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1

Experimental study of temperature effect on the growth and collapse of cavitation bubbles near a rigid boundary  

NASA Astrophysics Data System (ADS)

The effect of temperature on the dynamics of a laser-induced cavitation bubble is studied experimentally. The growth and collapse of the cavitation bubble are measured by two sensitive fiber-optic sensors based on optical beam deflection (OBD). Cavitation bubble tests are performed in water at different temperatures, and the temperature ranges from freezing point (0°C) to near boiling point. The results indicate that both the maximum bubble radius and bubble lifetime are increased with the increase of temperature. During the stage of bubble rapidly collapsing in the vicinity of a solid surface, besides laser ablation effect, both the first and second liquid-jet-induced impulses are also observed. They are both increased with liquid temperature increasing, and then reach a peak, followed by a decrease. The peak appears at the temperature which is approximately the average of freezing and boiling points. The mechanism of liquid temperature influence on cavitation erosion is also discussed.

Liu, Xiu-mei; Long, Zheng; He, Jie; Li, Bei-bei; Liu, Xin-hua; Zhao, Ji-yun; Lu, Jian; Ni, Xiao-wu

2013-07-01

2

Nonlinear bubble dynamics of cavitation.  

PubMed

For cavitation clouds generated in a standing sound wave driven by an ultrasonic horn, the nonlinear acoustic wave equation governing cavitation dynamics is numerically solved together with the bubble motion equation under an approximation. This conceptual calculation can qualitatively reproduce the observed characteristics of cavitation. PMID:22400656

An, Yu

2012-01-09

3

Growth and collapse of cavitation bubbles near a curved rigid boundary  

NASA Astrophysics Data System (ADS)

Laser-induced cavitation bubbles near a curved rigid boundary are observed experimentally using high-speed photography. An image theory is applied to obtain information on global bubble motion while a boundary integral method is employed to gain a more detailed understanding of the behaviour of a liquid jet that threads a collapsing bubble, creating a toroidal bubble. Comparisons between the theory and experiment show that when a comparable sized bubble is located near a rigid boundary the bubble motion is significantly influenced by the surface curvature of the boundary, which is characterized by a parameter [zeta], giving convex walls for [zeta] < 1, concave walls for [zeta] > 1 and a flat wall when [zeta] = 1. If a boundary is slightly concave, the most pronounced migration occurs at the first bubble collapse. The velocity of a liquid jet impacting on the far side of the bubble surface tends to increase with decreasing parameter [zeta]. In the case of a convex boundary, the jet velocity is larger than that generated in the flat boundary case. Although the situation considered here is restricted to axisymmetric motion without mean flow, this result suggests that higher pressures can occur when cavitation bubbles collapse near a non-flat boundary. Bubble separation, including the pinch-off phenomenon, is observed in the final stage of the collapse of a bubble, with the oblate shape at its maximum volume attached to the surface of a convex boundary, followed by bubble splitting which is responsible for further bubble proliferation.

Tomita, Y.; Robinson, P. B.; Tong, R. P.; Blake, J. R.

2002-09-01

4

Shock Waves in Bubbly Cavitating Flows: Part I. Shock Waves in Cloud Cavitation. Part II. Bubbly Cavitating Flows Through a Converging-Diverging Nozzle  

Microsoft Academic Search

Two problems are considered in this thesis: the nonlinear dynamics of a cloud of cavitation bubbles, and bubbly cavitating flows through a converging-diverging nozzle. The focus of the first problem is to explore the characteristics of the growth and collapse of a spherical cloud of bubbles. This is typical of the transient behaviour exhibited by a bubble cloud as it

Yi-Chun Wang

1996-01-01

5

Sonoporation from Jetting Cavitation Bubbles  

Microsoft Academic Search

The fluid dynamic interaction of cavitation bubbles with adherent cells on a substrate is experimentally investigated. We find that the nonspherical collapse of bubbles near to the boundary is responsible for cell detachment. High-speed photography reveals that a wall bounded flow leads to the detachment of cells. Cells at the edge of the circular area of detachment are found to

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

2006-01-01

6

Cavitation Bubble in Shear Flow  

NASA Astrophysics Data System (ADS)

In the orifice of liquid injectors at high pressure, cavitation occurs behind the sharp corners, where a strong pressure drop is present due to quick change in the flow direction. In addition, a high level of shear is present inside the boundary layer. Therefore, it is important to understand the influence of the shear on the cavitation. In this study, the deformation of a cavitation bubble in shear and extensional flows is numerically investigated. The Navier-Stokes equations are solved to observe the three-dimensional behavior of the bubble as it grows and collapses. During the collapse phase of the bubble, two re-entrant jets are observed on two sides of the bubble due to interaction of the bubble with the background flow. Re-entrant jets with enough strength could breakup the bubble into smaller bubbles. Post processing of the results is done to cast the disturbance by the bubble on the liquid velocity field in terms of spherical harmonics. It is found that a quadrupole moment is created in addition to the monopole source. As the bubble collapses regions of high vorticity are created near the bubble interface.

Dabiri, Sadegh; Sirignano, William; Joseph, Daniel

2009-11-01

7

Vapor density measurements inside laser-induced cavitation bubbles  

NASA Astrophysics Data System (ADS)

12 Cavitation bubbles generated in water by Tm:YAG laser pulses were studied. Timer-resolved photography was applied to determine volume change with time and surface velocities of expanding and collapsing cavitation bubbles. A new method of determining vapor densities inside bubbles based on reflection changes of a fiber probe placed inside the cavitation bubble has been developed. Density distribution changes with time were measured spatially at 17 points within the bubble. Maximum bubble diameter was about 4.5 mm. Densities measured were compared to the growth of the bubble as shown by ultra fast imaging. Temporal and spatial pressure and temperature distribution will be computed from density distributions based on equilibrium values at maximum bubble extension.

Hosek, J.; Garen, W.; Neu, Walter; Schoenig, Hubert; Hopfmueller, A.

2001-01-01

8

Sonoporation from Jetting Cavitation Bubbles  

PubMed Central

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

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

2006-01-01

9

On the pressure of cavitation bubbles  

Microsoft Academic Search

Shock wave emission upon the collapse of a cavitation bubble attached to a rigid wall is investigated using high-speed photography with 200 million frames\\/s and 5ns exposure time. At a distance of 68?m from the bubble wall, the shock pressure is 1.3±0.3GPa. The shock pressure decays proportionally to r?1.5 with increasing distance from the bubble. An estimation of the peak

E. A. Brujan; T. Ikeda; Y. Matsumoto

2008-01-01

10

Cavitation Bubble in Shear Flow  

Microsoft Academic Search

In the orifice of liquid injectors at high pressure, cavitation occurs behind the sharp corners, where a strong pressure drop is present due to quick change in the flow direction. In addition, a high level of shear is present inside the boundary layer. Therefore, it is important to understand the influence of the shear on the cavitation. In this study,

Sadegh Dabiri; William Sirignano; Daniel Joseph

2009-01-01

11

Shock Waves in Bubbly Cavitating Flows: Part I. Shock Waves in Cloud Cavitation. Part II. Bubbly Cavitating Flows Through a Converging-Diverging Nozzle.  

NASA Astrophysics Data System (ADS)

Two problems are considered in this thesis: the nonlinear dynamics of a cloud of cavitation bubbles, and bubbly cavitating flows through a converging-diverging nozzle. The focus of the first problem is to explore the characteristics of the growth and collapse of a spherical cloud of bubbles. This is typical of the transient behaviour exhibited by a bubble cloud as it passes a body or the blade of a ship propeller. The simulations employ the fully nonlinear, non-barotropic, homogeneous two-phase flow equations coupled with the Rayleigh-Plesset equation for the dynamics of individual bubbles. It was found that the collapse of the cloud is accompanied by the formation of an inward propagating bubbly shock wave. The focusing of the shock is responsible for the severe noise and damage potential in cloud cavitation. The second problem investigates the nonlinear behavior of bubbly cavitating flows through a converging -diverging nozzle. Two different flow regimes are found from steady state solutions: quasi-steady and quasi-unsteady. Bifurcation occurs as the flow transitions from one regime to the other. Unsteady solutions in a period of consecutive times are also presented. These solutions are characterized by large pressure pulses changing in both magnitude and location with time downstream of the throat. The characteristics of these pulses are similar to the shock pulses of the first problem and are produced by the local violent collapse of the bubbles in the flow.

Wang, Yi-Chun

12

Nonspherical laser-induced cavitation bubbles.  

PubMed

The generation of arbitrarily shaped nonspherical laser-induced cavitation bubbles is demonstrated with a optical technique. The nonspherical bubbles are formed using laser intensity patterns shaped by a spatial light modulator using linear absorption inside a liquid gap with a thickness of 40 microm. In particular we demonstrate the dynamics of elliptic, toroidal, square, and V-shaped bubbles. The bubble dynamics is recorded with a high-speed camera at framing rates of up to 300,000 frames per second. The observed bubble evolution is compared to predictions from an axisymmetric boundary element simulation which provides good qualitative agreement. Interesting dynamic features that are observed in both the experiment and simulation include the inversion of the major and minor axis for elliptical bubbles, the rotation of the shape for square bubbles, and the formation of a unidirectional jet for V-shaped bubbles. Further we demonstrate that specific bubble shapes can either be formed directly through the intensity distribution of a single laser focus, or indirectly using secondary bubbles that either confine the central bubble or coalesce with the main bubble. The former approach provides the ability to generate in principle any complex bubble geometry. PMID:20365461

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

2010-01-14

13

Nonspherical laser-induced cavitation bubbles  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

14

Observation of Microhollows Produced by Bubble Cloud Cavitation  

NASA Astrophysics Data System (ADS)

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.

Yamakoshi, Yoshiki; Miwa, Takashi

2012-07-01

15

Cavitation Bubble Dynamics and Noise Production  

Microsoft Academic Search

This paper presents a summary of some recent observations of the interaction between individual traveling cavitation bubbles and the nearly solid surface. These reveal a complex micro-fluid-mechanics associated withThe interaction of the bubble with the boundary layer, the surface and the large pressure gradients exterior to the boundary layer which normally occur in the vicinity of a minimum pressure point.

Christopher E. Brennen

16

Behavior of laser-induced cavitation bubbles in liquid nitrogen  

NASA Astrophysics Data System (ADS)

Initial behavior and the subsequent motion of a bubble in liquid nitrogen are investigated experimentally using high-speed photography. A bubble is generated by focusing a pulsed ruby laser into liquid nitrogen at 78.0 K, changing the ambient pressures up to 253.2 kPa which corresponds to the applied pressure (or overpressure), ?p, being 147.1 kPa. When the energy level of the laser beam at the focus exceeds an irradiance threshold, for instance 5.4×1011 W/cm2 for ?p=4.9 kPa, the optical breakdown occurs in the liquid nitrogen, followed by a series of high-speed phenomena such as plasma formation, shock wave emission, and vapor bubble generation. It is found that during a very short period after the plasma formation a bubble grows nonspherically reflecting from the plasma shape, but the bubble volume itself varies with time in the same way for all cases performed in the present experiment. The liquid inertia is a dominant factor affecting the bubble growth, while the thermal effect becomes remarkable during the bubble collapse, resulting in the retardation of the bubble motion. The characteristic behavior of a laser-induced cavitation bubble in liquid nitrogen is significantly influenced by the phase change of vapor at the bubble surface as well as by the vapor pressure inside the bubble. Immediately after the bubble rebound, instabilities are amplified over the bubble surface similar to those caused in the water case.

Tomita, Y.; Tsubota, M.; Nagane, K.; An-Naka, N.

2000-11-01

17

Dynamics and noise emission of laser induced cavitation bubbles in a vortical flow field  

NASA Astrophysics Data System (ADS)

The sound produced by the collapse of discrete cavitation bubbles was examined. Laser-generated cavitation bubbles were produced in both a quiescent and a vortical flow. The sound produced by the collapse of the cavitation bubbles was recorded, and its spectral content was determined. It was found that the risetime of the sound pulse produced by the collapse of single, spherical cavitation bubbles in quiescent fluid exceeded that of the slew rate of the hydrophone, which is consistent with previously published results. It was found that, as collapsing bubbles were deformed by the vortical flow, the acoustic impulse of the bubbles was reduced. Collapsing nonspherical bubbles often created a sound pulse with a risetime that exceeded that of the hydrophone slew rate, although the acoustic impulse created by the bubbles was influenced largely by the degree to which the bubbles became nonspherical before collapse. The noise produced by the slow growth of cavitation bubbles in the vortex core was not detectable. These results have implications for the interpretation of hydrodynamic cavitation noise produced by vortex cavitation.

Oweis, Ghanem F.; Choi, Jaehyug; Ceccio, Steven L.

2004-03-01

18

Inside a collapsing bubble: sonoluminescence and the conditions during cavitation.  

PubMed

Acoustic cavitation, the growth and rapid collapse of bubbles in a liquid irradiated with ultrasound, is a unique source of energy for driving chemical reactions with sound, a process known as sonochemistry. Another consequence of acoustic cavitation is the emission of light [sonoluminescence (SL)]. Spectroscopic analyses of SL from single bubbles as well as a cloud of bubbles have revealed line and band emission, as well as an underlying continuum arising from a plasma. Application of spectrometric methods of pyrometry as well as tools of plasma diagnostics to relative line intensities, profiles, and peak positions have allowed the determination of intracavity temperatures and pressures. These studies have shown that extraordinary conditions (temperatures up to 20,000 K; pressures of several thousand bar; and heating and cooling rates of >10(12) K s(1)) are generated within an otherwise cold liquid. PMID:18393682

Suslick, Kenneth S; Flannigan, David J

2008-01-01

19

Multiscale Modeling of Cavitating Bubbly Flows  

NASA Astrophysics Data System (ADS)

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 3DYNAFS^ 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.

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

2013-03-01

20

Suppression of cavitation inception by gas bubble injection: A numerical study focusing on bubble-bubble interaction  

Microsoft Academic Search

The dynamic behavior of cavitation and gas bubbles under negative pressure has been studied numerically to evaluate the effect of gas bubble injection into a liquid on the suppression of cavitation inception. In our previous studies, it was demonstrated by direct observation that cavitation occurs in liquid mercury when mechanical impacts are imposed, and this will cause cavitation damage in

Masato Ida; Takashi Naoe; Masatoshi Futakawa

2007-01-01

21

Bubble proliferation in the cavitation field of a shock wave lithotripter  

PubMed Central

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.

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

2011-01-01

22

Luminescence Spectra of Laser-induced Cavitation Bubbles  

Microsoft Academic Search

The luminescence spectra of laser-induced cavitation bubbles near rigid boundaries are measured for various relative distances between the bubble and the boundaries. We find that the luminescence spectra of bubbles collapsing near a single boundary consist of only a blackbody continuum. Luminescence from bubbles collapsing between two parallel rigid boundaries also contains OH* emission bands similar to those found in

Emil A. Brujan

2005-01-01

23

Cavitation bubble behavior inside a liquid jet  

Microsoft Academic Search

The growth and collapse of laser-induced vapor cavities inside axisymmetric free-falling liquid water jets have been studied. Bubbles of different size are generated at various distances from the jet axis and the effects on the jet interface are recorded by means of ultrafast cinematography. The configuration is characterized by two dimensionless parameters: the bubble to jet diameter ratio delta and

Etienne Robert; Jacques Lettry; Mohamed Farhat; Peter A. Monkewitz; François Avellan

2007-01-01

24

Cavitation Bubble Nucleation by Energetic Particles  

SciTech Connect

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.

West, C.D.

1998-12-01

25

Dynamics of cavitational bubbles and design of a hydrodynamic cavitational reactor: cluster approach.  

PubMed

In the present work, a cavity cluster of predetermined size has been considered to study the bubble dynamics in the hydrodynamic cavitation reactor. The effect of different operating and system parameters on the cavitational intensity has been numerically investigated. The yield of any cavitationally induced physical/chemical transformations depends not only on the collapse pressure of the cavities but also on the active volume of cavitation within the reactor. Empirical correlations have been developed to predict the collapse pressure and the active volume of cavitation as a function of different operating parameters based on the bubble dynamics studies. Recommendations are made for designing a cavitational reactor on the basis of the proposed empirical correlations. This work is a first step towards the designing and optimization of hydrodynamic cavitational reactor with cluster approach. PMID:15848106

Kanthale, Parag M; Gogate, Parag R; Pandit, Aniruddha B; Wilhelm, Anne Marie

2005-08-01

26

Spatio-temporal dynamics of cavitation bubble clouds in a low frequency reactor: comparison between theoretical and experimental results  

Microsoft Academic Search

The propagation of ultrasound through a liquid induces the growth of inceptions and germs into bubbles. In a low frequency reactor, fragmentary transient bubbles emerge due to the acoustic driving. They violently collapse in one cycle and fragment into many smaller bubbles than in turn cavitate. This violent collapse is responsible for the mechanical effects of ultrasounds effects. The latter

G Servant; J.-L Laborde; A Hita; J.-P Caltagirone; A Gérard

2001-01-01

27

Cavitation bubble behavior inside a liquid jet  

NASA Astrophysics Data System (ADS)

The growth and collapse of laser-induced vapor cavities inside axisymmetric free-falling liquid water jets have been studied. Bubbles of different size are generated at various distances from the jet axis and the effects on the jet interface are recorded by means of ultrafast cinematography. The configuration is characterized by two dimensionless parameters: the bubble to jet diameter ratio ? and the eccentricity coefficient ? defined as the radius of bubble generation divided by the jet radius. For high ? and V, microjets and droplets are ejected from the liquid jet at speeds exceeding 100 m/s. The observed jet fragmentation shows similarities with experiments conducted on a liquid mercury jet hit by a pulsed proton beam, a candidate configuration for future accelerator based facilities.

Robert, Etienne; Lettry, Jacques; Farhat, Mohamed; Monkewitz, Peter A.; Avellan, François

2007-06-01

28

Cavitation bubble dynamics in microfluidic gaps of variable height  

NASA Astrophysics Data System (ADS)

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?m 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.

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

2009-10-01

29

Cavitation bubble dynamics in microfluidic gaps of variable height.  

PubMed

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

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

2009-10-06

30

Interaction of Laser-Produced Cavitation Bubbles with Elastic Boundaries  

Microsoft Academic Search

\\u000a The behavior of a laser-produced cavitation bubble near an elastic boundary as well as the deformation of the boundary induced\\u000a by bubble motion are investigated by means of high-speed photography. The elastic boundary, used as a tissue phantom, consists\\u000a of a polyacrylamide (PAA) gel whose elastic properties can be controlled by modifying the water content of the sample. The\\u000a bubble

Alfred Vogel; Emil A. Brujan; Peter Schmidt; Kester Nahen

31

Observation of cavitation bubbles in monoleaflet mechanical heart valves.  

PubMed

Recently, cavitation on the surface of mechanical heart valves (MHVs) has been studied as a cause of fractures occurring in implanted MHVs. In the present study, we investigated the mechanism of MHV cavitation associated with the Björk-Shiley valve and the Medtronic Hall valve in an electrohydraulic total artificial heart (EHTAH). The valves were mounted in the mitral position in the EHTAH. The valve closing motion, pressure drop measurements, and cavitation capture were employed to investigate the mechanisms for cavitation in the MHV. There are no differences in valve closing velocity between the two valves, and its value ranged from 0.53 to 1.96 m/s. The magnitude of negative pressure increased with an increase in the heart rate, and the negative pressure in the Medtronic Hall valve was greater than that in the Björk-Shiley valve. Cavitation bubbles were concentrated at the edge of the valve stop; the major cause of these cavitation bubbles was determined to be the squeeze flow. The formation of cavitation bubbles depended on the valve closing velocity and the valve leaflet geometry. From the viewpoint of squeeze flow, the Björk-Shiley valve was less likely to cause blood cell damage than the Medtronic Hall valve in our EHTAH. PMID:15558332

Lee, Hwansung; Tsukiya, Tomonori; Homma, Akihiko; Kamimura, Tadayuki; Takewa, Yoshiaki; Tatsumi, Eisuke; Taenaka, Yoshiyuki; Takano, Hisateru; Kitamura, Soichiro

2004-01-01

32

The effect of dissolve gas concentration in the initial growth stage of multi cavitation bubbles. Differences between vacuum degassing and ultrasound degassing.  

PubMed

The sonochemical luminescence intensity from luminol was measured at a sampling rate of several kilohertz. This was noted at three different periods: first, the latent period in which no light emission occurs at all; second, the increased emission period from the start of light emission to the time when a steady state is reached; and third, the steady state period in which light emission occurs at the steady state value. When irradiated with ultrasound of different intensities, the times of the latent period and increased emission period are shorter for higher ultrasound intensities. To know how the dissolved oxygen content is involved in early-stage cavitation growth, an experiment was conducted using solutions with varying dissolved oxygen contents from 100% to 37%. For dissolved air content of 50% or less, it was found that the latent period was 30 times longer in a saturated condition. It was also found that the increased emission period was 10 times longer. However, the emission intensity in the steady state did not change at all even when the initial dissolved gas concentration of the sample was changed. From this, it was found that the reuse of collapsed bubbles takes place efficiently in the steady state. Dissolved oxygen was reduced by the use of a vacuum pump and by the degassing action of ultrasound, and it was discovered that the behavior of transient emission differed for the two ways of degassing. PMID:17681864

Yanagida, Hirotaka

2007-06-27

33

Luminescence Spectra of Laser-induced Cavitation Bubbles  

NASA Astrophysics Data System (ADS)

The luminescence spectra of laser-induced cavitation bubbles near rigid boundaries are measured for various relative distances between the bubble and the boundaries. We find that the luminescence spectra of bubbles collapsing near a single boundary consist of only a blackbody continuum. Luminescence from bubbles collapsing between two parallel rigid boundaries also contains OH* emission bands similar to those found in multi-bubble sonoluminescence. In both cases, the bubble interior temperature deduced from blackbody fits decreases with the distance between bubble and boundary. The shape instabilities of the collapse near a boundary and the consequent presence of high-velocity jets inside the bubble at its minimum volume will be discussed in connection with the generation of the OH* radicals.

Brujan, Emil A.

2005-03-01

34

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

NASA Astrophysics Data System (ADS)

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. No significant bubble translation was observed or calculated. The data support the conclusion that cavitation plays an important role in efficient stone comminution and hemolysis. The dual-pulse lithotripter, because of its localized and intensified cavitation field, yields the promise of improved stone comminution efficiency, reduced tissue damage, and accelerated treatment.

Sokolov, Dahlia L.

2002-08-01

35

Controlled permeation of cell membrane by single bubble acoustic cavitation  

PubMed Central

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, acoustic, 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 (7.44 MHz) 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 (1.5 MHz) ultrasound pulse (duration 13.3 or 40 µs) 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 radius of the pores was estimated from the measured TMC to be 0.106 ± 0.032 µm (n = 70) for acoustic pressure of 1.5 MPa (duration 13.3 µs), and increased to 0.171 ± 0.030 µm (n = 125) for acoustic pressure of 1.7 MPa and to 0.182 ± 0.052 µm (n=112) for a pulse duration of 40 µs (1.5 MPa). These results from controlled cell membrane permeation by cavitation of single bubbles revealed insights and key factors affecting sonoporation at the single cell level.

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

2011-01-01

36

A new approach to nucleation of cavitation bubbles at chemically modified surfaces.  

