphere, alone, cannot provide any information on the overpressure inside the bubble before explosion. This could explain the low energy partitioning between infrasound, seismic and explosive dynamics often observed on volcanoes.

  11. Sensitivity of free radicals production in acoustically driven bubble to the ultrasonic frequency and nature of dissolved gases.

    PubMed

    Merouani, Slimane; Hamdaoui, Oualid; Rezgui, Yacine; Guemini, Miloud

    2015-01-01

    Central events of ultrasonic action are the bubbles of cavitation that can be considered as powered microreactors within which high-energy chemistry occurs. This work presents the results of a comprehensive numerical assessment of frequency and saturating gases effects on single bubble sonochemistry. Computer simulations of chemical reactions occurring inside a bubble oscillating in liquid water irradiated by an ultrasonic wave have been performed for a wide range of ultrasonic frequencies (213-1100kHz) under different saturating gases (O2, air, N2 and H2). For O2 and H2 bubbles, reactions mechanism consisting in 25 reversible chemical reactions were proposed for studying the internal bubble-chemistry whereas 73 reversible reactions were taken into account for air and N2 bubbles. The numerical simulations have indicated that radicals such as OH, H, HO2 and O are created in the bubble during the strong collapse. In all cases, hydroxyl radical (OH) is the main oxidant created in the bubble. The production rate of the oxidants decreases as the driving ultrasonic frequency increases. The production rate of OH radical followed the order O2>air>N2>H2 and the order becomes more remarkable at higher ultrasonic frequencies. The effect of ultrasonic frequency on single bubble sonochemistry was attributed to its significant impact on the cavitation process whereas the effects of gases were attributed to the nature of the chemistry produced in the bubble at the strong collapse. It was concluded that, in addition to the gas solubility, the nature of the internal bubble chemistry is another parameter of a paramount importance that controls the overall sonochemical activity in aqueous solutions. PMID:25112684

  12. CO2 bubbling-based 'Nanobomb' System for Targetedly Suppressing Panc-1 Pancreatic Tumor via Low Intensity Ultrasound-activated Inertial Cavitation

    PubMed Central

    Zhang, Kun; Xu, Huixiong; Chen, Hangrong; Jia, Xiaoqing; Zheng, Shuguang; Cai, Xiaojun; Wang, Ronghui; Mou, Juan; Zheng, Yuanyi; Shi, Jianlin

    2015-01-01

    Noninvasive and targeted physical treatment is still desirable especially for those cancerous patients. Herein, we develop a new physical treatment protocol by employing CO2 bubbling-based 'nanobomb' system consisting of low-intensity ultrasound (1.0 W/cm2) and a well-constructed pH/temperature dual-responsive CO2 release system. Depending on the temperature elevation caused by exogenous low-intensity therapeutic ultrasound irradiation and the low pH caused by the endogenous acidic-environment around/within tumor, dual-responsive CO2 release system can quickly release CO2 bubbles, and afterwards, the generated CO2 bubbles waves will timely explode before dissolution due to triggering by therapeutic ultrasound waves. Related bio-effects (e.g., cavitation, mechanical, shock waves, etc) caused by CO2 bubbles' explosion effectively induce instant necrosis of panc-1 cells and blood vessel destruction within panc-1 tumor, and consequently inhibit the growth of panc-1 solid tumor, simultaneously minimizing the side effects to normal organs. This new physiotherapy employing CO2 bubbling-based 'nanobomb' system promises significant potentials in targetedly suppressing tumors, especially for those highly deadly cancers. PMID:26379793

  13. CO2 bubbling-based 'Nanobomb' System for Targetedly Suppressing Panc-1 Pancreatic Tumor via Low Intensity Ultrasound-activated Inertial Cavitation.

    PubMed

    Zhang, Kun; Xu, Huixiong; Chen, Hangrong; Jia, Xiaoqing; Zheng, Shuguang; Cai, Xiaojun; Wang, Ronghui; Mou, Juan; Zheng, Yuanyi; Shi, Jianlin

    2015-01-01

    Noninvasive and targeted physical treatment is still desirable especially for those cancerous patients. Herein, we develop a new physical treatment protocol by employing CO2 bubbling-based 'nanobomb' system consisting of low-intensity ultrasound (1.0 W/cm(2)) and a well-constructed pH/temperature dual-responsive CO2 release system. Depending on the temperature elevation caused by exogenous low-intensity therapeutic ultrasound irradiation and the low pH caused by the endogenous acidic-environment around/within tumor, dual-responsive CO2 release system can quickly release CO2 bubbles, and afterwards, the generated CO2 bubbles waves will timely explode before dissolution due to triggering by therapeutic ultrasound waves. Related bio-effects (e.g., cavitation, mechanical, shock waves, etc) caused by CO2 bubbles' explosion effectively induce instant necrosis of panc-1 cells and blood vessel destruction within panc-1 tumor, and consequently inhibit the growth of panc-1 solid tumor, simultaneously minimizing the side effects to normal organs. This new physiotherapy employing CO2 bubbling-based 'nanobomb' system promises significant potentials in targetedly suppressing tumors, especially for those highly deadly cancers. PMID:26379793

  14. Removal of Residual Cavitation Nuclei to Enhance Histotripsy Erosion of Model Urinary Stones

    PubMed Central

    Duryea, Alexander P.; Roberts, William W.; Cain, Charles A.; Hall, Timothy L.

    2015-01-01

    Histotripsy has been shown to be an effective treatment for model kidney stones, eroding their surface to tiny particulate debris via a cavitational bubble cloud. However, similar to shock wave lithotripsy, histotripsy stone treatments display a rate-dependent efficacy with pulses applied at low rate generating more efficient stone erosion in comparison to those applied at high rate. This is hypothesized to be the result of residual cavitation bubble nuclei generated by bubble cloud collapse. While the histotripsy bubble cloud only lasts on the order of 100 µs, these microscopic remnant bubbles can persist on the order of 1 second—inducing direct attenuation of subsequent histotripsy pulses and influencing bubble cloud dynamics. In an effort to mitigate these effects, we have developed a novel strategy to actively remove residual cavitation nuclei from the field using low-amplitude ultrasound pulses. Previous work has demonstrated that with selection of the appropriate acoustic parameters these bubble removal pulses can stimulate the aggregation and subsequent coalescence of microscopic bubble nuclei—effectively deleting them from the target volume. Here, we incorporate bubble removal pulses in histotripsy treatment of model kidney stones. It was found that when histotripsy is applied at low rate (1 Hz), bubble removal does not produce a statistically significant change in erosion. At higher pulse rates of 10, 100, and 500 Hz, incorporating bubble removal results in 3.7-, 7.5-, and 2.7-fold increases in stone erosion, respectively. High speed imaging indicates that the introduction of bubble removal pulses allows bubble cloud dynamics resulting from high pulse rates to more closely approximate those generated at the low rate of 1 Hz. These results corroborate previous work in the field of shock wave lithotripsy regarding the ill-effects of residual bubble nuclei, and suggest that high treatment efficiency can be recovered at high pulse rates through

  15. Complete Inhibition Of Ultrasound Induced Cytolysis In The Presence Of Inertial Cavitation

    NASA Astrophysics Data System (ADS)

    Sostaric, Joe Z.; Miyoshi, Norio; Riesz, Peter; De Graff, William G.; Mitchell, James B.

    2006-05-01

    The investigation of ultrasound for biotechnological applications including non-invasive surgery (HIFU), drug/gene delivery to cells (sonoporation) or through the skin (sonophoresis) and ultrasound assisted bioreactors has focused mainly on the physical effects of ultrasound. The beneficial effects of ultrasound rely on a number of application-dependent mechanisms, and may include tissue heating, acoustic streaming or cavitation. Although acoustic cavitation is necessary in some systems, cavitation bubbles simultaneously result in uncontrollable cell damage and cytolysis. Thus, the development of a number of biotechnological uses of ultrasound has been hampered by the necessity to constrain exposure parameters in order to prevent the occurrence of acoustic cavitation or to at least limit the detrimental effects of cavitation. The current study shows that non-toxic concentrations of specific n-alkyl solutes completely inhibit ultrasound induced cytolysis of in vitro suspensions of human leukemia cells (HL-60). Protection of the whole cell population from cytolysis is achieved even under extreme ultrasound exposure conditions that result in cytolysis of 100 % of the cell population in the absence of the n-alkyl solutes. Furthermore, the n-alkyl solutes did not hinder the process of inertial cavitation. This method may allow utilization of beneficial effects of ultrasound and cavitation while protecting cells from cavitation induced cytolysis and thereby presents new possibilities for ultrasound in medicine and biology.

  16. Equations of spatial hydrodynamic interaction of weakly nonspherical gas bubbles in liquid in an acoustic field

    NASA Astrophysics Data System (ADS)

    Davletshin, A. I.; Khalitova, T. F.

    2016-01-01

    A mathematical model of spatial hydrodynamic interaction of gas bubbles in liquid in an acoustic field taking into account small deformations of their surfaces is proposed. It is a system of ordinary differential equations of the second order in radii of the bubbles, the position vectors of their centers and the amplitudes of deviation of their shape from the spherical one in the form of spherical harmonics. The equations derived are of the first order of accuracy in A / R and of the fourth order in R / D, where R is the characteristic radius of the bubbles, A is the amplitude of characteristic deviation of their surface from the spherical one in the form of spherical harmonics, D is the characteristic distance between bubbles. The derivation of the equations is carried out by the method of spherical functions with the use of the Bernoulli integral, the kinematic and dynamic boundary conditions on the surface of the bubbles. The effects of viscosity and compressibility of the liquid are considered approximately, the gas in the bubbles is assumed homobaric.

  17. Thresholds of Transient Cavitation Produced by Pulsed Ultrasound in a Controlled Nuclei Environment.

    NASA Astrophysics Data System (ADS)

    Holland, Christy Katherine Smith

    The possibility of hazardous bioeffects from medical ultrasound examinations and therapy, although not demonstrated in current epidemiologic data, is still of interest to the medical community. In particular, concern persists over the potential of damage at the cellular level due to transient cavitation produced by diagnostic and high intensity therapeutic ultrasound. Transient cavitation is a discrete phenomenon which relies on the existence of stabilized nuclei, or pockets of gas within a host fluid, for its genesis. A convenient descriptor for assessing the likelihood of transient cavitation is the threshold pressure, or the minimum acoustic pressure necessary to initiate bubble growth and subsequent collapse. Experimental measurements of cavitation thresholds are presented here which elucidate the importance of ultrasound host fluid and nuclei parameters in determining these thresholds. These results are interpreted in the context of an approximate theory, included as an appendix, describing the relationship between these parameters and cavitation threshold pressures. An automated experimental apparatus has been developed to determine thresholds for cavitation produced in a fluid by short tone bursts of ultrasound at 0.76, 0.99, and 2.30 MHz. A fluid jet was used to convect potential cavitation nuclei through the focal region of the insonifying transducer. Potential nuclei tested include 1mum polystyrene spheres, microbubbles in the 1-10 μm range that are stabilized with human serum albumin, and whole blood constituents. Cavitation was detected by a passive acoustical technique which is sensitive to sound scattered from cavitation bubbles. Measurements of the transient cavitation threshold in water, in a fluid of higher viscosity, and in diluted whole blood are presented. Results from these experiments which permit the control of nuclei and host fluid properties are compared to the approximate analytical theory for the prediction of the onset of cavitation.

  18. Exploring bubble oscillation and mass transfer enhancement in acoustic-assisted liquid-liquid extraction with a microfluidic device

    PubMed Central

    Xie, Yuliang; Chindam, Chandraprakash; Nama, Nitesh; Yang, Shikuan; Lu, Mengqian; Zhao, Yanhui; Mai, John D.; Costanzo, Francesco; Huang, Tony Jun

    2015-01-01

    We investigated bubble oscillation and its induced enhancement of mass transfer in a liquid-liquid extraction process with an acoustically-driven, bubble-based microfluidic device. The oscillation of individually trapped bubbles, of known sizes, in microchannels was studied at both a fixed frequency, and over a range of frequencies. Resonant frequencies were analytically identified and were found to be in agreement with the experimental observations. The acoustic streaming induced by the bubble oscillation was identified as the cause of this enhanced extraction. Experiments extracting Rhodanmine B from an aqueous phase (DI water) to an organic phase (1-octanol) were performed to determine the relationship between extraction efficiency and applied acoustic power. The enhanced efficiency in mass transport via these acoustic-energy-assisted processes was confirmed by comparisons against a pure diffusion-based process. PMID:26223474

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Cavitation milling of natural cellulose to nanofibrils.

    PubMed

    Pinjari, Dipak Vitthal; Pandit, Aniruddha B

    2010-06-01

    Cavitation holds the promise of a new and exciting approach to fabricate both top down and bottom up nanostructures. Cavitation bubbles are created when a liquid boils under less than atmospheric pressure. The collapse process occurs supersonically and generates a host of physical and chemical effects. We have made an attempt to fabricate natural cellulose material using hydrodynamic as well as acoustic cavitation. The cellulose material having initial size of 63 micron was used for the experiments. 1% (w/v) slurry of cellulose sample was circulated through the hydrodynamic cavitation device or devices (orifice) for 6h. The average velocity of the fluid through the device was 10.81m/s while average pressure applied was 7.8 kg/cm(2). Cavitation number was found to be 2.61. The average particle size obtained after treatment was 1.36 micron. This hydrodynamically processed sample was sonicated for 1h 50 min. The average size of ultrasonically processed particles was found to be 301 nm. Further, the cellulose particles were characterized with X-ray diffraction (XRD) and differential scanning calorimetry (DSC) to see the effect of cavitation on crystallinity (X(c)) as well as on melting temperature (T(m)). Cellulose structures consist of amorphous as well as crystalline regions. The initial raw sample was 86.56% crystalline but due to the effect of cavitation, the crystallinity reduced to 37.76%. Also the melting temperature (T(m)) was found to be reduced from 101.78 degrees C of the original to 60.13 degrees C of the processed sample. SEM images for the cellulose (processed and unprocessed) shows the status and fiber-fiber alignment and its orientation with each other. Finally cavitation has proved to be very efficient tool for reduction in size from millimeter to nano scale for highly crystalline materials. PMID:20362487

  1. The role of heating, cavitation and acoustic streaming in mediating ultrasound-induced changes of TGF-beta gene expression in bone cells

    NASA Astrophysics Data System (ADS)

    Harle, J.; Mayia, F.

    2004-01-01

    This paper relates ultrasound-induced changes in bone cell function to quantitative data assessing the level of several interaction mechanisms within the exposure environment. Characterisation of ultrasound fields in terms of resultant levels of heating, cavitation and acoustic streaming may provide a novel means of accurately assessing the likelihood of biological effects in vitro.

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

    NASA Astrophysics Data System (ADS)

    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

  3. A method for predicting the number of active bubbles in sonochemical reactors.

    PubMed

    Merouani, Slimane; Ferkous, Hamza; Hamdaoui, Oualid; Rezgui, Yacine; Guemini, Miloud

    2015-01-01

    Knowledge of the number of active bubbles in acoustic cavitation field is very important for the prediction of the performance of ultrasonic reactors toward most chemical processes induced by ultrasound. The literature in this field is scarce, probably due to the complicated nature of the phenomena. We introduce here a relatively simple semi-empirical method for predicting the number of active bubbles in an acoustic cavitation field. By coupling the bubble dynamics in an acoustical field with chemical kinetics occurring in the bubble during oscillation, the amount of the radical species OH and HO2 and molecular H2O2 released by a single bubble was estimated. Knowing that the H2O2 measured experimentally during sonication of water comes from the recombination of hydroxyl (OH) and perhydroxyl (HO2) radicals in the liquid phase and assuming that in sonochemistry applications, the cavitation is transient and the bubble fragments at the first collapse, the number of bubbles formed per unit time per unit volume is then easily determined using material balances for H2O2, OH and HO2 in the liquid phase. The effect of ultrasonic frequency on the number of active bubbles was examined. It was shown that increasing ultrasonic frequency leads to a substantial increase in the number of bubbles formed in the reactor. PMID:25127247

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

    NASA Astrophysics Data System (ADS)

    Ohsaka, K.

    2003-05-01

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

  5. Reply to "Comment on `Acoustical observation of bubble oscillations induced by bubble popping' "

    NASA Astrophysics Data System (ADS)

    Ding, Junqi

    2015-03-01

    We reported on the sound pressure generated by aqueous foam bursts in our paper [Ding et al., Phys. Rev. E 75, 041601 (2007), 10.1103/PhysRevE.75.041601]. Blanc et al., [Phys. Rev. E 91, 036401 (2015), 10.1103/PhysRevE.91.036401] found that sound from one of three mechanisms of bubble burst (the prepopping) actually results from an acausal artifact of the signal processing performed by their acquisition system which lies outside of its prescribed working frequency range. We examined the same hardware used in our paper and found that the frequency range is not the cause of the artifact. The prepopping sound was a result from a built-in finite impulse response filter of analog-to-digital converters in the Brüel & Kjær data acquisition system.

  6. Aspherical bubble dynamics and oscillation times

    SciTech Connect

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

    1999-03-01

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

  7. Bubbles

    NASA Astrophysics Data System (ADS)

    Prosperetti, Andrea

    2004-06-01

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

  8. Histotripsy-Induced Cavitation Cloud Initiation Thresholds in Tissues of Different Mechanical Properties

    PubMed Central

    Vlaisavljevich, Eli; Maxwell, Adam; Warnez, Matthew; Johnsen, Eric; Cain, Charles A.; Xu, Zhen

    2014-01-01

    Histotripsy is an ultrasound ablation method that depends on the initiation and maintenance of a cavitation bubble cloud to fractionate soft tissue. This paper studies how tissue properties impact the pressure threshold to initiate the cavitation bubble cloud. Our previous study showed that shock scattering off one or more initial bubbles, expanded to sufficient size in the focus, plays an important role in initiating a dense cavitation cloud. In this process, the shock scattering causes the positive pressure phase to be inverted, resulting in a scattered wave that has the opposite polarity of the incident shock. The inverted shock is superimposed on the incident negative pressure phase to form extremely high negative pressures, resulting in a dense cavitation cloud growing toward the transducer. We hypothesize that increased tissue stiffness impedes the expansion of initial bubbles, reducing the scattered tensile pressure, and thus requiring higher initial intensities for cloud initiation. To test this hypothesis, 5-cycle histotripsy pulses at pulse repetition frequencies (PRFs) of 10, 100, or 1000 Hz were applied by a 1-MHz transducer focused inside mechanically tunable tissue-mimicking agarose phantoms and various ex vivo porcine tissues covering a range of Young’s moduli. The threshold to initiate a cavitation cloud and resulting bubble expansion were recorded using acoustic backscatter detection and optical imaging. In both phantoms and ex vivo tissue, results demonstrated a higher cavitation cloud initiation threshold for tissues of higher Young’s modulus. Results also demonstrated a decrease in bubble expansion in phantoms of higher Young’s modulus. These results support our hypothesis, improve our understanding of the effect of histotripsy in tissues with different mechanical properties, and provide a rational basis to tailor acoustic parameters for fractionation of specific tissues. PMID:24474139

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

    PubMed

    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. PMID:27106317

  10. Influence of surface tension on cavitation noise spectra and particle removal efficiency in high frequency ultrasound fields

    NASA Astrophysics Data System (ADS)

    Camerotto, Elisabeth; Brems, Steven; Hauptmann, Marc; Pacco, Antoine; Struyf, Herbert; Mertens, Paul W.; De Gendt, Stefan

    2012-12-01

    Physical cleaning methods are applied in the semiconductor industry and have become increasingly challenging due to the continued scaling of semiconductors device elements. Cavitation and acoustic phenomena are known to play a fundamental role in megasonic cleaning. Hence, a better understanding of cavitation phenomena in multi-bubble systems is crucial. Here, a study on the effects of lower bulk surface tension and different O2 concentrations on the bubble activity in the megahertz range is presented. A lower bulk surface tension (45 mN/m) with respect to ultra pure water (72 mN/m) is obtained by adding a non-ionic surface-active agent (Triton X-100). After a thorough surfactant characterization, a Triton X-100-containing cleaning solution is investigated under pulsed and continuous acoustic fields, for different acoustic amplitudes and gas concentrations. It is demonstrated that cavitation activity, measured by means of ultraharmonic cavitation noise, is enhanced in presence of a lower surface tension, under continuous acoustic fields. In addition, cavitation measurements performed under pulsed fields reveal the existence of optimal pulse-off times, for which a maximum of activity is observed. These optimal pulse-off time values are linked to the bubble dissolution theoretical times and experimentally verified. To end, cavitation noise measurements are correlated to cleaning performance in megasonic fields by means of particle removal and damage tests on patterned wafers. A clear increase in particle removal efficiency of 78 nm SiO2 particles is obtained when Triton X-100 is employed, at the optimized process conditions. In addition, the number of defects due to cavitation bubbles is significantly reduced for lower surface tension, at particle removal efficiencies <60%. The results here reported constitute a different approach towards more efficient megasonic cleaning processes.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Investigation of a Method to Reduce Cavitation in Diesel Engine Bearings

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Honaker, Robert W.

    1998-01-01

    Sonoluminescence is the effect of producing light from sound and occurs when a gas bubble is trapped in a fluid filled cavity and is forced to collapse under a barrage of sound waves. Frenzel and Schultes discovered this phenomenon in 1934 while exposing acoustic waves to photographic plates. This effect was not well understood until 1988 when Crum and Gaitan discovered the necessary conditions for producing single bubble sonoluminescence in the laboratory. The luminescence is a result of the bubble violently collapsing from sound waves and this shares a close association with vibratory cavitation. Cavitation erosion is known to cause damage to rotational machinery when the collapse is near to surfaces due to the high pressures associated with bubble collapse. With these high pressures and temperatures there is a considerable amount of damage to the outside layer of a bearing, thereby, reducing its useful life. An experiment was constructed to generate sonoluminescence in the laboratory in order to obtain a greater understanding of this phenomenon and its association with bubble cavitation. Most of the research was done to investigate how to obtain single bubble sonoluminescence under different conditions and to determine how to detect it. Success in this has inspired several theories on how to use the methods for generating sonoluminescence to control cavitation in fluids under industrial conditions.

  13. Two-Bubble Acoustic Tweezing Cytometry for Biomechanical Probing and Stimulation of Cells

    PubMed Central

    Chen, Di; Sun, Yubing; Gudur, Madhu S.R.; Hsiao, Yi-Sing; Wu, Ziqi; Fu, Jianping; Deng, Cheri X.

    2015-01-01

    The study of mechanotransduction relies on tools that are capable of applying mechanical forces to elicit and assess cellular responses. Here we report a new (to our knowledge) technique, called two-bubble acoustic tweezing cytometry (TB-ATC), for generating spatiotemporally controlled subcellular mechanical forces on live cells by acoustic actuation of paired microbubbles targeted to the cell adhesion receptor integrin. By measuring the ultrasound-induced activities of cell-bound microbubbles and the actin cytoskeleton contractile force responses, we determine that TB-ATC elicits mechanoresponsive cellular changes via cyclic, paired displacements of integrin-bound microbubbles driven by the attractive secondary acoustic radiation force (sARF) between the bubbles in an ultrasound field. We demonstrate the feasibility of dual-mode TB-ATC for both subcellular probing and mechanical stimulation. By exploiting the robust and unique interaction of ultrasound with microbubbles, TB-ATC provides distinct advantages for experimentation and quantification of applied forces and cellular responses for biomechanical probing and stimulation of cells. PMID:25564850

  14. Two-bubble acoustic tweezing cytometry for biomechanical probing and stimulation of cells.

    PubMed

    Chen, Di; Sun, Yubing; Gudur, Madhu S R; Hsiao, Yi-Sing; Wu, Ziqi; Fu, Jianping; Deng, Cheri X

    2015-01-01

    The study of mechanotransduction relies on tools that are capable of applying mechanical forces to elicit and assess cellular responses. Here we report a new (to our knowledge) technique, called two-bubble acoustic tweezing cytometry (TB-ATC), for generating spatiotemporally controlled subcellular mechanical forces on live cells by acoustic actuation of paired microbubbles targeted to the cell adhesion receptor integrin. By measuring the ultrasound-induced activities of cell-bound microbubbles and the actin cytoskeleton contractile force responses, we determine that TB-ATC elicits mechanoresponsive cellular changes via cyclic, paired displacements of integrin-bound microbubbles driven by the attractive secondary acoustic radiation force (sARF) between the bubbles in an ultrasound field. We demonstrate the feasibility of dual-mode TB-ATC for both subcellular probing and mechanical stimulation. By exploiting the robust and unique interaction of ultrasound with microbubbles, TB-ATC provides distinct advantages for experimentation and quantification of applied forces and cellular responses for biomechanical probing and stimulation of cells. PMID:25564850

  15. The secondary Bjerknes force between two gas bubbles under dual-frequency acoustic excitation.

    PubMed

    Zhang, Yuning; Zhang, Yuning; Li, Shengcai

    2016-03-01

    The secondary Bjerknes force is one of the essential mechanisms of mutual interactions between bubbles oscillating in a sound field. The dual-frequency acoustic excitation has been applied in several fields such as sonochemistry, biomedicine and material engineering. In this paper, the secondary Bjerknes force under dual-frequency excitation is investigated both analytically and numerically within a large parameter zone. The unique characteristics (i.e., the complicated patterns of the parameter zone for sign change and the combination resonances) of the secondary Bjerknes force under dual-frequency excitation are revealed. Moreover, the influence of several parameters (e.g., the pressure amplitude, the bubble distance and the phase difference between sound waves) on the secondary Bjerknes force is also investigated numerically. PMID:26584991

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

    PubMed

    Merouani, Slimane; Hamdaoui, Oualid

    2016-09-01

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

  17. Attached cavitation at a small diameter ultrasonic horn tip

    NASA Astrophysics Data System (ADS)

    Žnidarčič, Anton; Mettin, Robert; Cairós, Carlos; Dular, Matevž

    2014-02-01

    Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids, for instance, for cell disruption or sonochemical reactions. They are operated typically in the frequency range up to about 50 kHz and have tip diameters from some mm to several cm. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e., below the acoustic driving frequency. Here, we present a systematic study of the cavitation dynamics in water at a 20 kHz horn tip of 3 mm diameter. The system was investigated by high-speed imaging with simultaneous recording of the acoustic emissions. Measurements were performed under variation of acoustic power, air saturation, viscosity, surface tension, and temperature of the liquid. Our findings show that the liquid properties play no significant role in the dynamics of the attached cavitation at the small ultrasonic horn. Also the variation of the experimental geometry, within a certain range, did not change the dynamics. We believe that the main two reasons for the peculiar dynamics of cavitation on a small ultrasonic horn are the higher energy density on a small tip and the inability of the big tip to "wash" away the gaseous bubbles. Calculation of the somewhat adapted Strouhal number revealed that, similar to the hydrodynamic cavitation, values which are relatively low characterize slow cavitation structure dynamics. In cases where the cavitation follows the driving frequency this value lies much higher - probably at Str > 20. In the spirit to distinguish the observed phenomenon with other cavitation dynamics at ultrasonic transducer surfaces, we suggest to term the observed phenomenon of attached cavities partly covering the full horn

  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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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. Trapping of Embolic Particles in a Vessel Phantom by Cavitation-Enhanced Acoustic Streaming

    PubMed Central

    Maxwell, Adam D.; Park, Simone; Vaughan, Benjamin L.; Cain, Charles A.; Grotberg, James B.; Xu, Zhen

    2014-01-01

    Cavitation clouds generated by short, high-amplitude, focused ultrasound pulses were previously observed to attract, trap, and erode thrombus fragments in a vessel phantom. This phenomenon may offer a noninvasive method to capture and eliminate embolic fragments flowing through the bloodstream during a cardiovascular intervention. In this article, the mechanism of embolus trapping was explored by particle image velocimetry (PIV). PIV was used to examine the fluid streaming patterns generated by ultrasound in a vessel phantom with and without crossflow of blood-mimicking fluid. Cavitation enhanced streaming, which generated fluid vortices adjacent to the focus. The focal streaming velocity, uf, was as high as 120 cm/s, while mean crossflow velocities, uc, were imposed up to 14 cm/s. When a solid particle 3-4 mm diameter was introduced into crossflow, it was trapped near the focus. Increasing uf promoted particle trapping while increasing uc promoted particle escape. The maximum crossflow Reynolds number at which particles could be trapped, Rec, was approximately linear with focal streaming number, Ref, i.e. Rec = 0.25Ref + 67.44 (R2=0.76) corresponding to dimensional velocities uc=0.084uf + 3.122 for 20 < uf < 120 cm/s. The fluidic pressure map was estimated from PIV and indicated a negative pressure gradient towards the focus, trapping the embolus near this location. PMID:25109407

  20. Trapping of embolic particles in a vessel phantom by cavitation-enhanced acoustic streaming

    NASA Astrophysics Data System (ADS)

    Maxwell, Adam D.; Park, Simone; Vaughan, Benjamin L.; Cain, Charles A.; Grotberg, James B.; Xu, Zhen

    2014-09-01

    Cavitation clouds generated by short, high-amplitude, focused ultrasound pulses were previously observed to attract, trap, and erode thrombus fragments in a vessel phantom. This phenomenon may offer a noninvasive method to capture and eliminate embolic fragments flowing through the bloodstream during a cardiovascular intervention. In this article, the mechanism of embolus trapping was explored by particle image velocimetry (PIV). PIV was used to examine the fluid streaming patterns generated by ultrasound in a vessel phantom with and without crossflow of blood-mimicking fluid. Cavitation enhanced streaming, which generated fluid vortices adjacent to the focus. The focal streaming velocity, uf, was as high as 120 cm/s, while mean crossflow velocities, uc, were imposed up to 14 cm/s. When a solid particle 3-4 mm diameter was introduced into crossflow, it was trapped near the focus. Increasing uf promoted particle trapping while increasing uc promoted particle escape. The maximum crossflow Reynolds number at which particles could be trapped, Rec, was approximately linear with focal streaming number, Ref, i.e. Rec = 0.25Ref + 67.44 (R2 = 0.76) corresponding to dimensional velocities uc = 0.084uf + 3.122 for 20 < uf < 120 cm/s. The fluidic pressure map was estimated from PIV and indicated a negative pressure gradient towards the focus, trapping the embolus near this location.