PubMed

Cavitation at the solid surface normally begins with nucleation, in which defects or assembled molecules located at a liquid-solid interface act as nucleation centers and are actively involved in the evolution of cavitation bubbles. Here, we propose a simple approach to evaluate the behavior of cavitation bubbles formed under high intensity ultrasound (20 kHz, 51.3 W cm(-2)) at solid surfaces, based on sonication of patterned substrates with a small roughness (less than 3 nm) and controllable surface energy. A mixture of octadecylphosphonic acid (ODTA) and octadecanethiol (ODT) was stamped on the Si wafer coated with different thicknesses of an aluminium layer (20-500 nm). We investigated the growth mechanism of cavitation bubble nuclei and the evolution of individual pits (defects) formed under sonication on the modified surface. A new activation behavior as a function of Al thickness, sonication time, ultrasonic power and temperature is reported. In this process cooperativity is introduced, as initially formed pits further reduce the energy to form bubbles. Furthermore, cavitation on the patterns is a controllable process, where up to 40-50 min of sonication time only the hydrophobic areas are active nucleation sites. This study provides a convincing proof of our theoretical approach on nucleation. PMID:21448506

Belova, Valentina; Shchukin, Dmitry G; Gorin, Dmitry A; Kopyshev, Alexey; Möhwald, Helmuth

2011-03-29

37

Luminescence from acoustic-driven laser-induced cavitation bubbles  

PubMed

The influence of a continuous sound field on the first oscillation cycle and on the cavitation luminescence of a transient laser-induced bubble is investigated experimentally. The variation of the collapse phase is predicted with a simple numerical model and compared with experiment. Bubble dynamics is mainly influenced by three parameters: the phase of bubble generation, the size of the bubble, and the amplitude of the sound field. The experimentally found enhancement and reduction of the luminescence is discussed and several suggestions are made for further boosting of the collapse strength. PMID:11046430

Ohl

2000-02-01

38

Luminescence from acoustic-driven laser-induced cavitation bubbles  

NASA Astrophysics Data System (ADS)

The influence of a continuous sound field on the first oscillation cycle and on the cavitation luminescence of a transient laser-induced bubble is investigated experimentally. The variation of the collapse phase is predicted with a simple numerical model and compared with experiment. Bubble dynamics is mainly influenced by three parameters: the phase of bubble generation, the size of the bubble, and the amplitude of the sound field. The experimentally found enhancement and reduction of the luminescence is discussed and several suggestions are made for further boosting of the collapse strength.

Ohl, Claus-Dieter

2000-02-01

39

Cavitation erosion by single laser-produced bubbles  

NASA Astrophysics Data System (ADS)

In order to elucidate the mechanism of cavitation erosion, the dynamics of a single laser-generated cavitation bubble in water and the resulting surface damage on a flat metal specimen are investigated in detail. The characteristic effects of bubble dynamics, in particular the formation of a high-speed liquid jet and the emission of shock waves at the moment of collapse are recorded with high-speed photography with framing rates of up to one million frames/s. Damage is observed when the bubble is generated at a distance less than twice its maximum radius from a solid boundary ([gamma]=2, where [gamma]=s/Rmax, s is the distance between the boundary and the bubble centre at the moment of formation and Rmax is the maximum bubble radius). The impact of the jet contributes to the damage only at small initial distances ([gamma][less-than-or-eq, slant]0.7). In this region, the impact velocity rises to 83 m s[minus sign]1, corresponding to a water hammer pressure of about 0.1 GPa, whereas at [gamma]>1, the impact velocity is smaller than 25 m s[minus sign]1. The largest erosive force is caused by the collapse of a bubble in direct contact with the boundary, where pressures of up to several GPa act on the material surface. Therefore, it is essential for the damaging effect that bubbles are accelerated towards the boundary during the collapse phases due to Bjerknes forces. The bubble touches the boundary at the moment of second collapse when [gamma]<2 and at the moment of first collapse when [gamma]<1. Indentations on an aluminium specimen are found at the contact locations of the collapsing bubble. In the range [gamma]=1.7 to 2, where the bubble collapses mainly down to a single point, one pit below the bubble centre is observed. At [gamma][less-than-or-eq, slant]1.7, the bubble shape has become toroidal, induced by the jet flow through the bubble centre. Corresponding to the decay of this bubble torus into multiple tiny bubbles each collapsing separately along the circumference of the torus, the observed damage is circular as well. Bubbles in the ranges [gamma][less-than-or-eq, slant]0.3 and [gamma]=1.2 to 1.4 caused the greatest damage. The overall diameter of the damaged area is found to scale with the maximum bubble radius. Owing to the possibility of generating thousands of nearly identical bubbles, the cavitation resistance of even hard steel specimens can be tested.

Philipp, A.; Lauterborn, W.

1998-04-01

40

Interaction of laser-induced cavitation bubbles with composite surfaces  

NASA Astrophysics Data System (ADS)

The dynamics of a laser-induced cavitation bubble near a composite surface, consisting of either a thin rigid plate glued on a foam rubber (composite surface A) or a deformable rubber plate glued on a foam rubber (composite surface B), was investigated experimentally with high-speed photography. To understand the interaction between a cavitation bubble and a composite surface, the dynamic properties of the composite surfaces were measured with a modal analysis by providing a maximum frequency to 5 kHz, since the period of the bubble motion with the radius of 1 mm is about 200 ?s. It was found that bubble migration was significantly influenced by the dynamic property of composite surfaces, showing a range of response between the free surface and rigid boundary cases. For one of the composite surfaces with a deformable rubber, bubble splitting was generated for ?<1.1, where ?=L/Rmax with L being the initial bubble location and Rmax the maximum bubble radius. A neutral bubble collapse occurred at a specified bubble location defined as ?N that was fairly correlated with the compliance, Gn, of the composite surfaces. The value of ?N decreased with increasing Gn.

Tomita, Y.; Kodama, T.

2003-09-01

41

Collapse of cavitation bubbles in blood  

Microsoft Academic Search

The behaviour of a single bubble in blood and in water is studied by using a non-Newtonian model of spherical bubble dynamics. This model considers the compressibility of the liquid surrounding the bubble, the shear-thinning characteristic of liquid viscosity, liquid density and surface tension. It was found that, for values of the maximum bubble radius larger than 10-1 mm, the

E.-A. Brujan

2000-01-01

42

Collapse of cavitation bubbles in blood  

Microsoft Academic Search

The behaviour of a single bubble in blood and in water is studied by using a non-Newtonian model of spherical bubble dynamics. This model considers the compressibility of the liquid surrounding the bubble, the shear-thinning characteristic of liquid viscosity, liquid density and surface tension. It was found that, for values of the maximum bubble radius larger than 10?1 mm, the

E.-A. Brujan

2000-01-01

43

Bubbly Cavitating Flow Generation and Investigation of Its Erosional Nature for Biomedical Applications  

Microsoft Academic Search

This paper presents a study that investigates the de- structive energy output resulting from hydrodynamic bubbly cav- itation in microchannels and its potential use in biomedical appli- cations. The research performed in this study includes results from bubbly cavitation experiments and findings showing the destruc- tive effects of bubbly cavitating flow on selected solid specimens and live cells. The bubbles

Ali Ko?ar; Muhsincan ?e?en; Ozlem Oral; Zeynep Itah; Devrim Gozuacik

2011-01-01

44

Trapping cavitation bubbles with a self-focused laser beam  

NASA Astrophysics Data System (ADS)

We observed that laser-induced cavitation bubbles in water can be trapped in a self-focused laser beam. Both optical imaging and acoustic detection have been utilized to confirm bubble trapping. Transverse and longitudinal trapping forces were measured to be as large as 87 and 11 pN, respectively. This result is contrary to conventional wisdom, since the mechanism of trapping in conventional optical tweezers implies that a low-index particle (a bubble being the limiting case) should be antitrapped.

Ye, Jing Yong; Chang, Guoqing; Norris, Theodore B.; Tse, Christine; Zohdy, Marwa J.; Hollman, Kyle W.; O'Donnell, Matthew; Baker, James R., Jr.

2004-09-01

45

Trapping cavitation bubbles with a self-focused laser beam.  

PubMed

We observed that laser-induced cavitation bubbles in water can be trapped in a self-focused laser beam. Both optical imaging and acoustic detection have been utilized to confirm bubble trapping. Transverse and longitudinal trapping forces were measured to be as large as 87 and 11 pN, respectively. This result is contrary to conventional wisdom, since the mechanism of trapping in conventional optical tweezers implies that a low-index particle (a bubble being the limiting case) should be antitrapped. PMID:15460881

Ye, Jing Yong; Chang, Guoqing; Norris, Theodore B; Tse, Christine; Zohdy, Marwa J; Hollman, Kyle W; O'Donnell, Matthew; Baker, James R

2004-09-15

46

The liquid micro-jet from laser induced cavitation bubbles.  

NASA Astrophysics Data System (ADS)

A vaporous cavitation bubble grows spherically in an infinite medium to a maximum radius, collapses in a spherical manner to a minimum volume, and then may rebound one or more times or disintegrate. When the bubble collapses above a solid boundary, the asymmetry of the surrounding flow field will cause the upper bubble surface to cave in, resulting in a fast liquid jet that penetrates its lower surface and continues towards the solid boundary. This fast jet formation is one perceived mechanism for cavitation damage in hydro-machinery. If a hole is intentionally drilled in the solid boundary underneath the collapsing bubble, the fast micro-jet can continue its path and be cultivated for a variety of applications such as micro surgery of soft tissue. In this study, cavitation bubbles are generated by focusing the pulsed IR beam from an Nd-YAG laser above a solid surface. The forming liquid micro-jet is investigated in the cases of blank and drilled solid boundaries.

Abboud, Jack; Oweis, Ghanem

2007-11-01

47

Dynamics of Laser-Induced Cavitation Bubble near Solid Boundary  

NASA Astrophysics Data System (ADS)

The dynamics of a laser-induced cavitation bubble created near solid boundary is investigated using a new force sensor together with a hydrophone. The experimental results indicate that liquid-jet formation and acoustic transient emission are general features of bubble dynamics; liquid-jet formation occurs earlier than that of the acoustic transient. A comparison of the liquid jet energy and acoustic energy reveals that the acoustic transient, rather than the liquid jet, plays a vital role in the damping mechanism during the second collapse for ?=0.75 (?=L/Rmax, where Rmax being the maximum bubble radius and L denoting the distance of the cavity inception from the boundary); moreover, the amplitudes of acoustic transients and liquid jet versus the nondimensional distance ? are also derived, which are valuable in hydraulic cavitation, laser lithotripsy and laser ophthalmology.

Zhao, Rui; Liang, Zhong-cheng; Xu, Rong-qing; Lu, Jian; Ni, Xiao-wu

2008-07-01

48

Collapse of cavitation bubbles in blood  

NASA Astrophysics Data System (ADS)

The behaviour of a single bubble in blood and in water is studied by using a non-Newtonian model of spherical bubble dynamics. This model considers the compressibility of the liquid surrounding the bubble, the shear-thinning characteristic of liquid viscosity, liquid density and surface tension. It was found that, for values of the maximum bubble radius larger than 10-1 mm, the collapse of a bubble in a constant pressure field in blood is more violent than in water. It suggests that the amount of collateral damage of the biological tissue induced by bubble collapse during high-speed rotational angioplasty and laser-induced angioplasty can be underestimated by experiments in vitro using water as ambient liquid.

Brujan, E.-A.

2000-04-01

49

Single cavitation bubble generation and observation of the bubble collapse flow induced by a pressure wave  

Microsoft Academic Search

This study utilizes a U-shape platform device to generate a single cavitation bubble for a detailed analysis of the flow field\\u000a characteristics and the cause of the counter jet during the process of bubble collapse caused by sending a pressure wave.\\u000a A high speed camera is used to record the flow field of the bubble collapse at different distances from

Sheng-Hsueh Yang; Shenq-Yuh Jaw; Keh-Chia Yeh

2009-01-01

50

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

PubMed

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

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

2000-10-01

51

Effect of Gas Content on the Oscillation of a Laser-Induced Cavitation Bubble  

NASA Astrophysics Data System (ADS)

The oscillation of a cavitation bubble and the effect of gas content inside a cavity on the bubble motion are investigated by theory and experiment. Based on the cavitation model, the numerical study yields the gas content dependence of the amplitude and duration of the bubble oscillation in liquids. In experiment, the temporal oscillation of a single laser-induced cavitation bubble is obtained by means of a sensitive fiber-optic sensor based on optical beam deflection. The characteristic bubble parameters are determined, including the maximum (minimum) radii, oscillation duration and bubble energy, which all decrease with the oscillation. Besides, combining the cavitation theory with experimental data, the variation of gas content within the bubble during each oscillation is estimated, which increases with the oscillation cycle. Our results reveal the competitive interplay of the bubble energy and gas content during the bubble motion and the bubble energy in effect outweighs the latter.

Chen, X.; Xu, R. Q.; Yang, B.; Lu, J.; Ni, X. W.

52

On the Formation of Centered Shock Waves in Gas Bubbles under the Conditions of Acoustic Cavitation  

Microsoft Academic Search

The possibility of the formation of centered shock waves in collapsing gas bubbles under the conditions of acoustic cavitation is considered. In this case, the overturning of the front of compression waves occurs at the instant the waves reach the center of the cavitation bubble, resulting in the highest possible temperatures and pressures inside the bubble. Examination of the magnetohydrodynamic

V. S. Malyshevskii

2004-01-01

53

Interaction dynamics of spatially separated cavitation bubbles in water  

NASA Astrophysics Data System (ADS)

We present a high-speed photographic analysis of the interaction of cavitation bubbles generated in two spatially separated regions by femtosecond laser-induced optical breakdown in water. Depending on the relative energies of the femtosecond laser pulses and their spatial separation, different kinds of interactions, such as a flattening and deformation of the bubbles, asymmetric water flows, and jet formation were observed. The results presented have a strong impact on understanding and optimizing the cutting effect of modern femtosecond lasers with high repetition rates (>1 MHz).

Tinne, Nadine; Schumacher, Silvia; Nuzzo, Valeria; Arnold, Cord L.; Lubatschowski, Holger; Ripken, Tammo

2010-11-01

54

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

Microsoft Academic Search

The use of high frequency ultrasound in chemical systems is of major interest to optimize chemical procedures. Characterization of an open air 477kHz 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

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

2000-01-01

55

Interactions of inertial cavitation bubbles with stratum corneum lipid bilayers during low-frequency sonophoresis.  

PubMed

Interactions of acoustic cavitation bubbles with biological tissues play an important role in biomedical applications of ultrasound. Acoustic cavitation plays a particularly important role in enhancing transdermal transport of macromolecules, thereby offering a noninvasive mode of drug delivery (sonophoresis). Ultrasound-enhanced transdermal transport is mediated by inertial cavitation, where collapses of cavitation bubbles microscopically disrupt the lipid bilayers of the stratum corneum. In this study, we describe a theoretical analysis of the interactions of cavitation bubbles with the stratum corneum lipid bilayers. Three modes of bubble-stratum corneum interactions including shock wave emission, microjet penetration into the stratum corneum, and impact of microjet on the stratum corneum are considered. By relating the mechanical effects of these events on the stratum corneum structure, the relationship between the number of cavitation events and collapse pressures with experimentally measured increase in skin permeability was established. Theoretical predictions were compared to experimentally measured parameters of cavitation events. PMID:14645045

Tezel, Ahmet; Mitragotri, Samir

2003-12-01

56

Interactions of Inertial Cavitation Bubbles with Stratum Corneum Lipid Bilayers during Low-Frequency Sonophoresis  

PubMed Central

Interactions of acoustic cavitation bubbles with biological tissues play an important role in biomedical applications of ultrasound. Acoustic cavitation plays a particularly important role in enhancing transdermal transport of macromolecules, thereby offering a noninvasive mode of drug delivery (sonophoresis). Ultrasound-enhanced transdermal transport is mediated by inertial cavitation, where collapses of cavitation bubbles microscopically disrupt the lipid bilayers of the stratum corneum. In this study, we describe a theoretical analysis of the interactions of cavitation bubbles with the stratum corneum lipid bilayers. Three modes of bubble-stratum corneum interactions including shock wave emission, microjet penetration into the stratum corneum, and impact of microjet on the stratum corneum are considered. By relating the mechanical effects of these events on the stratum corneum structure, the relationship between the number of cavitation events and collapse pressures with experimentally measured increase in skin permeability was established. Theoretical predictions were compared to experimentally measured parameters of cavitation events.

Tezel, Ahmet; Mitragotri, Samir

2003-01-01

57

Numerical Computation of Shock Waves in a Spherical Cloud of Cavitation Bubbles  

Microsoft Academic Search

The nonlinear dynamics of a spherical cloud of cavitation bubbles have been simulated numerically in order to learn more about the physical phenomena occurring in cloud cavitation. A finite cloud of nuclei is subject to a de- crease in the ambient pressure which causes the cloud to cavitate. A subsequent pressure recovery then causes the cloud to collapse. This is

Yi-Chun Wang; Christopher E. Brennen

1999-01-01

58

Luminescence spectra of laser-induced cavitation bubbles near rigid boundaries  

Microsoft Academic Search

The luminescence spectra of laser-induced cavitation bubbles near rigid boundaries are measured for various relative distances between the bubble and the boundaries. We find that the luminescence spectra of bubbles collapsing near a single boundary consist only of a blackbody continuum. Luminescence from bubbles collapsing between two parallel rigid boundaries contains OH- emission bands similar to those found in multibubble

Emil A. Brujan; Gary A. Williams

2005-01-01

59

The Art, Craft and Science of Modelling Jet Impact in a Collapsing Cavitation Bubble  

Microsoft Academic Search

One of the key characteristics of the asymmetric collapse of a cavitation bubble near a rigid boundary is the development of a high speed liquid jet that penetrates the interior of the bubble, impacting on the other side to yield a toroidal bubble. After the formation of the toroidal bubble, a vigorous splash may occur that can lead to pressures

J. R. Blake; Y. Tomita; R. P. Tong

1997-01-01

60

[Key problems in using ultrasonic cavitating bubble as a gene or drug vector].  

PubMed

Ultrasound, serveing as an oscillating source, can induce cavitation in liquids; and the bubble produced in this process is a very promising kind of vector for gene delivery and drug target release, owing to its unique properties. This article involves the cavitation mechanism, the control over sonoporation, and the influence of ultrasound contrast agent. The status quo of research and the challenges encountered are discussed. This overview is devoted to providing a theoretical basis for clinical use of cavitating bubble vector. PMID:19947504

Zhang, Yiwei; Chen, Tiejun; Lin, Shuhong

2009-10-01

61

High-speed photographic study of the interaction of cavitation bubbles with a boundary  

Microsoft Academic Search

This paper re-examines the collapse of a single cavitation bubble in front of a boundary. A range of different diameter cavitation bubbles were generated by focusing a pulse from a Q-switched Nd:YAG laser of varying energy. High speed shadow photography and Schlieren techniques are used to visualize the collapse process and the resulting bubble deformation at a distance s from

W. P. Schiffers; S. J. Shaw; Y. H. Jin; David C. Emmony

1997-01-01

62

On the temporal stability of steady-state quasi-1D bubbly cavitating nozzle flow solutions  

Microsoft Academic Search

Quasi-1D unsteady bubbly cavitating nozzle flows are considered by employing a homogeneous bubbly liquid flow model, where the non-linear dynamics of cavitating bubbles is described by a modified Rayleigh-Plesset equation. The various damping mechanisms are considered by a single damping coefficient lumping them together in the form of viscous dissipation and by assuming a polytropic law for the expansion and

Senay Pasinlioglu; Can F. Delale; Gunter H. Schnerr

2009-01-01

63

[Cavitation and boiling of bubbles at the focal region during high intensity focused ultrasound exposure].  

PubMed

High intensity focused ultrasound (HIFU) is a very complex transient process and can cause tissue coagulation necrosis. The cavitation and boiling behaviour of bubbles in the focal region play very important roles throughout an injury process. This paper reviews the research done by domestic and foreign scholars on behaviours of bubbles in HIFU irradiation process and summarizes in the focal region bubble cavitation and boiling generation, related detective means and relationships with hyperecho, temperature rise of the focus and injury shape. PMID:23198445

Zhong, Mingsong; Ai, Huijian; Li, Faqi

2012-10-01

64

Sonoporation of suspension cells with a single cavitation bubble in a microfluidic confinement.  

PubMed

We report here the sonoporation of HL60 (human promyelocytic leukemia) suspension cells in a microfluidic confinement using a single laser-induced cavitation bubble. Cavitation bubbles can induce membrane poration of cells located in their close vicinity. Membrane integrity of suspension cells placed in a microfluidic chamber is probed through either the calcein release out of calcein-loaded cells or the uptake of trypan blue. Cells that are located farther away than four times Rmax (maximum bubble radius) from the cavitation bubble center remain fully unaffected, while cells closer than 0.75 Rmax become porated with a probability of >75%. These results enable us to define a distance of 0.75 Rmax as a critical interaction distance of the cavitation bubble with HL60 suspension cells. These experiments suggest that flow-induced poration of suspension cells is applicable in lab-on-a-chip systems, and this might be an interesting alternative to electroporation. PMID:18030385

Gac, Séverine Le; Zwaan, Ed; van den Berg, Albert; Ohl, Claus-Dieter

2007-09-14

65

Single cavitation bubble dynamics in micro-channels near free and rigid boundaries  

NASA Astrophysics Data System (ADS)

It is well known that cavitation bubbles jet towards a rigid interface and away from a free surface. Yet, cavitation bubbles between a free and a rigid boundary show more complex deformation and the direction of jetting depends on a delicate interplay of attractive and repulsive forces. We re-investigate this regime in the context of microfluidics. We use laser-induced cavitation bubbles and high-speed photography to study their dynamics. The cavitation bubble is located between two channel walls (500 ?m apart) and a free surface. We vary the distance of both the free interface and the bubble from the walls. In most of the parameter space we observe the expected dynamics. Yet, between these scenarios we find jetting directed towards the liquid-air interface as well as axisymmetric collapse without a jet. Additionally, we find complex dynamics of the free interface.

Enriquez, Oscar; van der Meer, Devaraj; Lohse, Detlef; Ohl, Claus-Dieter

2010-11-01

66

Control of Plasma and Cavitation Bubble in Liquid-Phase Laser Ablation Using Supersonic Waves  

NASA Astrophysics Data System (ADS)

We examined the effects of a supersonic wave on laser-induced plasma and ablation-induced cavitation bubbles in liquid-phase laser ablation. The effect of the supersonic wave on laser-induced plasma was the change in the optical emission intensity. We observed an intense optical emission when the ablation target was irradiated with a laser pulse at a negative phase of the sound pressure of the supersonic wave. The effect of the supersonic wave on ablation-induced cavitation bubbles was the repetitive formation and collapse of the bubbles at the same frequency as the supersonic wave. The ablation-induced cavitation bubbles served as a ``seed'', and the repetitive formation and collapse of the cavitation bubbles were driven by the sound pressure of the supersonic wave.

Takada, Noriharu; Fujikawa, Akinori; Sasaki, Koichi

2011-12-01

67

Bubbles slowing down economic growth  

Microsoft Academic Search

To analyze the effects of bubbles on economic growth, we study a three-period life overlapping generations economy with accumulation of physical and human capital, using an extension of Azariadis and Drazen (1990). We characterize the balanced growth paths and the local dynamics both in the model without bubbles and with bubbles. Tirole (1985)'s study of bubbles is extended to the

Philippe MICHEL

1992-01-01

68

Resonance fluorescence spectroscopy in laser-induced cavitation bubbles.  

PubMed

Laser-induced breakdown spectroscopy (LIBS) in liquids using a double-pulse Q-switched Nd:YAG laser system has provided reliable results that give trace detection limits in water. Resonant laser excitation has been added to enhance detection sensitivity. A primary laser pulse (at 532 nm), transmitted via an optical fiber, induces a cavitation bubble and shockwave at a target immersed in a 10 mg l(-1)-100 mg l(-1) indium (In) water suspension. The low-pressure rear of the shockwave induces bubble expansion and a resulting reduction in cavity pressure as it extends away from the target. Shortly before the maximum diameter is expected, a secondary laser pulse (also at 532 nm) is fed into the bubble in order to reduce quenching processes. The plasma field generated is then resonantly excited by a fiber-guided dye laser beam to increase detection selectivity. The resulting resonance fluorescence emission is optically detected and processed by an intensified optical multichannel analyzer system. PMID:16520936

Koch, Sandra; Garen, Walter; Neu, Walter; Reuter, Rainer

2006-03-07

69

Evidence for nuclear emissions during neutron seeded acoustic bubble cavitation  

NASA Astrophysics Data System (ADS)

In cavitation experiments with deuterated acetone, statistically significant tritium decay activity above background levels was detected. In addition, evidence for statistically significant neutron emissions near 2.5 MeV was also observed, as would be expected for deuterium-deuterium fusion. Control experiments with normal acetone did not result in tritium activity or neutron emissions. Hydrodynamic shock code simulations supported the observed data and indicated compressed, hot (106-107 K) bubble implosion conditions, as required for thermonuclear fusion reactions. Separate experiments with additional fluids are under way and results appear to support those observed with acetone. Scalability potential to higher yields, as well as evidence for neutron-tritium branching ratios are presented.

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

2002-11-01

70

Ultrasound measurements of cavitation bubble radius for femtosecond laser-induced breakdown in water  

PubMed Central

A recently developed ultrasound technique is evaluated by measuring the behavior of a cavitation bubble that is induced in water by a femtosecond laser pulse. The passive acoustic emission during optical breakdown is used to estimate the location of the cavitation bubble’s origin. In turn, the position of the bubble wall is defined based on the active ultrasonic pulse-echo signal. The results suggest that the developed ultrasound technique can be used for quantitative measurements of femtosecond laser-induced microbubbles.

Aglyamov, Salavat R.; Karpiouk, Andrei B.; Bourgeois, Frederic; Ben-Yakar, Adela; Emelianov, Stanislav Y.

2008-01-01

71

LES numerical simulation of cavitation Bubble shedding on ALE 25 and ALE 15 hydrofoils  

Microsoft Academic Search

A cavitation calculation scheme is developed and applied to ALE 15 and ALE 25 hydrofoils, based on the Bubble Two-phase Flow (BTF) cavity model with a Large Eddy Simulation (LES) methodology. The Navier-Stokes equations including cavitation bubble clusters are solved through the finite-volume approach with a time-marching scheme. Simulations are carried out in a 3-D field with a hydrofoil ALE

De-min LIU; Shu-hong LIU; Yu-lin WU; Hong-yuan XU

2009-01-01

72

Spatio-temporal dynamics of cavitation bubble clouds in a low frequency reactor: comparison between theoretical and experimental results.  

PubMed

The propagation of ultrasound through a liquid induces the growth of inceptions and germs into bubbles. In a low frequency reactor, fragmentary transient bubbles emerge due to the acoustic driving. They violently collapse in one cycle and fragment into many smaller bubbles than in turn cavitate. This violent collapse is responsible for the mechanical effects of ultrasounds effects. The latter bubbles gather in a ball-shaped cloud and migrate to pressure antinodes. During their migration, their nonexplosive collapses mainly contribute to activate chemical reactions by producing OH. radicals. Mathematical modelling is performed as a new approach to predict the bubbles field. Through numerical simulation, we determinate emergence sites of mechanically active cavitation bubbles. Calculus are compared with aluminium foil degradation. The modelling of bubble migration allow us to have an insight on the privileged sites of the chemical reactions. Validation of the modelling is made through direct comparison with chemiluminescence photo. All experiments and computations are made in a 28.2 kHz sonoreactor. PMID:11441594

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

2001-07-01

73

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

NASA Astrophysics Data System (ADS)

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 (106 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.

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

2004-04-01

74

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

NASA Astrophysics Data System (ADS)

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.

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

2010-09-01

75

The final stage of the collapse of a cavitation bubble close to a rigid boundary  

NASA Astrophysics Data System (ADS)

The final stage of the collapse of a laser-produced cavitation bubble close to a rigid boundary is studied both experimentally and theoretically. The temporal evolution of the liquid jet developed during bubble collapse, shock wave emission and the behavior of the ``splash'' effect are investigated by using high-speed photography with up to 5 million frames/second. For a full understanding of the bubble-boundary interaction, numerical simulations are conducted by using a boundary integral method with an incompressible liquid impact model. The results of the numerical calculations provided the pressure contours and the velocity vectors in the liquid surrounding the bubble as well as the bubble profiles. The comparisons between experimental and numerical data are favorable with regard to both bubble shape history and translational motion of the bubble. The results are discussed with respect to the mechanism of cavitation erosion.

Brujan, E. A.; Keen, G. S.; Vogel, A.; Blake, J. R.

2002-01-01

76

[Quantitative evaluation of cavitation bubble fields induced by lithotripter shock waves].  

PubMed

Extracorporeal shock wave lithotripsy is the world-wide standard therapy for renal stones. The rare-faction phase of the shock wave can induce cavitation within the body. Cavitation contributes to stone disintegration but also to medical side effects. The aim of this study was to evaluate the spatial and size distribution of the cavitation bubble fields. To this end, the bubble fields were photographed digitally and evaluated automatically by image processing. The influence of various medium (water) and shock wave parameters was investigated. Water purity, i.e. the number of cavitation nuclei, was the most critical medium parameter which has to be controlled. At oxygen levels higher than 4 mg/l, cavitation increased rapidly when high shock wave frequencies of 2 Hz were used. PMID:12465304

Luderer, T; Bohris, C; Bellemann, M E

2002-01-01

77

Dynamics of laser-induced cavitation bubbles near an elastic boundary used as a tissue phantom  

Microsoft Academic Search

The behavior of a laser-produced cavitation bubble near an elastic boundary as well as the deformation of the boundary induced by bubble motion are investigated by means of high-speed photography and acoustic measurements. The elastic boundary, used as a tissue phantom, consists of a polyacrylamide (PAA) gel whose elastic properties can be controlled, by modifying the water content of the

Emil-Alexandru Brujan; Kester Nahen; Peter Schmidt; Alfred Vogel

2000-01-01

78

Dynamics of laser-induced cavitation bubbles near an elastic boundary  

Microsoft Academic Search

The interaction of a laser-induced cavitation bubble with an elastic boundary and its dependence on the distance between bubble and boundary are investigated ex- perimentally. The elastic boundary consists of a transparent polyacrylamide (PAA) gel with 80% water concentration with elastic modulus E =0 :25 MPa. At this E- value, the deformation and rebound of the boundary is very pronounced

PETER S CHMIDT; ALFRED V OGEL

2001-01-01

79

Manipulation and Microrheology of Carbon Nanotubes with Laser-Induced Cavitation Bubbles  

Microsoft Academic Search

Multiwalled carbon nanotubes (MWCNT) are exposed to a transient and strong liquid jet flow created by a pair of differently sized laser-induced cavitation bubbles. The position and size of the bubbles are controlled with a spatial light modulator within a 15mum thick liquid gap. Depending on the tube's position with respect to this jet flow, rotation, translation, and a bending

P. A. Quinto-Su; X. H. Huang; S. R. Gonzalez-Avila; T. Wu; C. D. Ohl

2010-01-01

80

Quantitative ultrasound method to detect and monitor laser-induced cavitation bubbles.  

PubMed

An ultrasound technique to measure the spatial and temporal behavior of the laser-induced cavitation bubble is introduced. The cavitation bubbles were formed in water and in gels using a nanosecond pulsed Nd:YAG laser operating at 532 nm. A focused, single-element, 25-MHz ultrasound transducer was employed both to detect the acoustic emission generated by plasma expansion and to acoustically probe the bubble at different stages of its evolution. The arrival time of the passive acoustic emission was used to estimate the location of the cavitation bubble's origin and the time of flight of the ultrasound pulse-echo signal was used to define its spatial extent. The results of ultrasound estimations of the bubble size were compared and found to be in agreement with both the direct optical measurements of the stationary bubble and the theoretical estimates of bubble dynamics derived from the well-known Rayleigh model of a cavity collapse. The results of this study indicate that the proposed quantitative ultrasound technique, capable of detecting and accurately measuring laser-induced cavitation bubbles in water and in a tissue-like medium, could be used in various biomedical and clinical applications. PMID:18601556

Karpiouk, Andrei B; Aglyamov, Salavat R; Bourgeois, Frederic; Ben-Yakar, Adela; Emelianov, Stanislav Y

81

Generation of laser-induced cavitation bubbles with a digital hologram  

PubMed Central

We demonstrate a method using a spatial light modulator (SLM) to generate arbitrary 2-D spatial configurations of laser induced cavitation bubbles. The SLM acts as a phase hologram that controls the light distribution in the focal plane of a microscope objective. We generate cavitation bubbles over an area of 380x380 ?m2 with a 20x microscope objective through absorption of the pulsed laser light in a liquid ink solution. We demonstrate the ability to accurately position up to 34 micrometer sized bubbles using laser energies of 56 ?J.

Quinto-Su, P. A.; Venugopalan, V.; Ohl, C. D.

2010-01-01

82

Generation of laser-induced cavitation bubbles with a digital hologram.  

PubMed

We demonstrate a method using a spatial light modulator (SLM) to generate arbitrary 2-D spatial configurations of laser induced cavitation bubbles. The SLM acts as a phase hologram that controls the light distribution in the focal plane of a microscope objective. We generate cavitation bubbles over an area of 380 x 380 microm(2) with a 20x microscope objective through absorption of the pulsed laser light in a liquid ink solution. We demonstrate the ability to accurately position up to 34 micrometer sized bubbles using laser energies of 56 microJ. PMID:19581988

Quinto-Su, P A; Venugopalan, V; Ohl, C-D

2008-11-10

83

Particle tracking velocimetry of the flow field around a collapsing cavitation bubble  

Microsoft Academic Search

The velocity field in the vicinity of a laser-generated cavitation bubble in water is investigated by means of particle tracking\\u000a velocimetry (PTV). Two situations are explored: a bubble collapsing spherically and a bubble collapsing aspherically near\\u000a a rigid wall. In the first case, the accuracy of the PTV method is assessed by comparing the experimental data with the flow\\u000a field

Dennis Kröninger; Karsten Köhler; Thomas Kurz; Werner Lauterborn

2010-01-01

84

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

NASA Astrophysics Data System (ADS)

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack.

Mahdi, M.; Ebrahimi, R.; Shams, M.

2011-06-01

85

Visualization of Acoustically Induced Cavitation Bubbles and Microjets with the Aid of a High-Speed Camera  

Microsoft Academic Search

Under ultrasonic irradiation at a frequency of approximately 42 kHz, model experiments in water have been performed to visualize the dynamic behavior of acoustic cavitation bubbles with a high-speed digital camera. The clustered cavitation multibubble moves linearly in random directions. The behavior of the clustered cavitation multibubble is discussed in relation to the behavior of a microjet as well as

Takashi Kubo; Mamoru Kuwabara; Jian Yang

2005-01-01

86

Observation of cavitation bubbles in monoleaflet mechanical heart valves  

Microsoft Academic Search

Recently, cavitation on the surface of mechanical heart valves (MHVs) has been studied as a cause of fractures occurring in implanted MHVs. In the present study, we investigated the mechanism of MHV cavitation associated with the Björk–Shiley valve and the Medtronic Hall valve in an electrohydraulic total artificial heart (EHTAH). The valves were mounted in the mitral position in the

Hwansung Lee; Tomonori Tsukiya; Akihiko Homma; Tadayuki Kamimura; Yoshiaki Takewa; Eisuke Tatsumi; Yoshiyuki Taenaka; Hisateru Takano; Soichiro Kitamura

2004-01-01

87

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

PubMed

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. PMID:19571922

Martí-López, L; Ocaña, R; Porro, J A; Morales, M; Ocaña, J L

2009-07-01

88

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

SciTech Connect

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.

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

2009-07-01

89

Measurements of cavitation bubble dynamics based on a beam-deflection probe  

NASA Astrophysics Data System (ADS)

We present an optodynamic measurement of a laser-induced cavitation bubble and its oscillations based on a scanning technique using a laser beam-deflection probe. The deflection of the beam was detected with a fast quadrant photodiode which was built into the optical probe. The applied experimental setup enabled us to carry out one- or two-dimensional scanning of the cavitation bubble, automatic control of the experiment, data acquisition and data processing. Shadow photography was used as a comparative method during the experiments.

Gregor?i?, Peter; Petkovšek, Rok; Možina, Janez; Mo?nik, Griša

2008-12-01

90

Collapse of a cavitation bubble generated by low voltage discharge in water  

NASA Astrophysics Data System (ADS)

The article presents experimental results of the optical study of cavitation bubble collapse close to a solid boundary in water. The bubble was generated by discharge of two low-voltage capacitors. High-speed CCD camera was used to record the time evolution of the bubble size. High-power halogen lamp was used for illumination. The system was synchronized by pulse generator connected to an oscilloscope. The velocity of the re-entrant jet was estimated from the time resolved photography for different maximum bubble sizes.

Müller, Miloš; Unger, Ji?í; Bud'arek, Tomáš; Zima, Patrik

2012-04-01

91

Evidence for hydrogen generation in laser- or spark-induced cavitation bubbles  

NASA Astrophysics Data System (ADS)

The growing use of focused lasers or electric sparks to generate cavitation bubbles raises concerns about the possible alteration of gas content during the initiation process and its effect on bubble dynamics. We provide experimental evidence that hydrogen molecules are produced for such plasma-induced bubbles. We performed spectral analysis of the light emitted by the plasma and monitored the dissolved hydrogen concentration in water. The mass of dissolved hydrogen was found proportional to the potential energy of the rebound bubble for both laser and spark methods. Nevertheless, hydrogen concentration was found 2.7 times larger with the spark.

Sato, Takehiko; Tinguely, Marc; Oizumi, Masanobu; Farhat, Mohamed

2013-02-01

92

Multifocal laser surgery: Cutting enhancement by hydrodynamic interactions between cavitation bubbles  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

93

Luminescence spectra of laser-induced cavitation bubbles near rigid boundaries  

NASA Astrophysics Data System (ADS)

The luminescence spectra of laser-induced cavitation bubbles near rigid boundaries are measured for various relative distances between the bubble and the boundaries. We find that the luminescence spectra of bubbles collapsing near a single boundary consist only of a blackbody continuum. Luminescence from bubbles collapsing between two parallel rigid boundaries contains OH- emission bands similar to those found in multibubble sonoluminescence. In both cases, the bubble interior temperature deduced from blackbody fits decreases with the distance between bubble and boundary. The shape instabilities of the collapse near a boundary and the consequent presence of high-velocity jets inside the bubble at its minimum volume are discussed in connection with the generation of the OH- radicals.

Brujan, Emil A.; Williams, Gary A.

2005-07-01

94

Luminescence spectra of laser-induced cavitation bubbles near rigid boundaries.  

PubMed

The luminescence spectra of laser-induced cavitation bubbles near rigid boundaries are measured for various relative distances between the bubble and the boundaries. We find that the luminescence spectra of bubbles collapsing near a single boundary consist only of a blackbody continuum. Luminescence from bubbles collapsing between two parallel rigid boundaries contains O H- emission bands similar to those found in multibubble sonoluminescence. In both cases, the bubble interior temperature deduced from blackbody fits decreases with the distance between bubble and boundary. The shape instabilities of the collapse near a boundary and the consequent presence of high-velocity jets inside the bubble at its minimum volume are discussed in connection with the generation of the O H- radicals. PMID:16090083

Brujan, Emil A; Williams, Gary A

2005-07-12

95

The final stage of the collapse of a cavitation bubble close to a rigid boundary  

Microsoft Academic Search

The final stage of the collapse of a laser-produced cavitation bubble close to a rigid boundary is studied both experimentally and theoretically. The temporal evolution of the liquid jet developed during bubble collapse, shock wave emission and the behavior of the “splash” effect are investigated by using high-speed photography with up to 5 million frames\\/second. For a full understanding of

E. A. Brujan; G. S. Keen; A. Vogel; J. R. Blake

2002-01-01

96

Dynamics of laser-induced cavitation bubbles near an elastic boundary  

Microsoft Academic Search

The interaction of a laser-induced cavitation bubble with an elastic boundary and its dependence on the distance between bubble and boundary are investigated experimentally. The elastic boundary consists of a transparent polyacrylamide (PAA) gel with 80% water concentration with elastic modulus E = 0.25 MPa. At this E-value, the deformation and rebound of the boundary is very pronounced providing particularly

Emil-Alexandru Brujan; Kester Nahen; Peter Schmidt; Alfred Vogel

2001-01-01

97

The final stage of the collapse of a cavitation bubble close to a rigid boundary  

Microsoft Academic Search

The final stage of the collapse of a laser-produced cavitation bubble close to a rigid boundary is studied both experimentally and theoretically. The temporal evolution of the liquid jet developed during bubble collapse, shock wave emission and the behavior of the ``splash'' effect are investigated by using high-speed photography with up to 5 million frames\\/second. For a full understanding of

E. A. Brujan; G. S. Keen; A. Vogel; J. R. Blake

2002-01-01

98

Dynamics of laser-induced cavitation bubbles near elastic boundaries: influence of the elastic modulus  

Microsoft Academic Search

The interaction of a laser-induced cavitation bubble with an elastic boundary is investigated experimentally by high-speed photography and acoustic measurements. The elastic material consists of a polyacrylamide (PAA) gel whose elastic properties can be controlled by modifying the water content of the sample. The elastic modulus, E, is varied between 0.017 MPa and 2.03 MPa, and the dimensionless bubble boundary

Emil-Alexandru Brujan; Kester Nahen; Peter Schmidt; Alfred Vogel

2001-01-01

99

Dynamics of laser-induced cavitation bubbles near elastic boundaries: influence of the elastic modulus  

Microsoft Academic Search

The interaction of a laser-induced cavitation bubble with an elastic boundary is investigated experimentally by high-speed photography and acoustic measurements. The elastic material consists of a polyacrylamide (PAA) gel whose elastic proper- ties can be controlled by modifying the water content of the sample. The elastic modulus, E, is varied between 0.017 MPa and 2.03 MPa, and the dimensionless bubble{boundary

PETER S CHMIDT; ALFRED V OGEL

2001-01-01

100

Probing nanotubes and red blood cells with laser-induced cavitation bubbles  

NASA Astrophysics Data System (ADS)

A spatial light modulator (SLM) is used to simultaneously create arrays of laser-induced cavitation bubbles. The different bubble geometries result in the creation of a directed, transient and strong liquid flow. Due to the fast dynamics of the cavitation bubbles the flow is actuated on very short temporal (?s) and spatial (?m) scales. We show two examples of the use of laser-induced cavitation bubbles to probe and manipulate small objects: multiwalled carbon nanotubes (MWCNT) and red blood cells (RBCs). In the case of MWCNT, we use a pair of bubbles to displace and bend the nanotubes. By measuring the time it takes for the nanotube to recover its original shape we can estimate the flexural rigidity and the bending modulus. The shape recovery is recorded with a high-speed camera at up to 300,000 frames per second (fps). We found the flexural rigidity to be on the range of 0.98 -- 6.6 x 10-19 Nm^2 and the Young's modulus on the order of 0.06-0.6 TPa for MWCNT with an average diameter of 117.8 ± 6.7 nm and a thickness of 4.6 ± 0.75 nm. A similar approach is used to study the mechanical properties of RBC's, where multiple cells are elongated due to the radial flow induced by a single bubble. We study the shape recovery of the RBCs and find a significant difference when they are treated with an enzyme.

Quinto-Su, Pedro; Huang, Xiaohu; Kuss, Claudia; Gonzalez, Roberto; Preiser, Peter; Wu, Tom; Ohl, Claus-Dieter

2009-11-01

101

Frequency spectrum of the noise emitted by two interacting cavitation bubbles in strong acoustic fields.  

PubMed

The dynamics and acoustic emission of two interacting cavitation bubbles exposed to strong acoustic fields with a frequency of 515 KHz are investigated numerically in this paper. After comparing the dynamics of a single bubble excited by the given pressure waves, bubbles with ambient radii of 2 and 5 ?m were chosen to be studied to discuss the influence of the mutual bubble-bubble interaction on the dynamic behaviors and acoustic emission of the bubbles. The results show that, aside from the external driving pressure waves, the interaction between the bubbles imposes an extra nonlinear effect on the oscillations of the bubbles and that the dynamics of the smaller bubble could be suppressed gradually with the enhancement of this mutual interaction by decreasing the distance between the bubbles. Moreover, the improvement in the oscillation nonlinearity of the bubbles due to the change in the ambient circumstance could readily be observed from the frequency spectra of the bubbles' acoustic emission, which interprets the change by exhibiting an appropriate development of the subharmonics, the ultraharmonics, and the broadband component. PMID:22587185

Jiang, Liang; Liu, Fengbing; Chen, Haosheng; Wang, Jiadao; Chen, Darong

2012-03-22

102

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

Microsoft Academic Search

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

Emil-Alexandru Brujan; Alfred Vogel

2006-01-01

103

Green manufacturing process — surface pre-treatment with micro bubble cavitation  

Microsoft Academic Search

In this paper, an innovative process, which utilizes micro-bubble cavitation in water for surface roughening pre-treatment prior to plating or laminating, is presented. No hazardous chemical is employed to comply with green process. In semiconductor industry, this surface damaging mechanism or surface roughening is a required process with chemicals. Massive amount of water were polluted and extra time was wasted

Steven C. Kuo

2007-01-01

104

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

PubMed Central

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.

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

105

Dynamics of silver nanoparticle formation and agglomeration inside the cavitation bubble after pulsed laser ablation in liquid.  

PubMed

The formation of nanoparticles within the laser-induced cavitation bubble is studied in situ using small angle X-ray scattering with high spatiotemporal resolution. Directly after laser ablation, two different particle fractions consisting of compact primary particles of 8-10 nm size and agglomerates of 40-60 nm size are formed. The abundance of these species is strongly influenced by the dynamics of the oscillating cavitation bubble. Primary particle mass is most abundant during maximal expansion of the first bubble and reappears a little weaker in the rebound. In contrast to this, the mass abundance of agglomerates is relatively low in the first bubble but strongly increases during first bubble collapse and following rebound. Although most of the ablated material is trapped inside the bubble and follows its oscillation, a minor fraction of both species could be detected outside the cavitation bubble even before its final collapse. PMID:23183423

Wagener, Philipp; Ibrahimkutty, Shyjumon; Menzel, Andreas; Plech, Anton; Barcikowski, Stephan

2013-03-01

106

Cardiovascular cavitation  

Microsoft Academic Search

This article reviews the role of cavitation in the therapeutic applications of ultrasound and laser surgery, and the cavitation effects in mechanical heart valves. Whenever laser pulses are used to ablate or disrupt tissue in a liquid environment, cavitation bubbles are produced which interact with the tissue. The interaction between cavitation bubbles and tissue during pulsed laser surgery may cause

Emil-Alexandru Brujan

2009-01-01

107

Interaction of lithotripter shockwaves with single inertial cavitation bubbles  

NASA Astrophysics Data System (ADS)

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.

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

108

Dynamics of laser-induced cavitation bubbles near an elastic boundary  

NASA Astrophysics Data System (ADS)

The interaction of a laser-induced cavitation bubble with an elastic boundary and its dependence on the distance between bubble and boundary are investigated experimentally. The elastic boundary consists of a transparent polyacrylamide (PAA) gel with 80% water concentration with elastic modulus E = 0.25 MPa. At this E-value, the deformation and rebound of the boundary is very pronounced providing particularly interesting features of bubble dynamics. It is shown by means of high-speed photography with up to 5 million frames s[minus sign]1 that bubble splitting, formation of liquid jets away from and towards the boundary, and jet-like ejection of the boundary material into the liquid are the main features of this interaction. The maximum liquid jet velocity measured was 960 m s[minus sign]1. Such high-velocity jets penetrate the elastic boundary even through a water layer of 0.35 mm thickness. The jetting behaviour arises from the interaction between the counteracting forces induced by the rebound of the elastic boundary and the Bjerknes attraction force towards the boundary. General principles of the formation of annular and axial jets are discussed which allow the interpretation of the complex dynamics. The concept of the Kelvin impulse is examined with regard to bubble migration and jet formation. The results are discussed with respect to cavitation erosion, collateral damage in laser surgery, and cavitation-mediated enhancement of pulsed laser ablation of tissue.