  1. Bubbles trapped at the coupling surface of the treatment head significantly reduce acoustic energy delivered in shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

    The coupling efficiency of a "dry head" electromagnetic lithotripter (Dornier Compact Delta) was studied in vitro. A fiber-optic probe hydrophone (FOPH-500) was positioned in a test tank filled with degassed water. The tank was coupled through a semi-transparent latex membrane to the water-filled cushion of the lithotripter head, so that bubbles (air pockets) trapped between the two coupling surfaces could be easily observed and photographed. When gel was applied to both the latex membrane and the water cushion, numerous bubbles (some several millimeters in diameter) could be seen at the coupling interface. Hydrophone measurements in the geometric focus of the lithotripter showed that the acoustic pressure could be two times lower when bubbles were present than when they were manually removed. In our in vitro design, trapped bubbles could be easily observed and therefore removed from the acoustic path. However, during patient treatment with a dry-head lithotripter one cannot see whether bubbles are trapped against the skin. This study provides a demonstration of the dramatic effect that trapped bubbles can have on the amount of acoustic energy actually delivered for treatment.

  2. Cavitation in ultrasound and shockwave therapy

    NASA Astrophysics Data System (ADS)

    Colonius, Tim

    2014-11-01

    Acoustic waves, especially high-intensity ultrasound and shock waves, are used for medical imaging and intra- and extra-corporeal manipulation of cells, tissue, and urinary calculi. Waves are currently used to treat kidney stone disease, plantar fasciitis, and bone nonunion, and they are being investigated as a technique to ablate cancer tumors and mediate drug delivery. In many applications, acoustic waves induce the expansion and collapse of preexisting or newly cavitating bubbles whose presence can either mediate the generation of localized stresses or lead to collateral damage, depending on how effectively they can be controlled. We describe efforts aimed at simulating the collapse of bubbles, both individually and in clusters, with the aim to characterize the induced mechanical stresses and strains. To simulate collapse of one or a few bubbles, compressible Euler and Navier-Stokes simulations of multi-component materials are performed with WENO-based shock and interface capturing schemes. Repetitive insonification generates numerous bubbles that are difficult to resolve numerically. Such clouds are also important in traditional engineering applications such as caveating hydrofoils. Models that incorporate the dynamics of an unresolved dispersed phase consisting of the bubble cloud are also developed. The results of several model problems including bubble collapse near rigid surfaces, bubble collapse near compliant surfaces and in small capillaries are analyzed. The results are processed to determine the potential for micron-sized preexisting gas bubbles to damage capillaries. The translation of the fundamental fluid dynamics into improvements in the design and clinical application of shockwave lithotripters will be discussed. NIH Grant PO1-DK043881.

  3. A New Unsteady Model for Dense Cloud Cavitation in Cryogenic Fluids

    NASA Technical Reports Server (NTRS)

    Hosangadi, A.; Ahuja, V.

    2005-01-01

    A new unsteady, cavitation model is presented wherein the phase change process (bubble growth/collapse) is coupled to the acoustic field in a cryogenic fluid. It predicts the number density and radius of bubbles in vapor clouds by tracking both the aggregate surface area and volume fraction of the cloud. Hence, formulations for the dynamics of individual bubbles (e.g. Rayleigh-Plesset equation) may be integrated within the macroscopic context of a dense vapor cloud i.e. a cloud that occupies a significant fraction of available volume and contains numerous bubbles. This formulation has been implemented within the CRUNCH CFD, which has a compressible real fluid formulation, a multi-element, unstructured grid framework, and has been validated extensively for liquid rocket turbopump inducers. Detailed unsteady simulations of a cavitating ogive in liquid nitrogen are presented where time-averaged mean cavity pressure and temperature depressions due to cavitation are compared with experimental data. The model also provides the spatial and temporal history of the bubble size distribution in the vapor clouds that are shed, an important physical parameter that is difficult to measure experimentally and is a significant advancement in the modeling of dense cloud cavitation.

  4. Nonlinear Acoustics in Fluids

    NASA Astrophysics Data System (ADS)

    Lauterborn, Werner; Kurz, Thomas; Akhatov, Iskander

    At high sound intensities or long propagation distances at in fluids sufficiently low damping acoustic phenomena become nonlinear. This chapter focuses on nonlinear acoustic wave properties in gases and liquids. The origin of nonlinearity, equations of state, simple nonlinear waves, nonlinear acoustic wave equations, shock-wave formation, and interaction of waves are presented and discussed. Tables are given for the nonlinearity parameter B/A for water and a range of organic liquids, liquid metals and gases. Acoustic cavitation with its nonlinear bubble oscillations, pattern formation and sonoluminescence (light from sound) are modern examples of nonlinear acoustics. The language of nonlinear dynamics needed for understanding chaotic dynamics and acoustic chaotic systems is introduced.

  5. Xylem cavitation resistance can be estimated based on time-dependent rate of acoustic emissions.

    PubMed

    Nolf, Markus; Beikircher, Barbara; Rosner, Sabine; Nolf, Anton; Mayr, Stefan

    2015-10-01

    Acoustic emission (AE) analysis allows nondestructive monitoring of embolism formation in plant xylem, but signal interpretation and agreement of acoustically measured hydraulic vulnerability with reference hydraulic techniques remain under debate. We compared the hydraulic vulnerability of 16 species and three crop tree cultivars using hydraulic flow measurements and acoustic emission monitoring, proposing the use of time-dependent AE rates as a novel parameter for AE analysis. There was a linear correlation between the water potential (Ψ) at 50% loss of hydraulic conductivity (P50 ) and the Ψ at maximum AE activity (Pmaxrate ), where species with lower P50 also had lower Pmaxrate (P < 0.001, R(2)  = 0.76). Using AE rates instead of cumulative counts for AE analysis allows more efficient estimation of P50 , while excluding problematic AE at late stages of dehydration. PMID:26010417

  6. Harness cavitation to improve processing

    SciTech Connect

    Pandit, A.G.; Moholkar, V.S.

    1996-07-01

    Mention cavitation to most chemical engineers, and they undoubtedly think of it as an operational problem. Indeed, the rapid creation and then collapse of bubbles, which is after all what cavitation involves, can destroy pumps and erode other equipment. Cavitation, however, also can have a positive side--presuming it is designed for and not unplanned. In this article, the authors look at how cavitation can be harnessed to improve processes, and the mechanisms for inducing cavitation--ultrasonics and hydrodynamics--and their likely roles. Sonication, that is, the use of ultrasound, is the conventional approach for creating cavitation, and so they turn to it first. Over the past few years, a number of groups have attempted to solve the problem of scale-up and design of ultrasonic reactors. The authors review the systems that already exist and also explore a simpler and efficient alternative to the ultrasonic reactor, the hydrodynamic cavitation reactor.

  7. The role of large bubbles detected from acoustic measurements on the dynamics of Erta 'Ale lava lake (Ethiopia)

    NASA Astrophysics Data System (ADS)

    Bouche, E.; Vergniolle, S.; Staudacher, T.; Nercessian, A.; Delmont, J.-C.; Frogneux, M.; Cartault, F.; Le Pichon, A.

    2010-06-01

    The activity at the surface of the lava lake on Erta 'Ale volcano (Ethiopia) shows that large bubbles are regularly breaking at a fixed position on the lava lake. This is also where the small lava fountains are sometimes produced. Since this location is likely to be directly above the volcanic conduit feeding the lava lake, we have done continuous measurements between March 22 and 26, 2003 to understand the degassing of a volcano in permanent activity. The bubble size has been first estimated from videos, which once combined with the acoustic pressure, can constrain the source of the sound. The gas volume and overpressure stayed roughly constant, between 36-700 m3 and 4 × 103-1.8 × 104 Pa, respectively. Simultaneous thermal measurements showed regular peaks, which occurred when the crust was broken by a large bubble, hence gave a direct indication on the typical return time between the bubbles (1 h). These spherical cap bubbles had a high Reynolds number, 4600-20000, therefore a wake, periodically unstable, formed and detached from the bubble bottom. The bubbly wake, if the detachment occurs close to the surface, can explain the duration of lava fountains, measured on the videos. The periodic arrival of bubbly wakes, which mostly detach from the driving spherical cap within the lava lake, could explain the absence of cooling at Erta 'Ale, Erebus (Antartica), Villarica (Chile) and Nyiragongo (Democratic Republic of Congo) without invoking a convective downflow of magma in the conduit, as previously done.

  8. Optoacoustic tweezers: a programmable, localized cell concentrator based on opto-thermally generated, acoustically activated, surface bubbles.

    PubMed

    Xie, Yuliang; Zhao, Chenglong; Zhao, Yanhui; Li, Sixing; Rufo, Joseph; Yang, Shikuan; Guo, Feng; Huang, Tony Jun

    2013-05-01

    We present a programmable, biocompatible technique for dynamically concentrating and patterning particles and cells in a microfluidic device. Since our technique utilizes opto-thermally generated, acoustically activated, surface bubbles, we name it "optoacoustic tweezers". The optoacoustic tweezers are capable of concentrating particles/cells at any prescribed locations in a microfluidic chamber without the use of permanent structures, rendering it particularly useful for the formation of flexible, complex cell patterns. Additionally, this technique has demonstrated excellent biocompatibility and can be conveniently integrated with other microfluidic units. In our experiments, micro-bubbles were generated by focusing a 405 nm diode laser onto a gold-coated glass chamber. By properly tuning the laser, we demonstrate precise control over the position and size of the generated bubbles. Acoustic waves were then applied to activate the surface bubbles, causing them to oscillate at an optimized frequency. The resulting acoustic radiation force allowed us to locally trap particles/cells, including 15 μm polystyrene beads and HeLa cells, around each bubble. Cell-adhesion tests were also conducted after cell concentrating to confirm the biocompatibility of this technique. PMID:23511348

  9. Can Cavitation Be Anticipated?

    SciTech Connect

    Allgood, G.O.; Dress, W.B.; Hylton, J.O.; Kercel, S.W.

    1999-04-25

    The major problem with cavitation in pumps and hydraulic systems is that there is no effective (conventional) method for detecting or predicting its inception. The traditional method of recognizing cavitation in a pump is to declare the event occurring when the total head drops by some arbitrary value (typically 3%) in response to a pressure reduction at the pump inlet. However, the device is already seriously cavitating when this happens. What is actually needed is a practical method to detect impending rather than incipient cavitation. Whereas the detection of incipient cavitation requires the detection of features just after cavitation starts, the anticipation of cavitation requires the detection and identification of precursor features just before it begins. Two recent advances that make this detection possible. The first is acoustic sensors with a bandwidth of 1 MHz and a dynamic range of 80 dB that preserve the fine details of the features when subjected to coarse vibrations. The second is the application of Bayesian parameter estimation which makes it possible to separate weak signals, such as those present in cavitation precursors, from strong signals, such as pump vibration. Bayesian parameter estimation derives a model based on cavitation hydrodynamics and produces a figure of merit of how well it fits the acquired data. Applying this model to an anticipatory engine should lead to a reliable method of anticipating cavitation before it occurs. This paper reports the findings of precursor features using high-performance sensors and Bayesian analysis of weak acoustic emissions in the 100-1000kHz band from an experimental flow loop.

  10. Cavitating vortex generation by a submerged jet

    SciTech Connect

    Belyakov, G. V.; Filippov, A. N.

    2006-05-15

    The surface geometry of a cavitating vortex is determined in the limit of inviscid incompressible flow. The limit surface is an ovaloid of revolution with an axis ratio of 5: 3. It is shown that a cavitating vortex ring cannot develop if the cavitation number is lower than a certain critical value. Experiments conducted at various liquid pressures and several jet exit velocities confirm the existence of a critical cavitation number close to 3. At cavitation numbers higher than the critical one, the cavitating vortex ring does not develop. At substantially lower cavitation numbers (k {<=} 0.1), an elongated asymmetric cavitation bubble is generated, with an axial reentrant jet whose length can exceed the initial jet length by several times. This flow structure is called an asymmetric cavitating vortex, even though steady motion of this structure has not been observed.

  11. Acoustic Cluster Therapy: In Vitro and Ex Vivo Measurement of Activated Bubble Size Distribution and Temporal Dynamics.

    PubMed

    Healey, Andrew John; Sontum, Per Christian; Kvåle, Svein; Eriksen, Morten; Bendiksen, Ragnar; Tornes, Audun; Østensen, Jonny

    2016-05-01

    Acoustic cluster technology (ACT) is a two-component, microparticle formulation platform being developed for ultrasound-mediated drug delivery. Sonazoid microbubbles, which have a negative surface charge, are mixed with micron-sized perfluoromethylcyclopentane droplets stabilized with a positively charged surface membrane to form microbubble/microdroplet clusters. On exposure to ultrasound, the oil undergoes a phase change to the gaseous state, generating 20- to 40-μm ACT bubbles. An acoustic transmission technique is used to measure absorption and velocity dispersion of the ACT bubbles. An inversion technique computes bubble size population with temporal resolution of seconds. Bubble populations are measured both in vitro and in vivo after activation within the cardiac chambers of a dog model, with catheter-based flow through an extracorporeal measurement flow chamber. Volume-weighted mean diameter in arterial blood after activation in the left ventricle was 22 μm, with no bubbles >44 μm in diameter. After intravenous administration, 24.4% of the oil is activated in the cardiac chambers. PMID:26831341

  12. A New Unsteady Model for Dense Cloud Cavitation in Cryogenic Fluids

    NASA Technical Reports Server (NTRS)

    Hosangadi, Ashvin; Ahuja, Vineet

    2005-01-01

    Contents include the following: Background on thermal effects in cavitation. Physical properties of hydrogen. Multi-phase cavitation with thermal effect. Solution procedure. Cavitation model overview. Cavitation source terms. New cavitation model. Source term for bubble growth. One equation les model. Unsteady ogive simulations: liquid nitrogen. Unsteady incompressible flow in a pipe. Time averaged cavity length for NACA15 flowfield.

  13. Photodistruptive laser nucleation of ultrasonic cavitation for biomedical applications

    NASA Astrophysics Data System (ADS)

    Miller, Doug L.; Spooner, Greg J.; Williams, Alun R.

    2001-07-01

    Pulses of high intensity laser light, when focused into transparent materials, may produce localized electron-ion plasmas through optical breakdown. By simultaneously incorporating the resulting volume of vaporized material within the focal volume of a high intensity ultrasound source, the photodisruption (1.05 micrometers wavelength) void served as a nucleation site for ultrasonic cavitation. Dilute suspensions of canine erythrocytes in phosphate buffered saline were exposed in a flow-through exposure chamber and the percentage of lysed cells was used as a measure of the biologically effective cavitation activity produced in the chamber. Brief (about 30 microsecond(s) ) acoustic emissions were detected from the photodisruption alone (indicating laser nucleation of bubbles), but the cell lysis produced was undetectable against the background. However, combined exposure greatly increased both the duration of the acoustic emissions (up to 1.5 ms) and the amount of cell lysis above an ultrasonic pressure amplitude threshold of about 4.3 MPa at 2.5 MHz. The amount of cell lysis (sometimes approaching 100%) increased with increasing ultrasonic intensity, laser pulse energy and laser PRF. Addition of 5% serum albumin enhanced the effect, apparently by stabilizing bubbles and nuclei. Photodisruptive laser nucleation of ultrasonic cavitation can provide controlled and synergistic enhancement of bioeffects.

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

    PubMed

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

    2015-10-01

    The study of the interaction of bubbles with shock waves and ultrasound is sometimes termed 'acoustic cavitation'. It is of importance in many biomedical applications where sound waves are applied. The use of shock waves and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics-bubble interactions, with a focus on shock wave-bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the 'resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a shock wave complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving shock wave-bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead. PMID:26442143

  15. Trans-Stent B-Mode Ultrasound and Passive Cavitation Imaging.

    PubMed

    Haworth, Kevin J; Raymond, Jason L; Radhakrishnan, Kirthi; Moody, Melanie R; Huang, Shao-Ling; Peng, Tao; Shekhar, Himanshu; Klegerman, Melvin E; Kim, Hyunggun; McPherson, David D; Holland, Christy K

    2016-02-01

    Angioplasty and stenting of a stenosed artery enable acute restoration of blood flow. However, restenosis or a lack of re-endothelization can subsequently occur depending on the stent type. Cavitation-mediated drug delivery is a potential therapy for these conditions, but requires that particular types of cavitation be induced by ultrasound insonation. Because of the heterogeneity of tissue and stochastic nature of cavitation, feedback mechanisms are needed to determine whether the sustained bubble activity is induced. The objective of this study was to determine the feasibility of passive cavitation imaging through a metal stent in a flow phantom and an animal model. In this study, an endovascular stent was deployed in a flow phantom and in porcine femoral arteries. Fluorophore-labeled echogenic liposomes, a theragnostic ultrasound contrast agent, were injected proximal to the stent. Cavitation images were obtained by passively recording and beamforming the acoustic emissions from echogenic liposomes insonified with a low-frequency (500 kHz) transducer. In vitro experiments revealed that the signal-to-noise ratio for detecting stable cavitation activity through the stent was greater than 8 dB. The stent did not significantly reduce the signal-to-noise ratio. Trans-stent cavitation activity was also detected in vivo via passive cavitation imaging when echogenic liposomes were insonified by the 500-kHz transducer. When stable cavitation was detected, delivery of the fluorophore into the arterial wall was observed. Increased echogenicity within the stent was also observed when echogenic liposomes were administered. Thus, both B-mode ultrasound imaging and cavitation imaging are feasible in the presence of an endovascular stent in vivo. Demonstration of this capability supports future studies to monitor restenosis with contrast-enhanced ultrasound and pursue image-guided ultrasound-mediated drug delivery to inhibit restenosis. PMID:26547633

  16. The condition of the resonant break-up of a gas bubble subjected to an acoustic wave in liquid

    NASA Astrophysics Data System (ADS)

    Vanovskiy, V. V.; Petrov, A. G.

    2015-12-01

    The problem of a gas bubble break-up in liquid is considered in the conditions of the frequencies resonance of the radial and nth axially symmetric deformational mode 2:1. The nonlinear energy transfer between the modes is described using an efficient Krylov-Bogolyubov averaging technique. It is shown that the deformational mode magnitude can be some orders larger than the radial mode magnitude which is damped by the thermal, viscous and acoustic dissipation. The estimative criterion of bubble break-up is obtained in the cases of slow and fast acoustic wave start. The obtained pressure magnitudes in the wave for break-up are very small and the mechanism can have strong medical and technical applications.

  17. Cavitation studies in microgravity

    NASA Astrophysics Data System (ADS)

    Kobel, Philippe; Obreschkow, Danail; Farhat, Mohamed; Dorsaz, Nicolas; de Bosset, Aurele

    The hydrodynamic cavitation phenomenon is a major source of erosion for many industrial systems such as cryogenic pumps for rocket propulsion, fast ship propellers, hydraulic pipelines and turbines. Erosive processes are associated with liquid jets and shockwaves emission fol-lowing the cavity collapse. Yet, fundamental understanding of these processes requires further cavitation studies inside various geometries of liquid volumes, as the bubble dynamics strongly depends the surrounding pressure field. To this end, microgravity represents a unique platform to produce spherical fluid geometries and remove the hydrostatic pressure gradient induced by gravity. The goal of our first experiment (flown on ESA's parabolic flight campaigns 2005 and 2006) was to study single bubble dynamics inside large spherical water drops (having a radius between 8 and 13 mm) produced in microgravity. The water drops were created by a micro-pump that smoothly expelled the liquid through a custom-designed injector tube. Then, the cavitation bubble was generated through a fast electrical discharge between two electrodes immersed in the liquid from above. High-speed imaging allowed to analyze the implications of isolated finite volumes and spherical free surfaces on bubble evolution, liquid jets formation and shock wave dynamics. Of particular interest are the following results: (A) Bubble lifetimes are shorter than in extended liquid volumes, which could be explain by deriving novel corrective terms to the Rayleigh-Plesset equation. (B) Transient crowds of micro-bubbles (smaller than 1mm) appeared at the instants of shockwaves emission. A comparison between high-speed visualizations and 3D N-particle simulations of a shock front inside a liquid sphere reveals that focus zones within the drop lead to a significantly increased density of induced cavitation. Considering shock wave crossing and focusing may hence prove crucially useful to understand the important process of cavitation erosion

  18. Aerator Combined With Bubble Remover

    NASA Technical Reports Server (NTRS)

    Dreschel, Thomas W.

    1993-01-01

    System produces bubble-free oxygen-saturated water. Bubble remover consists of outer solid-walled tube and inner hydrophobic, porous tube. Air bubbles pass from water in outer tube into inner tube, where sucked away. Developed for long-term aquaculture projects in space. Also applicable to terrestrial equipment in which entrained bubbles dry membranes or give rise to cavitation in pumps.

  19. Tissue differentiation using laser-induced shock waves by detection of acoustic transients through an optical wave-guide

    NASA Astrophysics Data System (ADS)

    Tschepe, Johannes; Ahrens, Thomas; Helfmann, Juergen; Mueller, Gerhard J.; Gapontsev, Valentin P.

    1993-05-01

    Some physical phenomena which occur during the fragmentation of calculi by laser induced optical break down are presented. With in vitro experiments it could be shown that the energy of the laser induced plasma and of the cavitation bubble (induced by the plasma) depends by the nature of the tissue. The laser induced plasma and the cavitation bubble generate shock waves. These sound waves are transferred via the laser fiber and detected with a piezo- electrical sensor at the proximal end. The acoustic signal contains information on the potential energy of the bubble, which depends on the energy of the plasma. The possibility of measuring the energy dependent acoustic transients allows to distinguish between hard and soft tissue and by this it is suitable for controlling the laser lithotripsy process. The transmission of acoustic transients through silica glass fibers is investigated by theoretical calculations. It shows the feasibility of silica glass fibers as an acoustic wave guide.

  20. Radial oscillation of a gas bubble in a fluid as a problem in canonical perturbation theory

    NASA Astrophysics Data System (ADS)

    Stephens, James

    2006-11-01

    The oscillation of a gas bubble is in a fluid is of interest in many areas of physics and technology. Lord Rayleigh treated the pressure developed in the collapse of cavitation bubbles and developed an expression for the collapse period. Minnaert developed a harmonic oscillator approximation to bubble oscillation in his study of the sound produced by running water. Besides recent interest in bubble oscillation in connection to sonoluminescence, an understanding of oscillating bubbles is of important to oceanographers studying the sound spectrum produced by water waves, geophysicists employing air guns as acoustic probes, mechanical engineers concerned with erosion of turbine blades, and military engineers concerned with the acoustic signatures developed by the propeller screws of ships and submarines. For the oceanographer, Minnaert's approximation is useful, for the latter two examples, Lord Rayleigh's analysis is appropriate. For the case of the airgun, a period of twice Rayleigh's period for the ``total collapse'' of the cavitation bubble is often cited as a good approximation for the period of an air bubble ejected from an air gun port, typically at ˜2000 psi), however for the geophysical example, numerical integration is employed from the outset to determine the dynamics of the bubble and the emitted acoustic energy. On the one hand, a bubble can be treated as a harmonic oscillator in the small amplitude regime, whereas even in the relatively moderate pressure regime characteristic of air guns the oscillation is strongly nonlinear and amplitude dependent. Is it possible to develop an analytic approximation that affords insight into the behavior of a bubble beyond the harmonic approximation of Minnaert? In this spirit, the free radial oscillation of a gas bubble in a fluid is treated as a problem in canonical perturbation theory. Several orders of the expansion are determined in order to explore the dependence of the oscillation frequency with bubble amplitude

  1. On the influence of stochastic pulsations of a bubble on its translational motion

    NASA Astrophysics Data System (ADS)

    Melnikov, N. P.

    2016-06-01

    This communication is devoted to theoretical analysis of the dynamics of a solitary cavitation bubble pulsating in a compressible viscous liquid under the action of a nonuniform acoustic field. The system of two nonlinear ordinary second-order differential equations is integrated numerically. In the range of acoustic field parameters corresponding to the principal resonance region, the bubble performs large-scale spatial oscillations. It is shown that in a very small range of initial radii, the bubble stops its oscillatory motion due to stochastic pulsations and is expelled into the region of the acoustic-pressure block. Therefore, stochastic pulsations of the bubble radically change the form of the solution to the system of the above-mentioned equations.

  2. Submicron-Bubble-Enhanced Focused Ultrasound for Blood–Brain Barrier Disruption and Improved CNS Drug Delivery

    PubMed Central

    Ting, Chien-Yu; Lee, Ya-Hsuan; Huang, Chih-Ying; Ma, Yan-Jung; Wei, Kuo-Chen; Yen, Tzu-Chen; Yeh, Chih-Kuang

    2014-01-01

    The use of focused ultrasound (FUS) with microbubbles has been proven to induce transient blood–brain barrier opening (BBB-opening). However, FUS-induced inertial cavitation of microbubbles can also result in erythrocyte extravasations. Here we investigated whether induction of submicron bubbles to oscillate at their resonant frequency would reduce inertial cavitation during BBB-opening and thereby eliminate erythrocyte extravasations in a rat brain model. FUS was delivered with acoustic pressures of 0.1–4.5 MPa using either in-house manufactured submicron bubbles or standard SonoVue microbubbles. Wideband and subharmonic emissions from bubbles were used to quantify inertial and stable cavitation, respectively. Erythrocyte extravasations were evaluated by in vivo post-treatment magnetic resonance susceptibility-weighted imaging, and finally by histological confirmation. We found that excitation of submicron bubbles with resonant frequency-matched FUS (10 MHz) can greatly limit inertial cavitation while enhancing stable cavitation. The BBB-opening was mainly caused by stable cavitation, whereas the erythrocyte extravasation was closely correlated with inertial cavitation. Our technique allows extensive reduction of inertial cavitation to induce safe BBB-opening. Furthermore, the safety issue of BBB-opening was not compromised by prolonging FUS exposure time, and the local drug concentrations in the brain tissues were significantly improved to 60 times (BCNU; 18.6 µg versus 0.3 µg) by using chemotherapeutic agent-loaded submicron bubbles with FUS. This study provides important information towards the goal of successfully translating FUS brain drug delivery into clinical use. PMID:24788566

  3. Research on the noise induced by cavitation under the asymmetric cavitation condition in a centrifugal pump

    NASA Astrophysics Data System (ADS)

    Lu, J. X.; Yuan, S. Q.; Yuan, J. P.; Ren, X. D.; Pei, J.; Si, Q. R.

    2015-12-01

    An experimental investigation has been carried out to research the noise induced by cavitation under the asymmetric cavitation (AC) condition in a centrifugal pump. The acoustic pressure signals at the pump inlet and outlet were measured respectively during the development of cavitation in a closed hydraulic test rig. It could be found that both the pump inlet and outlet acoustic pressures changed obviously with the development of cavitation. The time domain and the power spectrum density of the pump inlet and outlet acoustic pressure pulsations were analyzed. The broadband pulses of the acoustic pressure pulsations were found and the reasons for the phenomenon were given.

  4. Dramatic effect of superfluidity on the collapse of 4He vapor bubbles

    NASA Astrophysics Data System (ADS)

    Qu, An; Trimeche, A.; Jacquier, Ph.; Grucker, J.

    2016-05-01

    The lifetime of cavitation bubbles produced by an acoustic wave focused in liquid helium-4 is investigated. This lifetime is found to be different by orders of magnitude depending on whether the liquid is superfluid or not. We show that if the liquid is in the superfluid state, the bubble lifetime is well explained by a purely mechanical model, corresponding to the so-called Rayleigh regime. In the normal state, the Rayleigh-Plesset regime applies, in which heat diffusion plays a crucial role and dramatically increases the bubble lifetime.

  5. Dynamics of cavitation clouds within a high-intensity focused ultrasonic beam

    NASA Astrophysics Data System (ADS)

    Lu, Yuan; Katz, Joseph; Prosperetti, Andrea

    2013-07-01

    In this experimental study, we generate a 500 kHz high-intensity focused ultrasonic beam, with pressure amplitude in the focal zone of up to 1.9 MPa, in initially quiescent water. The resulting pressure field and behavior of the cavitation bubbles are measured using high-speed digital in-line holography. Variations in the water density and refractive index are used for determining the spatial distribution of the acoustic pressure nonintrusively. Several cavitation phenomena occur within the acoustic partially standing wave caused by the reflection of sound from the walls of the test chamber. At all sound levels, bubbly layers form in the periphery of the focal zone in the pressure nodes of the partial standing wave. At high sound levels, clouds of vapor microbubbles are generated and migrate in the direction of the acoustic beam. Both the cloud size and velocity vary periodically, with the diameter peaking at the pressure nodes and velocity at the antinodes. A simple model involving linearized bubble dynamics, Bjerknes forces, sound attenuation by the cloud, added mass, and drag is used to predict the periodic velocity of the bubble cloud, as well as qualitatively explain the causes for the variations in the cloud size. The analysis shows that the primary Bjerknes force and drag dominate the cloud motion, and suggests that the secondary Bjerknes force causes the oscillations in the cloud size.