Brujan, Emil-Alexandru; Nahen, Kester; Schmidt, Peter; Vogel, Alfred

2001-04-01

109

Bubble Growth in Lunar Basalts  

NASA Astrophysics Data System (ADS)

Although Moon is usually said to be volatile-"free", lunar basalts are often vesicular with mm-size bubbles. The vesicular nature of the lunar basalts suggests that they contained some initial gas concentration. A recent publication estimated volatile concentrations in lunar basalts (Saal et al. 2008). This report investigates bubble growth on Moon and compares with that on Earth. Under conditions relevant to lunar basalts, bubble growth in a finite melt shell (i.e., growth of multiple regularly-spaced bubbles) is calculated following Proussevitch and Sahagian (1998) and Liu and Zhang (2000). Initial H2O content of 700 ppm (Saal et al. 2008) or lower is used and the effect of other volatiles (such as carbon dioxide, halogens, and sulfur) is ignored. H2O solubility at low pressures (Liu et al. 2005), concentration-dependent diffusivity in basalt (Zhang and Stolper 1991), and lunar basalt viscosity (Murase and McBirney 1970) are used. Because lunar atmospheric pressure is essentially zero, the confining pressure on bubbles is completely supplied by the overlying magma. Due to low H2O content in lunar basaltic melt (700 ppm H2O corresponds to a saturation pressure of 75 kPa), H2O bubbles only grow in the upper 16 m of a basalt flow or lake. A depth of 20 mm corresponds to a confining pressure of 100 Pa. Hence, vesicular lunar rocks come from very shallow depth. Some findings from the modeling are as follows. (a) Due to low confining pressure as well as low viscosity, even though volatile concentration is very low, bubble growth rate is extremely high, much higher than typical bubble growth rates in terrestrial melts. Hence, mm-size bubbles in lunar basalts are not strange. (b) Because the pertinent pressures are so low, bubble pressure due to surface tension plays a main role in lunar bubble growth, contrary to terrestrial cases. (c) Time scale to reach equilibrium bubble size increases as the confining pressure increases. References: (1) Liu Y, Zhang YX (2000) Earth Planet. Sci. Lett. 181, 251. (2) Liu Y, Zhang YX, Behrens H (2005) J. Volcanol. Geotherm. Res. 143, 219. (3) Murase T, McBirney A (1970) Science 167, 1491. (4) Proussevitch AA, Sahagian DL (1998) J. Geophys. Res. 103, 18223. (5) Saal AE, Hauri EH, Cascio ML, et al. (2008) Nature 454, 192. (6) Zhang YX, Stolper EM (1991) Nature 351, 306.

Zhang, Y.

2009-05-01

110

Design of experimental setup for investigation of cavitation bubble collapse close to a solid wall  

NASA Astrophysics Data System (ADS)

The article describes experimental setup for investigation of the impact load from collapsing cavitation bubble on a solid wall. A vapour bubble is generated inside a cubic chamber by local heating of water inside a thin channel in a button. The bubble collapse is initiated by a piezoelectric actuator attached to the flexible wall of the chamber. A laser diode with a linear CCD sensor are used to detect the bubble position during its buoyancy-driven rise to the upper wall of the chamber. The bubble collapse impact load is measured using a PVDF piezoelectric transducer glued to the upper wall of the chamber and recorded by high-speed CCD camera illuminated by a high-power LED diode. The pressure inside the chamber is measured by the dynamic pressure transducer. All the system components are controlled and synchronized by an oscilloscope and pulse generator using the LabView software.

Müller, Miloš; Zima, Patrik; Unger, Ji?í; Živný, Martin

2012-04-01

111

Dynamics of laser-induced cavitation bubbles near elastic boundaries: influence of the elastic modulus  

NASA Astrophysics Data System (ADS)

The interaction of a laser-induced cavitation bubble with an elastic boundary is investigated experimentally by high-speed photography and acoustic measurements. The elastic material consists of a polyacrylamide (PAA) gel whose elastic properties can be controlled by modifying the water content of the sample. The elastic modulus, E, is varied between 0.017 MPa and 2.03 MPa, and the dimensionless bubble boundary distance, [gamma], is for each value of E varied between [gamma] = 0 and [gamma] = 2.2. In this parameter space, jetting behaviour, jet velocity, bubble migration and bubble oscillation time are determined. The jetting behaviour varies between liquid jet formation towards or away from the elastic boundary, and formation of an annular jet which results in bubble splitting and the subsequent formation of two very fast axial liquid jets flowing in opposite directions. The liquid jet directed away from the boundary reaches a maximum velocity between 300 ms[minus sign]1 and 600 ms[minus sign]1 (depending on the elastic modulus of the sample) while the peak velocity of the jet directed towards the boundary ranges between 400 ms[minus sign]1 and 800 ms[minus sign]1 (velocity values averaged over 1 [mu]s). Penetration of the elastic boundary by the liquid jet is observed for PAA samples with an intermediate elastic modulus between 0.12 and 0.4 MPa. In this same range of elastic moduli and for small [gamma]-values, PAA material is ejected into the surrounding liquid due to the elastic rebound of the sample surface that was deformed during bubble expansion and forms a PAA jet upon rebound. For stiffer boundaries, the bubble behaviour is mainly characterized by the formation of an axial liquid jet and bubble migration directed towards the boundary, as if the bubble were adjacent to a rigid wall. For softer samples, the bubble behaviour becomes similar to that in a liquid with infinite extent. During bubble collapse, however, material is torn off the PAA sample when bubbles are produced close to the boundary. We conclude that liquid jet penetration into the boundary, jet-like ejection of boundary material, and tensile-stress-induced deformations of the boundary during bubble collapse are the major mechanisms responsible for cavitation erosion and for cavitation-enhanced ablation of elastic materials as, for example, biological tissues.

Brujan, Emil-Alexandru; Nahen, Kester; Schmidt, Peter; Vogel, Alfred

2001-04-01

112

Collapse and rebound of a laser-induced cavitation bubble  

NASA Astrophysics Data System (ADS)

A strong laser pulse that is focused into a liquid produces a vapor cavity, which first expands and then collapses with subsequent rebounds. In this paper a mathematical model of the spherically symmetric motion of a laser-induced bubble is proposed. It describes gas and liquid dynamics including compressibility, heat, and mass transfer effects and nonequilibrium processes of evaporation and condensation on the bubble wall. It accounts also for the occurrence of supercritical conditions at collapse. Numerical investigations of the collapse and first rebound have been carried out for different bubble sizes. The results show a fairly good agreement with experimental measurements of the bubble radius evolution and the intensity of the outgoing shock wave emitted at collapse. Calculations with a small amount of noncondensable gas inside the bubble show its strong influence on the dynamics.

Akhatov, I.; Lindau, O.; Topolnikov, A.; Mettin, R.; Vakhitova, N.; Lauterborn, W.

2001-10-01

113

Modeling of hydrodynamic cavitation reactors based on orifice plates considering hydrodynamics and chemical reactions occurring in bubble  

Microsoft Academic Search

In the present work, a model has been developed for predicting the cavitational intensity in a hydrodynamic cavitation reactor based on the use of orifice plates considering the hydrodynamic conditions and the different chemical reactions taking place inside the cavity. The model is based on a set of ordinary differential equations and considers the bubble hydrodynamics and heat exchange including

Amit Sharma; Parag R. Gogate; Amit Mahulkar; Aniruddha B. Pandit

2008-01-01

114

The role of bubbles and cavitation in the production of thermal lesions from high-intensity focused ultrasound  

NASA Astrophysics Data System (ADS)

Rapid hyperthermia resulting in tissue necrosis is a key physical mechanism for focused ultrasound surgery (FUS). At therapeutic intensities, tissue heating is often accompanied by cavitation activity. Although it is well known that bubbles promote mechanical damage, in vitro and in vivo experiments have shown that under certain conditions bubble activity can double the heating rate. With a view towards harnessing bubbles and cavitation for useful clinical work, we report the results of in vitro experiments and modeling for the dynamic and thermal behavior of bubbles subjected to 1-megahertz ultrasound at mega-pascal pressures. The dominant bubble-related heating mechanism depends critically on the bubble size distribution which, in turn, depends on insonation control parameters (acoustic pressure, pulse duration), medium properties (notably dissolved gas concentration), and bubble-destroying shape instabilities. The evidence points to a range of control parameters for which bubble-enhanced FUS can be assured. [Work supported by DARPA and the U.S. Army.

Roy, Ronald A.; Holt, R. Glynn; Yang, Xinmai; Edson, Patrick

2002-11-01

115

High-speed photographic study of the interaction of cavitation bubbles with a boundary  

NASA Astrophysics Data System (ADS)

This paper re-examines the collapse of a single cavitation bubble in front of a boundary. A range of different diameter cavitation bubbles were generated by focusing a pulse from a Q-switched Nd:YAG laser of varying energy. High speed shadow photography and Schlieren techniques are used to visualize the collapse process and the resulting bubble deformation at a distance s from the boundary with high temporal and spatial resolution. A sequence of Schlieren images taken with nanosecond time resolution displays the evolution of the cavity at the distance s from the solid surface. Additionally, the pressure distribution of the oscillating bubble especially in the region of the first collapse was recorded by a thin film transducer which is bonded to a pmma block. Both transducer output signals and Schlieren images confirm the formation of a liquid jet and also indicate the importance of the resulting fluid flow to stresses induced in the solid. In an attempt to visualize the fluid flow a flexible rubber film was placed near an oscillating bubble in free space. As expected jet formation in this case is not observed, however unusual fluid flow effects around the bubble can be seen.

Schiffers, W. P.; Shaw, S. J.; Jin, Y. H.; Emmony, David C.

1997-05-01

116

Novel laser-induced cavitation: the constrained ring bubble  

NASA Astrophysics Data System (ADS)

Using high speed photography at sub-microsecond temporal resolution, we observed laser-induced cavitation within a thin film of liquid. In accordance with the literature, focusing a pulse of a gaussian-like intensity distribution into the liquid, instigated a disk-shaped cavity. The propagation of an acoustic transient, generated during the formation and expansion of the cavity, is evidenced by secondary cavitation stimulated in the surrounding liquid. Introducing a laguerre-gauss holographic diffractive optic element into the beam path, re-distributes the optical energy into the socalled 'doughnut mode', with an axial intensity minimum. Focusing this modulated pulse into the liquid induced a ringshaped cavity with a notably different dynamic to that of the disk cavity, due primarily to the encapsulated droplet, which is present from cavity initiation through expansion and subsequent deflation. In this paper we present initial observations on the novel dynamics of the ring-shaped cavity and discuss several of the distinctive features. Particularly the secondary cavitation induced in the surrounding liquid, and the implicated multiplexing of the acoustic transient generated during the ring-cavity expansion, is of interest.

Prentice, Paul; Zolotovskaya, Svetlana; Rafailov, Edik

2010-02-01

117

Surface cleaning from laser-induced cavitation bubbles  

NASA Astrophysics Data System (ADS)

When bubbles expand and collapse close to boundaries, a shear flow is generated which is able to remove particles from the surface, thus locally cleaning it. Here the authors demonstrate experimentally with microparticle tracking velocimetry that the strongest forcing of particles occurs during a very brief time interval of the bubble oscillation period. During this interval a jet flow impacts and spreads radially along the surface, thus transporting the particles with it.

Ohl, Claus-Dieter; Arora, Manish; Dijkink, Rory; Janve, Vaibhav; Lohse, Detlef

2006-08-01

118

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

119

Cavitations Development In a Liquid Behind Strong Acoustic Waves  

NASA Astrophysics Data System (ADS)

The generation of bubbles behind an acoustic pulse is theoretically and experimentally investigated in the paper. It was found out that at growth of the amplitude of falling wave two different modes of cavitations development occur: ``chain'' mechanism of duplication of cavitations germs is replaced by mechanism of ``real'' liquid cavitations, when the liquid is initially filled with a set of cavitations nuclei and apparent bubble occurrence is caused by different periods of nucleus growth from them.

Voronin, D. V.; Teslenko, V. S.

2008-06-01

120

Shock wave emission from laser-induced cavitation bubbles in polymer solutions  

Microsoft Academic Search

The role of extensional viscosity on the acoustic emission from laser-induced cavitation bubbles in polymer solutions and near a rigid boundary is investigated by acoustic measurements. The polymer solutions consist of a 0.5% polyacrylamide (PAM) aqueous solution with a strong elastic component and a 0.5% carboxymethylcellulose (CMC) aqueous solution with a weak elastic component. A reduction of the maximum amplitude

Emil-Alexandru Brujan

2008-01-01

121

Interaction of laser-produced cavitation bubbles with an elastic tissue model  

Microsoft Academic Search

We investigated the interaction of a laser-induced cavitation bubble with an elastic tissue model by high-speed photography with up to 5 Mill. frames\\/sec. The elastic material consisted of a transparent polyacrylamide (PAA) gel whose elastic properties can be controlled by modifying the water content to mimic various biological tissues. The elastic modulus E of the PAA sample was varied between

Alfred Vogel; Emil A. Brujan; Peter Schmidt; Kester Nahen

2001-01-01

122

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

PubMed Central

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??s, 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.

2012-01-01

123

Dynamics of laser-induced cavitation bubbles near an elastic boundary used as a tissue phantom  

NASA Astrophysics Data System (ADS)

The behavior of a laser-produced cavitation bubble near an elastic boundary as well as the deformation of the boundary induced by bubble motion are investigated by means of high-speed photography and acoustic measurements. The elastic boundary, used as a tissue phantom, consists of a polyacrylamide (PAA) gel whose elastic properties can be controlled, by modifying the water content of the sample, to mimic various biological tissues. The bubble dynamics is strongly dependent on the dimensionless distance ?=s/Rmax between bubble and boundary and on the elastic properties of the boundary. For example, in the case of a PAA gel with 80% water concentration, the general features of the bubble dynamics are, for ?>0.8, bubble migration and jet formation directed away from the boundary, for 0.8>?>0.2, formation of a mushroom-like shape of the bubble during collapse, bubble splitting and penetration of a re-entrant liquid jet into the boundary while, for ?<0.52, jet formation of PAA-material directed away from the elastic boundary occurs. The latter phenomenon can be used to enhance the efficiency of laser-induced tissue ablation. .

Brujan, Emil-Alexandru; Nahen, Kester; Schmidt, Peter; Vogel, Alfred

2000-07-01

124

Bubble Dynamics in Polymer Solutions Undergoing Shear.  

National Technical Information Service (NTIS)

Hydraulic cavitation and its effects have been reported to be substantially inhibited and subsequently suppressed by the addition of minute quantities of water-soluble polymer. Modelling the growth and collapse of a single cavitation bubble in water has b...

P. S. Kezios

1985-01-01

125

Numerical analysis of a cavitation bubble in the vicinity of an elastic membrane  

NASA Astrophysics Data System (ADS)

A numerical simulation has been carried out to study the interaction of a cavitation bubble and an elastic membrane. Boundary element method is used to simulate the physics of the membrane between two fluids which are assumed to be same (water) for simplicity. The intent of this paper is to clearly investigate the bubble–membrane interaction. Elasticity of the membrane plays an important role on the behavior of the bubble. For example, a bubble near a ‘stiff’ membrane (high elasticity), jets toward it (the same as the rigid boundary). The influence of two main parameters, namely, dimensionless distance of the bubble center to the membrane initial position (H?) and the dimensionless elasticity of the membrane (E?) are discussed. We have considered the dimensionless distance of the bubble center to the membrane initial position in the range of 0.5 ? H? ? 1 and a membrane of dimensionless elasticity in the range of 0.01 ? E? ? 10. An increase in H? leads to a decrease in the membrane displacement from its initial position. Also, increasing of E? leads to a change in the behavior of the bubble from spherical collapse to jetting toward the membrane (in a same H?) and decreasing in membrane displacement.

Shervani-Tabar, M. T.; Hajizadeh Aghdam, A.; Khoo, B. C.; Farhangmehr, V.; Farzaneh, B.

2013-10-01

126

Acoustic transient generation by holmium-laser-induced cavitation bubbles  

NASA Astrophysics Data System (ADS)

The acoustic effects of free-running 2.12 micron Cr:Tm:Ho:YAG laser pulses delivered in water are studied. Laser pulses of 10 to 1200 mJ energy and 230 microsecs duration (full width at half-maximum) are used. Delivery fiber diameters of 200 - 600 microns are investigated. Combined fast flash video imaging and needle probe hydrophone pressure sensing are used. The experimental results show that the laser-induced water vapor bubbles can generate strong acoustic transients at the bubble collapse several hundreds of microsecs after the start of the laser pulse. Pressures of up to 3600 bar are measured. Above a laser fluence threshold of 40 J/sq cm the pressure amplitude increases sharply, reaching a maximum value between 100 and 200 J/sq cm. At higher fluences up to more than 1000 J/sq cm, the pressure amplitude is found to decrease again. A two-phase mechanism is proposed to describe the complex bubble dynamics generated by the free-running pulses: The isotropic expansion of an initially superheated water volume is followed by a continuous ablation phase. The results suggest a mechanism of possible unwanted acoustic damage during Holmium laser medical applications in a liquid environment.

Asshauer, T.; Rink, K.; Delacretaz, G.

1994-11-01

127

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

SciTech Connect

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.

Francis, M. W.; Ruggles, A. E. [Department of Nuclear Engineering, University of Tennessee 315 Pasqua Engineering Building, Knoxville, TN 37996-2300 (United States)

2009-03-10

128

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

NASA Astrophysics Data System (ADS)

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.

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

2009-03-01

129

Dynamic of cavitation bubble in a flowing liquid with a pressure gradient  

NASA Astrophysics Data System (ADS)

In the present study, a high energy pulsed laser is used to generate a millimetric cavitation bubble within a water flow over a symmetric hydrofoil. The bubble is initiated at different locations in the vicinity of the hydrofoil leading edge. A high speed camera is used to observe the motion of the bubble as it travels along the hydrofoil suction side. Besides the standoff parameter, we have found that the pressure gradient plays a major role on bubble dynamic and subsequent phenomena. For a specific initial location of the bubble, the micro-jet is no more directed towards the hydrofoil surface, as commonly observed in still water. In this case, we have also observed a spectacular behaviour of the cavity rebound, which migrates towards the solid surface despite of the outward direction of the micro-jet. This result differs from the behaviour of a bubble near a solid surface in water at rest or water flowing uniformly since the micro-jet is normally directed toward the solid.

Tinguely, Marc; Farhat, Mohamed

2009-11-01

130

Hybrid cavitation methods for water disinfection: simultaneous use of chemicals with cavitation  

Microsoft Academic Search

This study brings out the potential efficacy of hybrid techniques for water disinfection. The techniques studied include, hydrodynamic cavitation, acoustic cavitation and treatment with chemicals such as ozone and hydrogen peroxide. The phenomena of cavitation which involves formation, growth and violent collapse of vapor bubbles in a liquid media is known to generate a high intensity pressure which affects the

K. K. Jyoti; A. B. Pandit

2003-01-01

131

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

NASA Astrophysics Data System (ADS)

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.

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

132

Pit clustering in cavitation erosion  

Microsoft Academic Search

An investigation of the erosion effects of cavitation on a thin aluminium foil was made. Cavitation was generated in a small tank with capacity of about 500ml of clean water. The growth and collapse of bubbles was triggered by means of ultrasound. The sustained damage was measured by evaluating the area of the damaged surface in time intervals of 4s.

Matevž Dular; Aljaž Osterman

2008-01-01

133

The Effects of Jet Cavitation on the Growth of Microcystis Aeruginosa  

Microsoft Academic Search

Different operating factors of jet cavitation method affecting one of cyanobacterial's (Microcystis aeruginosa) growths were investigated. The inhibition on M. aeruginosa growth by the jet cavitation method depended strongly on the hydraulic characteristics of cavitation tube, inlet pressure, cavitation number, light and different algae concentrations. The inhibitive efficiency of 64.58% in field water sample was obtained by this method. Moreover,

YUNFENG XU; JI YANG; YALIN WANG; FENG LIU; JINPING JIA

2006-01-01

134

Manipulation and Microrheology of Carbon Nanotubes with Laser-Induced Cavitation Bubbles  

NASA Astrophysics Data System (ADS)

Multiwalled carbon nanotubes (MWCNT) are exposed to a transient and strong liquid jet flow created by a pair of differently sized laser-induced cavitation bubbles. The position and size of the bubbles are controlled with a spatial light modulator within a 15?m thick liquid gap. Depending on the tube’s position with respect to this jet flow, rotation, translation, and a bending deformation is observed with a high-speed camera recording at up to 300 000 frames per second. By measuring the decay time of the respective bending modes we determine the flexural rigidity of MWCNTs to be on the range of 0.45-4.06×10-19Nm2. The average diameter of the MWCNTs is 117.8±6.7nm with a thickness of 4.6±0.75nm, yielding a Young’s modulus between 0.033-0.292 TPa.

Quinto-Su, P. A.; Huang, X. H.; Gonzalez-Avila, S. R.; Wu, T.; Ohl, C. D.

2010-01-01

135

Shock wave emission from laser-induced cavitation bubbles in polymer solutions.  

PubMed

The role of extensional viscosity on the acoustic emission from laser-induced cavitation bubbles in polymer solutions and near a rigid boundary is investigated by acoustic measurements. The polymer solutions consist of a 0.5% polyacrylamide (PAM) aqueous solution with a strong elastic component and a 0.5% carboxymethylcellulose (CMC) aqueous solution with a weak elastic component. A reduction of the maximum amplitude of the shock wave pressure and a prolongation of the oscillation period of the bubble were found in the elastic PAM solution. It might be caused by an increased resistance to extensional flow which is conferred upon the liquid by the polymer additive. In both polymer solutions, however, the shock pressure decays proportionally to r(-1) with increasing distance r from the emission centre. PMID:18378271

Brujan, Emil-Alexandru

2008-03-04

136

Manipulation and microrheology of carbon nanotubes with laser-induced cavitation bubbles.  

PubMed

Multiwalled carbon nanotubes (MWCNT) are exposed to a transient and strong liquid jet flow created by a pair of differently sized laser-induced cavitation bubbles. The position and size of the bubbles are controlled with a spatial light modulator within a 15 microm thick liquid gap. Depending on the tube's position with respect to this jet flow, rotation, translation, and a bending deformation is observed with a high-speed camera recording at up to 300,000 frames per second. By measuring the decay time of the respective bending modes we determine the flexural rigidity of MWCNTs to be on the range of 0.45-4.06x10(-19) N m2. The average diameter of the MWCNTs is 117.8+/-6.7 nm with a thickness of 4.6+/-0.75 nm, yielding a Young's modulus between 0.033-0.292 TPa. PMID:20366365

Quinto-Su, P A; Huang, X H; Gonzalez-Avila, S R; Wu, T; Ohl, C D

2010-01-07

137

Interaction of laser-produced cavitation bubbles with an elastic tissue model  

NASA Astrophysics Data System (ADS)

We investigated the interaction of a laser-induced cavitation bubble with an elastic tissue model by high-speed photography with up to 5 Mill. frames/sec. The elastic material consisted of a transparent polyacrylamide (PAA) gel whose elastic properties can be controlled by modifying the water content to mimic various biological tissues. The elastic modulus E of the PAA sample was varied between 0.017 and 2 MPa. The dimensionless bubble-boundary distance (gamma) (distance between laser focus and sample boundary, scaled by the maximum bubble radius) was for each value of E varied between (gamma) = 0 and (gamma) = 2.2. In this parameter space, we determined the jetting behavior, jet velocity, jet penetration into the PAA sample and bubble- induced removal of PAA material. The jetting behavior varies between unidirectional jets towards or away from the boundary, and formation of an annular jet which results in bubble splitting and subsequent formation of two very fast axial jets flowing simultaneously towards the boundary and away from it. General principles of the formation of annular and axial jets are discussed which allow to interpret the complex dynamics. The liquid jet directed away form the boundary reaches a maximum velocity between 300 m/s and 600 m/s (depending on E) while the peak velocity of the jet directed towards the boundary ranges between 400 m/s and 960 m/s. The peak velocities near an elastic material are 10 times higher than close to a rigid boundary. The liquid jet penetrates PAA samples with an elastic modulus in the intermediate range 0.12 < E < 0.4 MPa. In this same range of elastic moduli and for small (gamma) - values, PAA material is ejected into the surrounding liquid due to the elastic rebound of the sample surface that was deformed during bubble expansion. The surface of the PAA sample is, furthermore, lifted during bubble collapse when a region of low pressure develops between bubble and sample. For stiffer boundaries, only an axial liquid jet towards the boundary is formed, similar to the bubble dynamics next to a rigid wall. For softer sample, the liquid jet is directed away from the boundary, and material is torn off the PAA sample during bubble collapse, if the bubble is produced close to the boundary. These processes play an important role for the efficiency and side effects of pulsed laser surgery inside the human body.

Vogel, Alfred; Brujan, Emil A.; Schmidt, Peter; Nahen, Kester

2001-07-01

138

Bubble growth in superheated He-II  

SciTech Connect

Bubble growth in superheated He-II is controlled by the transfer of heat to the surface of the growing bubble by nonlinear Gorter-Mellink counterflow. The present work presents analytic formulas for the bubble radius as a function of time in the limiting cases of small and large superheats. The formulas include the effect of the inertial reaction of the surrounding liquid to the expansion of the bubble. A numerical example shows that bubble velocities of the order of meters per second are possible. A related problem, involving only heat transfer but no movement of the liquid, is the motion of the free surface of superheated He-II in a very long tube. This problem has a similarity solution. The interfacial velocity in the tube is much smaller than the bubble growth velocity. 1 ref.

Dresner, L.

1988-01-01

139

Red blood cell rheology using single controlled laser-induced cavitation bubbles.  

PubMed

The deformability of red blood cells (RBCs) is an important property that allows the cells to squeeze through small capillary vessels and can be used as an indicator for disease. We present a microfluidic based technique to quantify the deformability of RBCs by stretching a collection of RBCs on a timescale of tens of microseconds in a microfluidic chamber. This confinement constrains the motion of the cell to the imaging plane of the microscope during a transient cavitation bubble event generated with a focused and pulsed laser. We record and analyze the shape recovery of the cells with a high-speed camera and obtain a power law in time, consistent with other dynamic rheological results of RBCs. The extracted exponents are used to characterize the elastic properties of the cells. We obtain statistically significant differences of the exponents between populations of untreated RBCs and RBCs treated with two different reagents: neuraminidase reduces the cell rigidity, while wheat germ agglutinin stiffens the cell confirming previous experiments. This cavitation based technique is a candidate for high-throughput screening of elastic cell properties because many cells can be probed simultaneously in situ, thus with no pre-treatment. PMID:21183972

Quinto-Su, Pedro A; Kuss, Claudia; Preiser, Peter R; Ohl, Claus-Dieter

2010-12-23

140

Modelling of dendritic growth and bubble formation  

NASA Astrophysics Data System (ADS)

A two-dimensional lattice Boltzmann method (LBM)-cellular automaton (CA) model is developed for the simulation of dendritic growth and bubble formation during alloy solidification. In the model, a kinetic LBM, which describes flow dynamics through the evolution of distribution functions of moving pseudo-particles, is adopted to numerically solve the gas-liquid two-phase flow based on the Shan-Chen multiphase scheme. The kinetics of dendritic growth is determined according to a local solute equilibrium approach. The present model takes into account the effect of liquid-solid phase transformation on the nucleation and growth of bubbles. The interaction mechanism between dendrites and bubbles is also embedded in the model. The wettability of a bubble on a smooth solid surface is simulated. The simulated contact angles with various interaction coefficients agree well with the data calculated from an empirical formula derived from the Young's equation. The proposed model is applied to simulate dendritic growth and bubble formation under directional solidification conditions. The simulated results are compared with those observed experimentally during solidification of a transparent organic material. The simulation results reveal some dynamic features of bubble nucleation, growth, and motion, as well as the interaction between the dendritic growth and bubble formation during solidification.

Wu, W.; Zhu, M. F.; Sun, D. K.; Dai, T.; Y Han, Q.; Raabe, D.

2012-07-01

141

Numerical correlation of the cavitation bubble collapse load and frequency with the pitting damage of flame quenched Cu–9Al–4.5Ni–4.5Fe alloy  

Microsoft Academic Search

In this study, the collapsing loads of cavitation bubbles generated by an ultrasonic vibratory device have been quantitatively evaluated for the as-casted and flame-quenched Cu–8.8Al–4.5Ni–4.5Fe (Al–bronze) alloys and their effects on the surface pitting after a short cavitation exposure have been numerically studied. The cavitation bubble collapsing loads were determined by measuring the cavitation pulse signal (Vout) and converting it

M. K. Lee; S. M. Hong; G. H. Kim; K. H. Kim; C. K. Rhee; W. W. Kim

2006-01-01

142

Modeling of initial bubble growth rates during high-intensity focused ultrasound  

NASA Astrophysics Data System (ADS)

In therapeutic applications of biomedical ultrasound, it is important to understand the behavior of cavitation bubbles. For applications that use high-intensity focused ultrasound (HIFU), both large negative acoustic pressures and heating can independently lead to bubble formation. Although neglected previously, heating during HIFU is expected to affect the growth and dissolution of bubbles by both raising the vapor pressure and promoting outgassing from gas-saturated tissues. Herein, the dynamics of a single, spherical bubble in water have been modeled using the Gilmore equation closed with an energy balance on bubble contents for calculation of pressures inside the bubble. Moreover, heat and mass transfer at the bubble wall are incorporated using the Eller-Flynn zeroth-order approximation for gas diffusion, an estimation of non-equilibrium phase change based on the kinetic theory of gases, and assumed shapes for the spatial temperature distribution in the surrounding liquid [Yasui, J. Phys. Soc. Jpn. 65, 2830-2840 (1996)]. This model allows explicit coupling of the ambient heating during HIFU to the thermodynamic state of an oscillating bubble and is currently being used to explore the growth rates of initially small, undetectable bubbles exposed to various HIFU treatment protocols. [Work supported by NIH T32-EB-001650, NIH DK43881, and NSBRI SMS00203.

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

2005-04-01

143

Dynamics of ultrasound-induced cavitation bubbles in non-Newtonian liquids and near a rigid boundary  

NASA Astrophysics Data System (ADS)

The dynamics of ultrasound-induced cavitation bubbles situated in non-Newtonian liquids and near a rigid boundary are investigated experimentally by acoustic measurements and high-speed photography with up to 4 million frames/s. The non-Newtonian liquids consist of a 0.5% polyacrylamide (PAM) aqueous solution with a strong elastic component and a 0.5% carboxymethylcellulose aqueous solution with a weak elastic component. The maximum velocity of the re-entrant liquid jet and the pressure amplitude of the acoustic transients emitted during first bubble collapse are diminished by the polymer additives. The most significant reduction was found in the elastic PAM solution. It might be caused by an increased resistance to extensional flow which is conferred upon the liquid by the polymer additive. The results are discussed with respect to the mechanisms of cavitation erosion of rigid materials. The material presented may also be useful for comparison with future numerical work.

Brujan, E. A.; Ikeda, T.; Matsumoto, Y.

2004-07-01

144

Shock-wave propagation and cavitation bubble oscillation by Nd:YAG laser ablation of a metal in water.  

PubMed

A highly sensitive fiber-optic sensor based on optical beam deflection is applied for investigating the propagation of a laser-induced plasma shock wave, the oscillation of a cavitation bubble diameter, and the development of a bubble-collapse-induced shock wave when a Nd:YAG laser pulse is focused upon an aluminum surface in water. By the sequence of experimental waveforms detected at different distances, the attenuation properties of the plasma shock wave and of the bubble-collapse-induced shock wave are obtained. Besides, based on characteristic signals, both the maximum and the minimum bubble radii at each oscillation cycle are determined, as are the corresponding oscillating periods. PMID:15181804

Chen, Xiao; Xu, Rong-Qing; Chen, Jian-Ping; Shen, Zhong-Hua; Jian, Lu; Ni, Xiao-Wu

2004-06-01

145

Dynamics of ultrasound-induced cavitation bubbles in non-Newtonian liquids and near a rigid boundary  

Microsoft Academic Search

The dynamics of ultrasound-induced cavitation bubbles situated in non-Newtonian liquids and near a rigid boundary are investigated experimentally by acoustic measurements and high-speed photography with up to 4 million frames\\/s. The non-Newtonian liquids consist of a 0.5% polyacrylamide (PAM) aqueous solution with a strong elastic component and a 0.5% carboxymethylcellulose aqueous solution with a weak elastic component. The maximum velocity

E. A. Brujan; T. Ikeda; Y. Matsumoto

2004-01-01

146

Development of a PVDF sensor array for measurement of the impulsive pressure generated by cavitation bubble collapse  

Microsoft Academic Search

To study the impulsive pressure generated by cavitation bubble collapse, a PVDF piezoelectric array of pressure sensors is developed. The sensor array is fabricated directly on a 25 ?m thick aluminum-metalized polarized PVDF film using a laser micro-machining technique. Dynamic calibration of the sensor array is accomplished in a gas shock tube. The average response time of the PVDF sensors to

Yi-Chun Wang; Ching-Hung Huang; Yung-Chun Lee; Ho-Hsun Tsai

2006-01-01

147

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

Microsoft Academic Search

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

E.-A. Brujan

2005-01-01

148

Transient and permanent cavitation in collagen gels by laser-induced thermoelastic pressure waves  

NASA Astrophysics Data System (ADS)

Laser-induced cavitation inside model objects--gels with various collagen concentrations (10 - 20%) was studied. Cavitation was produced by thermoelastic pressure waves generated under stress-confined conditions. Gel slabs were irradiated in air by nanosecond laser pulses from both sides. Under these conditions bipolar pressure pulses with compressional and tensile phases were generated on each side of the gel slabs. Due to interaction of these pressure pulses transient compression and tension with the amplitude two times higher are produced in the middle of the gel slabs. The tensile phase can induced cavitation. Two types of cavitation were found: transient (with bubble collapse) and permanent leading to formation of stable bubbles. To measure threshold of transient and permanent cavitation two methods were proposed. Transient cavitation was detected by scattering of a He-Ne probe beam from the cavitation bubbles and observed only for gels with low collagen concentration. Transient cavitation threshold for the gel with 10%-concentration amounts 28 bar. Transient cavitation lasts for approximately 3 microsecond(s) (approximately 1 microsecond(s) --growth for cavitation bubbles and approximately 2 microsecond(s) --collapse). Permanent cavitation threshold and total volume of permanent bubbles were studied by optical microscopy. Permanent cavitation can be divided into three types: cavitation with the following collapse accompanied by rupture and formation of small residual cavitation bubbles for gels with low (approximately 10%) collagen concentration; cavitation without collapse and with coalescence resulting in large bubble formation for gels with approximately 14% collagen concentration; cavitation without coalescence for gels with high approximately 20% collagen concentration.

Esenaliev, Rinat O.; Jacques, Steven L.

1996-05-01

149

Bioeffects caused by changes in acoustic cavitation bubble density and cell concentration: a unified explanation based on cell-to-bubble ratio and blast radius.  

PubMed

Acoustic cavitation has been shown to load drugs, proteins and DNA into viable cells as a complex function of acoustic and nonacoustic parameters. To better understand and quantify this functionality, DU145 prostate cancer cell suspensions at different cell concentrations (2.5 x 10(5) to 4.0 x 10(7) cells/mL) were exposed to 500 kHz ultrasound (US) over a range of acoustic energy exposures (2 to 817 J/cm(2); peak negative pressures of 0.64 to 2.96 MPa; exposure times of 120 to 2000 ms) in the presence of different initial concentrations of Optison contrast agent bubbles (3.6 x 10(4) to 9.3 x 10(7) bubbles/mL). As determined by flow cytometry, molecular uptake of calcein and cell viability both increased with increasing cell density; viability decreased and uptake was unaffected by increasing initial contrast agent concentration. When normalized relative to the initial contrast agent concentration (e.g., cells killed per bubble), bioeffects increased with increasing cell density and decreased with increasing bubble concentration. These varying effects of contrast agent concentration and cell density were unified through an overall correlation with cell-to-bubble ratio. Additional analysis led to estimation of "blast radii" over which bubbles killed or permeabilized cells; these radii were as much as 3 to 90 times the bubble radius. Combined, these results suggest that extensive molecular uptake into cells at high viability occurs for low-energy exposure US applied at a high cell-to-bubble ratio. PMID:12946524

Guzmán, Héctor R; McNamara, Andrew J; Nguyen, Daniel X; Prausnitz, Mark R

2003-08-01

150

Creep crack growth by diffusive cavitation  

Microsoft Academic Search

The model by Raj and Baik in which a macroscopic crack advances by the growth and coalescence of microvoids is reanalyzed and extended to include the effect of surface diffusion and small scale power-law creep. Using a boundary integral method, the analysis is valid when the stress intensity factor is the load parameter which determines the crack tip stress field.

Jin

2008-01-01

151

Controlled manipulation and in situ mechanical measurement of single co nanowire with a laser-induced cavitation bubble.  

PubMed

The flow induced by a single laser-induced cavitation bubble is used to manipulate individual Co nanowires. The short-lived (<20 ?s) bubble with a maximum size of 45 ?m is created in an aqueous solution with a laser pulse. Translation, rotation, and radial motion of the nanowire can be selectively achieved by varying the initial distance and orientation of the bubble with respect to the nanowire. Depending on the initial distance, the nanowire can be either pushed away or pulled toward the laser focus. No translation is observed for a distance further than approximately 60 ?m, while at closer distance, the nanowire can be bent as a result of the fast flow induced during the bubble collapse. Studying the dynamics of the shape recovery allows an estimation of the Young's modulus of the nanowire. The low measured Young's modulus (in a range from 9.6 to 13.0 GPa) of the Co nanowire is attributed to a softening effect due to structural defects and surface oxidation layer. Our study suggests that this bubble-based technique allows selectively transporting, orienting, and probing individual nanowires and may be exploited for constructing functional nanodevices. PMID:20804216

Huang, Xiaohu; Quinto-Su, Pedro A; Gonzalez-Avila, S Roberto; Wu, Tom; Ohl, Claus-Dieter

2010-10-13

152

Waveform analysis of cavitation in a globe valve.  

PubMed

Cavitation is a dynamic phenomenon occurring in fluid flows, where the local static pressure is lower than the saturated vapor pressure at working temperature. The growth and collapse of cavitation bubbles leads to corrosion and pitting of metal surfaces. Considering the fact that erosion by cavitation is still one of the current problems, it is important to detect the initiation, fully developed point of cavitation and to analyze its characteristics. In this research, an attempt is made to study acoustic waveform of cavitation in the globe valve. The waveform is transformed by Fast Fourier Transform and its important parameters such as amplitude, energy, frequency and so on are analyzed. PMID:19328513

Jazi, A Masjedian; Rahimzadeh, H

2009-02-20

153

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

PubMed

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

Louisnard, O

2011-06-25

154

Using cavitation for delignification of wood.  

PubMed

The Kraft process is the most widely used chemical process for the removal of lignin and other polymers from wood to obtain cellulosic pulp fibres. In the present study, the effect of cavitation (growth and violent collapse of vapour bubbles in a liquid) on delignification of wood was investigated. Steam was introduced in the reactor in order to study the effect of steam driven hybrid cavitation on delignification. The results obtained were subjected to kinetic analysis. The rates of delignification obtained using hydrodynamic cavitation were about 4-5 orders of magnitude greater than those obtained using acoustic cavitation (rate constants for delignification were 9.78×10(-6) and 6.8×10(-1)min(-1) for acoustic and hydrodynamic cavitation, respectively). The energy imparted by the pump in the hydrodynamic cavitation reactor was much higher than that imparted by the acoustic devices and this was considered to be the cause of the higher delignification rates. PMID:22325900

Baxi, Pranav B; Pandit, Aniruddha B

2012-01-20

155

Influence of high acoustic pressure amplitudes for spherically cavitating gas bubbles in a compressible fluid  

Microsoft Academic Search

In the present paper, a numerical solution is obtained for a nonlinear differential equation describing the radial motion of a pulsating gas bubble in a compressible fluid. The dependence of the erosion and luminescence of activating gas bubbles on the acoustic pressure amplitude is analyzed, and a physical explanation of this effect is proposed. The behavior of the bubble radius

H.-J. Rath

1979-01-01

156

A numerical study on the effects of cavitation on orifice flow  

NASA Astrophysics Data System (ADS)

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.

Dabiri, S.; Sirignano, W. A.; Joseph, D. D.

2010-04-01

157

Study of cavitation phenomena based on a technique for visualizing bubbles in a liquid pressurized chamber  

Microsoft Academic Search

In this paper, the influence of nozzle geometry on cavitation and near-nozzle spray behavior under liquid pressurized ambient is studied. For this purpose, eight steel drilled plates, with different diameters and degrees of conicity of their holes, are analyzed. A special near-nozzle field visualization technique, using a test rig pressurized with fuel, is used. Due to the difference in refractive

R. Payri; F. J. Salvador; J. Gimeno; J. de la Morena

2009-01-01

158

Bubble dynamics in boiling under high heat flux pulse heating  

Microsoft Academic Search

A new theoretical model of bubble behavior in boiling water under high heat flux pulse is presented. The essence of the model is nucleation in the superheated liquid followed by instantaneous formation of a vapor film, rapid bubble growth due to the pressure impulse, and cavitation bubble collapse. To check the model, boiling of methanol under 5 â¼ 50 MW

A. Asai

1991-01-01

159

Stability of bubbles in a linear elastic medium: Implications for bubble growth in marine sediments  

NASA Astrophysics Data System (ADS)

Methane bubbles in muddy fine-grained sediments grow initially through a process of elastic expansion, punctuated by discrete fracture events (LEFM-growth). The ability of the surrounding sediments to support a stress and actively resist expansion can, under conditions of low gas production or high sediment toughness, result in the cessation of growth and the presence of stable bubbles. Thus, it is possible for a bubble to stop growing despite the presence of a source in the sediments that continues to produce gas. This contrasts with growth of bubbles in a fluid medium, which cannot support a stress and so will continue to grow as long as a surrounding source provides gas. This "no-growth" condition is the result of the coupling between gas supply (methane production or supersaturation) and the sediment mechanics. Here we quantify this condition and present a criterion for the switch between no-growth and the LEFM growth regimes. We apply this theory to the sediments of Eckernförde Bay, in the Kiel Bight, Germany, and despite the absence of measurements for the key sediment mechanical properties, we can provide a qualitative explanation for the sizes and shapes of the observed bubble population with depth in the sediment. We also show how the release of hydrostatic pressure can stimulate growth, by pushing otherwise stable bubbles into the LEFM growth regime. This could provide a mechanism for the release of bubbles during periods of low water, such as during low tide or wave events.

Algar, C. K.; Boudreau, B. P.

2010-09-01

160

Mechanical heart valve cavitation.  

PubMed

Cavitation was first directly related to mechanical heart valves in the mid 1980s after a series of valve failures observed with the Edwards-Duromedics valve. The damages observed indicated that cavitation could be responsible. Later, several in vitro studies visualized the bubble formation and collapse of cavitation at mechanical heart valves. It was suggested that cavitation could also cause damage to the formed elements of blood and thereby enhance the risk of thromboembolic complications seen in mechanical heart valve patients. Therefore, an applicable technique for in vivo detection of cavitation is required. This article reviews techniques developed for in vivo detection of cavitation and suggests focus for future studies. PMID:16293013

Johansen, Peter

2004-09-01

161

Observation and quantification of gas bubble formation on a mechanical heart valve.  

PubMed

Clinical studies using transcranial Doppler ultrasonography in patients with mechanical heart valves (MHV) have detected gaseous emboli. The relationship of gaseous emboli release and cavitation on MHV has been a subject of debate in the literature. To study the influence of cavitation and gas content on the formation and growth of stable gas bubbles, a mock circulatory loop, which employed a Medtronic-Hall pyrolytic carbon disk valve in the mitral position, was used. A high-speed video camera allowed observation of cavitation and gas bubble release on the inflow valve surfaces as a function of cavitation intensity and carbon dioxide (CO2) concentration, while an ultrasonic monitoring system scanned the aortic outflow tract to quantify gas bubble production by calculating the gray scale levels of the images. In the absence of cavitation, no stable gas bubbles were formed. When gas bubbles were formed, they were first seen a few milliseconds after and in the vicinity of cavitation collapse. The volume of the gas bubbles detected in the aortic track increased with both increased CO2 and increased cavitation intensity. No correlation was observed between O2 concentration and bubble volume. We conclude that cavitation is an essential precursor to stable gas bubble formation, and CO2, the most soluble blood gas, is the major component of stable gas bubbles. PMID:11036552

Lin, H Y; Bianccucci, B A; Deutsch, S; Fontaine, A A; Tarbell, J M

2000-08-01

162

Microparticle Induced Cavitation  

NASA Astrophysics Data System (ADS)

Initiation of the cavitation process requires nuclei that include gases dissolved in the bulk liquid, trapped pockets of gas on solid surfaces such as walls, and trapped pockets of gas on microparticles. Due to imperfect wetting, pockets of gas are trapped and stabilized in crevices on any available surfaces. These gas nuclei act as weaknesses in the liquid initiating rupture and bubble formation. The initial size distribution of the nuclei is an important parameter in determining whether or not the initial microbubble might grow and detach. This implies a critical initial bubble radius necessary for growth. Experiments consisting of high speed photography of the growth of bubbles from surfaces with known nuclei size distributions were performed at different gas saturation levels to observe the effects of nuclei size and dissolved gas content on bubble growth and the detachment process. Measurements of bubble production frequency, bubble diameter, and surface contact angle were made to quantify the amount of gas being released in to the bulk liquid. Liquids examined were distilled water and jet fuel.

Davis, Michael

2005-11-01

163

The growth of fission gas bubbles in irradiated uranium dioxide  

Microsoft Academic Search

The growth of fission gas bubbles from supersaturated solution in irradiated uranium dioxide has been studied by electron microscopy under isothermal annealing conditions between 1300° and 1500°C. Measurements of the kinetics of bubble growth have enabled the diffusion coefficients of atomic xenon and krypton in irradiated uranium dioxide to be determined. The diffusion coefficients obtained may be expressed by the

R. M. Cornell

1969-01-01

164

Effects of cavitation on high-pressure atomization  

NASA Astrophysics Data System (ADS)

Although disintegration and breakup of a liquid jet emerging from a nozzle has been studied for a long time, the effects of nozzle internal flow and specifically cavitation on the breakup of liquid jets have not been well understood. In the orifice of liquid injectors at high pressure, cavitation occurs behind the sharp corners, where a strong pressure drop is present due to quick change in the flow direction. In addition, a high level of shear stress is present inside the boundary layer. Therefore, it is important to understand the influence of the shear on the cavitation. There are two main questions to be answered: What is the effect of the shear stress on the cavitation inception? And, how does the shear stress influence the cavitation bubble dynamics? In order to answer the above questions, the laminar flow of a liquid through the orifice of an atomizer is studied by means of numerical solution of Navier-Stokes equations. The total-stress criterion for cavitation is applied to find the regions where cavitation is likely to occur and compared with those of the traditional pressure criterion. Results show that the viscous stress has significant effects on cavitation inception. Cavitation bubble dynamics is also affected by the presence of shear strain or normal strain in the flow. Interaction between a single cavitation bubble and strained flow is considered in the next part. As a result of interaction between the shear flow and the bubble, two re-entrant jets are observed on two sides of the bubble during the collapse phase. Re-entrant jets with enough strength could breakup the bubble into smaller bubbles. Finally, four sources of disturbances are proposed that could be responsible for the improvement of atomization due to cavitation. Three of these sources are monopoles, quadrupoles and the vorticity generated during the bubble growth and collapse. It is shown that the monopole sources have the strongest contribution to the disturbances at the orifice exit. The other mechanism is the roll-up of the separated vortex sheet inside the orifice due to the disturbances caused by cavitation bubbles.