  6. Cavitation erosion of silver plated coating at different temperatures and pressures

    SciTech Connect

    Hattori, Shuji; Motoi, Yoshihiro; Kikuta, Kengo; Tomaru, Hiroshi

    2014-04-11

    Cavitation often occurs in inducer pumps used for space rockets. Silver plated coating on the inducer liner faces the damage of cavitation. Therefore, it is important to study about the cavitation erosion resistance for silver plated coating at several operating conditions in the inducer pumps. In this study, the cavitation erosion tests were carried for silver plated coating in deionized water and ethanol at several liquid temperatures (273K–400K) and pressures (0.10MPa–0.48MPa). The mass loss rate is evaluated in terms of thermodynamic parameter Σ proposed by Brennen [9], suppression pressure p–p{sub v} (p{sub v}: saturated vapor pressure) and acoustic impedance ρc (ρ: density and c: sound speed). Cavitation bubble behaviors depending on the thermodynamic effect and the liquid type were observed by high speed video camera. The mass loss rate is formulated by thermodynamic parameter Σ, suppression pressure p–p{sub v} and acoustic impedance ρc.

  7. High speed observation of HIFU-induced cavitation cloud near curved rigid boundaries

    NASA Astrophysics Data System (ADS)

    Zuo, Z. G.; Wang, F. B.; Liu, S. H.; Wu, S. J.

    2015-01-01

    This paper focuses on the experimental study of the influence of surface curvature to the behaviour of HIFU-induced cavitation cloud. A Q-switched ruby pulse laser is used to induce cavitation nuclei in deionized water. A piezoelectric ultrasonic transducer (1.7 MHz) provides a focused ultrasound field to inspire the nucleus to cavitation cloud. A PZT probe type hydrophone is applied for measuring the HIFU sound field. It was observed that the motion of cavitation cloud located near the boundary is significantly influenced by the distance between cloud and boundary, as well as the curvature of the boundary. The curvature was defined by parameters λ and ξ. Convex boundary, concave boundary, and flat boundary correspond to ξ <1, ξ >1 and ξ = 1, respectively. Different behaviours of the cloud, including the migration of the cloud, the characteristics of oscillation, etc., were observed under different boundary curvatures by high-speed photography. Sonoluminescence of the acoustic cavitation bubble clouds were also studied to illustrate the characteristics of acoustic streaming.

  8. Current Status in Cavitation Modeling

    NASA Technical Reports Server (NTRS)

    Singhal, Ashok K.; Avva, Ram K.

    1993-01-01

    Cavitation is a common problem for many engineering devices in which the main working fluid is in liquid state. In turbomachinery applications, cavitation generally occurs on the inlet side of pumps. The deleterious effects of cavitation include: lowered performance, load asymmetry, erosion and pitting of blade surfaces, vibration and noise, and reduction of the overall machine life. Cavitation models in use today range from rather crude approximations to sophisticated bubble dynamics models. Details about bubble inception, growth and collapse are relevant to the prediction of blade erosion, but are not necessary to predict the performance of pumps. An engineering model of cavitation is proposed to predict the extent of cavitation and performance. The vapor volume fraction is used as an indicator variable to quantify cavitation. A two-phase flow approach is employed with the assumption of the thermal equilibrium between liquid and vapor. At present velocity slip between the two phases is selected. Preliminary analyses of 2D flows shows qualitatively correct results.

  9. Extreme impact and cavitation forces of a biological hammer: strike forces of the peacock mantis shrimp Odontodactylus scyllarus.

    PubMed

    Patek, S N; Caldwell, R L

    2005-10-01

    Mantis shrimp are renowned for their unusual method of breaking shells with brief, powerful strikes of their raptorial appendages. Due to the extreme speeds of these strikes underwater, cavitation occurs between their appendages and hard-shelled prey. Here we examine the magnitude and relative contribution of the impact and cavitation forces generated by the peacock mantis shrimp Odontodactylus scyllarus. We present the surprising finding that each strike generates two brief, high-amplitude force peaks, typically 390-480 micros apart. Based on high-speed imaging, force measurements and acoustic analyses, it is evident that the first force peak is caused by the limb's impact and the second force peak is due to the collapse of cavitation bubbles. Peak limb impact forces range from 400 to 1501 N and peak cavitation forces reach 504 N. Despite their small size, O. scyllarus can generate impact forces thousands of times their body weight. Furthermore, on average, cavitation peak forces are 50% of the limb's impact force, although cavitation forces may exceed the limb impact forces by up to 280%. The rapid succession of high peak forces used by mantis shrimp suggests that mantis shrimp use a potent combination of cavitation forces and extraordinarily high impact forces to fracture shells. The stomatopod's hammer is fundamentally different from typical shell-crushing mechanisms such as fish jaws and lobster claws, and may have played an important and as yet unexamined role in the evolution of shell form. PMID:16169943

  10. Cavitation effect of holmium laser pulse applied to ablation of hard tissue underwater.

    PubMed

    Lü, Tao; Xiao, Qing; Xia, Danqing; Ruan, Kai; Li, Zhengjia

    2010-01-01

    To overcome the inconsecutive drawback of shadow and schlieren photography, the complete dynamics of cavitation bubble oscillation or ablation products induced by a single holmium laser pulse [2.12 microm, 300 micros (FWHM)] transmitted in different core diameter (200, 400, and 600 microm) fibers is recorded by means of high-speed photography. Consecutive images from high-speed cameras can stand for the true and complete process of laser-water or laser-tissue interaction. Both laser pulse energy and fiber diameter determine cavitation bubble size, which further determines acoustic transient amplitudes. Based on the pictures taken by high-speed camera and scanned by an optical coherent microscopy (OCM) system, it is easily seen that the liquid layer at the distal end of the fiber plays an important role during the process of laser-tissue interaction, which can increase ablation efficiency, decrease heat side effects, and reduce cost. PMID:20799845

  11. Properties of sound attenuation around a two-dimensional underwater vehicle with a large cavitation number

    NASA Astrophysics Data System (ADS)

    Ye, Peng-Cheng; Pan, Guang

    2015-06-01

    Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering. Project supported by the National Natural Science Foundation of China (Grant Nos. 51279165 and 51479170) and the National Defense Basic Scientific Research Program of China (Grant No. B2720133014).

  12. Sonoluminescence characterization of inertial cavitation inside a BSA phantom treated by pulsed HIFU.

    PubMed

    Yin, Hui; Chang, Nan; Xu, Shanshan; Wan, Mingxi

    2016-09-01

    The aim of this study was to investigate the inertial cavitation inside a phantom treated by pulsed HIFU (pHIFU). Basic bovine serum albumin (BSA) phantoms without any inherent ultrasound contrast agents (UCAs) or phase-shift nano-emulsions (PSNEs) were used. During the treatment, sonoluminescence (SL) recordings were performed to characterize the spatial distribution of inertial cavitation adjacent to the focal region. High-speed photographs and thermal coagulations, comparing with the SL results, were also recorded and presented. A series of pulse parameters (pulse duration (PD) was between 1 and 23 cycles and pulse repetition frequency (PRF) was between 0.5kHz and 100kHz) were performed to make a systematic investigation under certain acoustic power (APW). Continuous HIFU (cHIFU) investigation was also performed to serve as control group. It was found that, when APW was 19.5W, pHIFU with short PD was much easier to form SL adjacent to the focal region inside the phantom, while it was difficult for cHIFU to generate cavitation bubbles. With appropriate PD and PRF, the residual bubbles of the previous pulses could be stimulated by the incident pulses to oscillate in a higher level and even violently collapse, resulting to enhanced physical thermogenesis. The experimental results showed that the most violent inertial cavitation occurs when PD was set to 6 cycles (5μs) and PRF to 10kHz, while the highest level of thermal coagulation was observed when PD was set to 10 cycles. The cavitational and thermal characteristics were in good correspondence, exhibiting significant potentiality regarding to inject-free cavitation bubble enhanced thermal ablation under lower APW, compared to the conventional thermotherapy. PMID:27150756

  13. Acoustic Cavitation Enhances Focused Ultrasound Ablation with Phase-Shift Inorganic Perfluorohexane Nanoemulsions: An In Vitro Study Using a Clinical Device

    PubMed Central

    Zhao, Lu-Yan; Zou, Jian-Zhong; Chen, Zong-Gui; Liu, Shan; Jiao, Jiao; Wu, Feng

    2016-01-01

    Purpose. To investigate whether acoustic cavitation could increase the evaporation of a phase-shift inorganic perfluorohexane (PFH) nanoemulsion and enhance high intensity focused ultrasound (HIFU) ablation. Materials and Methods. PFH was encapsulated by mesoporous silica nanocapsule (MSNC) to form a nanometer-sized droplet (MSNC-PFH). It was added to a tissue-mimicking phantom, whereas phosphate buffered saline (PBS) was added as a control (PBS-control). HIFU (Pac = 150 W, t = 5/10 s) exposures were performed in both phantoms with various duty cycles (DC). US images, temperature, and cavitation emissions were recorded during HIFU exposure. HIFU-induced lesions were measured and calculated. Results. Compared to PBS-control, MSNC-PFH nanoemulsion could significantly increase the volume of HIFU-induced lesion (P < 0.01). Peak temperatures were 78.16 ± 5.64°C at a DC of 100%, 70.17 ± 6.43°C at 10%, 53.17 ± 4.54°C at 5%, and 42.00 ± 5.55°C at 2%, respectively. Inertial cavitation was much stronger in the pulsed-HIFU than that in the continuous-wave HIFU exposure. Compared to 100%-DC exposure, the mean volume of lesion induced by 5 s exposure at 10%-DC was significantly larger, but smaller at 2%-DC. Conclusions. MSNC-PFH nanoemulsion can significantly enhance HIFU ablation. Appropriate pulsed-HIFU exposure could significantly increase the volume of lesion and reduce total US energy required for HIFU ablation. PMID:27419138

  14. Acoustic Cavitation Enhances Focused Ultrasound Ablation with Phase-Shift Inorganic Perfluorohexane Nanoemulsions: An In Vitro Study Using a Clinical Device.

    PubMed

    Zhao, Lu-Yan; Zou, Jian-Zhong; Chen, Zong-Gui; Liu, Shan; Jiao, Jiao; Wu, Feng

    2016-01-01

    Purpose. To investigate whether acoustic cavitation could increase the evaporation of a phase-shift inorganic perfluorohexane (PFH) nanoemulsion and enhance high intensity focused ultrasound (HIFU) ablation. Materials and Methods. PFH was encapsulated by mesoporous silica nanocapsule (MSNC) to form a nanometer-sized droplet (MSNC-PFH). It was added to a tissue-mimicking phantom, whereas phosphate buffered saline (PBS) was added as a control (PBS-control). HIFU (P ac = 150 W, t = 5/10 s) exposures were performed in both phantoms with various duty cycles (DC). US images, temperature, and cavitation emissions were recorded during HIFU exposure. HIFU-induced lesions were measured and calculated. Results. Compared to PBS-control, MSNC-PFH nanoemulsion could significantly increase the volume of HIFU-induced lesion (P < 0.01). Peak temperatures were 78.16 ± 5.64°C at a DC of 100%, 70.17 ± 6.43°C at 10%, 53.17 ± 4.54°C at 5%, and 42.00 ± 5.55°C at 2%, respectively. Inertial cavitation was much stronger in the pulsed-HIFU than that in the continuous-wave HIFU exposure. Compared to 100%-DC exposure, the mean volume of lesion induced by 5 s exposure at 10%-DC was significantly larger, but smaller at 2%-DC. Conclusions. MSNC-PFH nanoemulsion can significantly enhance HIFU ablation. Appropriate pulsed-HIFU exposure could significantly increase the volume of lesion and reduce total US energy required for HIFU ablation. PMID:27419138

  15. Secondary shock wave emissions from cavitation in lithotripsy

    NASA Astrophysics Data System (ADS)

    Chitnis, Parag V.; Cleveland, Robin O.

    2005-04-01

    We investigate the role of secondary shock waves (SSWs) generated by cavitation in lithotripsy. Acoustic pressure was measured with a fiber optic probe hydrophone and cavitation using a dual passive cavitation detector (PCD) consisting of two confocal transducers. An artificial stone (~7 mm diameter and ~9 mm length) was placed at the focus of an electrohydraulic lithotripter. The fiber was inserted through a hole drilled through the stone so that the tip was at the proximal surface. SSWs were identified by matching the time of arrival to that of the inertial collapse signature acquired by the PCD. Measurements of SSWs were obtained for 50% of SWs fired at 20 kV and 1 Hz. The peak positive pressure for the SSW was p+=33.7+/-14.8 MPa, which was comparable to the pressure induced by the incident SW (p+=42.6+/-6 MPa). The peak pressure in water was p+=23.2+/-4.4 MPa. The PCD also recorded acoustic emissions from forced collapse of pre-existing bubbles caused by the incident SW. We propose that both the reflection from the semi-rigid stone boundary and SSW from the forced collapse contribute to the observed increase in the peak pressure of the incident SW in presence of a stone. [Work supported by NIH.

  16. Effect of charge on the dynamics of an acoustically forced bubble

    NASA Astrophysics Data System (ADS)

    Hongray, Thotreithem; Ashok, B.; Balakrishnan, J.

    2014-06-01

    The effect of charge on the dynamics of a gas bubble undergoing forced oscillations in a liquid due to incidence of an ultrasonic wave is theoretically investigated. The limiting values of the possible charge a bubble may physically carry are obtained. The presence of charge influences the regime in which the bubble's radial oscillations fall. The extremal compressive and expansive dimensions of the bubble are also studied as a function of the amplitude of the driving pressure. It is shown that the limiting value of the bubble charge is dictated both by the minimal value reachable of the bubble radius as well as the amplitude of the driving ultrasonic pressure wave. A non-dimensional ratio ζ is defined that is a comparative measure of the extremal values the bubble can expand or contract to, and we find the existence of an unstable regime for ζ as a function of the driving pressure amplitude, Ps. This unstable regime is gradually suppressed with increasing bubble size. The Blake and the upper transient pressure thresholds for the system are then discussed.

  17. An In Vitro Study of the Correlation Between Bubble Distribution, Acoustic Emission, and Cell Damage by Contrast Ultrasound

    PubMed Central

    Fowlkes, J. Brian; Miller, Douglas L.

    2009-01-01

    The objective of this study was to investigate the influences of total exposure duration and pulse-to-pulse bubble distribution on contrast-mediated cell damage. Murine macrophage cells were grown as monolayers on thin polyester sheets. Contrast agent microbubbles were attached to these cells by incubation. Focused ultrasound exposures (Pr = 2 MPa) were implemented at a frequency of 2.25 MHz with 46 cycle pulses and pulse repetition frequencies (PRF) of 1 kHz, 500 Hz, 100 Hz, and 10 Hz in a degassed water bath at 10 or 100 pulses. A 1 MHz receive transducer measured the scattered signal. The frequency spectrum was normalized to a control spectrum from linear scatterers. Photomicrographs were captured before, during, and after exposure at a frame rate of 2000 fps and a pixel resolution of 960 × 720. Results clearly show that cell death is increased, up to 60%, by increasing total exposure duration from 0 ms to 100 ms. There was an increasing difference in cell damage between a 10-pulse exposure and a 100-pulse exposure with increasing PRF. The greatest change in damage occurred at 1000 Hz PRF with a 53% increase between 10-pulse and 100-pulse exposures. For each pulse from 0 to 10, an overlay of the 2 μm bubble count with corresponding emission shows consistent behavior in its pulse-to-pulse changes, indicating a correlation between acoustic emission, bubble distribution, and cell damage. PMID:19411217

  18. Ultrasonic atomization of liquids in drop-chain acoustic fountains

    PubMed Central

    Simon, Julianna C.; Sapozhnikov, Oleg A.; Khokhlova, Vera A.; Crum, Lawrence A.; Bailey, Michael R.

    2015-01-01

    When focused ultrasound waves of moderate intensity in liquid encounter an air interface, a chain of drops emerges from the liquid surface to form what is known as a drop-chain fountain. Atomization, or the emission of micro-droplets, occurs when the acoustic intensity exceeds a liquid-dependent threshold. While the cavitation-wave hypothesis, which states that atomization arises from a combination of capillary-wave instabilities and cavitation bubble oscillations, is currently the most accepted theory of atomization, more data on the roles of cavitation, capillary waves, and even heat deposition or boiling would be valuable. In this paper, we experimentally test whether bubbles are a significant mechanism of atomization in drop-chain fountains. High-speed photography was used to observe the formation and atomization of drop-chain fountains composed of water and other liquids. For a range of ultrasonic frequencies and liquid sound speeds, it was found that the drop diameters approximately equalled the ultrasonic wavelengths. When water was exchanged for other liquids, it was observed that the atomization threshold increased with shear viscosity. Upon heating water, it was found that the time to commence atomization decreased with increasing temperature. Finally, water was atomized in an overpressure chamber where it was found that atomization was significantly diminished when the static pressure was increased. These results indicate that bubbles, generated by either acoustic cavitation or boiling, contribute significantly to atomization in the drop-chain fountain. PMID:25977591

  19. CAVITATION DAMAGE STUDY VIA A NOVEL REPETITIVE PRESSURE PULSE APPROACH

    SciTech Connect

    Wang, Jy-An John; Ren, Fei; Wang, Hong

    2010-01-01

    Cavitation damage can significantly affect system performance. Thus, there is great interest in characterizing cavitation damage and improving materials resistance to cavitation damage. In this paper, we present a novel methodology to simulate cavitation environment. A pulsed laser is utilized to induce optical breakdown in the cavitation media, with the emission of shock wave and the generation of bubbles. The pressure waves induced by the optical breakdown fluctuate/propagate within the media, which enables the cavitation to occur and to further develop cavitation damage at the solid boundary. Using the repetitive pulsed-pressure apparatus developed in the current study, cavitation damage in water media was verified on stainless steel and aluminum samples. Characteristic cavitation damages such as pitting and indentation are observed on sample surfaces using scanning electron microscopy.

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

    NASA Astrophysics Data System (ADS)

    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 (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern 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.

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

    PubMed

    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 (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern 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. PMID:26429474

  2. Passive cavitation imaging with ultrasound arrays

    PubMed Central

    Salgaonkar, Vasant A.; Datta, Saurabh; Holland, Christy K.; Mast, T. Douglas

    2009-01-01

    A method is presented for passive imaging of cavitational acoustic emissions using an ultrasound array, with potential application in real-time monitoring of ultrasound ablation. To create such images, microbubble emissions were passively sensed by an imaging array and dynamically focused at multiple depths. In this paper, an analytic expression for a passive image is obtained by solving the Rayleigh–Sommerfield integral, under the Fresnel approximation, and passive images were simulated. A 192-element array was used to create passive images, in real time, from 520-kHz ultrasound scattered by a 1-mm steel wire. Azimuthal positions of this target were accurately estimated from the passive images. Next, stable and inertial cavitation was passively imaged in saline solution sonicated at 520 kHz. Bubble clusters formed in the saline samples were consistently located on both passive images and B-scans. Passive images were also created using broadband emissions from bovine liver sonicated at 2.2 MHz. Agreement was found between the images and source beam shape, indicating an ability to map therapeutic ultrasound beams in situ. The relation between these broadband emissions, sonication amplitude, and exposure conditions are discussed. PMID:20000921

  3. Combined passive detection and ultrafast active imaging of cavitation events induced by short pulses of high-intensity ultrasound.

    PubMed

    Gateau, Jérôme; Aubry, Jean-François; Pernot, Mathieu; Fink, Mathias; Tanter, Mickaël

    2011-03-01

    The activation of natural gas nuclei to induce larger bubbles is possible using short ultrasonic excitations of high amplitude, and is required for ultrasound cavitation therapies. However, little is known about the distribution of nuclei in tissues. Therefore, the acoustic pressure level necessary to generate bubbles in a targeted zone and their exact location are currently difficult to predict. To monitor the initiation of cavitation activity, a novel all-ultrasound technique sensitive to single nucleation events is presented here. It is based on combined passive detection and ultrafast active imaging over a large volume using the same multi-element probe. Bubble nucleation was induced using a focused transducer (660 kHz, f-number = 1) driven by a high-power electric burst (up to 300 W) of one to two cycles. Detection was performed with a linear array (4 to 7 MHz) aligned with the single-element focal point. In vitro experiments in gelatin gel and muscular tissue are presented. The synchronized passive detection enabled radio-frequency data to be recorded, comprising high-frequency coherent wave fronts as signatures of the acoustic emissions linked to the activation of the nuclei. Active change detection images were obtained by subtracting echoes collected in the unnucleated medium. These indicated the appearance of stable cavitating regions. Because of the ultrafast frame rate, active detection occurred as quickly as 330 μs after the high-amplitude excitation and the dynamics of the induced regions were studied individually. PMID:21429844

  4. Combined passive detection and ultrafast active imaging of cavitation events induced by short pulses of high-intensity ultrasound

    PubMed Central

    Gateau, Jérôme; Aubry, Jean-François; Pernot, Mathieu; Fink, Mathias; Tanter, Mickaël

    2011-01-01

    The activation of natural gas nuclei to induce larger bubbles is possible using short ultrasonic excitations of high amplitude, and is required for ultrasound cavitation therapies. However, little is known about the distribution of nuclei in tissues. Therefore, the acoustic pressure level necessary to generate bubbles in a targeted zone and their exact location are currently difficult to predict. In order to monitor the initiation of cavitation activity, a novel all-ultrasound technique sensitive to single nucleation events is presented here. It is based on combined passive detection and ultrafast active imaging over a large volume and with the same multi-element probe. Bubble nucleation was induced with a focused transducer (660kHz, f#=1) driven by a high power (up to 300 W) electric burst of one to two cycles. Detection was performed with a linear array (4–7MHz) aligned with the single-element focal point. In vitro experiments in gelatin gel and muscular tissue are presented. The synchronized passive detection enabled radio-frequency data to be recorded, comprising high-frequency coherent wave fronts as signatures of the acoustic emissions linked to the activation of the nuclei. Active change detection images were obtained by subtracting echoes collected in the unucleated medium. These indicated the appearance of stable cavitating regions. Thanks to the ultrafast frame rate, active detection occurred as soon as 330 μs after the high amplitude excitation and the dynamics of the induced regions were studied individually. PMID:21429844

  5. Tip Vortex Cavitation

    NASA Astrophysics Data System (ADS)

    Maines, Brant H.; Arndt, Roger E. A.

    2000-11-01

    Cavitation in vortical flows is a problem of practical importance, that is relatively unexplored. Vortical structures of importance range from the eddies occurring randomly in space and time in turbulent flows to the developed vortices that occur at the tips of lifting surfaces and at the hubs of propellers and hydraulic turbines. A variety of secondary flow phenomena such as the horse shoe vortices that form around bridge piers, chute blocks and struts, and the secondary vortices found in the clearance passages of turbomachinery are also important cavitation sites. Tip vortex cavitation can be viewed as a canonical problem that captures many of the essential physics associated with vortex cavitation in general. This paper describes the inception process and focuses on the high levels of tension that can be sustained in the flow, which appears to scale with the blade loading. High speed video visualization indicates that the details of how free stream nuclei are ingested plays a major role in the nucleation and inception process. A new photographic technique was used to obtain high quality images of the bubble growth process at framing rates as high as 40,000 fps. Sponsored by the Office of Naval Research

  6. Direct visualization of microalgae rupture by ultrasound-driven bubbles

    NASA Astrophysics Data System (ADS)

    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.

  7. Temporal and spatial detection of HIFU-induced inertial and hot-vapor cavitation with a diagnostic ultrasound system.

    PubMed

    Farny, Caleb H; Holt, R Glynn; Roy, Ronald A

    2009-04-01

    The onset and presence of inertial cavitation and near-boiling temperatures in high-intensity focused ultrasound (HIFU) therapy have been identified as important indicators of energy deposition for therapy guidance. Passive cavitation detection is commonly used to detect bubble emissions, where a fixed-focus single-element acoustic transducer is typically used as a passive cavitation detector (PCD). This technique is suboptimal for clinical applications, because most PCD transducers are tightly focused and afford limited spatial coverage of the HIFU focal region. A Terason 2000 Ultrasound System was used as a PCD array to expand the spatial detection region for cavitation by operating in passive mode, obtaining the radiofrequency signals corresponding to each scan line and filtering the contribution from scattering of the HIFU signal harmonics. This approach allows for spatially resolved detection of both inertial and stable cavitation throughout the focal region. Measurements with the PCD array during sonication with a 1.1-MHz HIFU source in tissue phantoms were compared with single-element PCD and thermocouple sensing. Stable cavitation signals at the harmonics and superharmonics increased in a threshold fashion for temperatures >90 degrees C, an effect attributed to high vapor pressure in the cavities. Incorporation of these detection techniques in a diagnostic ultrasound platform could result in a powerful tool for improving HIFU guidance and treatment. PMID:19110368

  8. The physical acoustics of HIFU exposure: A suite of in vitro studies

    NASA Astrophysics Data System (ADS)

    Roy, Ronald A.; Holt, R. Glynn; Cleveland, Robin O.

    2001-05-01

    Exposing tissue and blood media to high-intensity focused ultrasound leads to a broad range of physical and biological effects. In addition to tissue heating from thermo-viscous absorption, one encounters nonlinear and second order phenomena such as wave-front shocking, radiation stress, acoustic streaming, bubble nucleation and cavitation. All of these processes impact one's ability to effect controlled tissue heating. This paper reviews a suite of studies under way at Boston University that focus on developing a quantitative understanding of the physical acoustics of high-intensity focused ultrasound. We describe research into HIFU heating and both uniform and flow-through tissue phantom and address the potentially critical roles played by bubbles and acoustic cavitation. [Work supported by the U.S. Army and the Center for Subsurface Sensing and Imaging Systems via NSF ERC Award No. EEC-9986821.

  9. Boundary conditions for simulations of oscillating bubbles using the non-linear acoustic approximation

    NASA Astrophysics Data System (ADS)

    King, J. R. C.; Ziolkowski, A. M.; Ruffert, M.

    2015-03-01

    We have developed a new boundary condition for finite volume simulations of oscillating bubbles. Our method uses an approximation to the motion outside the domain, based on the solution at the domain boundary. We then use this approximation to apply boundary conditions by defining incoming characteristic waves at the domain boundary. Our boundary condition is applicable in regions where the motion is close to spherically symmetric. We have tested our method on a range of one- and two-dimensional test cases. Results show good agreement with previous studies. The method allows simulations of oscillating bubbles for long run times (5 ×105 time steps with a CFL number of 0.8) on highly truncated domains, in which the boundary condition may be applied within 0.1% of the maximum bubble radius. Conservation errors due to the boundary conditions are found to be of the order of 0.1% after 105 time steps. The method significantly reduces the computational cost of fixed grid finite volume simulations of oscillating bubbles. Two-dimensional results demonstrate that highly asymmetric bubble features, such as surface instabilities and the formation of jets, may be captured on a small domain using this boundary condition.

  10. Continuous Cavitation Designed for Enhancing Radiofrequency Ablation via a Special Radiofrequency Solidoid Vaporization Process.

    PubMed

    Zhang, Kun; Li, Pei; Chen, Hangrong; Bo, Xiaowan; Li, Xiaolong; Xu, Huixiong

    2016-02-23

    Lowering power output and radiation time during radiofrequency (RF) ablation is still a challenge. Although it is documented that metal-based magnetothermal conversion and microbubbles-based inertial cavitation have been tried to overcome above issues, disputed toxicity and poor magnetothermal conversion efficiency for metal-based nanoparticles and violent but transient cavitation for microbubbles are inappropriate for enhancing RF ablation. In this report, a strategy, i.e., continuous cavitation, has been proposed, and solid menthol-encapsulated poly lactide-glycolide acid (PLGA) nanocapsules have been constructed, as a proof of concept, to validate the role of such a continuous cavitation principle in continuously enhancing RF ablation. The synthesized PLGA-based nanocapsules can respond to RF to generate menthol bubbles via distinctive radiofrequency solidoid vaporization (RSV) process, meanwhile significantly enhance ultrasound imaging for HeLa solid tumor, and further facilitate RF ablation via the continuous cavitation, as systematically demonstrated both in vitro and in vivo. Importantly, this RSV strategy can overcome drawbacks and limitations of acoustic droplet vaporization (ADV) and optical droplet vaporization (ODV), and will probably find broad applications in further cancer theranostics. PMID:26800221

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

    PubMed

    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. PMID:11894990

  12. Large Volume Coagulation Utilizing Multiple Cavitation Clouds Generated by Array Transducer Driven by 32 Channel Drive Circuits

    NASA Astrophysics Data System (ADS)

    Nakamura, Kotaro; Asai, Ayumu; Sasaki, Hiroshi; Yoshizawa, Shin; Umemura, Shin-ichiro

    2013-07-01

    High-intensity focused ultrasound (HIFU) treatment is a noninvasive treatment, in which focused ultrasound is generated outside the body and coagulates a diseased tissue. The advantage of this method is minimal physical and mental stress to the patient, and the disadvantage is the long treatment time caused by the smallness of the therapeutic volume by a single exposure. To improve the efficiency and shorten the treatment time, we are focusing attention on utilizing cavitation bubbles. The generated microbubbles can convert the acoustic energy into heat with a high efficiency. In this study, using the class D amplifiers, which we have developed, to drive the array transducer, we demonstrate a new method to coagulate a large volume by a single HIFU exposure through generating cavitation bubbles distributing in a large volume and vibrating all of them. As a result, the coagulated volume by the proposed method was 1.71 times as large as that of the conventional method.

  13. CAVITATIONAL HYDROTHERMAL OXIDATION: A NEW REMEDIATION PROCESS

    EPA Science Inventory

    This research will explore the emerging science of sonochemistry and its technological applications for organic waste remediation, particularly for water and soil purification. Ultrasound can induce unusual high-energy chemistry through the process of acoustic cavitation: the for...