Dabiri Satari, Sadegh

165

Growth of a supersymmetric bubble: Inhomogeneity effects  

SciTech Connect

In a dense star, the Pauli exclusion principle functions as an enormous energy storage mechanism. Supersymmetry could provide a way to recapture this energy. If there is a transition to an exactly supersymmetric (SUSY) phase, the trapped energy can be released with consequences similar to gamma ray burst observations. Previous zeroth order calculations have been based on the behavior in a prototypical white dwarf of solar mass and earth radius (such as Sirius B) and have neglected density inhomogeneity. In this article we show that the effects of density inhomogeneity and of variations in masses and radii are substantial enough to encourage further exploration of the SUSY star model. In addition, the effects discussed here have possible applications to the growth of bubbles in other phase transition models in dense matter.

Clavelli, L. [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487 (United States)

2005-09-01

166

Acoustic cavitation as a mechanism of fragmentation of hot molten droplets in in cool liquids. [LMFBR  

Microsoft Academic Search

A mechanism that explains several of the observations of fragmentation of hot molten drops in coolants is presented. The mechanism relates the fragmentation to the development of acoustic cavitation and subsequent bubble growth within the molten material. The cavitation is assumed due to the severe pressure excursions calculated within the hot material as a result of the pressure pulses accompanying

M. Kazimi; C. Watson; D. Lanning; W. Rohsenow; N. Todreas

1976-01-01

167

Jet formation and shock wave emission during collapse of ultrasound-induced cavitation bubbles and their role in the therapeutic applications of high-intensity focused ultrasound  

NASA Astrophysics Data System (ADS)

The dynamics of inertial cavitation bubbles produced by short pulses of high-intensity focused ultrasound near a rigid boundary are studied to get a better understanding of the role of jet formation and shock wave emission during bubble collapse in the therapeutic applications of ultrasound. The bubble dynamics are investigated by high-speed photography with up to 2 million frames/s and acoustic measurements, as well as by numerical calculations. The significant parameter of this study is the dimensionless stand-off, ?, which is defined as the distance of the bubble centre at its maximum expansion scaled by the maximum bubble radius. High-speed photography is applied to observe the bubble motion and the velocity of the liquid jet formed during bubble collapse. Hydrophone measurements are used to determine the pressure and the duration of the shock wave emitted during bubble rebound. Calculations yield the variation with time of the bubble wall, the maximum velocity and the kinetic energy of the re-entrant jet. The comparisons between experimental and numerical data are favourable with regard to both shape history and translational motion of the bubble. The acoustic energy constitutes the largest individual amount in the energy balance of bubble collapse. The ratio of the shock wave energy, measured at 10 mm from the emission centre, to the cavitation bubble energy was 1:2.4 at ? = 1.55 and 1:3.5 at ? = 1. At this distance, the shock wave pressure ranges from 0.122 MPa, at ? = 1, to 0.162 MPa, at ? = 1.55, and the temporal duration at the half maximum level is 87 ns. The maximum jet velocity ranges from 27 m s-1, at ? = 1, to 36 m s-1, at ? = 1.55. For ? < 1.2, the re-entrant jet can generate an impact pressure on the nearby boundary larger than 50 MPa. We discuss the implications of the results for the therapeutic applications of high-intensity focused ultrasound.

Brujan, E. A.; Ikeda, T.; Matsumoto, Y.

2005-10-01

168

Cavitation in elastomeric solids: A defect-growth theory  

NASA Astrophysics Data System (ADS)

A new theory is introduced to study the phenomenon of cavitation in soft solids that, contrary to existing approaches, simultaneously: (i) applies to large (including compressible and anisotropic) classes of nonlinear elastic solids, (ii) allows to consider general 3D loading conditions with arbitrary triaxiality, and (iii) incorporates direct information on the initial shape, spatial distribution, and mechanical properties of the underlying defects at which cavitation can initiate. The basic idea is to cast cavitation in elastomeric solids as the homogenization problem of nonlinear elastic materials containing random distributions of zero-volume cavities, or defects. In spite of the generality of the proposed approach, the relevant calculations amount to solving tractable Hamilton-Jacobi equations, in which the initial size of the cavities plays the role of "time" and the applied load plays the role of "space."

Lopez-Pamies, Oscar; Idiart, Martin; Nakamura, Toshio

2011-03-01

169

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

PubMed

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

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

2012-03-01

170

Bubble and bubble cloud dynamics  

NASA Astrophysics Data System (ADS)

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

Matsumoto, Yoichiro

2000-07-01

171

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

NASA Astrophysics Data System (ADS)

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

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

172

Aspherical bubble dynamics and oscillation times  

SciTech Connect

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.

Vogel, A.; Noack, J. [Meizinisches Laserzentrum Luebeck (Germany); Chapyak, E.J.; Godwin, R.P. [Los Alamos National Lab., NM (United States)

1999-06-01

173

Evolution of a Collection of Bubbles with Application to Wakes, Bubble Screens, and Cloud Noise.  

National Technical Information Service (NTIS)

Contents: Bubble Dynamics and Cavitation Inception in Non-Uniform Flow Fields; Bubble Interactions with Vortices; Cavitation Dynamics at Microscale Level; Viscous Interaction Between Bubble and Line Vortex; The Motion of a Spherical Body Below a Free Surf...

G. L. Chahine

1994-01-01

174

Cavitation luminescence of argon-saturated alkali-metal solutions from a conical bubble  

NASA Astrophysics Data System (ADS)

In 1,2-propanediol solutions containing sodium chloride, spectra of luminescence from a collapsed conical bubble have been detected. Results show that the spectra consist of a broad continuum background, on which a resonance line arising from de-excitation of sodium atom at 589 nm and two satellite diffuse bands at ~554 nm and 620 nm respectively are superimposed. These are confirmed to be the emission from alkali-metal-argon exciplexes and are suggested to occur when the mixtures of alkali metal vapour and argon are rapidly compressed. The intracavity density of argon deduced from the line shift of Na resonance line data is estimated to be about 2 × 1026 m-3.

Jing, Ha; Jie He, Shou; Fang, Wang; Min, Song Jian

2008-10-01

175

Cavitation in elastomeric solids: I—A defect-growth theory  

Microsoft Academic Search

It is by now well established that loading conditions with sufficiently large triaxialities can induce the sudden appearance of internal cavities within elastomeric (and other soft) solids. The occurrence of such instabilities, commonly referred to as cavitation, can be attributed to the growth of pre-existing defects into finite sizes. This paper introduces a new theory to study the phenomenon of

Oscar Lopez-Pamies; Martín I. Idiart; Toshio Nakamura

2011-01-01

176

Underwater explosions and cavitation phenomena  

Microsoft Academic Search

Some aspects of underwater explosions and cavitation phenomena have been studied by using a thermodynamic equation of state for water and a one-dimensional Lagrangian hydrocode. The study showed that surface cavitation is caused by the main blast wave and a bubble pulse from rebound of a release wave moving toward the center of the exploding bubble. Gravity has little effect

Kamegai

1979-01-01

177

Cavitation Research and Ship Propeller Design  

Microsoft Academic Search

The role of cavitation research in the design of ship propellers and the influence of research on propeller design is reviewed. The historical development of research on bubble cavitation is an example of a lack of communication between research and design. Research on sheet cavitation is starting now and simplifications such as two dimensional cavitation are being made. It is

G. Kuiper

1997-01-01

178

Statistical characteristics of cavitation noise  

NASA Astrophysics Data System (ADS)

Cavitation noise originates as a superposition of pressure waves emitted during oscillations of individual cavitation bubbles. These pressure waves contain useful information on bubbles generating them and efforts are done to extract it. Unfortunately the pressure waves emitted by different bubbles usually overlap heavily and thus in experiments it makes sense to measure statistical characteristics only. Typical statistical characteristics determined experimentally encompass autospectral densities and instantaneous autospectra. To be able to extract information concerning the oscillating bubbles, suitable models of both cavitation bubbles and cavitation noise are necessary. It has been found out recently that a reasonable insight into the cavitation noise structure may be obtained by simulating cavitation noise on a computer and comparing statistical characteristics of simulated cavitation noise with those determined experimentally. By varying different parameters in theoretical models used to simulate the noise, a good agreement between the simulated and measured cavitation noise statistical characteristics can be obtained. The models parameters thus found may be then analyzed from a physical point of view and conclusions on behavior of cavitation bubbles can be drawn. [Work supported by the Ministry of Education of the Czech Republic as the research Project No. MSM 245100304.

Vokurka, Karel

2002-11-01

179

Cavitation in trees  

NASA Astrophysics Data System (ADS)

Sap is transported under tension (i.e. negative pressure) in trees, according to the tension-cohesion theory. Since water is physically instable under negative pressure, a risk of cavitation is possible. Techniques have been developed during the past two decennia to study cavitation in trees. Trees appear remarkably immune to cavitation events. Cavities form only when extreme water stresses occur or when sap freezes. Nucleation is heterogeneous in trees, presumably caused by the aspiration of air bubbles through conduit walls. Threshold xylem pressures for cavitation vary greatly between species, in concordance with the great functional and ecological diversity of trees. To cite this article: H. Cochard, C. R. Physique 7 (2006).

Cochard, Hervé

2006-11-01

180

Percolation models for boiling and bubble growth in porous media  

SciTech Connect

We analyze the liquid-to-vapor phase change in single-component fluids in porous media at low superheats. Conditions typical to steam injection in porous media are taken. We examine nucleation, phase equilibria and their stability, and the growth of vapor bubbles. Effects of pore structure are emphasized. It is shown that at low supersaturations, bubble growth can be described as a percolation process. In the absence of spatial gradients, macroscopic flow properties are calculated in terms of nucleation parameters. A modification of gradient percolation is also proposed in the case of spatial temperature gradients, when solid conduction predominates. 22 refs., 10 figs., 1 tab.

Yortsos, Y.C.

1991-05-01

181

Visualization and simulation of bubble growth in pore networks  

SciTech Connect

Bubble nucleation and bubble growth in porous media is an important problem encountered in processes, such as pressure depletion and boiling. To understand its basic aspects, experiments and numerical simulations in micromodel geometries were undertaken. Experiments of bubble growth by pressure depletion were carried out in 2-D etched-glass micromodels and in Hele-Shaw cells. Nucleation of bubbles and the subsequent growth of gas clusters were visualized. Contrary to the bulk or to Hele-Shaw cells, gas clusters in the micromodel have irregular and ramified shapes and share many of the features of an external invasion process (e.g. of percolation during drainage). A pore network numerical model was developed to simulate the growth of multiple gas clusters under various conditions. The model is based on the solution of the convection-diffusions equation and also accounts for capillary and viscous forces, which play an important role in determining the growth patterns. Numerical simulation resulted in good agreement with the experimental results.

Li, Xuehai; Yortsos, Y.C.

1994-03-01

182

MICROLAYER FORMATION, EVAPORATION AND BUBBLE GROWTH IN NUCLEATE BOILING  

Microsoft Academic Search

A numerical study of microlayer formation and evaporation is reported in which computer programs developed in order to predict the isothermal (initial) and the instantaneous microlayer thicknesses as well as the time varying mass evaporated from the microlayer for any specified bubble growth rate are presented. The results of these programs show that the isothermal microlayer thickness (delta)(,0)(r) is of

HASSAN EL-BANNA SAAD FATH

1981-01-01

183

Microlayer Formation, Evaporation and Bubble Growth in Nucleate Boiling  

Microsoft Academic Search

A numerical study of microlayer formation and evaporation is reported in which computer programs developed in order to predict the isothermal (initial) and the instantaneous microlayer thicknesses as well as the time varying mass evaporated from the microlayer for any specified bubble growth rate are presented. The results of these programs show that the isothermal microlayer thickness ??(r) is of

Hassan El-Banna Saad Fath

1981-01-01

184

Micropumping of liquid by directional growth and selective venting of gas bubbles  

Microsoft Academic Search

We introduce a new mechanism to pump liquid in microchannels based on the directional growth and displacement of gas bubbles in conjunction with the non-directional and selective removal of the bubbles. A majority of the existing bubble-driven micropumps employs boiling despite the unfavorable scaling of energy consumption for miniaturization because the vapor bubbles can be easily removed by condensation. Other

Dennis Desheng Meng; Chang-Jin “CJ” Kim

2008-01-01

185

Gas bubble formation and growth processes in thin gold films bombarded by Argon ion beams  

Microsoft Academic Search

Transmission electron microscopy has been applied to the study of gas bubble formation and growth processes in gold irradiated with 25 keV Ar ions to fluences of 10 to 10 ions\\/cm (293 K ? T ? 673 K.) The dependence of main swelling parameters (mean bubble diameter, mean bubble concentration, gas bubble volume fraction) on irradiation temperature and total dose

F. Vasiliu; V. Teodorescu

1975-01-01

186

Bubbles  

NASA Astrophysics Data System (ADS)

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.

Prosperetti, Andrea

2004-06-01

187

A theoretical model for bubble enhanced ultrasound heating due to time-dependent bubble size distributions  

NASA Astrophysics Data System (ADS)

Substantial in vitro and in vivo evidence shows that cavitation activity can affect tissue heating in focused ultrasound surgery and acoustic hemostasis applications. In particular, the heating rate in tissue increases significantly after cavitation sets in. Exploitation of this phenomenon for clinical use requires knowledge of, among other parameters, the time-dependent bubble size distribution sustained during insonation. Difficulties associated with the measurement of bubble sizes during in vitro or in vivo experiments call for a theoretical approach to the problem. We will present a theoretical model that estimates the time-dependent distribution of bubble equilibrium radii. Shape instability thresholds and rectified diffusion thresholds bound asymptotic bubble size distributions, and the instantaneous size distributions are governed by growth rates. The temperature rise caused by such bubble activity is calculated and compared with experimental data. [Work supported by DARPA and the U.S. Army.

Xinmai, Yang; Holt, R. Glynn; Edson, Patrick; Roy, Ronald A.

2002-11-01

188

Introduction to Cavitation and Supercavitation.  

National Technical Information Service (NTIS)

Cavitation, i.e. the appearance of vapor bubbles and pockets inside an initially homogeneous liquid medium, occurs in very different situations. According to the flow configuration (shape and relative motion of the walls limiting the flow field, or physic...

J. M. Michel

2001-01-01

189

Blood vessel rupture by cavitation  

Microsoft Academic Search

Cavitation is thought to be one mechanism for vessel rupture during shock wave lithotripsy treatment. However, just how cavitation\\u000a induces vessel rupture remains unknown. In this work, a high-speed photomicrography system was set up to directly observe\\u000a the dynamics of bubbles inside blood vessels in ex vivo rat mesenteries. Vascular rupture correlating to observed bubble dynamics\\u000a were examined by imaging

Hong Chen; Andrew A. Brayman; Michael R. Bailey; Thomas J. Matula

2010-01-01

190

Numerical method for predicting ship propeller cavitation noise  

Microsoft Academic Search

During ship travels in high-velocity, propeller cavitation noise predominates in the radiated noise sources. However, experiential data regress method was use to predicate propeller cavitation noise in the past. In this article, propeller cavitation noise has been calculated by numerical computation method. From the engineering point of view, ship propeller has been disposed as a dipole bubble. Bubble volume pulse

Yong-Kun Zhang; Ying Xiong

2011-01-01

191

Search for neutron emission in laser-induced cavitation  

NASA Astrophysics Data System (ADS)

Laser-induced cavitation bubbles in heavy water are investigated at different parameter settings. Neutrons are searched for in close temporal proximity to cavitation luminescence flashes with an estimated detection efficiency of 4%. No neutrons in coincidence with cavitation luminescence have been detected. This yields an upper limit of emitted neutrons per bubble collapse of 5 × 10-4.

Geisler, R.; Schmidt-Ott, W.-D.; Kurz, T.; Lauterborn, W.

2004-05-01

192

Axisymmetric and three-dimensional boundary integral simulations of bubble growth from an underwater orifice  

Microsoft Academic Search

The formation of bubbles from an underwater orifice is studied by means of a boundary integral method. Since the bubble process is highly transient the flow field is assumed to be irrotational. A potential-flow boundary-integral formulation is employed to simulate the growth of a bubble from a needle in an unbounded domain and in a tube. The geometry of the

Hasan O?uz; Jun Zeng

1997-01-01

193

The life cycle of individual boiling bubbles: Insights from beyond optical imaging  

NASA Astrophysics Data System (ADS)

With a high-speed camera, we have investigated the dynamics of individual vapor bubbles boiling on a laser-heated surface. Their sizes and shapes as they grow and depart from a surface are correlated with simultaneous thermal imaging measurements of the boiling surface using thermoreflectance-based microscopy to measure temperatures of individual stochastic events. Analysis of both the thermal profiles and the bubble shapes suggests the presence of an evaporating liquid microlayer under the developing bubble. Tuning surface and heating properties, we control the shapes of bubbles, ranging from regular periodic growth and departure to stochastic bubbles which exhibit rapid cavitation-like expansion and collapse. Unlike typical cavitation bubbles which collapse and form jets pointed towards the surface, jets from bubbles observed during boiling were observed to be directed away from the surface. By tuning the wettability of the substrate, we will report on how wettability affects the strength and direction of these jets.

Parker, Scott; Bae, Sung Chul; Cahill, David; Granick, Steve

2012-02-01

194

Comparison of electrohydraulic lithotripters with rigid and pressure-release ellipsoidal reflectors. II. Cavitation fields.  

PubMed

Dramatically different cavitation was produced by two separate acoustic pulses that had different shapes but similar duration, frequency content, and peak positive and negative pressure. Both pulses were produced by a Dornier HM-3 style lithotripter: one pulse when the ellipsoidal reflector was rigid, the other when the reflector was pressure release. The cavitation, or bubble action, generated by the conventional rigid-reflector pulse was nearly 50 times longer lived and 3-13 times stronger than that produced by the pressure-release-reflector pulse. Cavitation durations measured by passive acoustic detection and high-speed video agreed with calculations based on the Gilmore equation. Cavitation intensity, or destructive potential, was judged (1) experimentally by the size of pits in aluminum foil detectors and (2) numerically by the calculated amplitude of the shock wave emitted by a collapsing bubble. The results indicate that the trailing positive spike in the pressure-release-reflector waveform stifles bubble growth and mitigates the collapse, whereas the trough after the positive spike in the rigid-reflector waveform triggers inertially driven growth and collapse. The two reflectors therefore provide a tool to compare effects in weakly and strongly cavitating fields and thereby help assess cavitation's role in lithotripsy. PMID:10462818

Bailey, M R; Blackstock, D T; Cleveland, R O; Crum, L A

1999-08-01

195

Bubbles  

NASA Astrophysics Data System (ADS)

``Vanitas vanitatum et omnia vanitas": bubbles are emptiness, non-liquid, a tiny cloud shielding a mathematical singularity. Born from chance, a violent and brief life ending in the union with the (nearly) infinite. But a wealth of phenomena spring forth from this nothingness: underwater noise, sonoluminescence, boiling, many others. Ultimately, diffusive processes govern much of the physics, and the difference between the diffusivity of heat and dissolved gases in ordinary liquids holds the key to the striking differences between gas and vapor bubbles.

Prosperetti, Andrea

2002-11-01

196

Plasma and Cavitation Dynamics during Pulsed Laser Microsurgery invivo  

NASA Astrophysics Data System (ADS)

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.

Hutson, M. Shane; Ma, Xiaoyan

2007-10-01

197

Plasma and cavitation dynamics during pulsed laser microsurgery in vivo.  

PubMed

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. PMID:17995217

Hutson, M Shane; Ma, Xiaoyan

2007-10-10

198

Erosive Destruction by Cavitation Flow Erosive Zerstoerungen durch Stroemungskavitation.  

National Technical Information Service (NTIS)

An intensive erosion cavitation chamber is developed and used to prove the corrosive and erosive effects of bubble explosion on metal surfaces. The mechanical loads during initial fluidic impact on soft aluminum are studied for erosive cavitation intensit...

H. Louis

1973-01-01

199

The Research and Development of a Cavitating Water Jet Cleaning System for Removing Marine Growth and Fouling from Offshore Platform Structures.  

National Technical Information Service (NTIS)

The objective of this program was to develop the technology to demonstrate the use of controlled cavitation erosion to remove marine growth from off-shore structures. The major advantage of a cavitation system would be the smaller energy input requirement...

A. P. Thiruvengadam J. T. Parker W. H. Bohli

1979-01-01

200

Bubble Bubble  

NSDL National Science Digital Library

With magic bubble solution, a boy discovers that he can blow any kind of bubble imaginable: a kangaroo, a bird, a car, or a boat. Mercer Mayer's colorful illustrations enliven this engaging tale of mysterious bubbles.

Mayer, Mercer

2009-11-11

201

Experimental analysis of bubble growth, departure and interactions during pool boiling on artificial nucleation sites  

SciTech Connect

The present work describes experimental results of pentane pool boiling, simplified to the cases of boiling on a single or on two adjacent nucleation sites. Bubbles growths have been recorded by a high speed camera under various wall superheat conditions. Bubble volume has been plotted as a function of time, and an experimental growth law has been proposed. Oscillations were observed during growth, showing the interaction of one bubble with the preceding bubble released from the same nucleation site. Lateral coalescence has been visualized and the images have brought to the fore the capillary effects on the distortion of the interface. (author)

Siedel, S.; Cioulachtjian, S.; Bonjour, J. [CETHIL - UMR5008 CNRS INSA-Lyon Univ. Lyon1, Bat. Sadi Carnot, 9 rue de la Physique, INSA-Lyon, F-69621 Villeurbanne Cedex (France)

2008-09-15

202

Numerical prediction of impact force in cavitating flows  

NASA Astrophysics Data System (ADS)

An analytical method including a macroscopic cavitation model based on the homogeneous flow theory and a microscopic cavitation model based on the bubble dynamic was proposed for the prediction of the impact force caused by cavitation bubbles collapse in cavitating flows. A Large Eddy Simulation (LES) solver incorporated the macroscopic cavitation model was applied to simulate the unsteady cavitating flows. Based on the simulated flow field, the evolution of the cavitation bubbles was determined by a microscopic cavitation model from the resolution of a Rayleigh-Plesset equation including of the effects of the surface tension, the viscosity and compressibility of fluid, thermal conduction and radiation, the phase transition of water vapor at interface and chemical reactions. The cavitation flow around a hydrofoil was simulated to validate the macroscopic cavitation model. A good quantitative agreement was obtained between the prediction and the experiment. The proposed analytical method was applied to predict the impact force at cavitation bubbles collapse on a KT section in cavitating flows. It was found that the shock pressure caused by cavitation bubble collapse is very high. The impact force was predicted accurately comparing with the experimental data.

Zhu, B.; Wang, H.