  14. Cavitating Langmuir turbulence in the terrestrial aurora.

    PubMed

    Isham, B; Rietveld, M T; Guio, P; Forme, F R E; Grydeland, T; Mjølhus, E

    2012-03-01

    Langmuir cavitons have been artificially produced in Earth's ionosphere, but evidence of naturally occurring cavitation has been elusive. By measuring and modeling the spectra of electrostatic plasma modes, we show that natural cavitating, or strong, Langmuir turbulence does occur in the ionosphere, via a process in which a beam of auroral electrons drives Langmuir waves, which in turn produce cascading Langmuir and ion-acoustic excitations and cavitating Langmuir turbulence. The data presented here are the first direct evidence of cavitating Langmuir turbulence occurring naturally in any space or astrophysical plasma. PMID:22463417

  15. Radial oscillation of a gas bubble in a fluid as a problem in canonical perturbation theory

    NASA Astrophysics Data System (ADS)

    Stephens, James

    2005-11-01

    The oscillation of a gas bubble is in a fluid is of interest in many areas of physics and technology. Lord Rayleigh treated the pressure developed in the collapse of cavitation bubbles and developed an expression for the collapse period. Minnaert developed a harmonic oscillator approximation to bubble oscillation in his study of the sound produced by running water. Oscillating bubbles are important to oceanographers studying the sound spectrum produced by water waves, geophysicists employing air guns as acoustic probes, mechanical engineers concerned with erosion of turbine blades, and military engineers concerned with the acoustic signatures developed by the propeller screws of ships and submarines. For the oceanographer, Minnaert's approximation is useful, for the latter two examples, Lord Rayleigh's analysis is appropriate. On the one hand, a bubble can be treated as a harmonic oscillator in the small amplitude regime, whereas even in the relatively moderate pressure regime characteristic of air guns the oscillation is strongly nonlinear and amplitude dependent. Is it possible to develop an analytic approximation that affords insight into the behavior of a bubble beyond the harmonic approximation of Minnaert? In this spirit, the free radial oscillation of a gas bubble in a fluid is treated as a problem in canonical perturbation theory. Several orders of the expansion are determined in order to explore the dependence of the oscillation frequency with bubble amplitude. The expansion to second order is inverted to express the time dependence of the oscillation.

  16. Numerical simulation of high-speed cavitating flows in submerged water jet

    NASA Astrophysics Data System (ADS)

    Peng, G.; Shimizu, S.

    2013-12-01

    Properties of existing cavitation models are discussed and a compressible mixture flow method based a simplified estimation of bubble cavitation is then presented for numerical simulation of high-speed water jets accompanied by intensive cavitation. Two-phase fluid media of cavitating flow are treated as a mixture of liquid and bubbles, and the mean flow is computed by solving RANS equations for compressible fluids considering the effect of bubble expansion a/o contraction. The intensity of cavitation is evaluated by the gas volume fraction, which is governed by the compressibility of bubble-liquid mixture corresponding to the status of mean flow field. Numerical results of cavitating water jet issuing from a submerged nozzle are presented and its applicability to intensively cavitating jets is demonstrated.

  17. A numerical model for the evolution of internal structure of cavitation cloud

    NASA Astrophysics Data System (ADS)

    Du, Tezhuan; Wang, Yiwei; Liao, Lijuan; Huang, Chenguang

    2016-07-01

    Bubble size distributions in cloud cavitation are important in cavitating flows. In this study, a numerical model was developed to study the evolution of the internal structure of cloud cavitation. The model includes (1) an evolution equation of bubble number density, which considers the bubble breakup effect and (2) the multiphase Reynolds-averaged Navier-Stokes equations with a modified cavitation model for background cavitating flows. The proposed model was validated with a flow over a projectile. Results show that the numerical model can predict the evolution of the internal structure of cloud cavitation. Comparisons of the proposed model and Singhal model were discussed. The effects of re-entrant jet and bubble number density on cavitating flows were also investigated.

  18. Bacterial Sterilization Using Cavitating Jet

    NASA Astrophysics Data System (ADS)

    Azuma, Yohei; Kato, Hiroharu; Usami, Ron; Fukushima, Tadamasa

    In this paper, a new sterilization method using cavitating flow is presented. Water with bacteria was pressurized up to 105 MPa and flushed out through two very small nozzles 0.1-0.31 mm in diameter, where a cavitating jet was generated containing bubbles that collapsed downstream. First, the effects of jet velocity and cavitation number on the sterilization rate of Escherichia coli JCM1649T (E. coli) were examined. The sterilization rate increased with jet velocity. The rate was proportional to the 3rd power of the velocity. All the E. coli cells were killed by three successive treatments at V=355.7 m/s and cavitation number σ=0.154. The sterilization rate has a peak depending on cavitation number at the low-jet-velocity region of less than 300 m/s. An experiment was also performed to compare two types of bacteria, E. coli, as typical Gram-negative bacteria and Bacillus subtilis JCM1465T (B. subtilis), as typical Gram-positive bacteria. Additional tests were performed using Pseudomonas putida JCM13063T, Gram-negative bacteria and Bacillus halodurans JCTM9153, Gram-positive bacteria. The sterilization rate of the Gram-positive bacteria was much lower than that of the Gram-negative bacteria under the same experimental conditions. Gram-positive bacteria have a thicker peptidoglycan layer than Gram-negative bacteria. This may be the reason why B. subtilis is more resistant to the mechanical stress caused by cavitating flow.

  19. Experimental and Theoretical Investigations of Cavitation in Water

    NASA Technical Reports Server (NTRS)

    Ackeret, J.

    1945-01-01

    The cavitation in nozzles on airfoils of various shape and on a sphere are experimentally investigated. The limits of cavitation and the extension of the zone of the bubbles in different stages of cavitation are photographically established. The pressure in the bubble area is constant and very low, jumping to high values at the end of the area. The analogy with the gas compression shock is adduced and discussed. The collapse of the bubbles under compression shock produces very high pressures internally, which must be contributory factors to corrosion. The pressure required for purely mechanical corrosion is also discussed.

  20. POD study of aerated cavitation in a venturi nozzle

    NASA Astrophysics Data System (ADS)

    Tomov, P.; Danlos, A.; Khelladi, S.; Ravelet, F.; Sarraf, C.; Bakir, F.

    2015-12-01

    The fact of injecting bubbles into a cavitating flow influences typical cavitating behavior. Cavitation and aerated cavitation experiments has been carried out on a symmetrical venturi nozzle with convergent/divergent angles of 18° and 8°, respectively. A snapshot Proper Orthogonal Decomposition (POD) technique is used to identify different modes in terms of discharge flow velocity, pressure and injected quantity of air. The energy spectrum per given mode is also presented. The first four modes are outlined in the present paper for an aerated and non-aerated cavitating flows.

  1. Mechanisms of thrombolysis acceleration by cavitation

    NASA Astrophysics Data System (ADS)

    Weiss, Hope; Selvaraj, Prashanth; Ahadi, Golnaz; Voie, Arne; Hoelscher, Thilo; Okita, Kohei; Matsumoto, Yoichiro; Szeri, Andrew

    2012-11-01

    Recent studies, in vitro and in vivo, have shown that High Intensity Focused Ultrasound (HIFU) accelerates thrombolysis, the dissolution of blood clots, for ischemic stroke. Although the mechanisms are not fully understood, cavitation is thought to play an important role in sonothrombolysis. The damage to a blood clot's fibrin fiber network from cavitation in a HIFU field is studied using two independent approaches for an embedded bubble. One method is extended to the more important scenario of a bubble outside a blood clot that collapses asymmetrically creating a jet towards the clot. There is significantly more damage potential from a bubble undergoing cavitation collapse outside the clot compared to a rapidly expanding bubble embedded within the clot structure. Also, the effects of the physical properties of skull bone when a HIFU wave propagates through it are examined by use of computer simulation. The dynamics of a test bubble placed at the focus is used in understanding of the pressure field. All other things being equal, the analysis suggests that skull thickness can alter the wave at the focus, which in turn can change the nature of cavitation bubble dynamics and the amount of energy available for clot damage. Now at MSOE.

  2. Experimental investigation of cavitation in pump inlet

    NASA Astrophysics Data System (ADS)

    Sikora, Roman; Bureček, Adam; Hružík, Lumír; Vašina, Martin

    2015-05-01

    The article deals with experimental research of cavitation development in inlet tube of hydraulic pump. The pressures in inlet and outlet tube of the pump and flow rate were measured. Mineral oil was used as working fluid. The cavitation was visually evaluated in transparent inlet tube. The inlet tube underpressure was achieved by throttle valve. The relationship between the generation of bubbles and the inlet pressure is evaluated.

  3. Bubble diagnostics

    DOEpatents

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

    2003-01-01

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

  4. Enhancement of heat and mass transfer by cavitation

    NASA Astrophysics Data System (ADS)

    Zhang, Y. N.; Zhang, Y. N.; Du, X. Z.; Xian, H. Z.

    2015-01-01

    In this paper, a brief summary of effects of cavitation on the heat and mass transfer are given. The fundamental studies of cavitation bubbles, including its nonlinearity, rectified heat and mass diffusion, are initially introduced. Then selected topics of cavitation enhanced heat and mass transfer were discussed in details including whales stranding caused by active sonar activity, pool boiling heat transfer, oscillating heat pipe and high intensity focused ultrasound treatment.

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

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2009-04-01

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

  6. Real-time two-dimensional imaging of microbubble cavitation

    NASA Astrophysics Data System (ADS)

    Vignon, Francois; Shi, W. T.; Powers, J. E.; Liu, J.; Drvol, L.; Lof, J.; Everbach, C.; Gao, S.; Xie, F.; Porter, T.

    2012-10-01

    Ultrasound cavitation of microbubble contrast agents has a potential for therapeutic applications, including sonothrombolysis in acute ischemic stroke. For safety, efficacy, and reproducibility of treatment, it is critical to evaluate the cavitation state (e.g. stable versus inertial forms of cavitation) and intensity in and around a treatment area. Acoustic Passive Cavitation Detectors (PCDs) have been used but do not provide spatial information. This paper presents a prototype of a 2D cavitation imager capable of producing images of the dominant cavitation state and intensity in a region of interest at a frame rate of 0.6Hz. The system is based on a modified ultrasound scanner (iE33, Philips) with a sector imaging probe (S5-1). Cavitation imaging is based on the spectral analysis of the acoustic signal radiated by the cavitating microbubbles: ultraharmonics of the excitation frequency indicate stable cavitation, while noise bands indicate inertial cavitation. The system demonstrates the capability to robustly identify stable and inertial cavitation thresholds of Definity microbubbles (Lantheus) in a vessel phantom through 3 ex-vivo human temporal bones, as well as to spatially map cavitation activities.

  7. Physical effects in cavitating flows

    NASA Technical Reports Server (NTRS)

    Plesset, M. S.

    1974-01-01

    The microscopic and macroscopic aspects of the physical effects of cavitating flows are discussed. The microscopic features are related to the properties of nuclei in liquids and to the moderate tensile strengths which are usually encountered in flows. The macroscopic features are concerned with the growth of vapor or gaseous cavities from a small initial size and with their eventual collapse. Mathematical models are developed to analyze the characteristics of: (1) tensile strength in liquids, (2) growth of vapor bubbles, and (3) collapse of vapor bubbles.

  8. Cavitation dynamics on the nanoscale

    SciTech Connect

    Kotaidis, Vassilios; Plech, Anton

    2005-11-21

    The ultrafast excitation of gold nanoparticle sols causes a strong nonequilibrium heating of the particle lattice and subsequently of the water shell close to the particle surface. Above a threshold in laser fluence, which is defined by the onset of homogeneous nucleation, nanoscale vapor bubbles develop around the particles, expand and collapse again within the first nanosecond after excitation. We show the existence of cavitation on the nanometer and subnanosecond time scale, described within the framework of continuum thermodynamics.

  9. Radiation induced cavitation: A possible phenomenon in liquid targets?

    SciTech Connect

    West, C.D.

    1998-07-01

    The proposed design of a new, short-pulse spallation neutron source includes a liquid mercury target irradiated with a 1 GeV proton beam. This paper explores the possibility that cavitation bubbles may be formed in the mercury and briefly discusses some design features that could avoid harmful effects should cavitation take place.

  10. Numerical investigation of cavitation performance on bulb tubular turbine

    NASA Astrophysics Data System (ADS)

    Sun, L. G.; Guo, P. C.; Zheng, X. B.; Luo, X. Q.

    2016-05-01

    The cavitation flow phenomena may occur in the bulb tubular turbine at some certain operation conditions, which even decrease the performance of units and causes insatiably noise and vibration when it goes worse. A steady cavitating flow numerical simulations study is carried out on the bulb tubular unit with the same blade pitch angle and different guide vane openings by using the commercial code ANSYS CFX in this paper. The phenomena of cavitation induction areas and development process are obtained and draws cavitation performance curves. The numerical results show that the travelling bubble cavity is the main types of cavitation development over a wide operating range of discharge and this type of cavitation begins to sensitive to the value of cavitation number when the discharge exceeding a certain valve, in this condition, it can lead to a severe free bubble formation with the gradually decrement of cavitation number. The reported cavitation performance curves results indicate that the flow blockage incident would happen because of a mount of free bubble formation in the flow passage when the cavity developed to certain extend, which caused head drop behavior and power broken dramatically and influenced the output power.

  11. Simultaneous pressure measurement and high-speed photography study of cavitation in a dynamically loaded journal bearing

    NASA Technical Reports Server (NTRS)

    Sun, D. C.; Brewe, David E.; Abel, Philip B.

    1994-01-01

    Cavitation of the oil film in a dynamically loaded journal bearing was studied using high-speed photography and pressure measurement simultaneously. Comparison of the visual and pressure data provided considerable insight into the occurrence and nonoccurrence of cavitation. It was found that (1) for the submerged journal bearing, cavitation typically occurred in the form of one bubble with the pressure in the cavitation bubble close to the absolute zero; and (2) for cavitation-producing operating conditions, cavitation did not always occur; with the oil film then supporting a tensile stress.

  12. Quantitative assessment of reactive oxygen species generation by cavitation incepted efficiently using nonlinear propagation effect

    NASA Astrophysics Data System (ADS)

    Yasuda, Jun; Yoshizawa, Shin; Umemura, Shin-ichiro

    2015-10-01

    Sonodynamic treatment is a treatment method that uses chemical bio-effect of cavitation bubbles. Reactive oxygen species that can kill cancerous tissue is induced by such chemical effect of cavitation bubbles and it is important to generate them efficiently for effective sonodynamic treatment. Cavitation cloud can be formed by an effect of nonlinear propagation and focus and in this study, it was experimentally investigated if cavitation cloud was useful for efficient generation of reactive oxygen species. As a result, it was demonstrated that cavitation cloud would be useful for efficient generation of reactive oxygen species.

  13. Experimental investigation on noise of cavitation nozzle and its chaotic behaviour

    NASA Astrophysics Data System (ADS)

    Zhang, Fenghua; Liu, Haifeng; Xu, Junchao; Tang, Chuanlin

    2013-07-01

    The researches of cavitation noise mainly focus on the incipiency and developing of cavitation to prevent the cavititation erosion in the hydraulic machinery, while there is few report about the collapse strength of cavitation bubbles produced by water jet through the cavitation nozzle to utilize efficiently the collapse energy of cavitation bubbles. The cavitation noise signals are collected with hydrophones for the cavitation nozzle and general nozzle at the target position and the nozzle exit separately in the conditions of different standoff distance. The features of signal's frequency spectrum and power spectrum are analyzed for various nozzles by way of classical methods. Meanwhile, based on chaotic theory, phase space reconstruction is processed and the maximum Lyapunov index is calculated separately for each cavitation signal's time series. The results of chaotic analysis are compared with the one of conventional analysis. The analyzed data show that there are the marked differences at the spectrum between the cavitation nozzle and general nozzle at the target position while the standoff distance is 35 mm, which mainly displays at the high frequency segment (60-120 kHz). The maximum Lyapunov index calculated appear at standoff distance 35 mm, which is an optimum standoff distance for the most bubbles to collapse at the target. At the nozzle exit, the noise signal of cavitation nozzle is different from the general nozzle, which also displays at the high frequency segment. The results demonstrate that the water jet modulated by the cavitation nozzle can produce effectually cavitation, and at the target position the amplitude and energy of noise spectrum in high frequency segment for cavitation nozzle are higher than conventional nozzle and the Lyapunov index of cavitation nozzle is larger than conventional nozzle as the standoff distance is less than 55 mm. The proposed research reveals that the cavitation noise produced by collapse of cavitation bubbles

  14. Counterbalancing the use of ultrasound contrast agents by a cavitation-regulated system.

    PubMed

    Desjouy, C; Fouqueray, M; Lo, C W; Muleki Seya, P; Lee, J L; Bera, J C; Chen, W S; Inserra, C

    2015-09-01

    The stochastic behavior of cavitation can lead to major problems of initiation and maintenance of cavitation during sonication, responsible of poor reproducibility of US-induced bioeffects in the context of sonoporation for instance. To overcome these disadvantages, the injection of ultrasound contrast agents as cavitation nuclei ensures fast initiation and lower acoustic intensities required for cavitation activity. More recently, regulated-cavitation devices based on the real-time modulation of the applied acoustic intensity have shown their potential to maintain a stable cavitation state during an ultrasonic shot, in continuous or pulsed wave conditions. In this paper is investigated the interest, in terms of cavitation activity, of using such regulated-cavitation device or injecting ultrasound contrast agents in the sonicated medium. When using fixed applied acoustic intensity, results showed that introducing ultrasound contrast agents increases reproducibility of cavitation activity (coefficient of variation 62% and 22% without and with UCA, respectively). Moreover, the use of the regulated-cavitation device ensures a given cavitation activity (coefficient of variation less 0.4% in presence of UCAs or not). This highlights the interest of controlling cavitation over time to free cavitation-based application from the use of UCAs. Interestingly, during a one minute sonication, while ultrasound contrast agents progressively disappear, the regulated-cavitation device counterbalance their destruction to sustain a stable inertial cavitation activity. PMID:25682465

  15. Stem Hydraulic Conductivity depends on the Pressure at Which It Is Measured and How This Dependence Can Be Used to Assess the Tempo of Bubble Pressurization in Recently Cavitated Vessels1[OPEN

    PubMed Central

    Liu, Jinyu; Tyree, Melvin T.

    2015-01-01

    Cavitation of water in xylem vessels followed by embolism formation has been authenticated for more than 40 years. Embolism formation involves the gradual buildup of bubble pressure (air) to atmospheric pressure as demanded by Henry’s law of equilibrium between gaseous and liquid phases. However, the tempo of pressure increase has not been quantified. In this report, we show that the rate of pressurization of embolized vessels is controlled by both fast and slow kinetics, where both tempos are controlled by diffusion but over different spatial scales. The fast tempo involves a localized diffusion from endogenous sources: over a distance of about 0.05 mm from water-filled wood to the nearest embolized vessels; this process, in theory, should take <2 min. The slow tempo involves diffusion of air from exogenous sources (outside the stem). The latter diffusion process is slower because of the increased distance of diffusion of up to 4 mm. Radial diffusion models and experimental measurements both confirm that the average time constant is >17 h, with complete equilibrium requiring 1 to 2 d. The implications of these timescales for the standard methods of measuring percentage loss of hydraulic conductivity are discussed in theory and deserve more research in future. PMID:26468516

  16. Non-Invasive Thrombolysis Using Pulsed Ultrasound Cavitation Therapy – Histotripsy

    PubMed Central

    Maxwell, Adam D.; Cain, Charles A.; Duryea, Alexander P.; Yuan, Lingqian; Gurm, Hitinder S.; Xu, Zhen

    2009-01-01

    Clinically available thrombolysis techniques are limited by either slow reperfusion (drugs) or invasiveness (catheters), and carry significant risks of bleeding. In this study, the feasibility of using histotripsy as an efficient and non-invasive thrombolysis technique was investigated. Histotripsy fractionates soft tissue through controlled cavitation using focused, short, high-intensity ultrasound pulses. In-vitro blood clots formed from fresh canine blood were treated by histotripsy. The treatment was applied using a focused 1-MHz transducer, with 5-cycle pulses at a pulse repetition rate of 1 kHz. Acoustic pressures varying from 2 – 12 MPa peak negative pressure were tested. Our results show that histotripsy can perform effective thrombolysis with ultrasound energy alone. Histotripsy thrombolysis only occurred at peak negative pressure ≥6 MPa when initiation of a cavitating bubble cloud was detected using acoustic backscatter monitoring. Blood clots weighing 330 mg were completely broken down by histotripsy in 1.5 – 5 minutes. The clot was fractionated to debris with >96% weight smaller than 5 μm diameter. Histotripsy thrombolysis treatment remained effective under a fast, pulsating flow (a circulatory model) as well as in static saline. Additionally, we observed that fluid flow generated by a cavitation cloud can attract, trap, and further break down clot fragments. This phenomenon may provide a non-invasive method to filter and eliminate hazardous emboli during thrombolysis. PMID:19854563

  17. Deformation of biological cells in the acoustic field of an oscillating bubble

    NASA Astrophysics Data System (ADS)

    Zinin, Pavel V.; Allen, John S., III

    2009-02-01

    In this work we develop a theoretical framework of the interaction of microbubbles with bacteria in the ultrasound field using a shell model of the bacteria, following an approach developed previously [P. V. Zinin , Phys. Rev. E 72, 61907 (2005)]. Within the shell model, the motion of the cell in an ultrasonic field is determined by the motion of three components: the internal viscous fluid, a thin elastic shell, and the surrounding viscous fluid. Several conclusions can be drawn from the modeling of sound interaction with a biological cell: (a) the characteristics of a cell’s oscillations in an ultrasonic field are determined both by the elastic properties of the shell the viscosities of all components of the system, (b) for dipole quadrupole oscillations the cell’s shell deforms due to a change in the shell area this oscillation depends on the surface area modulus KA , (c) the relative change in the area has a maximum at frequency fK˜(1)/(2π)KA/(ρa3) , where a is the cell’s radius and ρ is its density. It was predicted that deformation of the cell wall at the frequency fK is high enough to rupture small bacteria such as E . coli in which the quality factor of natural vibrations is less than 1 (Q<1) . For bacteria with high value quality factors (Q>1) , the area deformation has a strong peak near a resonance frequency fK ; however, the value of the deformation near the resonance frequency is not high enough to produce sufficient mechanical effect. The theoretical framework developed in this work can be extended for describing the deformation of a biological cell under any arbitrary, external periodic force including radiation forces unduced by acoustical (acoustical levitation) or optical waves (optical tweezers).

  18. Deformation of biological cells in the acoustic field of an oscillating bubble.

    PubMed

    Zinin, Pavel V; Allen, John S

    2009-02-01

    In this work we develop a theoretical framework of the interaction of microbubbles with bacteria in the ultrasound field using a shell model of the bacteria, following an approach developed previously [P. V. Zinin, Phys. Rev. E 72, 61907 (2005)]. Within the shell model, the motion of the cell in an ultrasonic field is determined by the motion of three components: the internal viscous fluid, a thin elastic shell, and the surrounding viscous fluid. Several conclusions can be drawn from the modeling of sound interaction with a biological cell: (a) the characteristics of a cell's oscillations in an ultrasonic field are determined both by the elastic properties of the shell the viscosities of all components of the system, (b) for dipole quadrupole oscillations the cell's shell deforms due to a change in the shell area this oscillation depends on the surface area modulus K{A} , (c) the relative change in the area has a maximum at frequency f{K} approximately 1/2pi square root[K{A}(rhoa;{3})] , where a is the cell's radius and rho is its density. It was predicted that deformation of the cell wall at the frequency f{K} is high enough to rupture small bacteria such as E . coli in which the quality factor of natural vibrations is less than 1 (Q<1). For bacteria with high value quality factors (Q>1) , the area deformation has a strong peak near a resonance frequency f{K} however, the value of the deformation near the resonance frequency is not high enough to produce sufficient mechanical effect. The theoretical framework developed in this work can be extended for describing the deformation of a biological cell under any arbitrary, external periodic force including radiation forces unduced by acoustical (acoustical levitation) or optical waves (optical tweezers). PMID:19391781

  19. Deformation of biological cells in the acoustic field of an oscillating bubble

    PubMed Central

    Zinin, Pavel V.; Allen, John S.

    2009-01-01

    In this work we develop a theoretical framework of the interaction of microbubbles with bacteria in the ultrasound field using a shell model of the bacteria, following an approach developed previously [P. V. Zinin et al., Phys. Rev. E 72, 61907 (2005)]. Within the shell model, the motion of the cell in an ultrasonic field is determined by the motion of three components: the internal viscous fluid, a thin elastic shell, and the surrounding viscous fluid. Several conclusions can be drawn from the modeling of sound interaction with a biological cell: (a) the characteristics of a cell’s oscillations in an ultrasonic field are determined both by the elastic properties of the shell the viscosities of all components of the system, (b) for dipole quadrupole oscillations the cell’s shell deforms due to a change in the shell area this oscillation depends on the surface area modulus KA, (c) the relative change in the area has a maximum at frequency fK∼12πKA/(ρa3), where a is the cell’s radius and ρ is its density. It was predicted that deformation of the cell wall at the frequency fK is high enough to rupture small bacteria such as E. coli in which the quality factor of natural vibrations is less than 1 (Q < 1). For bacteria with high value quality factors (Q > 1), the area deformation has a strong peak near a resonance frequency fK; however, the value of the deformation near the resonance frequency is not high enough to produce sufficient mechanical effect. The theoretical framework developed in this work can be extended for describing the deformation of a biological cell under any arbitrary, external periodic force including radiation forces unduced by acoustical (acoustical levitation) or optical waves (optical tweezers). PMID:19391781

  20. Transient cavitation produced by extracorporeal shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Cioanta, Iulian

    1998-12-01

    Two decades ago, a new medical procedure was introduced, allowing the fragmentation of kidney stones from outside the human body (noninvasively) using a shock wave device termed lithotripter ('stone crusher'). Considered as one of the most important medical inventions of this century, lithotripsy is currently used in more than 80% of urolithiasis cases. Experimental studies have shown that transient or inertial cavitation is generated by this procedure near the stones and in renal tissue. To find a correlation between the number of shocks delivered and the treatment efficiency, the acoustic emission (AE) generated by the oscillation of cavitation bubbles, and its relation with stone fragmentation and tissue damage during shock wave lithotripsy were studied. In vitro experiments were carried out to identify the correlation between the AE signals and the expansion and collapse of cavitation bubbles, which were captured by high-speed photography (20,000 frames per second). This correlation has been verified on four different electrohydraulic lithotripters, under multiple experimental conditions. The effects of tissue attenuation on AE and stone fragmentation were also studied. The in vitro results have further allowed the interpretation of AE signals from in vivo experiments with pigs. Although similar in general trend, in vivo AE signals are found to be shorter in expansion and longer in the total ringing times (including the rebound phenomenon) than for in vitro AE signals, indicating a tissue constraining effect on bubble oscillation. Based on this observation a new mechanism for renal vascular and tubular injury is proposed. In addition, changes in AE signals have been observed as the total number of shocks increases, and this dose dependence feature has allowed the determination of a threshold value for extended tissue injury at 20 kV. This result has been confirmed by histological analysis and by results of a theoretical model study of bubble oscillation in a

  1. Investigation of noninertial cavitation produced by an ultrasonic horn.

    PubMed

    Birkin, Peter R; Offin, Douglas G; Vian, Christopher J B; Leighton, Timothy G; Maksimov, Alexey O

    2011-11-01

    This paper reports on noninertial cavitation that occurs beyond the zone close to the horn tip to which the inertial cavitation is confined. The noninertial cavitation is characterized by collating the data from a range of measurements of bubbles trapped on a solid surface in this noninertial zone. Specifically, the electrochemical measurement of mass transfer to an electrode is compared with high-speed video of the bubble oscillation. This gas bubble is shown to be a "noninertial" event by electrochemical surface erosion measurements and "ring-down" experiments showing the activity and motion of the bubble as the sound excitation was terminated. These measurements enable characterization of the complex environment produced below an operating ultrasonic horn outside of the region where inertial collapse can be detected. The extent to which solid boundaries in the liquid cause the frequencies and shapes of oscillatory modes on the bubble wall to differ from their free field values is discussed. PMID:22088002

  2. A numerical study on the effects of cavitation on orifice flow

    NASA Astrophysics Data System (ADS)

    Dabiri, S.; Sirignano, W. A.; Joseph, D. D.

    2010-04-01

    Previous experimental studies have shown better atomization of sprays generated by high-pressure liquid injectors when cavitation occurs inside the nozzle. It has been proposed that the collapse of traveling cavitation bubbles increases the disturbances inside the liquid flow. These disturbances will later trigger the instabilities in the emerged jet and cause a shorter breakup distance. In this paper, effects of cavitation on increasing the disturbances in the flow through the orifice of an atomizer are studied. In previous cavitation models, spherical cavitation bubbles are considered. Here, the cavitation bubbles are allowed to deform as they travel through the orifice. Dynamics of the cavitation bubble, traveling in the separated shear layer in the orifice, is analyzed through a one-way coupling between the orifice flow and bubble dynamics. Effects of shear strain, normal strain, and pressure variation are examined. Three mechanisms are suggested that could be responsible for the increase in disturbances in the flow due to cavitation. These mechanisms are monopole, quadrupole, and vorticities generated during growth and collapse of cavitation bubbles. The effects of these mechanisms are estimated by postprocessing of the solutions to the Navier-Stokes equations to identify monopole and quadrupole behaviors.

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

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Koganezawa, Masato

    2005-06-01

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

  4. Photoacoustic cavitation for theranostics: mechanism, current progress and applications

    NASA Astrophysics Data System (ADS)

    Feng, Y.; Qin, D.; Wan, M.

    2015-12-01

    As an emerging cavitation technology, photoacoustic cavitation (PAC) means the formation of bubbles in liquids using focused laser and pre-established ultrasound synchronously. Its significant advantages include the decreased threshold of each modality and the precise location of cavitation determined by the focused laser. In this paper, a brief review of PAC is presented, including the physical mechanism description, the classic experimental technology, the representative results in variety of media, and its applications in biomedical imaging and therapy. Moreover, some preliminary results of PAC in perfluoropentane (PFP) liquid and PFP droplets investigated by passive cavitation detection (PCD) in our group are also presented.

  5. Analogy between fluid cavitation and fracture mechanics

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.; Mullen, R. L.; Braun, M. J.