2010-08-01

203

Impact vesiculation – a new trigger for volcanic bubble growth and degassing  

Microsoft Academic Search

We highlight a potentially important trigger for bubble growth and degassing in volcanic bombs. We have successfully triggered bubble growth in previously unvesiculated samples of silicate melt during experiments to simulate volcanic bomb impact, by firing pellets at, and dropping weights onto, melt samples. We call suggest the term 'impact vesiculation' to denote this phenomenon, in the laboratory and in

D. A. Rothery; J. M. Sumner; O. Spieler; D. B. Dingwell

2007-01-01

204

Impact vesiculation - a new trigger for volcanic bubble growth and degassing  

Microsoft Academic Search

We highlight a potentially important trigger for bubble growth and degassing in volcanic bombs. We have successfully triggered bubble growth in previously unvesiculated samples of silicate melt during experiments to simulate volcanic bomb impact, by firing pellets at, and dropping weights onto, melt samples. We call this phenomenon \\

D. A. Rothery; J. M. Sumner; O. Spieler; D. B. Dingwell

2007-01-01

205

Use of a dual-pulse lithotripter to generate a localized and intensified cavitation field.  

PubMed

Localizing cavitation to the kidney stone in extracorporeal shock wave lithotripsy may be desirable since cavitation appears to play a major role in both stone comminution and renal tissue damage. A method has been developed to localize and intensify cavitation damage in vitro. Cavitation fields in water were filmed with a high-speed digital video camera. In a conventional lithotripter (CL), the shock wave produced by a single source creates a 2 x 10 cm cylindrical cloud of bubbles in water. Bubbles in the CL field collapse simultaneously along the focal axis to produce a nearly uniform 1-mm x 8-cm line of pits in 25-microm-thick aluminum foil. Our dual-pulse lithotripter (DPL) uses two shock wave sources, facing each other, confocal, and triggered simultaneously to create a 4 x 5 cm cylindrical cloud of bubbles that collapse over a range of times and strengths such that the greatest pit damage on foils is contained within a few square millimeters of the focus. The time for bubbles to grow and collapse was measured with a focused hydrophone and compared with calculations based on the Gilmore equation. Pressure doubling due to synchronous arrival of the two pulses at the focus created increased bubble growth and increased foil pit depth. Asynchronous timing between the two pulses elsewhere in the DPL field resulted in disruption of radial dynamics and negligible pitting to foils. Translation of bubbles was also investigated, both numerically and experimentally. While net translation was calculated to be <0.3 mm in all cases, the rapid acceleration of bubbles in a small region may contribute to their premature destruction in that region. Overall, radial dynamics were found to be largely responsible for the observed pattern of cavitation in the dual-pulse lithotripsy field. PMID:11572377

Sokolov, D L; Bailey, M R; Crum, L A

2001-09-01

206

Bubble growth rates in nucleate boiling of water at subatmospheric pressures  

Microsoft Academic Search

The growth rate of vapor bubbles is experimentally investigated up to departure in water boiling at pressures ranging from 26.7 to 2.0 kPa. Comparison of the data with existing theory shows the substantial influence of liquid inertia during initial growth and the gradual influence of heat diffusion during advanced growth. The observed bubble growth is found to be in quantitative

S. J. D. van Stralen; W. M. Sluyter; M. S. Sohal; R. Cole

1975-01-01

207

The Research and Development of a Cavitating Water Jet Cleaning System for Removing Marine Growth and Fouling from Offshore Platform Structures: Feasibility Evaluation.  

National Technical Information Service (NTIS)

The technical feasibility of using the cavitating water jet technique for removing marine growth and protective coatings from steel substrate material has been demonstrated under laboratory conditions in the initial phase of the program. The test results ...

S. C. Howard D. R. Koogle A. A. Hochrein

1978-01-01

208

Electron irradiation effect on bubble formation and growth in a sodium borosilicate glass  

SciTech Connect

In this study, the authors studied simultaneous and intermittent electron irradiation effects on bubble growth in a simple sodium borosilicate glass during Xe ion implantation at 200 C. Simultaneous electron irradiation increases the average bubble size in the glass. This enhanced diffusion is also shown by the migration of Xe from bubbles into the matrix when the sample is irradiated by an electron beam after the Xe implantation.

Chen, X.; Birtcher, R. C.; Donnelly, S. E.

2000-02-08

209

Combined effect of viscosity and vorticity on single mode Rayleigh-Taylor instability bubble growth  

NASA Astrophysics Data System (ADS)

The combined effect of viscosity and vorticity on the growth rate of the bubble associated with single mode Rayleigh-Taylor instability is investigated. It is shown that the effect of viscosity on the motion of the lighter fluid associated with vorticity accumulated inside the bubble due to mass ablation may be such as to reduce the net viscous drag on the bubble exerted by the upper heavier fluid as the former rises through it.

Banerjee, Rahul; Mandal, Labakanta; Roy, S.; Khan, M.; Gupta, M. R.

2011-02-01

210

Combined effect of viscosity and vorticity on single mode Rayleigh-Taylor instability bubble growth  

SciTech Connect

The combined effect of viscosity and vorticity on the growth rate of the bubble associated with single mode Rayleigh-Taylor instability is investigated. It is shown that the effect of viscosity on the motion of the lighter fluid associated with vorticity accumulated inside the bubble due to mass ablation may be such as to reduce the net viscous drag on the bubble exerted by the upper heavier fluid as the former rises through it.

Banerjee, Rahul; Mandal, Labakanta; Roy, S.; Khan, M.; Gupta, M. R. [Department of Instrumentation Science and Centre for Plasma Studies, Jadavpur University, Kolkata 700032 (India)

2011-02-15

211

Cavitation and Superplasticity.  

National Technical Information Service (NTIS)

Cavitation occurs in many alloy systems during superplastic flow. Cavities either pre-exist or nucleate on grain boundaries and their subsequent growth, coalescence and interlinkage leads to premature failure. The presence of cavities in superplastically ...

N. Ridley

1987-01-01

212

Mechanism of the initial stage of bubble growth in a liquid close to the superheat limit  

SciTech Connect

The concept of the critical nucleus is the basis of the homogeneous nucleation theory which enables the upper limit of a superheat to be calculated. Only nucleus formation is considered. It is as if nuclei that reach the critical dimensions are removed from the system and replaced by an appropriate mass of liquid. The theory does not give any information concerning the dynamics of bubble growth either. Nevertheless, some researchers use the concept of the critical nucleus as the initial condition in a descritpion of the bubble growth in superheated liquid. A bubble begins to grow after the disturbance of the balance, when the pressure difference exceeds the surface tension. According to this scheme, the initial bubble growth results from the fact that the vapor pressure in the bubble is higher than that in the surrounding liquid.

Avksentyuk, B.P. [Institute of Thermophysics, Novosibirsk (Russian Federation)

1995-11-01

213

Gas-bubble growth mechanisms in the analysis of metal fuel swelling  

SciTech Connect

During steady-state irradiation, swelling rates associated with growth of fission-gas bubbles in metallic fast reactor fuels may be expected to remain small. As a consequence, bubble-growth mechanisms are not a major consideration in modeling the steady-state fuel behavior, and it is usually adequate to consider the gas pressure to be in equilibrium with the external pressure and surface tension restraint. On transient time scales, however, various bubble-growth mechanisms become important components of the swelling rate. These mechanisms include growth by diffusion, for bubbles within grains and on grain boundaries; dislocation nucleation at the bubble surface, or ''punchout''; and bubble growth by creep. Analyses of these mechanisms are presented and applied to provide information on the conditions and the relative time scales for which the various processes should dominate fuel swelling. The results are compared to a series of experiments in which the swelling of irradiated metal fuel was determined after annealing at various temperatures and pressures. The diffusive growth of bubbles on grain boundaries is concluded to be dominant in these experiments.

Gruber, E.E.; Kramer, J.M.

1986-06-01

214

Quasi-one-dimensional steady-state cavitating nozzle flows  

Microsoft Academic Search

Quasi-one-dimensional cavitating nozzle flows are considered by employing a homogeneous bubbly liquid flow model. The nonlinear dynamics of cavitating bubbles is described by a modified Rayleigh Plesset equation that takes into account bubble\\/bubble interactions by a local homogeneous mean-field theory and the various damping mechanisms by a damping coefficient, lumping them together in the form of viscous dissipation. The resulting

C. F. Delale; G. H. Schnerr; J. Sauer

2001-01-01

215

The role of cavitation in porous media desaturation under tension  

Microsoft Academic Search

A potential mechanism for liquid drainage in wet porous media based on cavitation of water (the spontaneous formation of water vapor bubbles) under tension is proposed. Cavitation theory applied to an idealized pore predicts considerable differences in drainage branches of characteristic curves determined under tension and with imposed positive pressure. A potentially important aspect of cavitation is the possibility of

Markus Tuller

216

Cavitation during desaturation of porous media under tension  

Microsoft Academic Search

A potential mechanism for liquid drainage in wet porous media based on cavitation of water (the spontaneous formation of water vapor bubbles) under tension is proposed. Cavitation theory applied to an idealized pore predicts considerable differences in drainage branches of characteristic curves determined under tension and with imposed positive pressure. A potentially important aspect of cavitation is the possibility of

Markus Tuller

2002-01-01

217

Cavitation Induced Lift Fluctuations  

NASA Astrophysics Data System (ADS)

For various reasons, liquid handling devices, such as pumps, turbines, marine propellers and hydrofoils must often operate in the cavitating regime. Considerable research has gone into avoiding cavitation but little effort has been made to understand the complex physics associated with operation in the partially cavitating regime. This is an experimental study of lift oscillations on a NACA 0015 hydrofoil. Fluctuating lift is measured at two different geometric scales in two different water tunnels. The spectral characteristics of the fluctuations are found to vary considerable over a range of 1.0 ?/2×? 8.5. The amplitude of the fluctuations can exceed 100% of the steady state lift and are associated with the periodic shedding of vortical clouds of bubbles into the flow. Two competing mechanisms are found for the induced shedding of cloud cavitation. At high values of ?/2×?, reentrant jet physics dominate, with sheet cavity oscillations at a frequency, based on cavity length, of fl/U equal 0.3. At low values of ?/2×? , bubbly flow shock wave phenomena dominate with a constant Strouhal number based on chord length of fc/U equal 0.2. A significant effect on the wake structure is also noted. Good agreement with numerical simulations based on the LES technique is generally found. Sponsored by the National Science Foundation and the Office of Naval Research.

Arndt, Roger E. A.; Keller, Anreas; Kjeldsen, Morten

1999-11-01

218

Nonequilibrium bubbles in a flowing langmuir monolayer.  

PubMed

We investigate the nonequilibrium behavior of two-dimensional gas bubbles in Langmuir monolayers. A cavitation bubble is induced in liquid expanded phase by locally heating a Langmuir monolayer with an IR-laser. At low IR-laser power the cavitation bubble is immersed in quiescent liquid expanded monolayer. At higher IR-laser power thermo capillary flow around the laser-induced cavitation bubble sets in. The thermo capillary flow is caused by a temperature dependence of the gas/liquid line tension. The slope of the line tension with temperature is determined by measuring the thermo capillary flow velocity. Thermodynamically stable satellite bubbles are generated by increasing the surface area of the monolayer. Those satellite bubbles collide with the cavitation bubble. Upon collision the satellite bubbles either coalesce with the cavitation bubble or slide past the cavitation bubble. Moreover we show that the satellite bubbles can also be produced by the emission from the laser-induced cavitation bubbles. PMID:16853828

Muruganathan, Rm; Khattari, Z; Fischer, Th M

2005-11-24

219

Sonoporation: Mechanical DNA Delivery by Ultrasonic Cavitation  

Microsoft Academic Search

Development of nonviral gene transfer methods would be a valuable addition to the gene-therapy armamentarium, particularly for localized targeting of specific tissue volumes. Ultrasound can produce a variety of nonthermal bioeffects via acoustic cavitation including DNA delivery. Cavitation bubbles may induce cell death or transient membrane permeabilization (sonoporation) on a single cell level, as well as microvascular hemorrhage and disruption

Douglas L. Miller; Sorin V. Pislaru; James F. Greenleaf

2002-01-01

220

Cavitation Research and Ship Propeller Design.  

National Technical Information Service (NTIS)

The role of cavitation research in the design of ship propellers and the influence of research on propeller design is reviewed. The historical development of research on bubble cavitation is an example of a lack of communication between research and desig...

G. Kuiper

1998-01-01

221

Speculative Growth, Overreaction, and the Welfare Cost of Technology-Driven Bubbles  

Microsoft Academic Search

This paper develops a general equilibrium model to examine the consequences of technology-driven asset price bubbles for capital accumulation, growth, and welfare. Eq- uity prices in the model exhibit \\

Kevin J. Lansing

222

Bubble dynamics in boiling under high heat flux pulse heating  

SciTech Connect

A new theoretical model of bubble behavior in boiling water under high heat flux pulse is presented. The essence of the model is nucleation in the superheated liquid followed by instantaneous formation of a vapor film, rapid bubble growth due to the pressure impulse, and cavitation bubble collapse. To check the model, boiling of methanol under 5 {approximately} 50 MW m{sup {minus}2} heat flux pulse using a small thin film heater has been experimentally investigated. When the heat flux was relatively low (< 20 MW m{sup {minus}2}), a bubble grew in a hemispherical shape. When the heat flux was extremely high (> 20 MW m{sup {minus}2}), many small bubbles nucleated and combined into a vapor film. The bubble behavior in the latter case is explained well by the model.

Asai, A. (Canon Inc. Research Center, Kanagawa (Japan))

1991-11-01

223

Micropumping of liquid by directional growth and selective venting of gas bubbles.  

PubMed

We introduce a new mechanism to pump liquid in microchannels based on the directional growth and displacement of gas bubbles in conjunction with the non-directional and selective removal of the bubbles. A majority of the existing bubble-driven micropumps employs boiling despite the unfavorable scaling of energy consumption for miniaturization because the vapor bubbles can be easily removed by condensation. Other gas generation methods are rarely suitable for micropumping applications because it is difficult to remove the gas bubbles promptly from a pump loop. In order to eradicate this limitation, the rapid removal of insoluble gas bubbles without liquid leakage is achieved with hydrophobic nanopores, allowing the use of virtually any kind of bubbles. In this paper, electrolysis and gas injection are demonstrated as two distinctively different gas sources. The proposed mechanism is first proved by circulating water in a looped microchannel. Using H(2) and O(2) gas bubbles continuously generated by electrolysis, a prototype device with a looped channel shows a volumetric flow rate of 4.5-13.5 nL s(-1) with a direct current (DC) power input of 2-85 mW. A similar device with an open-ended microchannel gives a maximum flow rate of approximately 65 nL s(-1) and a maximum pressure head of approximately 195 Pa with 14 mW input. The electrolytic-bubble-driven micropump operates with a 10-100 times higher power efficiency than its thermal-bubble-driven counterparts and exhibits better controllability. The pumping mechanism is then implemented by injecting nitrogen gas bubbles to demonstrate the flexibility of bubble sources, which would allow one to choose them for specific needs (e.g., energy efficiency, thermal sensitivity, biocompatibility, and adjustable flow rate), making the proposed mechanism attractive for many applications including micro total analysis systems (microTAS) and micro fuel cells. PMID:18497918

Meng, Dennis Desheng; Kim, Chang-Jin C J

2008-04-24

224

A Model for Surface Induced Growth of Inert Gas Bubbles in Irradiated Copper-Boron Alloys  

SciTech Connect

A matrix containing inert gas bubbles dilates in direct proportion to the growth experienced by the gas bubbles. This phenomenon is termed as swelling. A model for the swelling induced by the growth of the helium gas bubbles in irradiated copper-boron alloys is presented. The bubbles grow by acquiring vacancies from the external surface, which acts as a source of vacancies. The vacancies reach the surface of the bubbles mainly via lattice diffusion and to a limited extent via diffusion through short-circuiting paths such as grain boundaries and dislocation pipes. The model predicts that overall swelling of the matrix varies as 1.5 power of time. Another consequence of the present model is that the growth rate of a gas bubble varies inversely as the cube of its distance from the external surface. The model has been applied to the data on irradiated copper-boron alloys and found to be in accord with the experimental results. The model is general and can be applied to the growth of all kinds of stationary inert gas bubbles trapped within a crystalline matrix. (authors)

Tiwari, G.P.; Ramadasan, E. [Post Irradiation Examination Division, Bhabha Atomic Research Division (India)

2006-07-01

225

An experimental investigation of bubble growth and detachment in vertical upflow and downflow boiling  

Microsoft Academic Search

A visual study of vapor bubble growth and departure in vertical upflow and downflow forced convection boiling is presented. A vertical flow boiling facility was constructed with a transparent, electrically-heated test section in which the ebullition process could be observed. High-speed digital images of flow boiling phenomena were obtained, which were used to measure bubble growth, departure diameters, and lift-off

G. E. Thorncroft; J. F. Klausner; R. Mei

1998-01-01

226

The role of gas in ultrasonically driven vapor bubble growth.  

PubMed

In this paper we study both experimentally and theoretically the dynamics of an ultrasound-driven vapor bubble of perfluoropentane (PFP) inside a droplet of the same liquid, immersed in a water medium superheated with respect to the PFP boiling point. We determine the temporal evolution of the bubble radius with ultra-high speed imaging at 20 million frames per second. In addition, we model the vapor-gas bubble dynamics, based on a Rayleigh-Plesset-type equation, including thermal and gas diffusion inside the liquid. We compare the numerical results with the experimental data and find good agreement. We underline the fundamental role of gas diffusion in order to prevent total recondensation of the bubble at collapse. PMID:23528293

Shpak, Oleksandr; Stricker, Laura; Versluis, Michel; Lohse, Detlef

2013-03-26

227

The role of gas in ultrasonically driven vapor bubble growth  

NASA Astrophysics Data System (ADS)

In this paper we study both experimentally and theoretically the dynamics of an ultrasound-driven vapor bubble of perfluoropentane (PFP) inside a droplet of the same liquid, immersed in a water medium superheated with respect to the PFP boiling point. We determine the temporal evolution of the bubble radius with ultra-high speed imaging at 20 million frames per second. In addition, we model the vapor-gas bubble dynamics, based on a Rayleigh-Plesset-type equation, including thermal and gas diffusion inside the liquid. We compare the numerical results with the experimental data and find good agreement. We underline the fundamental role of gas diffusion in order to prevent total recondensation of the bubble at collapse.

Shpak, Oleksandr; Stricker, Laura; Versluis, Michel; Lohse, Detlef

2013-04-01

228

Monitoring Cavitation in HIFU as an Aid to Assisting Treatment  

NASA Astrophysics Data System (ADS)

Rapid hypothermia resulting in tissue necrosis is often associated with bubble activity (normally from cavitation) in HIFU treatment. Indeed in some HIFU protocols, the evidence of cavitation is taken as an indicator of tissue lesions. In this paper we discuss two methods to delineate reliably the region in which cavitation occurs, so that a history of the cavitation events can be provided automatically during treatment. Results are shown on simulated images and from a clinical treatment session.

Hsieh, Chang-Yu; Smith, Penny Probert; Kennedy, James; Leslie, Thomas

2007-05-01

229

Mechanical heart valve cavitation: valve specific parameters.  

PubMed

Several aspects of mechanical heart valve cavitation, in particular of "severe" vapor cavitation, have been investigated in order to describe the phenomenon of cavitation itself and to classify various mechanical heart valves with respect to their tendency to cavitation. Furthermore, following the results of the measurements, a model for determination of time-dependent physical properties and dynamics of cavitation bubbles, such as size, pressure and temperature was developed. In order to classify the cavitation tendency of mechanical valves, a pulsatile hydraulic-driven circularly mock loop was used. Besides measurements of the relevant hemodynamic parameters, the leaflet velocities of the valves were also determined. In addition, numerous high-resolution pressure measurements, in particular the pressure drops necessary for the initiation of cavitation (local atrial pressure drop), were performed. For the investigation of bubble dynamics, a second pulsatile electro-magnetically-driven tester was used. The influence of density, viscosity and temperature of the fluid on the onset of cavitation was investigated. Cavitation events were recorded with a digital high-speed video camera (up to 40,500 frames/sec) for all investigated heart valves and under different conditions. A critical local upstream pressure drop (located within the model atrium after valve closure) of 450 mmHg was found for all valves as well as a valve specific correlation between left ventricular pressure gradient and local upstream pressure drop. Also, a valve dependent correlation between left ventricular pressure gradient and the local upstream pressure drop was provided. Finally, valve specific parameters were found to predict the cavitation tendency for a specific heart valve. The implementation of a suitable theoretical model allowed conclusions on bubble physics. High pressures (up to 800 bar) and temperatures (up to 1,300 degrees C) at bubble collapse have been determined. The influence of fluid parameters such as density, viscosity and temperature on the onset of cavitation is negligible within physiological range. Critical regions for cavitation for all mechanical heart valves were detected. All mechanical heart valves investigated show cavitation under different conditions (dp/dt) associated with high pressures and temperatures at bubble collapse. Cavitation bubble occurrence depends on valve design and location. PMID:15560680

Eichler, M J; Reul, H M

2004-10-01

230

Taxing the rich: recombinations and bubble growth during reionization  

NASA Astrophysics Data System (ADS)

Reionization is inhomogeneous for two reasons: the clumpiness of the intergalactic medium (IGM), and clustering of the discrete ionizing sources. While numerical simulations can in principle take both into account, they are at present limited by small box sizes. On the other hand, analytic models have only examined the limiting cases of a clumpy IGM (with uniform ionizing emissivity) and clustered sources (embedded in a uniform IGM). Here, we present the first analytic model that includes both factors. At first, recombinations can be ignored and ionized bubbles grow primarily through major mergers, because at any given moment the bubbles have a well-defined characteristic size. As a result, reionization resembles `punctuated equilibrium,' with a series of well-separated sharp jumps in the ionizing background. These features are local effects and do not reflect similar jumps in the global ionized fraction. We then combine our bubble model with a simple description of recombinations in the IGM. We show that the bubbles grow until recombinations balance ionizations, when their expansion abruptly halts. If the IGM density structure is similar to that at moderate redshifts, this limits the bubble radii to ~20 comoving Mpc; however, if the IGM is significantly clumpier at higher redshifts (because of minihalo formation, for example), the limit could be much smaller. Once a bubble reaches saturation, that region of the Universe has for all intents and purposes entered the `post-overlap' stage. Because different HII regions saturate over a finite time interval, the overlap epoch actually has a finite width. Our model also predicts a mean recombination rate several times larger than expected for a uniformly illuminated IGM. This picture naturally explains the substantial large-scale variation in Lyman-series opacity along the lines of sight to the known z > 6 quasars. More quasar spectra will shed light on the transition between the `bubble-dominated' topology characteristic of reionization and the `web-dominated' topology characteristic of the later Universe.

Furlanetto, Steven R.; Oh, S. Peng

2005-11-01

231

Cavitation induced by continuous wave lasers  

NASA Astrophysics Data System (ADS)

Laser induced cavitation bubbles in water results from either dielectric breakdown or the fast evaporation due to radiation absorption. The bubbles expand, reach a maximum radius and then supersonically collapse producing a by shock wave. So far, laser induced cavitation has been observed by using short pulsed (femto to nanosecond) lasers. In this report, we observe laser induced cavitation bubbles by using relatively low power (200 mW) cw light sources. A beam from a cw Nd:YAG laser (?=1.064 ?m) is tightly focused on saturated solution of copper nitrate salt. The large absorption coefficient at the illumination wavelength produces large thermal gradients and high peak temperatures leading to the formation of cavitation bubbles near the solution-glass interface. The collapse of the bubbles is so violent that they can be listened without any special device. Cavitation appears at quite regular time escales. The frequency of bubble formation depends on the laser intensity reaching frequencies as high as 4 KHz. We present detailed experimental results on the bubble formation using a phase contrast, light scattering and hydrophones.