    1983-01-01

    When the stresses imposed on a fluid are sufficiently large, rupture or cavitation can occur. Such conditions can exist in many two-phase flow applications, such as the choked flows, which can occur in seals and bearings. Nonspherical bubbles with large aspect ratios have been observed in fluids under rapid acceleration and high shear fields. These bubbles are geometrically similar to fracture surface patterns (Griffith crack model) existing in solids. Analogies between crack growth in solid and fluid cavitation are proposed and supported by analysis and observation (photographs). Healing phenomena (void condensation), well accepted in fluid mechanics, have been observed in some polymers and hypothesized in solid mechanics. By drawing on the strengths of the theories of solid mechanics and cavitation, a more complete unified theory can be developed.

  6. Optical Measurements of Cavitation in Tribological Contacts

    NASA Astrophysics Data System (ADS)

    Tang, Tian; Morris, Nick; Coupland, Jeremy

    2015-12-01

    The paper describes the use of a white light interformeter to measure the cavitation bubble and oil film thickness in a tribological contact and compares the results to theory. It is found that oil film thickness is best predicted by the theory proposed by Coyne and Elrod.

  7. Observation of cavitation during shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Bailey, Michael R.; Crum, Lawrence A.; Pishchalnikov, Yuri A.; McAteer, James A.; Pishchalnikova, Irina V.; Evan, Andrew P.; Sapozhnikov, Oleg A.; Cleveland, Robin O.

    2005-04-01

    A system was built to detect cavitation in pig kidney during shock wave lithotripsy (SWL) with a Dornier HM3 lithotripter. Active detection, using echo on B-mode ultrasound, and passive cavitation detection (PCD), using coincident signals on confocal, orthogonal receivers, were equally sensitive and were used to interrogate the renal collecting system (urine) and the kidney parenchyma (tissue). Cavitation was detected in urine immediately upon SW administration in urine or urine plus X-ray contrast agent, but in tissue, cavitation required hundreds of SWs to initiate. Localization of cavitation was confirmed by fluoroscopy, sonography, and by thermally marking the kidney using the PCD receivers as high intensity focused ultrasound sources. Cavitation collapse times in tissue and native urine were about the same but less than in urine after injection of X-ray contrast agent. Cavitation, especially in the urine space, was observed to evolve from a sparse field to a dense field with strong acoustic collapse emissions to a very dense field that no longer produced detectable collapse. The finding that cavitation occurs in kidney tissue is a critical step toward determining the mechanisms of tissue injury in SWL. [Work sup ported by NIH (DK43881, DK55674, FIRCA), ONRIFO, CRDF and NSBRI SMS00203.

  8. Probing the Bioeffects of Cavitation at the Single-Cell Level

    NASA Astrophysics Data System (ADS)

    Yuan, Fang

    The primary goal of this dissertation research is to develop an experimental system and associated techniques that can be used to investigate the bioeffects produced by cavitation bubbles at the single cell level. Such information has been lacking due to the randomness and complexity in cavitation inception and subsequent bubble-bubble interaction generated by an acoustic field typically used in therapeutic ultrasound applications. Connection between cavitation activities and bioeffects produced in cells nearby presents another challenge that has not been resolved satisfactorily. In this work, we developed a laser-based system for generating tandem bubbles with a maximum diameter about 50 microm (i.e., on the scale of a single cell) in a microfluidic channel of 25 microm in height and 800 microm in width. We further developed techniques for micropatterning of individual gold dots (15 nm thick and 6 microm in diameter) used for bubble generation, which are precisely aligned at various stand-off distances (SD) from individual islands (32 x 32 microm2) coated with fibronectin used for cell adhesion. The dynamics of tandem bubble interaction with resultant jet formation, microstreaming and vortex flow in the microfluidic channel were captured by high-speed imaging and particle image velocimetry (PIV). The deformation of the target cell was recorded by high-speed imaging as well (using a second camera) immediately after the tandem bubble interaction and assessment of membrane strain was aided with 2 microm sized polystyrene beads attached to the cell membrane. Membrane poration was characterized by uptake of fluorescent propodium iodide (PI) into the target cell, from which the normalized maximum pore size was estimated. Using this experimental system, we have observed the complete process of bubble-bubble interaction with resultant jetting flow, cell deformation, and localized pinpoint membrane rupture with progressive diffusion of macromolecules into the target cell

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

    PubMed

    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. PMID:26585023

  10. Periodic cavitation shedding in a cylindrical orifice

    NASA Astrophysics Data System (ADS)

    Stanley, C.; Barber, T.; Milton, B.; Rosengarten, G.

    2011-11-01

    Cavitation structures in a large-scale ( D = 8.25 mm), plain orifice style nozzle within a unique experimental rig are investigated using high-speed visualisation and digital image processing techniques. Refractive index matching with an acrylic nozzle is achieved using aqueous sodium iodide for the test fluid. Cavitation collapse length, unsteady shedding frequency and spray angles are measured for cavitation conditions from incipient to supercavitation for a range of Reynolds numbers, for a fixed L/ D ratio of 4.85. Periodic cavitation shedding was shown to occur with frequencies between 500 and 2,000 Hz for conditions in which cavitation occupied less than 30% of the nozzle length. A discontinuity in collapse length was shown to occur once the cavitation exceeded this length, coinciding with a loss of periodic shedding. A mechanism for this behaviour is discussed. Peak spray angles of approximately θ ≈ 14° were recorded for supercavitation conditions indicating the positive influence of cavitation bubble collapse on the jet atomisation process.

  11. Study on cavitation behavior during high-intensity focused ultrasound exposure by using optical and ultrasonic imaging

    NASA Astrophysics Data System (ADS)

    Taguchi, Kei; Takagi, Ryo; Yasuda, Jun; Yoshizawa, Shin; Umemura, Shin-ichiro

    2016-07-01

    Cavitation bubbles are known to enhance the heating effect of high-intensity focused ultrasound (HIFU). In our previous study, the use of a “triggered HIFU” sequence consisting of a high-intensity pulse and a relatively low-intensity burst was proposed as an effective method to utilize the effect of cavitation bubbles. However, the duration of each component in the sequence has not been optimized. In this study, optical imaging was carried out to observe the behavior of cavitation bubbles in a gel phantom during the triggered HIFU exposure. Ultrasound imaging using the pulse inversion method was also conducted to detect the behavior of the bubbles. The results suggest that the oscillation of cavitation bubbles become inactive as the duration of HIFU burst exposure increases to the order of 10 ms. It was also suggested that ultrasonic imaging has potential use for detecting a change in the oscillation of cavitation bubbles for optimizing a triggered HIFU sequence.

  12. Cavitation measurements on a pump-turbine model

    NASA Astrophysics Data System (ADS)

    Schmidt, H.; Kirschner, O.; Riedelbauch, S.

    2015-12-01

    When a hydraulic turbine is operated at off-design conditions, cavitation on the runner and other machine parts can occur. Vibration, noise and erosion caused by cavitation can damage the turbine and lead to a limitation of the operational range. To avoid damage of the turbine, it is fundamental to get knowledge of the presence of cavitation. In this paper, the acoustic emissions at a pump-turbine model at different operating conditions with and without the presence of cavitation were recorded and analysed. High speed video recordings were carried out simultaneously to validate the acoustic measurements. The main goal of the investigation was to compare the acoustic emissions with the visual observations at operating conditions with cavitation on the leading edge of the turbine runner. The analysis of the recorded signals and the visual observations are in good accordance for the investigated operating points.

  13. Removal of Residual Nuclei Following a Cavitation Event using Low-Amplitude Ultrasound

    PubMed Central

    Duryea, Alexander P.; Cain, Charles A.; Tamaddoni, Hedieh A.; Roberts, William W.; Hall, Timothy L.

    2014-01-01

    Microscopic residual bubble nuclei can persist on the order of 1 second following a cavitation event. These bubbles can limit the efficacy of ultrasound therapies such as shock wave lithotripsy and histotripsy, as they attenuate pulses that arrive subsequent to their formation and seed repetitive cavitation activity at a discrete set of sites (cavitation memory). Here, we explore a strategy for the removal of these residual bubbles following a cavitation event, using low amplitude ultrasound pulses to stimulate bubble coalescence. All experiments were conducted in degassed water and monitored using high speed photography. In each case, a 2 MHz histotripsy transducer was used to initiate cavitation activity (a cavitational bubble cloud), the collapse of which generated a population of residual bubble nuclei. This residual nuclei population was then sonicated using a 1 ms pulse from a separate 500 kHz transducer, which we term the ‘bubble removal pulse.’ Bubble removal pulse amplitudes ranging from 0 to 1.7 MPa were tested, and the backlit area of shadow from bubbles remaining in the field following bubble removal was calculated to quantify efficacy. It was found that an ideal amplitude range exists (roughly 180 – 570 kPa) in which bubble removal pulses stimulate the aggregation and subsequent coalescence of residual bubble nuclei, effectively removing them from the field. Further optimization of bubble removal pulse sequences stands to provide an adjunct to cavitation-based ultrasound therapies such as shock wave lithotripsy and histotripsy, mitigating the effects of residual bubble nuclei that currently limit their efficacy. PMID:25265172

  14. PIV Analysis of Cavitation Flow Characteristics of He II

    SciTech Connect

    Harada, K.; Murakami, M.

    2006-04-27

    In the present experimental study cavitation phenomena in both He I and He II flows were investigated through the application of the PIV technique and visual observation under the saturated vapor pressure condition. The cavitation flow was generated in the downstream regions of a Venturi channel and a converging jet nozzle driven by a contracting metal bellows. It is seen that cavitation inception is a kind of stochastic process and has definite temperature dependence. The spatial distribution of the cavitation bubble velocity is measured by using the PIV technique. Some differences in the cavitating flow pattern and the void fraction are found between He II and He I cavitating flows. The PIV result indicates that the void fraction for He II flow is larger than that for He I flow.

  15. Cavitation technology - a greener processing technique for the generation of pharmaceutical nanoemulsions.

    PubMed

    Sivakumar, Manickam; Tang, Siah Ying; Tan, Khang Wei

    2014-11-01

    Novel nanoemulsion-based drug delivery systems (DDS) have been proposed as alternative and effective approach for the delivery of various types of poorly water-soluble drugs in the last decade. This nanoformulation strategy significantly improves the cell uptake and bioavailability of numerous hydrophobic drugs by increasing their solubility and dissolution rate, maintaining drug concentration within the therapeutic range by controlling the drug release rate, and reducing systemic side effects by targeting to specific disease site, thus offering a better patient compliance. To date, cavitation technology has emerged to be an energy-efficient and promising technique to generate such nanoscale emulsions encapsulating a variety of highly potent pharmaceutical agents that are water-insoluble. The micro-turbulent implosions of cavitation bubbles tear-off primary giant oily emulsion droplets to nano-scale, spontaneously leading to the formation of highly uniform drug contained nanodroplets. A substantial body of recent literatures in the field of nanoemulsions suggests that cavitation is a facile, cost-reducing yet safer generation tool, remarkably highlighting its industrial commercial viability in the development of designing novel nanocarriers or enhancing the properties of existing pharmaceutical products. In this review, the fundamentals of nanoemulsion and the principles involved in their formation are presented. The underlying mechanisms in the generation of pharmaceutical nanoemulsion under acoustic field as well as the advantages of using cavitation compared to the conventional techniques are also highlighted. This review focuses on recent nanoemulsion-based DDS development and how cavitation through ultrasound and hydrodynamic means is useful to generate the pharmaceutical grade nanoemulsions including the complex double or submicron multiple emulsions. PMID:24755340

  16. Luminescence induced by spherically focused acoustic pulses in liquids

    NASA Astrophysics Data System (ADS)

    Sankin, G. N.

    2005-06-01

    The determination of the phase of the bubble oscillation at the instant of light emission, which is a key issue for understanding the origin of cavitation luminescence of liquids, is discussed. The observation of luminescence in the course of the nucleation and growth of a bubble up to its collapse is performed in a bipolar wave consisting of a compression phase followed by a rarefaction phase in the regime of a two-fraction bubble cluster formation. The space-time distributions of the luminescence intensity and pressure and the dynamics of the cluster in water and a glycerin solution are investigated at the early stage of cavitation. A correlation between the maximal density of light flashes and the positive pressure pulses in the field of superposition of the initial and secondary cavitation compression waves is revealed. It is shown that the spherical focusing of acoustic pulses both away from the boundaries of the liquid and near its free surface makes it possible to compare the luminescence intensities for different rates of the pressure decrease.

  17. A cavitation model for computations of unsteady cavitating flows

    NASA Astrophysics Data System (ADS)

    Zhao, Yu; Wang, Guoyu; Huang, Biao

    2016-04-01

    A local vortical cavitation (LVC) model for the computation of unsteady cavitation is proposed. The model is derived from the Rayleigh-Plesset equations, and takes into account the relations between the cavitation bubble radius and local vortical effects. Calculations of unsteady cloud cavitating flows around a Clark-Y hydrofoil are performed to assess the predictive capability of the LVC model using well-documented experimental data. Compared with the conventional Zwart's model, better agreement is observed between the predictions of the LVC model and experimental data, including measurements of time-averaged flow structures, instantaneous cavity shapes and the frequency of the cloud cavity shedding process. Based on the predictions of the LVC model, it is demonstrated that the evaporation process largely concentrates in the core region of the leading edge vorticity in accordance with the growth in the attached cavity, and the condensation process concentrates in the core region of the trailing edge vorticity, which corresponds to the spread of the rear component of the attached cavity. When the attached cavity breaks up and moves downstream, the condensation area fully transports to the wake region, which is in accordance with the dissipation of the detached cavity. Furthermore, using vorticity transport equations, we also find that the periodic formation, breakup, and shedding of the sheet/cloud cavities, along with the associated baroclinic torque, are important mechanisms for vorticity production and modification. When the attached cavity grows, the liquid-vapour interface that moves towards the trailing edge enhances the vorticity in the attached cavity closure region. As the re-entrant jet moves upstream, the wavy/bubbly cavity interface enhances the vorticity near the trailing edge. At the end of the cycle, the break-up of the stable attached cavity is the main reason for the vorticity enhancement near the suction surface.

  18. Numerical simulation on the cavitation of waterjet propulsion pump

    NASA Astrophysics Data System (ADS)

    Xia, C. Z.; Cheng, L.; Shang, Y. N.; Zhou, J. R.; Yang, F.; Jin, Y.

    2016-05-01

    Waterjet propulsion system is widely used in high speed vessels with advantages of simple transmission mechanism, low noise underwater and good manoeuvrability. Compared with the propeller, waterjet propulsion can be used flow stamping to increasing cavitation resistance at high speed. But under certain conditions, such as low ship speed or high ship speed, cavitation problem still exists. If water-jet propulsion pump is run in cavitation condition for a long time, then the cavitation will cause a great deal of noise CFD is applied to analysis and predict the process of production and development of cavitation in waterjet propulsion pump. Based on the cavitation model of Zwart-Gerber-Belamri and a mixture of homogeneous flow model, commercial CFD software CFX was taken for characteristics of cavitation under the three operating conditions. Commercial software ANSYS 14.0 is used to build entity model, mesh and numerical simulation. The grid independence analysis determine the grid number of mixed flow pump model is about 1.6 million and the grid number of water-jet pump system unit is about 2.7 million. The cavitation characteristics of waterjet pump under three operating conditions are studied. The results show that the cavitation development trend is similar design and small rate of flow condition .Under the design conditions Cavitation bubbles are mainly gathered in suction surface of blade near the inlet side of the hub under the primary stage, and gradually extended to the water side in the direction of the rim with the loss of the inlet total pressure. Cavitation appears in hub before the blade rim, but the maximum value of gas content in blade rim is bigger than that in hub. Under large flow conditions, bubble along the direction of wheel hub extends to the rim gradually. Cavitation is found in the pressure surface of blade near the hub region under the critical point of cavitation nearby. When NPSHa is lower than critical point, the area covering by bubbles

  19. Moving single bubble sonoluminescence in phosphoric acid and sulphuric acid solutions.

    PubMed

    Troia, A; Ripa, D Madonna; Spagnolo, R

    2006-04-01

    The phenomenon of sonoluminescence still presents some unsolved aspects. Recently [Y.T. Didenko, K. Suslick, Molecular Emission during Single Bubble Sonoluminescence, Nature 407 (2000) 877-879.], it was found that a single cavitating air bubble in polar aprotic liquids (including formamide and adiponitrile) can produce very strong sonoluminescence while undergoing macroscopic translation movements in the resonator, a condition known as moving single bubble sonoluminescing (MSBSL). Here we describe some experiments conducted in aqueous solutions of phosphoric and sulphuric acid. In these liquid media, it is possible to reproduce MSBSL and luminescence is emitted even if a trapped bubble is subjected to a strong shape instability, named in the literature "jittering phase". When a moving and luminescing bubble was present and the acoustic pressure gradually increased, we observed the generation of a discrete lattice of trapped bubbles. The bubbles in the lattice emit very intense light flashes and can change their position while maintaining the overall spatial distribution in time. Some preliminary results, obtained from Mie-scattering and measurements of relative light intensity, are reported. PMID:16309944

  20. Investigations of the Cavitation and Damage Thresholds of Histotripsy and Applications in Targeted Tissue Ablation

    NASA Astrophysics Data System (ADS)

    Vlaisavljevich, Eli

    Histotripsy is a noninvasive ultrasound therapy that controls acoustic cavitation to mechanically fractionate soft tissue. This dissertation investigates the physical thresholds to initiate cavitation and produce tissue damage in histotripsy and factors affecting these thresholds in order to develop novel strategies for targeted tissue ablation. In the first part of this dissertation, the effects of tissue properties on histotripsy cavitation thresholds and damage thresholds were investigated. Results demonstrated that the histotripsy shock scattering threshold using multi-cycle pulses increases in stiffer tissues, while the histotripsy intrinsic threshold using single-cycle pulses is independent of tissue stiffness. Further, the intrinsic threshold slightly decreases with lower frequencies and significantly decreases with increasing temperature. The effects of tissue properties on the susceptibility to histotripsy-induced tissue damage were also investigated, demonstrating that stiffer tissues are more resistant to histotripsy. Two strategies were investigated for increasing the effectiveness of histotripsy for the treatment of stiffer tissues, with results showing that thermal preconditioning may be used to alter tissue susceptibility to histotripsy and that lower frequency treatments may increase the efficiency of histotripsy tissue ablation due to enhanced bubble expansion. In the second part of this dissertation, the feasibility of using histotripsy for targeted liver ablation was investigated in an intact in vivo porcine model, with results demonstrating that histotripsy was capable of non-invasively creating precise lesions throughout the entire liver. Additionally, a tissue selective ablation approach was developed, where histotripsy completely fractionated the liver tissue surrounding the major hepatic vessels and gallbladder while being self-limited at the boundaries of these critical structures. Finally, the long-term effects of histotripsy liver

  1. Evaporation-induced cavitation in nanofluidic channels

    PubMed Central

    Duan, Chuanhua; Karnik, Rohit; Lu, Ming-Chang; Majumdar, Arun

    2012-01-01

    Cavitation, known as the formation of vapor bubbles when liquids are under tension, is of great interest both in condensed matter science as well as in diverse applications such as botany, hydraulic engineering, and medicine. Although widely studied in bulk and microscale-confined liquids, cavitation in the nanoscale is generally believed to be energetically unfavorable and has never been experimentally demonstrated. Here we report evaporation-induced cavitation in water-filled hydrophilic nanochannels under enormous negative pressures up to -7 MPa. As opposed to receding menisci observed in microchannel evaporation, the menisci in nanochannels are pinned at the entrance while vapor bubbles form and expand inside. Evaporation in the channels is found to be aided by advective liquid transport, which leads to an evaporation rate that is an order of magnitude higher than that governed by Fickian vapor diffusion in macro- and microscale evaporation. The vapor bubbles also exhibit unusual motion as well as translational stability and symmetry, which occur because of a balance between two competing mass fluxes driven by thermocapillarity and evaporation. Our studies expand our understanding of cavitation and provide new insights for phase-change phenomena at the nanoscale. PMID:22343530

  2. Towards numerical prediction of cavitation erosion.

    PubMed

    Fivel, Marc; Franc, Jean-Pierre; Chandra Roy, Samir

    2015-10-01

    This paper is intended to provide a potential basis for a numerical prediction of cavitation erosion damage. The proposed method can be divided into two steps. The first step consists in determining the loading conditions due to cavitation bubble collapses. It is shown that individual pits observed on highly polished metallic samples exposed to cavitation for a relatively small time can be considered as the signature of bubble collapse. By combining pitting tests with an inverse finite-element modelling (FEM) of the material response to a representative impact load, loading conditions can be derived for each individual bubble collapse in terms of stress amplitude (in gigapascals) and radial extent (in micrometres). This step requires characterizing as accurately as possible the properties of the material exposed to cavitation. This characterization should include the effect of strain rate, which is known to be high in cavitation erosion (typically of the order of several thousands s(-1)). Nanoindentation techniques as well as compressive tests at high strain rate using, for example, a split Hopkinson pressure bar test system may be used. The second step consists in developing an FEM approach to simulate the material response to the repetitive impact loads determined in step 1. This includes a detailed analysis of the hardening process (isotropic versus kinematic) in order to properly account for fatigue as well as the development of a suitable model of material damage and failure to account for mass loss. Although the whole method is not yet fully operational, promising results are presented that show that such a numerical method might be, in the long term, an alternative to correlative techniques used so far for cavitation erosion prediction. PMID:26442139

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

    SciTech Connect

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

    2005-10-01

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

  4. Acoustic Droplet Vaporization in Biology and Medicine

    PubMed Central

    Pitt, William G.

    2013-01-01

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

  5. Influence of the empirical coefficients of cavitation model on predicting cavitating flow in the centrifugal pump

    NASA Astrophysics Data System (ADS)

    Liu, Hou-lin; Wang, Jian; Wang, Yong; Zhang, Hua; Huang, Haoqin

    2014-03-01

    The phenomenon of cavitation is an unsteady flow, which is nearly inevitable in pump. It would degrade the pump performance, produce vibration and noise and even damage the pump. Hence, to improve accuracy of the nu¬merical prediction of the pump cavitation performance is much desirable. In the present work, a homogenous model, the Zwart-Gerber-Belamri cavitation model, is considered to investigate the influence of the empirical coefficients on predicting the pump cavitation performance, concerning a centrifugal pump. Three coefficients are analyzed, namely the nucleation site radius, evaporation and condensation coefficients. Also, the experiments are carried out to validate the numerical simulations. The results indicate that, to get a precise prediction, the approaches of declining the initial bubble radius, the condensation coefficient or increasing the evaporation coefficient are all feasible, especially for de¬clining the condensation coefficient, which is the most effective way.

  6. High-speed motion picture camera experiments of cavitation in dynamically loaded journal bearings

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    A high-speed camera was used to investigate cavitation in dynamically loaded journal bearings. The length-diameter ratio of the bearing, the speeds of the shaft and bearing, the surface material of the shaft, and the static and dynamic eccentricity of the bearing were varied. The results reveal not only the appearance of gas cavitation, but also the development of previously unsuspected vapor cavitation. It was found that gas cavitation increases with time until, after many hundreds of pressure cycles, there is a constant amount of gas kept in the cavitation zone of the bearing. The gas can have pressures of many times the atmospheric pressure. Vapor cavitation bubbles, on the other hand, collapse at pressures lower than the atmospheric pressure and cannot be transported through a high-pressure zone, nor does the amount of vapor cavitation in a bearing increase with time. Analysis is given to support the experimental findings for both gas and vapor cavitation.

  7. Study on Prediction of Underwater Radiated Noise from Propeller Tip Vortex Cavitation

    NASA Astrophysics Data System (ADS)

    Yamada, Takuyoshi; Sato, Kei; Kawakita, Chiharu; Oshima, Akira

    2015-12-01

    The method to predict underwater radiated noise from tip vortex cavitation was studied. The growth of a single cavitation bubble in tip vortex was estimated by substituting the tip vortex to Rankine combined vortex. The ideal spectrum function for the sound pressure generated by a single cavitation bubble was used, also the empirical factor for the number of collapsed bubbles per unit time was introduced. The estimated noise data were compared with measured ship's ones and it was found out that this method can estimate noise data within 3dB difference.

  8. Numerical study on the effective heating due to inertial cavitation in microbubble-enhanced HIFU therapy

    NASA Astrophysics Data System (ADS)

    Okita, Kohei; Sugiyama, Kazuyasu; Takagi, Shu; Matsumoto, Yoichiro

    2015-10-01

    The enhancement of heating due to inertial cavitation was focused in high-intensity focused ultrasound (HIFU) therapy. The influences of the rectified diffusion on microbubble-enhanced HIFU were examined numerically. A bubble dynamics equation in consideration of the spherical shell bubble and the elasticity of surrounding tissue was employed. Mass and heat transfer between the surrounding medium and the bubble were considered. The basic equations were discretized by finite difference method. The mixture phase and bubbles are coupled by the Euler-Lagrange method to take into account the interaction between ultrasound and bubbles. The mass transfer rate of gas from the surrounding medium to the bubble was examined as function of the initial bubble radius and the driving pressure amplitude. As the results, the pressure required to bubble growth was decreases with increasing the initial bubble radius. Thus, the injection of microbubble reduces the cavitation threshold pressure. On the other hand, the influence of the rectified diffusion on the triggered HIFU therapy which generates cavitation bubbles by high-intensity burst and induces the localized heating owing to cavitation bubble oscillation by low-intensity continuous waves. The calculation showed that the localized heating was enhanced by the increase of the equilibrium bubble size due to the rectified diffusion.

  9. Fundamental studies on cavitation melt processing

    NASA Astrophysics Data System (ADS)

    Tzanakis, I.; Hodnett, M.; Lebon, G. S. B.; Eskin, D. G.; Pericleous, K.

    2016-05-01

    The application of ultrasound to industrial casting processes has attracted research interest during the last 50 years. However, the transfer and scale-up of this advanced and promising technology to industry has been hindered by difficulties in treating large volumes of liquid metal due to the lack of understanding of certain fundamentals. In the current study experimental results on ultrasonic processing in deionised water and in liquid aluminium (Al) are reported. Cavitation activity was determined in both liquid environments and acoustic pressures were successfully measured using an advanced high-temperature cavitometer sensor. Results showed that highest cavitation intensity in the liquid bulk is achieved at lower amplitudes of the sonotrode tip than the maximum available, suggesting nonlinearity in energy transfer to the liquid, while the location of the sonotrode is seen to substantially affect cavitation activity within the liquid. Estimation of real-time acoustic pressures distributed inside a crucible with liquid Al was performed for the first time.

  10. Optimization of centrifugal pump cavitation performance based on CFD

    NASA Astrophysics Data System (ADS)

    Xie, S. F.; Wang, Y.; Liu, Z. C.; Zhu, Z. T.; Ning, C.; Zhao, L. F.

    2015-01-01

    In order to further improve the cavitation performance of a centrifugal pump, slots on impeller blade near inlet were studied and six groups of hydraulic model were designed. Base on cavitating flow feature inside a centrifugal pump, bubble growth and implosion are calculated from the Rayleigh-Plesset equation which describes the dynamic behavior of spherical bubble and RNG κ-epsilon model was employed to simulate and analyze the internal two-phase flow of the model pump under the same conditions. The simulation results show that slots on blade near inlet could improve the cavitation performance and cavitation performance improvement of the second group was more obvious. Under the same conditions, the pressure on the back of blade near inlet was higher than the pressure on the back of unmodified blade near inlet, and energy distribution in the flow channel between the two blades was more uniform with a small change of head.

  11. Relating xylem cavitation to transpiration in cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Acoustic emmisions (AEs) from xylem cavitation events are characteristic of transpiration processes. Even though a body of work employing AE exists with a large number of species, cotton and other agronomically important crops have either not been investigated, or limited information exists. A few s...

  12. High Speed Imaging of Cavitation around Dental Ultrasonic Scaler Tips

    PubMed Central

    Vyas, Nina; Pecheva, Emilia; Dehghani, Hamid; Sammons, Rachel L.; Wang, Qianxi X.; Leppinen, David M.; Walmsley, A. Damien

    2016-01-01

    Cavitation occurs around dental ultrasonic scalers, which are used clinically for removing dental biofilm and calculus. However it is not known if this contributes to the cleaning process. Characterisation of the cavitation around ultrasonic scalers will assist in assessing its contribution and in developing new clinical devices for removing biofilm with cavitation. The aim is to use high speed camera imaging to quantify cavitation patterns around an ultrasonic scaler. A Satelec ultrasonic scaler operating at 29 kHz with three different shaped tips has been studied at medium and high operating power using high speed imaging at 15,000, 90,000 and 250,000 frames per second. The tip displacement has been recorded using scanning laser vibrometry. Cavitation occurs at the free end of the tip and increases with power while the area and width of the cavitation cloud varies for different shaped tips. The cavitation starts at the antinodes, with little or no cavitation at the node. High speed image sequences combined with scanning laser vibrometry show individual microbubbles imploding and bubble clouds lifting and moving away from the ultrasonic scaler tip, with larger tip displacement causing more cavitation. PMID:26934340

  13. High Speed Imaging of Cavitation around Dental Ultrasonic Scaler Tips.

    PubMed

    Vyas, Nina; Pecheva, Emilia; Dehghani, Hamid; Sammons, Rachel L; Wang, Qianxi X; Leppinen, David M; Walmsley, A Damien

    2016-01-01

    Cavitation occurs around dental ultrasonic scalers, which are used clinically for removing dental biofilm and calculus. However it is not known if this contributes to the cleaning process. Characterisation of the cavitation around ultrasonic scalers will assist in assessing its contribution and in developing new clinical devices for removing biofilm with cavitation. The aim is to use high speed camera imaging to quantify cavitation patterns around an ultrasonic scaler. A Satelec ultrasonic scaler operating at 29 kHz with three different shaped tips has been studied at medium and high operating power using high speed imaging at 15,000, 90,000 and 250,000 frames per second. The tip displacement has been recorded using scanning laser vibrometry. Cavitation occurs at the free end of the tip and increases with power while the area and width of the cavitation cloud varies for different shaped tips. The cavitation starts at the antinodes, with little or no cavitation at the node. High speed image sequences combined with scanning laser vibrometry show individual microbubbles imploding and bubble clouds lifting and moving away from the ultrasonic scaler tip, with larger tip displacement causing more cavitation. PMID:26934340

  14. Calcium Is a Major Determinant of Xylem Vulnerability to Cavitation

    PubMed Central

    Herbette, Stephane; Cochard, Herve

    2010-01-01

    Xylem vulnerability to cavitation is a key parameter in the drought tolerance of trees, but little is known about the control mechanisms involved. Cavitation is thought to occur when an air bubble penetrates through a pit wall, and would hence be influenced by the wall's porosity. We first tested the role of wall-bound calcium in vulnerability to cavitation in Fagus sylvatica. Stems perfused with solutions of oxalic acid, EGTA, or sodium phosphate (NaPO4) were found to be more vulnerable to cavitation. The NaPO4-induced increase in vulnerability to cavitation was linked to calcium removal from the wall. In contrast, xylem hydraulic conductance was unaffected by the chemical treatments, demonstrating that the mechanisms controlling vulnerability to cavitation and hydraulic resistance are uncoupled. The NaPO4 solution was then perfused into stems from 13 tree species possessing highly contrasted vulnerability to cavitation. Calcium was found to be a major determinant of between-species differences in vulnerability to cavitation. This was evidenced in angiosperms as well as conifer species, thus supporting the hypothesis of a common mechanism in drought-induced cavitation. PMID:20547703

  15. Detailed Jet Dynamics in a Collapsing Bubble

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  16. Spark bubble interaction with a suspended particle

    NASA Astrophysics Data System (ADS)

    Ohl, Siew-Wan; Wu, Di Wei; Klaseboer, Evert; Cheong Khoo, Boo

    2015-12-01

    Cavitation bubble collapse is influenced by nearby surfaces or objects. A bubble near a rigid surface will move towards the surface and collapse with a high speed jet. When a hard particle is suspended near a bubble generated by electric spark, the bubble expands and collapses moving the particle. We found that within a limit of stand-off distance, the particle is propelled away from the bubble as it collapses. At a slightly larger stand-off distance, the bubble collapse causes the particle to move towards the bubble initially before moving away. The bubble does not move the particle if it is placed far away. This conclusion is important for applications such as drug delivery in which the particle is to be propelled away from the collapsing bubble.

  17. Hydrodynamic Nuclei Concentration Technique in Cavitation Research and Comparison to Phase-Doppler Measurements

    NASA Astrophysics Data System (ADS)

    Ebert, Eric; Kröger, Willfried; Damaschke, Nils

    2015-12-01

    Small particles, especially bubbles in the micro-meter range, influence the cavitation of the propellers. The prediction of cavitation inception and water quality measurements are important in cavitation research. The Hydrodynamic Nuclei Concentration (HDNC) technique can be used for reliable bubble concentration measurements in fluid flows. The HDNC technique bases on the analysis of scattered light from the cavitation nuclei in the water. The HDNC technique can distinguish between bubbles and solid particles. The particle type classification is important, because the number concentration of solid particles is often much higher than the nuclei concentration in cavitation tunnels and in seawater. Verification experiments show, that the HDNC technique reaches similar capabilities in number concentration estimation as Phase Doppler (PD) technique in much shorter acquisition time.

  18. Prediction of cavitation erosion for marine applications

    NASA Astrophysics Data System (ADS)

    Maquil, T.; Yakubov, S.; Rung, T.

    2015-12-01

    The paper presents the development of a cavitation erosion prediction method. The approach is tailored to marine applications and embedded into a VoF-based procedure for the simulation of turbulent flows. Supplementary to the frequently employed Euler-Euler models, Euler-Lagrange approaches are employed to simulate cavitation. The study aims to convey the merits of an Euler-Lagrange approach for erosion simulations. Accordingly, the erosion model is able to separate different damage mechanisms, e.g. micro-jets, single and collective bubble collapse, and also quantifies their contribution to the total damage. Emphasis is devoted to the prediction of the cavitation extend, the influence of compressible effects and the performance of the material damage model in practical applications. Examples included refer to 2D validation test cases and reveal a fair predictive accuracy.

  19. Observation of a cavitation cloud in tissue using correlation between ultrafast ultrasound images.

    PubMed

    Prieur, Fabrice; Zorgani, Ali; Catheline, Stefan; Souchon, Rémi; Mestas, Jean-Louis; Lafond, Maxime; Lafon, Cyril

    2015-07-01

    The local application of ultrasound is known to improve drug intake by tumors. Cavitating bubbles are one of the contributing effects. A setup in which two ultrasound transducers are placed confocally is used to generate cavitation in ex vivo tissue. As the transducers emit a series of short excitation bursts, the evolution of the cavitation activity is monitored using an ultrafast ultrasound imaging system. The frame rate of the system is several thousands of images per second, which provides several tens of images between consecutive excitation bursts. Using the correlation between consecutive images for speckle tracking, a decorrelation of the imaging signal appears due to the creation, fast movement, and dissolution of the bubbles in the cavitation cloud. By analyzing this area of decorrelation, the cavitation cloud can be localized and the spatial extent of the cavitation activity characterized. PMID:26168172

  20. Influence of cathodic and anodic currents on cavitation erosion

    SciTech Connect

    Auret, J.G.; Damm, O.F.R.A.; Wright, G.J. . Div. of Materials Science and Technology); Robinson, F.P.A. . Dept. of Metallurgy and Materials Engineering)

    1993-11-01

    A vibratory-type cavitation test rig was constructed to study the effect of polarizing currents applied to a cavitating body. The generation of gas by electrolysis reduced mechanical damage suffered by a cavitating body because of bubble collapse cushioning. However, the net effect on overall damage depended on several factors, including the intensity of mechanical attack, corrosion rate, and surface geometrical effects. A cathodic current was shown to always decrease the total volume loss rate, but the volume loss rate sometimes was increased and sometimes was reduced in the anodic current range.

  1. Effect of direct bubble-bubble interactions on linear-wave propagation in bubbly liquids

    NASA Astrophysics Data System (ADS)

    Fuster, D.; Conoir, J. M.; Colonius, T.

    2014-12-01

    We study the influence of bubble-bubble interactions on the propagation of linear acoustic waves in bubbly liquids. Using the full model proposed by Fuster and Colonius [J. Fluid Mech. 688, 253 (2011), 10.1017/jfm.2011.380], numerical simulations reveal that direct bubble-bubble interactions have an appreciable effect for frequencies above the natural resonance frequency of the average size bubble. Based on the new results, a modification of the classical wave propagation theory is proposed. The results obtained are in good agreement with previously reported experimental data where the classical linear theory systematically overpredicts the effective attenuation and phase velocity.

  2. AN EFFICIENT TREATMENT STRATEGY FOR HISTOTRIPSY BY REMOVING CAVITATION MEMORY

    PubMed Central

    Wang, Tzu-Yin; Xu, Zhen; Hall, Timothy L.; Fowlkes, J. Brian; Cain, Charles A.

    2012-01-01

    Cavitation memory effects occur when remnants of cavitation bubbles (nuclei) persist in the host medium and act as seeds for subsequent events. In pulsed cavitational ultrasound therapy, or histotripsy, this effect may cause cavitation to repeatedly occur at these seeded locations within a target volume, producing inhomogeneous tissue fractionation or requiring an excess number of pulses to completely homogenize the target volume. We hypothesized that by removing the cavitation memory, i.e., the persistent nuclei, the cavitation bubbles could be induced at random locations in response to each pulse; therefore, complete disruption of a tissue volume may be achieved with fewer pulses. To test the hypothesis, the cavitation memory was passively removed by increasing the intervals between successive pulses, Δt, from 2, 10, 20, 50 and 100, to 200 ms. Histotripsy treatments were performed in red blood cell tissue phantoms and ex vivo livers using 1-MHz ultrasound pulses of 10 cycles at P−/P+ pressure of 21/59 MPa. The phantom study allowed for direct visualization of the cavitation patterns and the lesion development process in real time using high-speed photography; the ex vivo tissue study provided validation of the memory effect in real tissues. Results of the phantom study showed an exponential decrease in the correlation coefficient between cavitation patterns in successive pulses from 0.5 ± 0.1 to 0.1 ± 0.1 as Δt increased from 2–200 ms; correspondingly, the lesion was completely fractionated with significantly fewer pulses for longer Δts. In the tissue study, given the same number of therapy pulses, complete and homogeneous tissue fractionation with well-defined lesion boundaries was achieved only for Δt ≥ 100 ms. These results indicated that the removal of the cavitation memory resulted in more efficient treatments and homogeneous lesions. PMID:22402025

  3. Measuring Cavitation with Synchrotron X-Rays

    NASA Astrophysics Data System (ADS)

    Duke, Daniel; Kastengren, Alan; Powell, Chris; X-Ray Fuel Spray Group, Energy Systems Division Team

    2012-11-01

    Cavitation plays an important role in the formation of sprays from small nozzles such as those found in fuel injection systems. A sharp-edged inlet from the sac into the nozzle of a diesel fuel injector is shown to inititate a strong sheet-like cavitation along the boundary layer of the nozzle throat, which is difficult to measure and can lead to acoustic damage. To investigate this phenomenon, a diagnostic technique capable of mapping the density field of the nozzle through regions of intense cavitation is required. Available visible-light techniques are limited to qualitative observations of the outer extent of cavitation zones. However, brilliant X-rays from a synchrotron source have negligible refraction and are capable of penetrating the full extent of cavitation zones. We present the early results of a novel application of line-of-sight, time-resolved X-ray radiography on a cavitating model nozzle. Experiments were conducted at Sector 7-BM of the Advanced Photon Source. Density and vapor distribution are measured from the quantitative absorption of monochromatic X-rays. The density field can then be tomographically reconstructed from the projections. The density is then validated against a range of compressible and incompressible numerical simulations. This research was performed at the 7-BM beamline of the Advanced Photon Source. We acknowledge the support of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 and the DOE Vehicle Technologies Program (DOE-EERE).

  4. Real-time temperature estimation and monitoring of HIFU ablation through a combined modeling and passive acoustic mapping approach

    NASA Astrophysics Data System (ADS)

    Jensen, C. R.; Cleveland, R. O.; Coussios, C. C.

    2013-09-01

    Passive acoustic mapping (PAM) has been recently demonstrated as a method of monitoring focused ultrasound therapy by reconstructing the emissions created by inertially cavitating bubbles (Jensen et al 2012 Radiology 262 252-61). The published method sums energy emitted by cavitation from the focal region within the tissue and uses a threshold to determine when sufficient energy has been delivered for ablation. The present work builds on this approach to provide a high-intensity focused ultrasound (HIFU) treatment monitoring software that displays both real-time temperature maps and a prediction of the ablated tissue region. This is achieved by determining heat deposition from two sources: (i) acoustic absorption of the primary HIFU beam which is calculated via a nonlinear model, and (ii) absorption of energy from bubble acoustic emissions which is estimated from measurements. The two sources of heat are used as inputs to the bioheat equation that gives an estimate of the temperature of the tissue as well as estimates of tissue ablation. The method has been applied to ex vivo ox liver samples and the estimated temperature is compared to the measured temperature and shows good agreement, capturing the effect of cavitation-enhanced heating on temperature evolution. In conclusion, it is demonstrated that by using PAM and predictions of heating it is possible to produce an evolving estimate of cell death during exposure in order to guide treatment for monitoring ablative HIFU therapy. Portions presented at the 13th International Symposium on Therapeutic Ultrasound, Heidelberg, Germany (2012).

  5. Optimization in design of scientific products for purposes of cavitation problems

    NASA Astrophysics Data System (ADS)

    Modorskii, V. Ya.; Gaynutdinova, D. F.; Gergel, V. P.; Barkalov, K. A.

    2016-06-01

    This paper presents an optimized computer simulation of cavitation phenomena that occurs when a piston moves in a closed liquid-filled pipe. We have developed physical and mathematical models in a three-dimensional dynamic setting, found out a dependence of cavitation parameters on vibration parameters and constructed a domain of vibration influence on concentration of air cavitation bubbles. We also detected a maximum that corresponds to a certain combination of vibration kinematic parameters.

  6. The bubble-dependent mechanism of FUS-induced blood-brain barrier opening in mice and in monkeys in vivo

    NASA Astrophysics Data System (ADS)

    Tung, Yao-Sheng; Marquet, Fabrice; Vlachos, Fotios; Feshitan, Jameel A.; Borden, Mark A.; Konofagou, Elisa E.

    2012-10-01

    The blood-brain barrier (BBB) prevents most neurological drugs from traversing from the cerebral microvasculature into the brain parenchyma. Previous studies have shown that the presence of bubbles in an acoustic field temporarily opens the BBB. The BBB opening pressure threshold was previously identified to lie between 0.30 and 0.46 MPa in the case of the smaller bubbles and between 0.15 and 0.30 MPa in the larger bubble case. However, the physical effects responsible for BBB opening remain unknown. In addition, the noninvasive in vivo cavitation detection with mono-dispersed microbubbles has not been studied as of yet. The purpose of this study is to unveil the physical mechanism of the FUS-induced BBB opening with monodispersed microbubbles. Lipid-shelled microbubbles with three different diameters (1-2, 4-5 and 6-8 μm) were manufactured in-house and size-isolated using differential centrifugation. Sixty-seven (n=67) mice were each injected intravenously with bubbles of either 1-2, 4-5 or 6-8 μm in diameter and the concentration of 107 numbers/mL. The right hippocampus of each mouse was then sonicated using focused ultrasound (1.5 MHz frequency; 100 cycles (67 μs) pulse length; 10 Hz pulse repetition frequency; 1 minute sonication duration) while the left hippocampus served as the control. A 10-MHz transducer was used as a passive cavitation detector (PCD) to determine the threshold of inertial cavitation (IC). Each mouse was sonicated at a specific acoustic peak-rarefactional pressure at 0.15, 0.30, 0.45 or 0.60 MPa in order to identify the threshold of BBB opening and IC. T1-weighted MRI was used to verify the BBB opening and spectrograms were generated in order to detect the IC onset and duration. Our results suggest that the BBB opens as a result of nonlinear (harmonic) bubble oscillation when the bubble diameter is similar to the capillary diameter and with inertial cavitation when it is not. The bubble may thus have to be in contact with the capillary

  7. Mass spectrometric sampling of a liquid surface by nanoliter droplet generation from bursting bubbles and focused acoustic pulses: application to studies of interfacial chemistry.

    PubMed

    Thomas, Daniel A; Wang, Lingtao; Goh, Byoungsook; Kim, Eun Sok; Beauchamp, J L

    2015-03-17

    The complex chemistry occurring at the interface between liquid and vapor phases contributes significantly to the dynamics and evolution of numerous chemical systems of interest, ranging from damage to the human lung surfactant layer to the aging of atmospheric aerosols. This work presents two methodologies to eject droplets from a liquid water surface and analyze them via mass spectrometry. In bursting bubble ionization (BBI), droplet ejection is achieved via the formation of a jet following bubble rupture at the surface of a liquid to yield 250 μm diameter droplets (10 nL volume). In interfacial sampling by an acoustic transducer (ISAT), droplets are produced by focusing pulsed piezoelectric transducer-generated acoustic waves at the surface of a liquid, resulting in the ejection of droplets of 100 μm in diameter (500 pL volume). In both experimental methodologies, ejected droplets are aspirated into the inlet of the mass spectrometer, resulting in the facile formation of gas-phase ions. We demonstrate the ability of this technique to readily generate spectra of surface-active analytes, and we compare the spectra to those obtained by electrospray ionization. Charge measurements indicate that the ejected droplets are near-neutral (<0.1% of the Rayleigh limit), suggesting that gas-phase ion generation occurs in the heated transfer capillary of the instrument in a mechanism similar to thermospray or sonic spray ionization. Finally, we present the oxidation of oleic acid by ozone as an initial demonstration of the ability of ISAT-MS to monitor heterogeneous chemistry occurring at a planar water/air interface. PMID:25699657

  8. Non-Newtonian effects on flow-generated cavitation and on cavitation in a pressure field

    NASA Technical Reports Server (NTRS)

    Ellis, A. T.; Ting, R. Y.

    1974-01-01

    Observations are presented which show that the stresses in a flow field of very dilute polymer are not well enough described by the Navier-Stokes equations to accurately predict cavitation. The contitutive equation for the particular polymer and concentration used is needed. The second-order fluid form in which accelerations are relatively important appears capable of explaining observed cavitation suppression by changing the pressure field due to flow. Bubble dynamics in stationary dilute polymer solutions are also examined and found to be little different from those in water.

  9. Influence of the liquid viscosity on the formation of bubble structures in a 20kHz field.

    PubMed

    Salinas, V; Vargas, Y; Louisnard, O; Gaete, L

    2015-01-01

    The cavitation field in a cylindrical vessel bottom-insonified by a 19.7kHz large area transducer is studied experimentally. By adding controlled amounts of Poly-Ethylene Glycol (PEG) to water, the viscosity of the liquid is varied between one- and nine-fold the viscosity of pure water. For each liquid, and for various displacement amplitudes of the transducer, the liquid is imaged by a high-speed camera and the acoustic field is measured along the symmetry axis. For low driving amplitudes, only a spherical cap bubble structure appears on the transducer, growing with amplitude, and the axial acoustic pressure field displays a standing-wave shape. Above some threshold amplitude of the transducer, a flare-like structure starts to build up, involving bubbles strongly expelled from the transducer surface, and the axial pressure profile becomes almost monotonic. Increasing more the driving amplitude, the structure extends in height, and the pressure profile remains monotonic but decreases its global amplitude. This behavior is similar for all the water-PEG mixtures used, but the threshold for structure formation increases with the viscosity of the liquid. The images of the bubble structures are interpreted and correlated to the measured acoustic pressure profiles. The appearance of traveling waves near the transducer, produced by the strong energy dissipated by inertial bubbles, is conjectured to be a key mechanism accompanying the sudden appearance of the flare-like structure. PMID:25082762

  10. One-way-coupling simulation of cavitation accompanied by high-speed droplet impact

    NASA Astrophysics Data System (ADS)

    Kondo, Tomoki; Ando, Keita

    2016-03-01

    Erosion due to high-speed droplet impact is a crucial issue in industrial applications. The erosion is caused by the water-hammer loading on material surfaces and possibly by the reloading from collapsing cavitation bubbles that appear within the droplet. Here, we simulate the dynamics of cavitation bubbles accompanied by high-speed droplet impact against a deformable wall in order to see whether the bubble collapse is violent enough to give rise to cavitation erosion on the wall. The evolution of pressure waves in a single water (or gelatin) droplet to collide with a deformable wall at speed up to 110 m/s is inferred from simulations of multicomponent Euler flow where phase changes are not permitted. Then, we examine the dynamics of cavitation bubbles nucleated from micron/submicron-sized gas bubble nuclei that are supposed to exist inside the droplet. For simplicity, we perform Rayleigh-Plesset-type calculations in a one-way-coupling manner, namely, the bubble dynamics are determined according to the pressure variation obtained from the Euler flow simulation. In the simulation, the preexisting bubble nuclei whose size is either micron or submicron show large growth to submillimeters because tension inside the droplet is obtained through interaction of the pressure waves and the droplet interface; this supports the possibility of having cavitation due to the droplet impact. It is also found, in particular, for the case of cavitation arising from very small nuclei such as nanobubbles, that radiated pressure from the cavitation bubble collapse can overwhelm the water-hammer pressure directly created by the impact. Hence, cavitation may need to be accounted for when it comes to discussing erosion in the droplet impact problem.

  11. An adaptive spectral estimation technique to detect cavitation in HIFU with high spatial resolution.

    PubMed

    Hsieh, Chang-Yu; Probert Smith, Penny; Mayia, Fares; Ye, Guoliang

    2011-07-01

    In ultrasound-guided high-intensity focused ultrasound (HIFU) therapy, the changes observed on tissue are subtle during treatment; some ultrasound-guided HIFU protocols rely on the observation of significant brightness changes as the indicator of tissue lesions. The occurrence of a distinct hyperechogenic region ("bright-up") around the focus is often associated with acoustic cavitation resulting in microbubble formation, but it may indicate different physical events such as larger bubbles from boiling (known to alter acoustic impedance) or sometimes lesion formation. A reliable method to distinguish and spatially localize these causes within the tissue would assist the control of HIFU delivery, which is the subject of this paper. Spectral analysis of the radio frequency (RF) signal underlying the B-mode image provides more information on the physical cause, but the usual techniques that are methods on the Fourier transform require a long series for good spectral resolution and so they give poor spatial resolution. This paper introduces an active spectral cavitation detection method to attain high spatial resolution (0.15 × 0.15 mm per pixel) through a parametric statistical method (ARMA modeling) used on finite-length data sets, which enables local changes to be identified more easily. This technique uses the characteristics of the signal itself to optimize the model parameters and structure. Its performance is assessed using synthesized cavitation RF data, and it is then demonstrated in ex vivo bovine liver during and after HIFU exposure. The results suggest that good spatial and spectral resolution can be obtained by the design of suitable algorithms. In ultrasound-guided HIFU, the technique provides a useful supplement to B-mode analysis, with no additional time penalty in data acquisition. PMID:21684454

  12. Bubble size distribution analysis and control in high frequency ultrasonic cleaning processes

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    In the semiconductor industry, the ongoing down-scaling of nanoelectronic elements has lead to an increasing complexity of their fabrication. Hence, the individual fabrication processes become increasingly difficult to handle. To minimize cross-contamination, intermediate surface cleaning and preparation steps are inevitable parts of the semiconductor process chain. Here, one major challenge is the removal of residual nano-particulate contamination resulting from abrasive processes such as polishing and etching. In the past, physical cleaning techniques such as megasonic cleaning have been proposed as suitable solutions. However, the soaring fragility of the smallest structures is constraining the forces of the involved physical removal mechanisms. In the case of "megasonic" cleaning -cleaning with ultrasound in the MHz-domain - the main cleaning action arises from strongly oscillating microbubbles which emerge from the periodically changing tensile strain in the cleaning liquid during sonication. These bubbles grow, oscillate and collapse due to a complex interplay of rectified diffusion, bubble coalescence, non-linear pulsation and the onset of shape instabilities. Hence, the resulting bubble size distribution does not remain static but alternates continuously. Only microbubbles in this distribution that show a high oscillatory response are responsible for the cleaning action. Therefore, the cleaning process efficiency can be improved by keeping the majority of bubbles around their resonance size. In this paper, we propose a method to control and characterize the bubble size distribution by means of "pulsed" sonication and measurements of acoustic cavitation spectra, respectively. We show that the so-obtained bubble size distributions can be related to theoretical predictions of the oscillatory responses of and the onset of shape instabilities for the respective bubbles. We also propose a mechanism to explain the enhancement of both acoustic and cleaning activity

  13. Experimental and numerical insights into seismo-acoustic signals generated during the expansion of rising and bursting large gas bubbles in low-viscosity magmas

    NASA Astrophysics Data System (ADS)

    Lane, Stephen; Corder, Steven; James, Michael

    2010-05-01

    Strombolian activity produces gas-rich, magma-poor eruptions suggesting the separation and concentration of volcanic gases within the plumbing system. These gases are assumed to rise as relatively large bubble rafts or individual 'slug' bubbles that can cause detectable seismic activity on interaction with conduit geometry. Rising within the magma column, a gas bubble must expand appreciably in order to maintain magma-static pressure, for instance volume would increase by a factor of c. 200 for a 1 km rise to the magma-atmosphere interface. For a near-conduit-filling gas slug this expansion is one-dimensional (i.e. length-wise) and increases in rate non-linearly on approach to the surface. As they ascend, small gas slugs can expand sufficiently rapidly to maintain approximate magma-static pressure, but large gas slugs become dynamically overpressured. In laboratory experiments, these unsteady flows of gas and liquid generate pressure changes measurable below the gas phase. They also cause apparatus motion that does not apparently relate directly to these changes. Computational fluid dynamic (CFD) simulation of experiments reproduces the pressure changes within the liquid and allows visualisation of the viscous shear force exerted on the conduit wall around and above the slug as it rises and expands. CFD simulations at volcanic scale then give estimates of the various force contributions that could occur in the natural system. During the experiments, pressure change driven by slug expansion and burst was also measured in the ambient atmosphere above the upper liquid surface. We present experimental evidence of a range of burst processes that depend on the degree of gas overpressure in the slug. These processes range from the quiescent formation of a relatively long-lived liquid film that bursts some time after the gas slug has reached the liquid surface, through complex transitional behaviour where the meniscus detaches from the tube walls to form a bubble, to

  14. Acoustics

    NASA Astrophysics Data System (ADS)

    The acoustics research activities of the DLR fluid-mechanics department (Forschungsbereich Stroemungsmechanik) during 1988 are surveyed and illustrated with extensive diagrams, drawings, graphs, and photographs. Particular attention is given to studies of helicopter rotor noise (high-speed impulsive noise, blade/vortex interaction noise, and main/tail-rotor interaction noise), propeller noise (temperature, angle-of-attack, and nonuniform-flow effects), noise certification, and industrial acoustics (road-vehicle flow noise and airport noise-control installations).

  15. Application of Hydrodynamic Cavitation for Food and Bioprocessing

    NASA Astrophysics Data System (ADS)

    Gogate, Parag R.

    Hydrodynamic cavitation can be simply generated by the alterations in the flow field in high speed/high pressure devices and also by passage of the liquid through a constriction such as orifice plate, venturi, or throttling valve. Hydrodynamic cavitation results in the formation of local hot spots, release of highly reactive free radicals, and enhanced mass transfer rates due to turbulence generated as a result of liquid circulation currents. These conditions can be suitably applied for intensification of different bioprocessing applications in an energy-efficient manner as compared to conventionally used ultrasound-based reactors. The current chapter aims at highlighting different aspects related to hydrodynamic cavitation, including the theoretical aspects for optimization of operating parameters, reactor designs, and overview of applications relevant to food and bioprocessing. Some case studies highlighting the comparison of hydrodynamic cavitation and acoustic cavitation reactors will also be discussed.

  16. Removal of Residual Nuclei Following a Cavitation Event: A Parametric Study

    PubMed Central

    Duryea, Alexander P.; Tamaddoni, Hedieh A.; Cain, Charles A.; Roberts, William W.; Hall, Timothy L.

    2015-01-01

    The efficacy of ultrasound therapies such as shock wave lithotripsy and histotripsy can be compromised by residual cavitation bubble nuclei that persist following the collapse of primary cavitation. In our previous work, we have developed a unique strategy for mitigating the effects of these residual bubbles using low amplitude ultrasound pulses to stimulate their aggregation and subsequent coalescence—effectively removing them from the field. Here, we further develop this bubble removal strategy through an investigation of the effect of frequency on the consolidation process. Bubble removal pulses ranging from 0.5 – 2 MHz were used to sonicate the population of residual nuclei produced upon collapse of a histotripsy bubble cloud. For each frequency, mechanical index (MI) values ranging from 0 to approximately 1.5 were tested. Results indicated that, when evaluated as a function of bubble removal pulse MI, the efficacy of bubble removal shows markedly similar trends for all frequencies tested. This behavior divides into three distinct regimes (with provided cutoffs being approximate): (1) MI < 0.2: Minimal effect on the population of remnant cavitation nuclei; (2) 0.2 < MI < 1: Aggregation and subsequent coalescence of residual bubbles, the extent of which trends toward a maximum; (3) MI > 1: Bubble coalescence is compromised as bubble removal pulses induce high magnitude inertial cavitation of residual bubbles. The major distinction in these trends came for bubble removal pulses applied at 2 MHz, which were observed to generate the most effective bubble coalescence of all frequencies tested. We hypothesize that this is a consequence of the secondary Bjerknes force being the major facilitator of the consolidation process, the magnitude of which increases when the bubble size distribution is far from resonance such that the phase difference of oscillation of individual bubbles is minimal. PMID:26719861

  17. Cavitation and water fluxes driven by ice water potential in Juglans regia during freeze-thaw cycles.

    PubMed

    Charra-Vaskou, Katline; Badel, Eric; Charrier, Guillaume; Ponomarenko, Alexandre; Bonhomme, Marc; Foucat, Loïc; Mayr, Stefan; Améglio, Thierry

    2016-02-01

    Freeze-thaw cycles induce major hydraulic changes due to liquid-to-ice transition within tree stems. The very low water potential at the ice-liquid interface is crucial as it may cause lysis of living cells as well as water fluxes and embolism in sap conduits, which impacts whole tree-water relations. We investigated water fluxes induced by ice formation during freeze-thaw cycles in Juglans regia L. stems using four non-invasive and complementary approaches: a microdendrometer, magnetic resonance imaging, X-ray microtomography, and ultrasonic acoustic emissions analysis. When the temperature dropped, ice nucleation occurred, probably in the cambium or pith areas, inducing high water potential gradients within the stem. The water was therefore redistributed within the stem toward the ice front. We could thus observe dehydration of the bark's living cells leading to drastic shrinkage of this tissue, as well as high tension within wood conduits reaching the cavitation threshold in sap vessels. Ultrasonic emissions, which were strictly emitted only during freezing, indicated cavitation events (i.e. bubble formation) following ice formation in the xylem sap. However, embolism formation (i.e. bubble expansion) in stems was observed only on thawing via X-ray microtomography for the first time on the same sample. Ultrasonic emissions were detected during freezing and were not directly related to embolism formation. These results provide new insights into the complex process and dynamics of water movements and ice formation during freeze-thaw cycles in tree stems. PMID:26585223

  18. Effect of the Test Basket on Lithotripter Shock Waves, Cavitation Field, and Stone Breakage

    NASA Astrophysics Data System (ADS)

    Pishchalnikov, Yuri A.; McAteer, James A.; Zancanaro, Anthony J.; Neucks, Joshua S.; Pishchalnikova, Irina V.; Williams, James C.

    2008-09-01

    The performance of shock wave (SW) lithotripters is often assessed by measuring the breakage efficiency of model stones. Such in vitro tests are usually performed by positioning the stones in plastic mesh baskets. We asked if the plastic mesh affects the properties of SWs, and whether this alteration influences cavitation fields and stone breakage efficiency. Experiments were conducted using a research electrohydraulic lithotripter patterned after the Dornier HM3 (HM3-clone), and a clinical electromagnetic lithotripter (XX-ES). Shock waves were measured at the geometric focus (F2) of the HM3-clone lithotripter using a fiber-optic probe hydrophone (FOPH-500). A 2.5×4 mm extruded polypropylene mesh was positioned ˜8 mm or ˜40 mm prefocally. Cavitation bubbles were recorded using a multiframe high-speed camera (Imacon 468). Breakage of gypsum cement stones was assessed using the XX-ES lithotripter. SWs generated by this lithotripter propagate downward, so that when stones were positioned in an open-top basket, SWs could reach the stone without passing through the mesh that held the stone. This was compared to a mesh basket in the form of a cylinder, with which SWs had to pass through the mesh to reach the stone. Acoustic measurements showed that the mesh had little effect on the leading positive-pressure phase of the SW, but attenuated to some degree the tensile component of the pulse. Proximity of the mesh to F2 affected the waveforms such that the mesh positioned at 40mm prefocally was almost acoustically transparent, but the effect was much more pronounced when the mesh was within several millimeters of F2. High-speed camera images showed that cavitation was reduced beyond the mesh. Stone breakage was less efficient when SWs had to pass through the mesh to reach the stone. When SWs had to pass through the mesh, the number of SWs to break stones was 634±125 SWs, which was greater (P<0.002) than the 448±44 SWs needed to break stones in the open-top basket. These

  19. Acoustic field interaction with a boiling system under terrestrial gravity and microgravity.

    PubMed

    Sitter, J S; Snyder, T J; Chung, J N; Marston, P L

    1998-11-01

    Pool boiling experiments from a platinum wire heater in FC-72 liquid were conducted under terrestrial and microgravity conditions, both with and without the presence of a high-intensity acoustic standing wave within the fluid. The purpose of this research was to study the interaction between an acoustic field and a pool boiling system in normal gravity and microgravity. The absence of buoyancy in microgravity complicates the process of boiling. The acoustic force on a vapor bubble generated from a heated wire in a standing wave was shown to be able to play the role of buoyancy in microgravity. The microgravity environment was achieved with 0.6 and 2.1-s drop towers. The sound was transmitted through the fluid medium by means of a half wavelength sonic transducer driven at 10.18 kHz. At high enough acoustic pressure amplitudes cavitation and streaming began playing an important role in vapor bubble dynamics and heat transfer. Several different fixed heat fluxes were chosen for the microgravity experiment and the effects of acoustics on the surface temperature of the heater were recorded and the vapor bubble movement was filmed. Video images of the pool boiling processes and heat transfer data are presented. PMID:9821335

  20. Elasticity effects on cavitation in a squeeze film damper undergoing noncentered circular whirl

    NASA Technical Reports Server (NTRS)

    Brewe, David E.

    1988-01-01

    Elasticity of the liner and its effects on cavitation were numerically determined for a squeeze film damper subjected to dynamic loading. The loading was manifested as a prescribed motion of the rotor undergoing noncentered circular whirl. The boundary conditions were implemented using Elrod's algorithm which conserves lineal mass flux through the moving cavitation bubble as well as the oil film region of the damper. Computational movies were used to analyze the rapidly changing pressures and vapor bubble dynamics throughout the dynamic cycle for various flexibilities in the damper liner. The effects of liner elasticity on cavitation were only noticeable for the intermediate and high values of viscosity used in this study.

  1. A Study on the Mechanism for Cavitation in the Mechanical Heart Valves with an Electrohydraulic Total Artificial Heart

    NASA Astrophysics Data System (ADS)

    Lee, Hwansung; Tsukiya, Tomonori; Homma, Akihiko; Kamimura, Tadayuki; Tatsumi, Eisuke; Taenaka, Yoshiyuki; Kitamura, Soichiro

    It has been conceived that the mechanical heart valves mounted in an artificial heart close much faster than in vivo use, resulting in cavitation bubbles formation. In this study, the mechanisms for cavitation in mechanical heart valves (MHVs) is investigated with monoleaflet and bileaflet valves in the mitral position with an electrohydraulic total artificial heart (EHTAH). The valve-closing velocity and pressure-drop through the valve were done, and a high-speed video camera was employed to investigate the mechanism for MHVs cavitation. The valve-closing velocity and pressure-drop of the bileaflet valves were less than that of the monoleaflet valves. Most of the cavitation bubbles in the monoleaflet valves were observed next to the edge of the valve stop and the inner side of the leaflet. With the bileaflet valves, cavitation bubbles were concentrated along the leaflet tip. Also, the number density of cavitation bubbles in the bileaflet valves was less than that of the monoleaflet valves. The number density of cavitation bubbles increased with an increase in the valve-closing velocity and the valve stop area. It is established that squeeze flow holds the key to cavitation in the mechanical heart valve. In a viewpoint of squeeze flow, the bileaflet valve with slow valve-closing velocity and small valve stop area, is safer to prevent of blood cell damage than the monoleaflet valves.

  2. Use of hydrodynamic cavitation in (waste)water treatment.

    PubMed

    Dular, Matevž; Griessler-Bulc, Tjaša; Gutierrez-Aguirre, Ion; Heath, Ester; Kosjek, Tina; Krivograd Klemenčič, Aleksandra; Oder, Martina; Petkovšek, Martin; Rački, Nejc; Ravnikar, Maja; Šarc, Andrej; Širok, Brane; Zupanc, Mojca; Žitnik, Miha; Kompare, Boris

    2016-03-01

    The use of acoustic cavitation for water and wastewater treatment (cleaning) is a well known procedure. Yet, the use of hydrodynamic cavitation as a sole technique or in combination with other techniques such as ultrasound has only recently been suggested and employed. In the first part of this paper a general overview of techniques that employ hydrodynamic cavitation for cleaning of water and wastewater is presented. In the second part of the paper the focus is on our own most recent work using hydrodynamic cavitation for removal of pharmaceuticals (clofibric acid, ibuprofen, ketoprofen, naproxen, diclofenac, carbamazepine), toxic cyanobacteria (Microcystis aeruginosa), green microalgae (Chlorella vulgaris), bacteria (Legionella pneumophila) and viruses (Rotavirus) from water and wastewater. As will be shown, hydrodynamic cavitation, like acoustic, can manifest itself in many different forms each having its own distinctive properties and mechanisms. This was until now neglected, which eventually led to poor performance of the technique. We will show that a different type of hydrodynamic cavitation (different removal mechanism) is required for successful removal of different pollutants. The path to use hydrodynamic cavitation as a routine water cleaning method is still long, but recent results have already shown great potential for optimisation, which could lead to a low energy tool for water and wastewater cleaning. PMID:26515938

  3. Quantitative evaluation of erosive cavitation pressure field from pits in material: fact or myth?

    NASA Astrophysics Data System (ADS)

    Choi, J.-K.; Chahine, G. L.

    2015-12-01

    Material pitting in a cavitating flow has been used for a long time as an indicator of the vague ‘cavitation intensity’ concept. Periodically, some researchers suggest pitting tests as a “simple” means to provide quantitative measurements of the amplitude of the impulsive pressures in the cavitation field, especially when combined with Tabor's formula or with simple finite element computations with static loads. This paper examines the viability of such a method using fully coupled bubble dynamics and material response, and strongly concludes that the commonly accepted idea is a myth, as different loading scenarios with the same amplitude of the cavitation impulsive pressure result in different pit aspect ratios.

  4. Modeling cavitation in a rapidly changing pressure field - application to a small ultrasonic horn.

    PubMed

    Žnidarčič, Anton; Mettin, Robert; Dular, Matevž

    2015-01-01

    Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e. below the acoustic driving frequency. The term "acoustic supercavitation" was proposed for this type of cavitation Žnidarčič et al. (2014) [1]. We tested several established hydrodynamic cavitation models on this problem, but none of them was able to correctly predict the flow features. As a specific characteristic of such acoustic cavitation problems lies in the rapidly changing driving pressures, we present an improved approach to cavitation modeling, which does not neglect the second derivatives in the Rayleigh-Plesset equation. Comparison with measurements of acoustic supercavitation at an ultrasonic horn of 20kHz frequency revealed a good agreement in terms of cavity dynamics, cavity volume and emitted pressure pulsations. The newly developed cavitation model is particularly suited for simulation of cavitating flow in highly fluctuating driving pressure fields. PMID:24889548

  5. Time-frequency analysis of transient pressure signals for a mechanical heart valve cavitation study.

    PubMed

    Yu, A A; White, J A; Hwang, N H

    1998-01-01

    A series of transient pressure signals (TPSs) can be measured using a miniature pressure transducer mounted near the tip of the inflow side of a mechanical heart valve (MHV) occluder during closure. A relationship appears to exist between the intensity and pattern of the TPS and the cavitation potential of a MHV. To study the relationship between MHV cavitation and the TPSs, we installed an MHV in a valve testing chamber of a digitally controlled burst test loop. A charge coupled device (CCD) camera and a personal computer based image grabbing program was used to visualize cavitation bubbles appearing on or near the occluder surface. One bileaflet MHV was used as the model for this study. Cavitation bubbles were observed within 300 microsec of the leaflet/housing impact. The valve was tested at various driving pressures between 100 and 1,300 mmHg. MHV cavitation bubble intensities were qualitatively classified into three categories: 1) strong, 2) weak, and 3) none. Digital images of the MHV occluder inflow surface were recorded simultaneously with the TPSs. TPSs were studied by the time-frequency analysis method (spectrogram) and correlated to MHV cavitation potential. The intensity of the cavitation bubbles was found to be associated with burst test loop driving pressures during leaflet closure. PMID:9804476

  6. Cavitational hydrothermal oxidation: A new remediation process. Annual progress report, September 1996--August 1997

    SciTech Connect

    Suslick, K.S.

    1997-11-21

    'During the past year, the authors have continued to make substantial scientific progress on the understanding of cavitation phenomena in aqueous media and applications of cavitation to remediation processes. The efforts have focused on three separate areas: sonoluminescence as a probe of conditions created during cavitational collapse in aqueous media, the use of cavitation for remediation of contaminated water, and an addition of the use of ultrasound in the synthesis of novel heterogeneous catalysts for hydrodehalogenation of halocarbons under mild conditions. In order to gain further understanding of the conditions present during cavitation, the author has continued his studies of sonoluminescence. He has made recent breakthroughs in the use of emission spectroscopy for temperature and pressure measurement of cavitation events, which he expects to publish shortly. He has been able to measure for the first time the temperature of cavitation in water during multi-bubble cavitation in the presence of aromatic hydrocarbons. The emission from excited states of C{sub 2} in water gives temperatures that are consistent with adiabatic compressional heating, with maximum temperatures of 4,300 K. Prior measurements of cavitation temperatures in low vapor pressure nonaqueous media gave somewhat higher temperatures of 5,000 K. This work lays permanently to rest exotic mechanisms for cavitational chemistry, at least for cavitation fields.'

  7. Cavitational hydrothermal oxidation: A new remediation process. 1998 annual progress report

    SciTech Connect

    Suslick, K.S.

    1998-06-01

    'The primary goal is to develop a quantitative understanding of cavitation phenomena in aqueous media and the development of applications of cavitation to remediation processes. Efforts have focused on three separate areas: sonoluminescence as a probe of conditions created during cavitational collapse in aqueous media, the use of cavitation for remediation of contaminated water, and an addition of the use of ultrasound in the synthesis of novel heterogeneous catalysts for hydrodehalogenation of halocarbons under mild conditions. This report summarizes work after one year of a three year project. In order to gain further understanding of the conditions present during cavitation, the author has continued his studies of sonoluminescence. He has made recent breakthroughs in the use of emission spectroscopy for temperature and pressure measurement of cavitation events, which he expects to publish shortly. He has been able to measure for the first time the temperature of cavitation in water during multi-bubble cavitation in the presence of aromatic hydrocarbons. The emission from excited states of C{sub 2} in water gives temperatures that are consistent with adiabatic compressional heating, with maximum temperatures of 4,300 K. Prior measurements of cavitation temperatures in low vapor pressure nonaqueous media gave somewhat higher temperatures of 5,000 K. This work lays permanently to rest exotic mechanisms for cavitational chemistry, at least for cavitation fields.'

  8. Cavitation damage in blood clots under HIFU

    NASA Astrophysics Data System (ADS)

    Weiss, Hope; Ahadi, Golnaz; Hoelscher, Thilo; Szeri, Andrew

    2010-11-01

    High Intensity Focused Ultrasound (HIFU) has been shown to accelerate thrombolysis, the dissolution of blood clots, in vitro and in vivo, for treatment of ischemic stroke. Cavitation in sonothrombolysis is thought to play an important role, although the mechanisms are not fully understood. The damage to a blood clot associated with bubble collapses in a HIFU field is studied. The region of damage caused by a bubble collapse on the fibrin network of the blood clot exposed to HIFU is estimated, and compared with experimental assessment of the damage. The mechanical damage to the network caused by a bubble is probed using two independent approaches, a strain based method and an energy based method. Immunoflourescent fibrin staining is used to assess the region of damage experimentally.

  9. Molecular dynamics investigation of nanoscale cavitation dynamics

    NASA Astrophysics Data System (ADS)

    Sasikumar, Kiran; Keblinski, Pawel

    2014-12-01

    We use molecular dynamics simulations to investigate the cavitation dynamics around intensely heated solid nanoparticles immersed in a model Lennard-Jones fluid. Specifically, we study the temporal evolution of vapor nanobubbles that form around the solid nanoparticles heated over ps time scale and provide a detail description of the following vapor formation and collapse. For 8 nm diameter nanoparticles we observe the formation of vapor bubbles when the liquid temperature 0.5-1 nm away from the nanoparticle surface reaches ˜90% of the critical temperature, which is consistent with the onset of spinodal decomposition. The peak heat flux from the hot solid to the surrounding liquid at the bubble formation threshold is ˜20 times higher than the corresponding steady state critical heat flux. Detailed analysis of the bubble dynamics indicates adiabatic formation followed by an isothermal final stage of growth and isothermal collapse.

  10. Sound field measurement in a double layer cavitation cluster by rugged miniature needle hydrophones.

    PubMed

    Koch, Christian

    2016-03-01

    During multi-bubble cavitation the bubbles tend to organize themselves into clusters and thus the understanding of properties and dynamics of clustering is essential for controlling technical applications of cavitation. Sound field measurements are a potential technique to provide valuable experimental information about the status of cavitation clouds. Using purpose-made, rugged, wide band, and small-sized needle hydrophones, sound field measurements in bubble clusters were performed and time-dependent sound pressure waveforms were acquired and analyzed in the frequency domain up to 20 MHz. The cavitation clusters were synchronously observed by an electron multiplying charge-coupled device (EMCCD) camera and the relation between the sound field measurements and cluster behaviour was investigated. Depending on the driving power, three ranges could be identified and characteristic properties were assigned. At low power settings no transient and no or very low stable cavitation activity can be observed. The medium range is characterized by strong pressure peaks and various bubble cluster forms. At high power a stable double layer was observed which grew with further increasing power and became quite dynamic. The sound field was irregular and the fundamental at driving frequency decreased. Between the bubble clouds completely different sound field properties were found in comparison to those in the cloud where the cavitation activity is high. In between the sound field pressure amplitude was quite small and no collapses were detected. PMID:24953962

  11. Bubbles of Metamorphosis

    NASA Astrophysics Data System (ADS)

    Prakash, Manu

    2011-11-01

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

  12. Modelling of flow with cavitation in centrifugal pump

    NASA Astrophysics Data System (ADS)

    Homa, D.; Wróblewski, W.

    2014-08-01

    The paper concerns flow modelling in centrifugal pump with special consideration of cavitation phenomena. Cavitation occurs when local pressure drops below the saturation pressure according to the temperature of the flow. Vapour bubbles are created and then they flow through the areas with higher pressure. The bubbles collapse rapidly generating pressure wave, noise and vibration. Working under cavitation condition is very dangerous to a pump and can significantly shorten its lifetime. The investigated centrifugal pump consists of three two-flow rotors and stators working on a single shaft. The modelling process started with grid independence study. When the grid was chosen, the pump performance curve was obtained using the single phase fluid model. Next, using the results from pump performance curve calculations, the cavitation characteristic was obtained. The constant capacity was held when the pressure at the inlet was reduced. The two - phase model was used with Zwart cavitation model. The results indicate that the pump work in safe range of parameters. The analysis also provides wide range of information about the areas of vapour appearance. The most endangered regions are leading edges of rotor. When pressure at the inlet drops to about one third of pressure that calculations started from the cavitation cloud appears in whole rotor. The intense of vapour bubbles creation is greater near the shroud of the pump, rather than near the hub. As cavitation is strongly unsteady phenomena, the transient calculations were performed to check if the results are close to those obtained using the steady state type. The differences are not significant.

  13. The Numerical Simulation of Unsteady Cavitation Evolution Induced by Pressure Wave

    NASA Astrophysics Data System (ADS)

    Khoo, B. C.; Zheng, J. G.

    2014-11-01

    The present study is focused on the numerical simulation of pressure wave propagation through the cavitating compressible liquid flow, its interaction with cavitation bubble and the resulting unsteady cavitation evolution. The compressibility effects of liquid water are taken into account and the cavitating flow is governed by one-fluid cavitation model which is based on the compressible Euler equations with the assumption that the cavitation is the homogeneous mixture of liquid and vapour which are locally under both kinetic and thermodynamic equilibrium. Several aspects of the method employed to solve the governing equations are outlined. The unsteady features of cavitating flow due to the external perturbation, such as the cavitation deformation and collapse and consequent pressure increase are resolved numerically and discussed in detail. It is observed that the cavitation bubble collapse is accompanied by the huge pressure surge of order of 100 bar, which is thought to be responsible for the material erosion, noise, vibration and loss of efficiency of operating underwater devices.

  14. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  15. Removal of Residual Cavitation Nuclei to Enhance Histotripsy Fractionation of Soft Tissue

    PubMed Central

    Duryea, Alexander P.; Cain, Charles A.; Roberts, William W.; Hall, Timothy L.

    2015-01-01

    Remnant bubble nuclei generated by primary cavitation collapse can limit the efficiency of histotripsy soft tissue fractionation. When these residual bubbles persist from one histotripsy pulse to the next, they can seed the repetitive nucleation of cavitation bubbles at a discrete set of sites within the focal volume. This effect—referred to as cavitation memory—manifests in inefficient lesion formation, as certain sites within the focal volume are overtreated while others remain undertreated. While the cavitation memory effect can be passively mitigated by using a low pulse repetition frequency (PRF) that affords remnant nuclei sufficient time for dissolution between successive pulses, this low PRF also results in slow lesion production. As such, it would be highly desirable to maintain the high per-pulse efficiency associated with low pulse rates when much higher PRFs are utilized. In this vein we have developed a strategy for the active removal of the remnant bubble nuclei following primary cavitation collapse, using low amplitude ultrasound sequences (termed bubble removal sequences) to stimulate the aggregation and subsequent coalescence of these bubbles. In this study, bubble removal sequences were incorporated in high-PRF histotripsy treatment (100 Hz) of a red blood cell tissue-mimicking phantom that allows for the visualization of lesion development in real-time. A series of reference treatments were also conducted at the low PRF of 1 Hz in order to provide a point of comparison when cavitation memory effects are minimal. It was found that bubble removal sequences as short as 1 ms are capable of maintaining the efficacious lesion development characteristics associated with the low PRF of 1 Hz when the much higher pulse rate of 100 Hz is used. These results were then extended to the treatment of a large volume within the tissue phantom, and optimal bubble removal sequences identified for the single-focal-spot case were utilized to homogenize a 10 × 10

  16. Effect of Noble Gases on Sonoluminescence Temperatures during Multibubble Cavitation

    SciTech Connect

    Didenko, Yuri T.; McNamara, William B. III; Suslick, Kenneth S.

    2000-01-24

    Sonoluminescence spectra were collected from Cr(CO){sub 6} solutions in octanol and dodecane saturated with various noble gases. The emission from excited-state metal atoms serves as an internal thermometer of cavitation. The intensity and temperature of sonoluminescence increases from He to Xe. The intensity of the underlying continuum, however, grows faster with increasing temperature than the line emission. Dissociation of solvent molecules within the bubble consumes a significant fraction of the energy generated by the collapsing bubble, which can limit the final temperature inside the bubble. (c) 2000 The American Physical Society.

  17. Controlled Cavitation for Scale-Free Heating, Gum Hydration and Emulsification in Food and Consumer Products

    NASA Astrophysics Data System (ADS)

    Mancosky, Douglas G.; Milly, Paul

    Cavitation is defined as the sudden formation and collapse of bubbles in liquid by means of a mechanical force. As bubbles rapidly form and collapse, pressurized shock waves, localized heating events and tremendous shearing forces occur. As microscopic cavitation bubbles are produced and collapse, shockwaves are given off into the liquid, which can result in heating and/or mixing, similar to ultrasound. These shockwaves can provide breakthrough benefits for the heating of liquids without scale buildup and/or the mixing of liquids with other liquids, gases or solids at the microscopic level to increase the efficiency of the reaction.

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

    PubMed

    Arbabi, A; Mastikhin, I V

    2012-12-01

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

  19. Flow velocity measurement with the nonlinear acoustic wave scattering

    SciTech Connect

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    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.

  20. Flow velocity measurement with the nonlinear acoustic wave scattering

    NASA Astrophysics Data System (ADS)

    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.

  1. Bubble levitation and translation under single-bubble sonoluminescence conditions.

    PubMed

    Matula, Thomas J

    2003-08-01

    Bubble levitation in an acoustic standing wave is re-examined for conditions relevant to single-bubble sonoluminescence. Unlike a previous examination [Matula et al., J. Acoust. Soc. Am. 102, 1522-1527 (1997)], the stable parameter space [Pa,R0] is accounted for in this realization. Forces such as the added mass force and drag are included, and the results are compared with a simple force balance that equates the Bjerknes force to the buoyancy force. Under normal sonoluminescence conditions, the comparison is quite favorable. A more complete accounting of the forces shows that a stably levitated bubble does undergo periodic translational motion. The asymmetries associated with translational motion are hypothesized to generate instabilities in the spherical shape of the bubble. A reduction in gravity results in reduced translational motion. It is hypothesized that such conditions may lead to increased light output from sonoluminescing bubbles. PMID:12942960

  2. Numerical investigation of bubble nonlinear dynamics characteristics

    SciTech Connect

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

    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.

  3. Numerical investigation of bubble nonlinear dynamics characteristics

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  4. The effect of reflector geometry on the acoustic field and bubble dynamics produced by an electrohydraulic shock wave lithotripter.

    PubMed

    Zhou, Yufeng; Zhong, Pei

    2006-06-01

    A theoretical model for the propagation of shock wave from an axisymmetric reflector was developed by modifying the initial conditions for the conventional solution of a nonlinear parabolic wave equation (i.e., the Khokhlov-Zabolotskaya-Kuznestsov equation). The ellipsoidal reflector of an HM-3 lithotripter is modeled equivalently as a self-focusing spherically distributed pressure source. The pressure wave form generated by the spark discharge of the HM-3 electrode was measured by a fiber optic probe hydrophone and used as source conditions in the numerical calculation. The simulated pressure wave forms, accounting for the effects of diffraction, nonlinearity, and thermoviscous absorption in wave propagation and focusing, were compared with the measured results and a reasonably good agreement was found. Furthermore, the primary characteristics in the pressure wave forms produced by different reflector geometries, such as that produced by a reflector insert, can also be predicted by this model. It is interesting to note that when the interpulse delay time calculated by linear geometric model is less than about 1.5 micros, two pulses from the reflector insert and the uncovered bottom of the original HM-3 reflector will merge together. Coupling the simulated pressure wave form with the Gilmore model was carried out to evaluate the effect of reflector geometry on resultant bubble dynamics in a lithotripter field. Altogether, the equivalent reflector model was found to provide a useful tool for the prediction of pressure wave form generated in a lithotripter field. This model may be used to guide the design optimization of reflector geometries for improving the performance and safety of clinical lithotripters. PMID:16838506

  5. The effect of reflector geometry on the acoustic field and bubble dynamics produced by an electrohydraulic shock wave lithotripter

    PubMed Central

    Zhou, Yufeng; Zhong, Pei

    2007-01-01

    A theoretical model for the propagation of shock wave from an axisymmetric reflector was developed by modifying the initial conditions for the conventional solution of a nonlinear parabolic wave equation (i.e., the Khokhlov–Zabolotskaya–Kuznestsov equation). The ellipsoidal reflector of an HM-3 lithotripter is modeled equivalently as a self-focusing spherically distributed pressure source. The pressure wave form generated by the spark discharge of the HM-3 electrode was measured by a fiber optic probe hydrophone and used as source conditions in the numerical calculation. The simulated pressure wave forms, accounting for the effects of diffraction, nonlinearity, and thermoviscous absorption in wave propagation and focusing, were compared with the measured results and a reasonably good agreement was found. Furthermore, the primary characteristics in the pressure wave forms produced by different reflector geometries, such as that produced by a reflector insert, can also be predicted by this model. It is interesting to note that when the interpulse delay time calculated by linear geometric model is less than about 1.5 μs, two pulses from the reflector insert and the uncovered bottom of the original HM-3 reflector will merge together. Coupling the simulated pressure wave form with the Gilmore model was carried out to evaluate the effect of reflector geometry on resultant bubble dynamics in a lithotripter field. Altogether, the equivalent reflector model was found to provide a useful tool for the prediction of pressure wave form generated in a lithotripter field. This model may be used to guide the design optimization of reflector geometries for improving the performance and safety of clinical lithotripters. PMID:16838506

  6. Experimental determination of cavitation thresholds in liquid water and mercury

    SciTech Connect

    Taleyarkhan, R.P.; Gulec, K.; West, C.D.; Haines, J.

    1998-09-01

    It is well-known that fluids (like solids) will break apart or form voids when put under sufficient tension. The present study has been motivated by the need to evaluate the impact of fluid cavitation in spallation neutron source target systems, more specifically for the proposed 1-MW Spallation Neutron Source (SNS) project, which is being designed in collaboration between Oak Ridge National Laboratory (ORNL), Los Alamos National Laboratory, Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, and Argonne National Laboratory. Indeed, results of SNS-specific simulations have indicated that the onset of cavitation could play a very significant role in reducing imposed stresses in structural components of the SNS. In general, the cavitation of fluids is target systems is important to consider for a variety of reasons. Its occurrence can have significant impact on heat transfer, pressure pulse generation, fluid jetting on to structures, surface erosion, stresses induced in enclosures, etc. Therefore, it is important to evaluate the threshold pressure under which the fluid in tension will undergo cavitation. Another major aspect concerns the possible onset of cavitation in an oscillating pressure field; i.e., one would need to know if fluids such as mercury and water will cavitate if the imposed tensile pressure in the fluid is of short duration. If indeed it takes sufficiently long for cavitation bubbles to nucleate, then it would be possible to disregard the complexities involved with addressing cavitation-related issues. This paper provides an overview of preliminary work done to date to derive information on cavitation onset in a relatively static and in a high-frequency environment.

  7. Precise spatial control of cavitation erosion in a vessel phantom by using an ultrasonic standing wave.

    PubMed

    Shi, Aiwei; Huang, Peixuan; Guo, Shifang; Zhao, Lu; Jia, Yingjie; Zong, Yujin; Wan, Mingxi

    2016-07-01

    In atherosclerotic inducement in animal models, the conventionally used balloon injury is invasive, produces excessive vessel injuries at unpredictable locations and is inconvenient in arterioles. Fortunately, cavitation erosion, which plays an important role in therapeutic ultrasound in blood vessels, has the potential to induce atherosclerosis noninvasively at predictable sites. In this study, precise spatial control of cavitation erosion for superficial lesions in a vessel phantom was realised by using an ultrasonic standing wave (USW) with the participation of cavitation nuclei and medium-intensity ultrasound pulses. The superficial vessel erosions were restricted between adjacent pressure nodes, which were 0.87 mm apart in the USW field of 1 MHz. The erosion positions could be shifted along the vessel by nodal modulation under a submillimetre-scale accuracy without moving the ultrasound transducers. Moreover, the cavitation erosion of the proximal or distal wall could be determined by the types of cavitation nuclei and their corresponding cavitation pulses, i.e., phase-change microbubbles with cavitation pulses of 5 MHz and SonoVue microbubbles with cavitation pulses of 1 MHz. Effects of acoustic parameters of the cavitation pulses on the cavitation erosions were investigated. The flow conditions in the experiments were considered and discussed. Compared to only using travelling waves, the proposed method in this paper improves the controllability of the cavitation erosion and reduces the erosion depth, providing a more suitable approach for vessel endothelial injury while avoiding haemorrhage. PMID:26964937

  8. Comparative CFD Investigation on the Performance of a New Family of Super-Cavitating Hydrofoils

    NASA Astrophysics Data System (ADS)

    Brizzolara, S.; Bonfiglio, L.

    2015-12-01

    We present a CFD characterization of a new type of super-cavitating hydrofoil section designed to have optimal performance both in super-cavitating conditions and in sub-cavitating conditions (including transitional regime). The basic concepts of the new profile family are first introduced. Lift, drag and cavity shapes at different cavitation numbers are calculated for a new foil and compared with those of conventional sub-cavitating and super-cavitating profiles. Numerical calculations confirm the superior characteristics of the new hydrofoil family, which is able to attain high lift and efficiency both in sub-cavitating and super-cavitating conditions. Numerical calculations are based on a multi-phase fully turbulent URANSE solver with a bubble dynamic cavitation model to follow the generation and evaporation of the vapor phase. The new profile family, initially devised for ultra-high speed hydrofoil crafts, may result useful for diverse applications such as super-cavitating or surface-piercing propellers or high-speed sailing boats.

  9. Fundamental Study of Cavitation Sensors Fabricated with Lead Zirconate Titanate Film Deposited by Hydrothermal Method: Analysis and Consideration of Output Signal from the Sensor

    NASA Astrophysics Data System (ADS)

    Seto, Yuki; Kawashima, Norimichi; Kuribayashi Kurosawa, Minoru; Takeuchi, Shinichi

    2008-05-01

    Small cavitation sensors were developed with hydrothermally synthesized lead zirconate titanate (PZT) on the outer surface of the Ti cylinder. Output signals from the fabricated cavitation sensor were analyzed in frequency domain with changing applied voltage to the Langevin transducer of the ultrasound exposure system. Frequency components from 1 to 5 MHz included in the output signal from the cavitation sensor were measured as the cavitation signal in order to distinguish the harmonic components from acoustic cavitation from those by nonlinear propagation in water. Broadband integrated voltage can be calculated by integrating harmonic components from 1 to 5 MHz included in the output signal from the cavitation sensor.

  10. An Anticipatory Model of Cavitation

    SciTech Connect

    Allgood, G.O.; Dress, W.B., Jr.; Hylton, J.O.; Kercel, S.W.

    1999-04-05

    The Anticipatory System (AS) formalism developed by Robert Rosen provides some insight into the problem of embedding intelligent behavior in machines. AS emulates the anticipatory behavior of biological systems. AS bases its behavior on its expectations about the near future and those expectations are modified as the system gains experience. The expectation is based on an internal model that is drawn from an appeal to physical reality. To be adaptive, the model must be able to update itself. To be practical, the model must run faster than real-time. The need for a physical model and the requirement that the model execute at extreme speeds, has held back the application of AS to practical problems. Two recent advances make it possible to consider the use of AS for practical intelligent sensors. First, advances in transducer technology make it possible to obtain previously unavailable data from which a model can be derived. For example, acoustic emissions (AE) can be fed into a Bayesian system identifier that enables the separation of a weak characterizing signal, such as the signature of pump cavitation precursors, from a strong masking signal, such as a pump vibration feature. The second advance is the development of extremely fast, but inexpensive, digital signal processing hardware on which it is possible to run an adaptive Bayesian-derived model faster than real-time. This paper reports the investigation of an AS using a model of cavitation based on hydrodynamic principles and Bayesian analysis of data from high-performance AE sensors.

  11. Bubble formation in microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1994-01-01

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

  12. The relative effects of cavitation and nonlinear ultrasound propagation on HIFU lesion dynamics in a tissue phantom

    NASA Astrophysics Data System (ADS)

    Khokhlova, Vera A.; Bailey, Michael R.; Reed, Justin; Kaczkowski, Peter J.

    2001-05-01

    The relative importance of the effects of acoustic nonlinearity and cavitation in HIFU lesion production is studied experimentally and theoretically in a polyacrylamide gel. A 2-MHz transducer of 40-mm diameter and 45-mm focal length was operated at different regimes of power, and in cw or duty-cycle regimes with equal mean intensity. Elevated static pressure was applied to suppress bubbles, increase boiling temperature, and thus to isolate the effect of acoustic nonlinearity in the enhancement of lesion production. Experimental data were compared with the results of simulations performed using a KZK acoustic model combined with the bioheat equation and thermal dose formulation. Boiling and the typical tadpole-shaped lesion shifting towards the transducer were observed under standard atmospheric pressure. No boiling was detected and a symmetric thermal lesion formed in the case of overpressure. A delay in lesion inception time was registered with overpressure, which was hypothesized to be due to suppressed microbubble dynamics. The effect of acoustic nonlinearity was revealed as a substantial decrease in the lesion inception time and an increase in the lesion size for high-amplitude waves under both standard and overpressure conditions. [Work supported by ONRIFO, NASA/NSBRI, NIH Fogarty, and CRDF grants.

  13. Neutron detection via bubble chambers.

    PubMed

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

    2005-01-01

    Research investigating the application of pressure-cycled bubble chambers to fast neutron detection is described. Experiments with a Halon-filled chamber showed clear sensitivity to an AmBe neutron source and insensitivity to a (137)Cs gamma source. Bubble formation was documented using high-speed photography, and a ceramic piezo-electric transducer element registered the acoustic signature of bubble formation. In a second set of experiments, the bubble nucleation response of a Freon-134a chamber to an AmBe neutron source was documented with high-speed photography. PMID:16005238

  14. Cavitation erosion: Using the target material as a pressure sensor

    NASA Astrophysics Data System (ADS)

    Roy, Samir Chandra; Franc, Jean-Pierre; Fivel, Marc

    2015-10-01

    Numerical prediction of mass loss due to cavitation erosion requires the knowledge of the hydrodynamic impact loads generated by cavitation bubble collapses. Experimental measurements of such impact loads using conventional pressure sensors are not reliable (if not impossible) due to the micron size and the very small duration of the loading. In this paper, a new method to estimate these loading conditions is proposed based on cavitation pitting tests and an iterative inverse finite element modeling. The principle of the method is as follows. First, numerous pits corresponding to localized plastically deformed regions are identified from a cavitation test performed in a dedicated tunnel. Then each pit is numerically reproduced by finite element simulations of the material response to a representative Gaussian pressure field supposed to mimic a single bubble collapse. This gives the size and pressure distribution of the bubble impacts. The prime objective of this study is to find out if the target material itself could be used as a pressure sensor or not, i.e., if the cavitation pits left on the surface of the tested specimen could provide the characteristics of the cavitating flow in terms of pressure fields independently of the target material. Pitting tests were done on three materials, namely, 7075 Aluminum alloy (Al-7075), 2205 duplex stainless steel (A-2205), and Nickel-Aluminum Bronze (NAB) at three different flow conditions and the impact loads have been estimated for each identified pit. Very interestingly, a statistical analysis shows that the estimated impact loads are material independent at all flow conditions, provided the material properties are characterized properly. It is also shown that for some materials, the constitutive parameters obtained from compression tests are not satisfactory.

  15. Detection of cystic structures using pulsed ultrasonically induced resonant cavitation

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph (Inventor); Kovach, John S. (Inventor)

    2002-01-01

    Apparatus and method for early detection of cystic structures indicative of ovarian and breast cancers uses ultrasonic wave energy at a unique resonance frequency for inducing cavitation in cystic fluid characteristic of cystic structures in the ovaries associated with ovarian cancer, and in cystic structures in the breast associated with breast cancer. Induced cavitation bubbles in the cystic fluid implode, creating implosion waves which are detected by ultrasonic receiving transducers attached to the abdomen of the patient. Triangulation of the ultrasonic receiving transducers enables the received signals to be processed and analyzed to identify the location and structure of the cyst.

  16. Plasma and Cavitation Dynamics during Pulsed Laser Microsurgery in vivo

    SciTech Connect

    Hutson, M. Shane; Ma Xiaoyan

    2007-10-12

    We compare the plasma and cavitation dynamics underlying pulsed laser microsurgery in water and in fruit fly embryos (in vivo)--specifically for nanosecond pulses at 355 and 532 nm. We find two key differences. First, the plasma-formation thresholds are lower in vivo --especially at 355 nm--due to the presence of endogenous chromophores that serve as additional sources for plasma seed electrons. Second, the biological matrix constrains the growth of laser-induced cavitation bubbles. Both effects reduce the disrupted region in vivo when compared to extrapolations from measurements in water.

  17. Pulsed ultrasound enhances the delivery of nitric oxide from bubble liposomes to ex vivo porcine carotid tissue

    PubMed Central

    Sutton, JT; Raymond, JL; Verleye, MC; Pyne-Geithman, GJ; Holland, CK

    2014-01-01

    Ultrasound-mediated drug delivery is a novel technique for enhancing the penetration of drugs into diseased tissue beds noninvasively. By encapsulating drugs into microsized and nanosized liposomes, the therapeutic can be shielded from degradation within the vasculature until delivery to a target site by ultrasound exposure. Traditional in vitro or ex vivo techniques to quantify this delivery profile include optical approaches, cell culture, and electrophysiology. Here, we demonstrate an approach to characterize the degree of nitric oxide (NO) delivery to porcine carotid tissue by direct measurement of ex vivo vascular tone. An ex vivo perfusion model was adapted to assess ultrasound-mediated delivery of NO. This potent vasodilator was coencapsulated with inert octafluoropropane gas to produce acoustically active bubble liposomes. Porcine carotid arteries were excised post mortem and mounted in a physiologic buffer solution. Vascular tone was assessed in real time by coupling the artery to an isometric force transducer. NO-loaded bubble liposomes were infused into the lumen of the artery, which was exposed to 1 MHz pulsed ultrasound at a peak-to-peak acoustic pressure amplitude of 0.34 MPa. Acoustic cavitation emissions were monitored passively. Changes in vascular tone were measured and compared with control and sham NO bubble liposome exposures. Our results demonstrate that ultrasound-triggered NO release from bubble liposomes induces potent vasorelaxation within porcine carotid arteries (maximal relaxation 31%±8%), which was significantly stronger than vasorelaxation due to NO release from bubble liposomes in the absence of ultrasound (maximal relaxation 7%±3%), and comparable with relaxation due to 12 μM sodium nitroprusside infusions (maximal relaxation 32%±3%). This approach is a valuable mechanistic tool for assessing the extent of drug release and delivery to the vasculature caused by ultrasound. PMID:25336947

  18. Nano bubbles in liquid of a noble-gas mixture.

    PubMed

    Yamamoto, Takenori; Ohnishi, Shuhei

    2010-02-01

    Large-scale molecular dynamics (MD) simulations with over one million atoms are used to investigate nano bubbles in Ar-Ne liquid. The simulations demonstrate cavitations in the stretched liquid, and bubble creation and collapse. We find that a small cavity created in the stretched liquid spontaneously transforms into a nano bubble with the homogeneous vapor region. The equilibrium spherical bubble of 11.4 nm in radius is obtained after the long-time MD run. The surface tension of the nano bubble is found to be larger than that of the flat surface. PMID:20094667

  19. Bubble evolution and properties in homogeneous nucleation simulations.

    PubMed

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

    2014-12-01

    We analyze the properties of naturally formed nanobubbles in Lennard-Jones molecular dynamics simulations of liquid-to-vapor nucleation in the boiling and the cavitation regimes. The large computational volumes provide a realistic environment at unchanging average temperature and liquid pressure, which allows us to accurately measure properties of bubbles from their inception as stable, critically sized bubbles, to their continued growth into the constant speed regime. Bubble gas densities are up to 50% lower than the equilibrium vapor densities at the liquid temperature, yet quite close to the gas equilibrium density at the lower gas temperatures measured in the simulations: The latent heat of transformation results in bubble gas temperatures up to 25% below those of the surrounding bulk liquid. In the case of rapid bubble growth-typical for the cavitation regime-compression of the liquid outside the bubble leads to local temperature increases of up to 5%, likely significant enough to alter the surface tension as well as the local viscosity. The liquid-vapor bubble interface is thinner than expected from planar coexistence simulations by up to 50%. Bubbles near the critical size are extremely nonspherical, yet they quickly become spherical as they grow. The Rayleigh-Plesset description of bubble-growth gives good agreement in the cavitation regime. PMID:25615216

  20. Bubble evolution and properties in homogeneous nucleation simulations

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  1. Detecting vapour bubbles in simulations of metastable water

    SciTech Connect

    González, Miguel A.; Abascal, Jose L. F.; Valeriani, Chantal E-mail: cvaleriani@quim.ucm.es; Menzl, Georg; Geiger, Philipp; Dellago, Christoph E-mail: cvaleriani@quim.ucm.es; Aragones, Juan L.; Caupin, Frederic

    2014-11-14

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

  2. Detecting vapour bubbles in simulations of metastable water

    NASA Astrophysics Data System (ADS)

    González, Miguel A.; Menzl, Georg; Aragones, Juan L.; Geiger, Philipp; Caupin, Frederic; Abascal, Jose L. F.; Dellago, Christoph; Valeriani, Chantal

    2014-11-01

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

  3. Cavitation distribution within large phantom vessel and mechanical damage formed on surrounding vessel wall.

    PubMed

    Qiao, Yangzi; Yin, Hui; Li, Zhaopeng; Wan, Mingxi

    2013-11-01

    Blood vessel is one of the most important targets encountered during focused ultrasound (FU) therapy. The lasting high temperature caused by continuous FU can result in structural modification of small vessel. For the vessel with a diameter larger than 2mm, convective cooling can significantly weaken the thermal effect of FU. Meanwhile, the continued presence of ultrasound will cause repetitive cavitation and acoustic microstreaming, making comprehension of continuous wave induced cavitation effect in large vessels necessary. The Sonoluminescence (SL) method, mechanical damage observation and high-speed camera were used in this study to investigate the combination effect of ultrasound contrast agents (UCAs) and continuous FU in large phantom vessels with a diameter of 10mm without consideration of thermal effect. When the focus was positioned at the proximal wall, cylindrical hole along the acoustic axis opposite the ultrasound wave propagation direction was observed at the input power equal to or greater than 50 W. When the focus was located at the distal wall, only small tunnels can be found. The place where the cylindrical hole formed was corresponding to where bubbles gathered and emitted brilliant light near the wall. Without UCAs neither such bright SL nor cylindrical hole can be found. However, the UCAs concentration had little influence on the SL distribution and the length of cylindrical hole. The SL intensity near the proximal vessel wall and the length of the cylindrical hole both increased with the input power. It is suggested that these findings need to be considered in the large vessel therapy and UCAs usage. PMID:23623758

  4. Effect of geometrical parameters on submerged cavitation jet discharged from profiled central-body nozzle

    NASA Astrophysics Data System (ADS)

    Yang, Minguan; Xiao, Shengnan; Kang, Can; Wang, Yuli

    2013-05-01

    The flow characteristics of cavitation jets are essential issues among relevant studies. The physical properties of the jet are largely determined by the geometrical parameters of the nozzle. The structure and cavitation jets characteristics of the angular-nozzle and the self-resonating cavitation nozzle have been extensively studied, but little research is conducted in the central-body cavitation nozzle mainly because of its hard processing and the cavitation jet effect not satisfactory. In this paper, a novel central-body nozzle (a non-plunger central-body nozzle with square outlet) is studied to solve above problems. Submerged jets discharged from the novel central-body nozzle are simulated, employing the full cavitation model. The impact of nozzle configuration on jet properties is analyzed. The analysis results indicate that when central-body relative diameter keeps constant, there is an optimal contraction degree of nozzle's outlet, which can induce intense cavitation in the jet. The central-body relative diameter also affects jet profiles. In the case of large central-body relative diameter, most of the bubbles settle in the jet core. On the contrary, a smaller relative diameter makes bubbles concentrate in the interface between the jet and its surrounding fluid. Moreover, the shorter outlet part allows the cavitation zone further extend in both the axial and racial directions. The research results further consummate the study on the central-body nozzles and the correlation between cavitation jet and the structure, and elementarily reveal the mechanism of cavitation jet produced in a non-plunger novel central-body nozzle and the effect of the structure parameters on the cavitation jet, moreover, provide the theoretical basis for the optimal design of the nozzle.

  5. Dynamics of Isolated Tip Vortex Cavitation

    NASA Astrophysics Data System (ADS)

    Pennings, Pepijn; Bosschers, Johan; van Terwisga, Tom

    2014-11-01

    Performance of ship propellers and comfort levels in the surroundings are limited by various forms of cavitation. Amongst these forms tip vortex cavitation is one of the first appearing forms and is expected to be mainly responsible for the emission of broadband pressure fluctuations typically occurring between the 4th to the 7th blade passing frequency (approx. 40--70 Hz). These radiated pressure pulses are likely to excite parts of the hull structure resulting in a design compromise between efficiency and comfort. Insight is needed in the mechanism of acoustic emission from the oscillations by a tip vortex cavity. In the current experimental study the tip vortex cavity from a blade with an elliptic planform and sections based on NACA 662 - 415 with meanline a = 0 . 8 is observed using high speed shadowgraphy in combination with blade force and acoustic measurements. An analytic model describing three main cavity deformation modes is verified and used to explain the origin of a cavity eigenfrequency or ``vortex singing'' phenomenon observed by Maines and Arndt (1997) on the tip vortex cavity originating from the same blade. As no hydrodynamic sound originating from the tip vortex cavity was observed it is posed that a tip flow instability is essential for ``vortex singing.'' This research was funded by the Lloyd's Register Foundation as part of the International Institute for Cavitation Research.

  6. Cavitation pressure in water

    NASA Astrophysics Data System (ADS)

    Herbert, Eric; Balibar, Sébastien; Caupin, Frédéric

    2006-10-01

    We investigate the limiting mechanical tension (negative pressure) that liquid water can sustain before cavitation occurs. The temperature dependence of this quantity is of special interest for water, where it can be used as a probe of a postulated anomaly of its equation of state. After a brief review of previous experiments on cavitation, we describe our method which consists in focusing a high amplitude sound wave in the bulk liquid, away from any walls. We obtain highly reproducible results, allowing us to study in detail the statistics of cavitation, and to give an accurate definition of the cavitation threshold. Two independent pressure calibrations are performed. The cavitation pressure is found to increase monotonically from -26MPa at 0°C to -17MPa at 80°C . While these values lie among the most negative pressures reported in water, they are still far away from the cavitation pressure expected theoretically and reached in the experiment by Angell and his group [Zheng , Science 254, 829 (1991)] (around -120MPa at 40°C ). Possible reasons for this discrepancy are considered.

  7. Mercury Cavitation Phenomenon in Pulsed Spallation Neutron Sources

    SciTech Connect

    Futakawa, Masatoshi; Naoe, Takashi; Kawai, Masayoshi

    2008-06-24

    Innovative researches will be performed at Materials and Life Science Experimental Facility in J-PARC, in which a mercury target system will be installed as MW-class pulse spallation neutron sources. Proton beams will be injected into mercury target to induce the spallation reaction. At the moment the intense proton beam hits the target, pressure waves are generated in the mercury because of the abrupt heat deposition. The pressure waves interact with the target vessel leading to negative pressure that may cause cavitation along the vessel wall. Localized impacts by micro-jets and/or shock waves which are caused by cavitation bubble collapse impose pitting damage on the vessel wall. The pitting damage which degrades the structural integrity of target vessels is a crucial issue for high power mercury targets. Micro-gas-bubbles injection into mercury may be useful to mitigate the pressure wave and the pitting damage. The visualization of cavitation-bubble and gas-bubble collapse behaviors was carried out by using a high-speed video camera. The differences between them are recognized.

  8. Stable Multibubble Sonoluminescence Bubble Patterns

    SciTech Connect

    Posakony, Gerald J.; Greenwood, Lawrence R.; Ahmed, Salahuddin

    2006-06-30

    Multibubble standing wave patterns can be generated from a flat piezoceramic transducer element propagating into water. By adding a second transducer positioned at 90 degrees from the transducer generating the standing wave, a 3-dimensional volume of stable single bubbles can be established. Further, the addition of the second transducer stabilizes the bubble pattern so that individual bubbles may be studied. The size of the bubbles and the separation of the standing waves depend on the frequency of operation. Two transducers, operating at frequencies above 500 kHz, provided the most graphic results for the configuration used in this study. At these frequencies stable bubbles exhibit a bright sonoluminescence pattern. Whereas stable SBSL is well-known, stable MBSL has not been previously reported. This paper includes discussions of the acoustic responses, standing wave patterns, and pictorial results of the separation of individual bubble of sonoluminescence in a multibubble sonoluminescence environment.

  9. Acoustic droplet vaporization for diagnostic and therapeutic applications

    NASA Astrophysics Data System (ADS)

    Kripfgans, Oliver Daniel

    A technology, termed Acoustic Droplet Vaporization (ADV), is developed whereby superheated droplets are caused to vaporize by application of an ultrasonic field. The droplet emulsion (90% <6 um diameter) is made by mixing saline, albumin, and perfluorocarbon at high speed. It has been observed that an acoustic pressure threshold exists above which the droplets vaporize into bubbles approximately 25-times the original droplet diameter. For frequencies between 1.5 and 8 MHz, the threshold decreases from 4.5 to 0.75 MPa peak rarefactional pressure. The single pulse efficiency of ADV has been measured as 26%. This technology might be useful for tissue occlusion in cancer treatment as well as for aberration correction in acoustic imaging. To demonstrate these potential applications, gas bubbles were made in vivo in animal models by ADV. It was found that ADV could be used to temporarily form large gas bubbles (>30 um) in vivo, which at large number density occluded targeted tissues and reduced the blood flow by 34%. Alternatively, for a very sparse droplet population, gas bubbles could serve as potential point beacons for phase aberration correction given their backscatter amplitudes of 24 dB above tissue background. Other possible applications include drug delivery, indicator for cryo therapy, pressure/radiation beacons, hyperthermia, and cavitation nuclei. ADV of individual droplets showed that during acoustic irradiation, droplets perform dipole-type oscillations and that such oscillations increased in amplitude with acoustic intensity. Smaller droplets required more acoustic intensity for vaporization than larger droplets; however, independent of droplet diameter, a maximum oscillation amplitude of 1.3 um, was required. This threshold corresponds to a Reynolds number of ˜5 x 104. Vaporization started either as a spot on the axis of oscillation close to a pole of the droplet, or homogeneously throughout the droplet's imaged cross-section. It is concluded that

  10. Cavitation microstreaming and material transport around microbubbles

    NASA Astrophysics Data System (ADS)

    Manasseh, Richard; Tho, Paul; Ooi, Andrew; Petkovic-Duran, Karolina; Zhu, Yonggang

    2010-01-01

    It has been suggested that cavitation microstreaming plays a role in the therapeutic action of microbubbles driven by ultrasound, such as the sonothrombolytic and sonoporative phenomena. Microscopic particle-image velocimetry experiments are presented, showing that many different microstreaming patterns are possible around a microbubble when it is on a surface. Each pattern is associated with a particular oscillation mode of the bubble and generates a different shear stress distribution. It was found that it is possible to change the flow pattern by changing the sound frequency. Microstreaming flows around bubbles could be responsible for mixing therapeutic agents into the surrounding blood, as well as assisting sonoporative delivery of molecules across cell membranes. Appropriate tuning of the driving frequency may benefit therapies.

  11. Development of Microbubble Contrast Agents with Biochemical Recognition and Tunable Acoustic Response

    NASA Astrophysics Data System (ADS)

    Nakatsuka, Matthew Allan Masao

    Microbubbles, consisting of gas-filled cores encapsulated within phospholipid or polymer shells, are the most widely used ultrasound contrast agents in the world. Because of their acoustic impedance mismatch with surrounding tissues and compressible gaseous interiors, they have high echogenicities that allow for efficient backscatter of ultrasound. They can also generate unique harmonic frequencies when insonated near their resonance frequency, depending on physical microbubble properties such as the stiffness and thickness of the encapsulating shell. Microbubbles are used to detect a number of cardiovascular diseases, but current methodologies lack the ability to detect and distinguish small, rapidly growing abnormalities that do not produce visible blockage or slowing of blood flow. This work describes the development, formulation, and validation of microbubbles with various polymer shell architectures designed to modulate their acoustic ability. We demonstrate that the addition of a thick disulfide crosslinked, poly(acrylic acid) encapsulating shell increases a bubble's resistance to cavitation and changes its resonance frequency. Modification of this shell architecture to use hybridized DNA strands to form crosslinks between the polymer chains allows for tuning of the bubble acoustic response. When the DNA crosslinks are in place, shell stiffness is increased so the bubbles do not oscillate and acoustic signal is muted. Subsequently, when these DNA strands are displaced, partial acoustic activity is restored. By using aptamer sequences with a specific affinity towards the biomolecule thrombin as the DNA crosslinking strand, this acoustic "ON/OFF" behavior can be specifically tailored towards the presence of a specific biomarker, and produces a change in acoustic signal at concentrations of thrombin consistent with acute deep venous thrombosis. Incorporation of the emulsifying agent poly(ethylene glycol) into the encapsulating shell improves microbubble yield

  12. Relating xylem cavitation to gas exchange in cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Acoustic emissions (AEs) from xylem cavitation events are characteristic of transpiration processes. Though a body of work using AE exists with a large number of species, cotton and other agronomically important crops have either not been investigated, or limited information exists. The objective of...

  13. Freezing of Xylem Sap Without Cavitation

    PubMed Central

    Hammel, H. T.

    1967-01-01

    Freezing of stem sections and entire twigs of hemlock (Tsuga canadensis) has been demonstrated to occur without increasing the resistance to the movement of water through the frozen part after rewarming. This was interpreted to mean that freezing did not produce cavitation in the xylem sap even though A) the sap was unquestionably frozen; B) it contained dissolved gases; and C) it was under tension before freezing and after. Freezing stem sections of some other evergreen gymnosperms during the summer again produced no evidence for cavitation of the xylem sap. On the other hand, freezing stem sections of some angiosperms invariably increased the resistance to sap flow leading to wilting and death in a few hours when the sap tension was at normal daytime values at the time of freezing. These results were interpreted to mean that the bordered pits on the tracheids of gymnosperms function to isolate the freezing sap in each tracheid so that the expansion of water upon freezing not only eliminates any existing tension but also develops positive pressure in the sap. Dissolved gases frozen out of solution may then be redissolved under this positive pressure as melting occurs. As the bubbles are reduced in size by this ice pressure developed in an isolated tracheid, further pressure is applied by the surface tension of the water against air. If the bubbles are redissolved or are reduced to sufficient small size by the time the tension returns to the sap as the last ice crystals melt, then the internal pressure from surface tension in any existing small bubbles may exceed the hydrostatic tension of the melted sap and the bubbles cannot expand and will continue to dissolve. PMID:16656485

  14. Cavitation guide for control valves

    SciTech Connect

    Tullis, J.P.

    1993-04-01

    This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines six cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation.

  15. A method for real-time in vitro observation of cavitation on prosthetic heart valves.

    PubMed

    Zapanta, C M; Liszka, E G; Lamson, T C; Stinebring, D R; Deutsch, S; Geselowitz, D B; Tarbell, J M

    1994-11-01

    A method for real-time in vitro observation of cavitation on a prosthetic heart valve has been developed. Cavitation of four blood analog fluids (distilled water, aqueous glycerin, aqueous polyacrylamide, and aqueous xanthan gum) has been documented for a Medtronic/Hall prosthetic heart valve. This method employed a Penn State Electrical Ventricular Assist Device in a mock circulatory loop that was operated in a partial filling mode associated with reduced atrial filling pressure. The observations were made on a valve that was located in the mitral position, with the cavitation occurring on the inlet side after valve closure on every cycle. Stroboscopic videography was used to document the cavity life cycle. Bubble cavitation was observed on the valve occluder face. Vortex cavitation was observed at two locations in the vicinity of the valve occluder and housing. For each fluid, cavity growth and collapse occurred in less than one millisecond, which provides strong evidence that the cavitation is vaporous rather than gaseous. The cavity duration time was found to decrease with increasing atrial pressure at constant aortic pressure and beat rate. The area of cavitation was found to decrease with increasing delay time at a constant aortic pressure, atrial pressure, and beat rate. Cavitation was found to occur in each of the fluids, with the most cavitation seen in the Newtonian fluids (distilled water and aqueous glycerin). PMID:7869722

  16. A High-Speed Imaging and Modeling Study of Dendrite Fragmentation Caused by Ultrasonic Cavitation

    NASA Astrophysics Data System (ADS)

    Shu, Da; Sun, Baode; Mi, Jiawei; Grant, Patrick S.

    2012-10-01

    The dynamic behavior of ultrasound-induced cavitation bubbles and their effect on the fragmentation of dendritic grains of a solidifying succinonitrile 1 wt pct camphor organic transparent alloy have been studied experimentally using high-speed digital imaging and complementary numerical analysis of sound wave propagation, cavitation dynamics, and the velocity field in the vicinity of an imploding cavitation bubble. Real-time imaging and analysis revealed that the violent implosion of bubbles created local shock waves that could shatter dendrites nearby into small pieces in a few tens of milliseconds. These catastrophic events were effective in breaking up growing dendritic grains and creating abundant fragmented crystals that may act as embryonic grains; therefore, these events play an important role in grain refinement of metallurgical alloys.

  17. Wetting and cavitation pathways on nanodecorated surfaces.

    PubMed

    Amabili, Matteo; Lisi, Emanuele; Giacomello, Alberto; Casciola, Carlo Massimo

    2016-03-28

    In this contribution we study the wetting and nucleation of vapor bubbles on nanodecorated surfaces via free energy molecular dynamics simulations. The results shed light on the stability of superhydrophobicity in submerged surfaces with nanoscale corrugations. The re-entrant geometry of the cavities under investigation is capable of sustaining a confined vapor phase within the surface roughness (Cassie state) both for hydrophobic and hydrophilic combinations of liquid and solid. The atomistic system is of nanometric size; on this scale thermally activated events can play an important role ultimately determining the lifetime of the Cassie state. Such a superhydrophobic state can break down by full wetting of the texture at large pressures (Cassie-Wenzel transition) or by nucleating a vapor bubble at negative pressures (cavitation). Specialized rare event techniques show that several pathways for wetting and cavitation are possible, due to the complex surface geometry. The related free energy barriers are of the order of 100kBT and vary with pressure. The atomistic results are found to be in semi-quantitative accord with macroscopic capillarity theory. However, the latter is not capable of capturing the density fluctuations, which determine the destabilization of the confined liquid phase at negative pressures (liquid spinodal). PMID:26905783

  18. Bubble dielectrophoresis

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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