Ramirez-San-Juan, J. C.; Rodriguez-Aboytes, E.; Korneev, N.; Baldovinos-Pantaleon, O.; Chiu-Zarate, R.; Gutiérrez-Juárez, G.; Dominguez-Cruz, R.; Ramos-García, R.

2007-09-01

232

Numerical Prediction of Cavitation Erosion Intensity in Cavitating Flows around a Clark Y 11.7% Hydrofoil  

NASA Astrophysics Data System (ADS)

A numerical prediction method of cavitation erosion is proposed. In this method, the analysis of bubbles in cavitating flows is performed and the intensity of cavitation erosion is evaluated by the impact pressure induced by spherical bubble collapse. In the present study, two-dimensional cavitating flow around the Clark Y 11.7 % hydrofoil is used to examine the proposed numerical prediction method. The proposed numerical method predicts that the intensities of cavitation erosion in noncavitating, attached cavitating and pseudo-supercavitating flows are far weaker than the intensity of cavitation erosion in a transient cavitating flow, and the intensity in the vicinity of the sheet cavity termination is high. These results correspond well to experimental results, and it is confirmed that systematic erosion characteristics are generally captured by this method. Furthermore, the velocity dependence of cavitation erosion is examined, and it is found that the exponent n in the relation between the intensity I and main flow velocity Uin (I ? Uinn) becomes large when the bubble radius is large and ranges between 4.3 and 7.0 in the present study. According to the bubble dynamics, the ambient pressure and the rate of increases in pressure increase as the main flow velocity, and the maximum internal pressure increase. Therefore, it is thought that smaller bubbles cause cavitation erosion when the main flow velocity is large.

Ochiai, Naoya; Iga, Yuka; Nohmi, Motohiko; Ikohagi, Toshiaki

233

Bubble Proliferation in Shock Wave Lithotripsy Occurs during Inertial Collapse  

NASA Astrophysics Data System (ADS)

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

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

2008-06-01

234

MTBE degradation by hydrodynamic induced cavitation.  

PubMed

Hydrodynamic induced cavitation generates imploding cavitation bubbles which can lead to degradation or even mineralisation of water constituents without addition of any chemicals. This technology overcomes the problems of ultrasound irradiation by the local production of a cavitation cloud close to the sonotrodes. Hydrodynamic cavitation can be stabilised downstream of the nozzle depending on the ambient pressure conditions. If the pressure is kept low, the imploding cavitation bubbles generate new cavities, analogous to a chain reaction, and elevate the radical synthesis inside the apparatus. During the pilot tests MTBE and ETBE were degraded and complete mineralisation started at a time delay of app. 30 min. The specific energy demand for MTBE degradation lies in the range of app. 200 Wh/ppm in the investigated concentration range of about 30 ppm. PMID:20453332

Schmid, A

2010-01-01

235

Growth of Gas Bubbles in Deformable Solids with Time-Dependent Heat and Mass Sources  

Microsoft Academic Search

The equations governing the growth of a spherical inert-gas bubble in a deformable solid resulting from the generation of gas atoms from time-dependent gas sources in the solid matrix are formulated for the general case which includes the effects of surface tension, heat diffusion and time-varying heat sources in the matrix. The dimensionless parameters controlling bubble dynamics are identified. Asymptotic

Wen-Jei Yang

1972-01-01

236

Gas bubble nucleation and growth in cohesive sediments  

Microsoft Academic Search

Sediment often contains a significant amount of organic material, which can be decomposed by bacterial activity. During this process and under anaerobic conditions that prevail in sediments, mainly methane and carbon dioxide are formed. These compounds will dissolve in the pore water, until the level of saturation is attained.Experiments show that gas bubble nucleation occurs already at a small oversaturation

Walther van Kesteren; Thijs van Kessel

2002-01-01

237

Nonequilibrium statistical theory of bubble nucleation and growth under neutron and proton irradiation  

SciTech Connect

Microstructural evolution in metals under particle irradiation is described by a non-equilibrium statistics method. This method gives a set of equations for the evolution of bubbles and an approximate solution for a distribution function of bubble size as a function of fluence and temperature. The distribution function gives the number of bubbles of radius r at time t, N(r,t)dr, as a function of size, r/r/sub 0/(r/sub 0/ is the radius of a bubble nucleus). It is found that N(r,t)dr increases with fluence. Also, the peak value of N(r,t)dt shifts to higher r/r/sub 0/ with increasing fluence. Nucleation depends mainly on helium concentration and defect cluster concentration while bubble growth is controlled mainly by the vacancy concentration and a fluctuation coefficient. If suitable material parameters are chosen, a reasonable distribution function for bubble size is obtained. The helium diffusion coefficient is found to be less than that for vacancies by five orders of magnitude. The fraction of helium remaining in matrix is less than 10/sup -2/; the majority of the helium is associated with the bubbles.

Yu, J.; Sommer, W.F.; Bradbury, J.N.

1986-01-01

238

Cavitation phenomenon in monoleaflet mechanical heart valves with electrohydraulic total artificial heart.  

PubMed

Recently, cavitation on the surface of mechanical heart valves has been studied as a cause of fractures occurring in implanted mechanical heart valves. In this study, to investigate the mechanism of cavitation bubbles associated with monoleaflet mitral valves in an electrohydraulic total artificial heart (EHTAH), and to select the best valves for our EHTAH system, we measured three parameters. First, an image was created of the cavitation bubbles using a high-speed camera. Second, pressure drop in the vicinity of the valve surface was measured using mini pressure sensor. Then, the closing of the valve was observed using a Laser displacement sensor. Most of the cavitation bubbles in the Medtronic Hall valve were observed at the edge of the valve stop. With the Omnicarbon valve, the cavitation bubbles were observed at the edge of the valve and on the inner side of the leaflet. On the other hand, cavitation bubbles were observed only on the inner side of the leaflet in Björk-Shiley valve. Cavitation bubbles concentrated on the edge of the valve stop; the major cause of these cavitation bubbles was determined to be the squeeze flow. The formation of cavitation bubbles depended on the valve closing velocity and the valve leaflet geometry. From a viewpoint of squeeze flow, a low closing velocity and a small size of the valve stop could minimize cavitation. PMID:15521218

Lee, H; Taenaka, Y; Kitamura, S

2004-09-01

239

A PRACTICAL APPLICATION OF SONOLUMINESCENCE TO THE EVALUATION OF THE CAVITATION POTENTIAL OF THE MECHANICAL HEART VALVE  

Microsoft Academic Search

One of the causes of the breakdown of the mechanical heart valves (MHVs) is cavitation. A reliable in vitro test method to evaluate the cavitation potential has to be developed for the patients' safety. It is the bubble implosion that damages the materials, thus observing the cavity implosion behavior is essential. According to sonoluminescence, the collapsing cavitation bubbles emit the

Koki TAKIURA; Tsuneo CHINZEI; Kou IMACHI

240

Experimental simulations of gas-driven eruptions: kinetics of bubble growth and effect of geometry  

Microsoft Academic Search

Simulated gas-driven eruptions using CO2–water-polymer systems are reported. Eruptions are initiated by rapidly decompressing CO2–saturated water containing up to 1.0?wt.% CO2. Both cylindrical test cells and a flask test cell were used to examine the effect of magma chamber\\/conduit geometry on eruption\\u000a dynamics. Bubble-growth kinetics are examined quantitatively in experiments using cylindrical test cells. Uninhibited bubble\\u000a growth can be roughly

Youxue Zhang

1998-01-01

241

THE NUCLEATION AND GROWTH OF GAS BUBBLES IN A NEWTONIAN FLUID: AN ENERGETIC VARIATIONAL PHASE FIELD APPROACH  

Microsoft Academic Search

In this paper, we study the nucleation and growth of gas bubbles in a Newtonian fluid. We employ a general energetic variational formulation with a phase-field method, and compare the analytical and numerical predictions of this new formulation with those of classical models. The new approach allows the study of bubble nucleation, growth and coalescence in a unified framework, and

AARON NABER; CHUN LIU; JAMES J. FENG

242

Acoustic cavitation structures produced by artificial implants of nuclei.  

PubMed

High-density controllable bubble structures are produced in the vicinity of radiating surface by artificially implant nuclei. Two kinds of typical cavitation structures produced by artificially implant nuclei are investigated. The focusing action and the physical origin of jet-induced cone-like bubble structure are analyzed. The sonochemical activity of cavitation structures is measured by using the standard method of potassium iodide dosimetry. The controllability of cavitation bubble cluster in the acoustic field is also discussed in this work. PMID:23948492

Bai, Lixin; Deng, Jingjun; Li, Chao; Xu, Delong; Xu, Weilin

2013-07-26

243

Bacterial Sterilization Using Cavitating Jet  

NASA Astrophysics Data System (ADS)

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 ?=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.

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

244

Observations of cavitation erosion pit formation.  

PubMed

Previous investigations showed that a single cavitation bubble collapse can cause more than one erosion pit (Philipp & Lauterborn [1]). But our preliminary study showed just the opposite - that in some cases a single cavitation pit can result from more than one cavitation event. The present study shows deeper investigation of this phenomenon. An investigation of the erosion effects of ultrasonic cavitation on a thin aluminum foil was made. In the study we observed the formation of individual pits by means of high speed cameras (>1000 fps) and quantitatively evaluated the series of images by stereoscopy and the shape from shading method. This enabled the reconstruction of the time evolution of the pit shape. Results show how the foil is deformed several times before a hole is finally punctured. It was determined that larger single pits result from several impacts of shock waves on the same area, which means that they are merely special cases of pit clusters (pit clusters where pits overlap perfectly). Finally it was shown that a thin foil, which is subjected to cavitation, behaves as a membrane. It was concluded that the physics behind erosion depends significantly on the means of generating cavitation (acoustic, hydrodynamic, laser light) and the specimen characteristics (thin foil, massive specimen), which makes comparison of results of materials resistance to cavitation from different experimental set-ups questionable. Further development of the shape from shading method in the scope of cavitation erosion testing will enable better evaluation of cavitation erosion models. PMID:23403307

Dular, Matevž; Delgosha, Olivier Coutier; Petkovšek, Martin

2013-01-31

245

Growth of a gas bubble in a supersaturated and slightly compressible liquid at low Mach number  

Microsoft Academic Search

In this paper, the growth of a gas bubble in a supersaturated and slightly compressible liquid is discussed. The mathematical\\u000a model is solved analytically by using the modified Plesset and Zwick method. The growth process is affected by: sonic speed\\u000a in the liquid, polytropic exponent, diffusion coefficient, initial concentration difference, surface tension, viscosity, adjustment\\u000a factor and void fraction. The famous

S. A. Mohammadein; K. G. Mohamed

246

Removal of nutrient limitations in forest gaps enhances growth rate and resistance to cavitation in subtropical canopy tree species differing in shade tolerance.  

PubMed

A 4-year fertilization experiment with nitrogen (N) and phosphorus (P) was carried out in natural gaps of a subtropical forest in northeastern Argentina. Saplings of six dominant canopy species differing in shade tolerance were grown in five control and five N?+?P fertilized gaps. Hydraulic architectural traits such as wood density, the leaf area to sapwood area ratio (LA : SA), vulnerability to cavitation (P50) and specific and leaf-specific hydraulic conductivity were measured, as well as the relative growth rate, specific leaf area (SLA) and percentage of leaf damage by insect herbivores. Plant growth rates and resistance to drought-induced embolisms increased when nutrient limitations were removed. On average, the P50 of control plants was -1.1 MPa, while the P50 of fertilized plants was -1.6 MPa. Wood density and LA : SA decreased with N?+?P additions. A trade-off between vulnerability to cavitation and efficiency of water transport was not observed. The relative growth rate was positively related to the total leaf surface area per plant and negatively related to LA : SA, while P50 was positively related to SLA across species and treatments. Plants with higher growth rates and higher total leaf area in fertilized plots were able to avoid hydraulic dysfunction by becoming less vulnerable to cavitation (more negative P50). Two high-light-requiring species exhibited relatively low growth rates due to heavy herbivore damage. Contrary to expectations, shade-tolerant plants with relatively high resistance to hydraulic dysfunction and reduced herbivory damage were able to grow faster. These results suggest that during the initial phase of sapling establishment in gaps, species that were less vulnerable to cavitation and exhibited reduced herbivory damage had faster realized growth rates than less shade-tolerant species with higher potential growth rates. Finally, functional relationships between hydraulic traits and growth rate across species and treatments were maintained regardless of soil nutrient status. PMID:23436182

Villagra, Mariana; Campanello, Paula I; Montti, Lia; Goldstein, Guillermo

2013-02-24

247

Enhanced Generic Phase-field Model of Irradiation Materials: Fission Gas Bubble Growth Kinetics in Polycrystalline UO2  

SciTech Connect

Experiments show that inter-granular and intra-granular gas bubbles have different growth kinetics which results in heterogeneous gas bubble microstructures in irradiated nuclear fuels. A science-based model predicting the heterogeneous microstructure evolution kinetics is desired, which enables one to study the effect of thermodynamic and kinetic properties of the system on gas bubble microstructure evolution kinetics and morphology, improve the understanding of the formation mechanisms of heterogeneous gas bubble microstructure, and provide the microstructure to macroscale approaches to study their impact on thermo-mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking. In our previous report 'Mesoscale Benchmark Demonstration, Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing', we developed a phase-field model to simulate the intra-granular gas bubble evolution in a single crystal during post-irradiation thermal annealing. In this work, we enhanced the model by incorporating thermodynamic and kinetic properties at grain boundaries, which can be obtained from atomistic simulations, to simulate fission gas bubble growth kinetics in polycrystalline UO2 fuels. The model takes into account of gas atom and vacancy diffusion, vacancy trapping and emission at defects, gas atom absorption and resolution at gas bubbles, internal pressure in gas bubbles, elastic interaction between defects and gas bubbles, and the difference of thermodynamic and kinetic properties in matrix and grain boundaries. We applied the model to simulate gas atom segregation at grain boundaries and the effect of interfacial energy and gas mobility on gas bubble morphology and growth kinetics in a bi-crystal UO2 during post-irradiation thermal annealing. The preliminary results demonstrate that the model can produce the equilibrium thermodynamic properties and the morphology of gas bubbles at grain boundaries for given grain boundary properties. More validation of the model capability in polycrystalline is underway.

Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert O.; Gao, Fei; Sun, Xin

2012-05-30

248

Studies on Pressure Response of Gas Bubbles Contributions of Condensed Droplets in Bubbles Generated by a Uniform Nucleation.  

National Technical Information Service (NTIS)

The response of a tiny gas bubble under reduced pressure is investigated in its relation to cavitation. Equations of motion are formulated for gas mixtures inside the bubble and numerical calculations performed for several examples. The conclusions are as...

Y. Matsumoto

1988-01-01

249

Theory of the nonsteady diffusion growth of a gas bubble in a supersaturated solution of gas in liquid  

Microsoft Academic Search

Using a self-similar approach a general nonsteady theory is elaborated for the case of the diffusion growth of a gas bubble in a supersaturated solution of gas in liquid. Due to the fact that the solution and the bubble in it are physically isolated, the self-similar approach accounts for the balance of the number of gas molecules in the solution

A. P. Grinin; F. M. Kuni; G. Yu. Gor

2008-01-01

250

Radiation induced cavitation: A possible phenomenon in liquid targets?  

SciTech Connect

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.

West, C.D.

1998-07-01

251

Tandem shock wave cavitation enhancement for extracorporeal lithotripsy  

Microsoft Academic Search

Extracorporeal shock wave lithotripsy (ESWL) has been successful for more than twenty years in treating patients with kidney stones. Hundreds of underwater shock waves are generated outside the patient's body and focused on the kidney stone. Stones fracture mainly due to spalling, cavitation and layer separation. Cavitation bubbles are produced in the vicinity of the stone by the tensile phase

Achim M Loske; Fernando E Prieto; Francisco Fernández; Javier van Cauwelaert

2002-01-01

252

Experimental investigation on noise of cavitation nozzle and its chaotic behaviour  

NASA Astrophysics Data System (ADS)

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 attributes mainly to the high frequency segment of the spectrum, which provides references for the research on cavitation noise.

Zhang, Fenghua; Liu, Haifeng; Xu, Junchao; Tang, Chuanlin

2013-07-01

253

(Creep cavitation in nickel aluminides)  

SciTech Connect

Work on creep cavitation has been performed in collaboration with Professor L. Martinez of the Instituto de Fisica of the Universidad Nacional de Mexico in Cuernavaca, Mexico. A joint manuscript on Influencing the Shape of Creep Cavities in Nickel Aluminides by Stress Changes'' has been finalized. All details required to perform urgently needed numerical calculations on the growth of creep cavities in the presence of creep deformation have been identified and clearly defined. Ideas for incorporating the stochastic aspects of creep cavitation (coalescence) have been developed and will improve our present understanding of creep cavitation in nickel aluminides.

Schneibel, J.H.

1987-08-18

254

Dynamics of diffusive bubble growth and pressure recovery in a bubbly rhyolitic melt embedded in an elastic solid  

Microsoft Academic Search

We present a model of gas exsolution and bubble expansion in a melt supersaturated in response to a sudden pressure drop. In our model, the melt contains a suspension of gas bubbles of identical sizes and is encased in a penny-shaped crack embedded in an elastic solid. The suspension is modeled as a three-dimensional lattice of spherical cells with slight

Bernard Chouet; Phillip Dawson; Masaru Nakano

2006-01-01

255

The role of cavitation microjets in the therapeutic applications of ultrasound  

Microsoft Academic Search

The dynamics of a gas bubble situated in a sound-irradiated liquid and near a rigid boundary was studied theoretically to get a better understanding of the role of cavitation microjets in the therapeutic applications of ultrasound (US). The boundary integral method was adopted to simulate the temporal development of the bubble shape, jet formation during bubble collapse and bubble migration.

E. A Brujan

2004-01-01

256

The role of cavitation in liposome formation.  

PubMed

Liposome size is a vital parameter of many quantitative biophysical studies. Sonication, or exposure to ultrasound, is used widely to manufacture artificial liposomes, yet little is known about the mechanism by which liposomes are affected by ultrasound. Cavitation, or the oscillation of small gas bubbles in a pressure-varying field, has been shown to be responsible for many biophysical effects of ultrasound on cells. In this study, we correlate the presence and type of cavitation with a decrease in liposome size. Aqueous lipid suspensions surrounding a hydrophone were exposed to various intensities of ultrasound and hydrostatic pressures before measuring their size distribution with dynamic light scattering. As expected, increasing ultrasound intensity at atmospheric pressure decreased the average liposome diameter. The presence of collapse cavitation was manifested in the acoustic spectrum at high ultrasonic intensities. Increasing hydrostatic pressure was shown to inhibit the presence of collapse cavitation. Collapse cavitation, however, did not correlate with decreases in liposome size, as changes in size still occurred when collapse cavitation was inhibited either by lowering ultrasound intensity or by increasing static pressure. We propose a mechanism whereby stable cavitation, another type of cavitation present in sound fields, causes fluid shearing of liposomes and reduction of liposome size. A mathematical model was developed based on the Rayleigh-Plesset equation of bubble dynamics and principles of acoustic microstreaming to estimate the shear field magnitude around an oscillating bubble. This model predicts the ultrasound intensities and pressures needed to create shear fields sufficient to cause liposome size change, and correlates well with our experimental data. PMID:17766335

Richardson, Eric S; Pitt, William G; Woodbury, Dixon J

2007-08-31

257

The Role of Cavitation in Liposome Formation  

PubMed Central

Liposome size is a vital parameter of many quantitative biophysical studies. Sonication, or exposure to ultrasound, is used widely to manufacture artificial liposomes, yet little is known about the mechanism by which liposomes are affected by ultrasound. Cavitation, or the oscillation of small gas bubbles in a pressure-varying field, has been shown to be responsible for many biophysical effects of ultrasound on cells. In this study, we correlate the presence and type of cavitation with a decrease in liposome size. Aqueous lipid suspensions surrounding a hydrophone were exposed to various intensities of ultrasound and hydrostatic pressures before measuring their size distribution with dynamic light scattering. As expected, increasing ultrasound intensity at atmospheric pressure decreased the average liposome diameter. The presence of collapse cavitation was manifested in the acoustic spectrum at high ultrasonic intensities. Increasing hydrostatic pressure was shown to inhibit the presence of collapse cavitation. Collapse cavitation, however, did not correlate with decreases in liposome size, as changes in size still occurred when collapse cavitation was inhibited either by lowering ultrasound intensity or by increasing static pressure. We propose a mechanism whereby stable cavitation, another type of cavitation present in sound fields, causes fluid shearing of liposomes and reduction of liposome size. A mathematical model was developed based on the Rayleigh-Plesset equation of bubble dynamics and principles of acoustic microstreaming to estimate the shear field magnitude around an oscillating bubble. This model predicts the ultrasound intensities and pressures needed to create shear fields sufficient to cause liposome size change, and correlates well with our experimental data.

Richardson, Eric S.; Pitt, William G.; Woodbury, Dixon J.

2007-01-01

258

Dynamical growth of the hadron bubbles during the quark-hadron phase transition  

NASA Astrophysics Data System (ADS)

The rate of dynamical growth of the hadron bubbles in a supercooled baryon free quark-gluon plasma is evaluated by solving the equations of relativistic fluid dynamics in all regions. For a nonviscous plasma, this dynamical growth rate is found to depend only on the range of correlation ? of order parameter fluctuation, and the radius R of the critical hadron bubble, the two length scales relevant for the description of the critical phenomena. Further, it is shown that the dynamical prefactor acquires an additive component when the medium becomes viscous. Interestingly, under certain reasonable assumptions for the velocity of the sound in the medium around the saddle configuration, the viscous and the nonviscous parts of the prefactor are found to be similiar to the results obtained by Csernai and Kapusta and Ruggeri and Friedman (for the case of zero viscosity), respectively.

Shukla, P.; Mohanty, A. K.; Gupta, S. K.

2001-01-01

259

Cavitation in vortical flows  

Microsoft Academic Search

Cavitation in vortical structures is a common, albeit complex, problem in engineering applications. Cavitating vortical structures can be found on the blade surfaces, in the clearance passages, and at the hubs of various types of turbomachinery. Cavitating microvortices at the trailing edge of attached sheet cavitation can be highly erosive. Cavitating hub vortices in the draft tubes of hydroturbines can

Roger E. A. Arndt

2002-01-01

260

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

PubMed

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

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

2010-04-01

261

Dynamics of laser-induced bubble and nanoparticles generation during ultra-short laser ablation of Pd in liquid  

NASA Astrophysics Data System (ADS)

In this work, the dynamics of multiple cavitation bubbles produced by femtosecond laser ablation of a palladium target submerged in acetone is studied by means of time-resolved fast shadowgraphy technique. The data have evidenced the periodic growth and collapse of the bubbles and the consequent emission of material together with the role played by the laser focus position. Comparing the results with the previsions of the Rayleigh–Plesset model a good agreement is found. The nanoparticles obtained under different focusing conditions are characterized by means of TEM analysis. Their dimension and distribution are correlated with the bubbles dynamics.

De Bonis, A.; Sansone, M.; D'Alessio, L.; Galasso, A.; Santagata, A.; Teghil, R.

2013-11-01

262

Shock-wave model of acoustic cavitation.  

PubMed

Shock-wave model of liquid cavitation due to an acoustic wave was developed, showing how the primary energy of an acoustic radiator is absorbed in the cavitation region owing to the formation of spherical shock-waves inside each gas bubble. The model is based on the concept of a hypothetical spatial wave moving through the cavitation region. It permits using the classical system of Rankine-Hugoniot equations to calculate the total energy absorbed in the cavitation region. Additionally, the model makes it possible to explain some newly discovered properties of acoustic cavitation that occur at extremely high oscillatory velocities of the radiators, at which the mode of bubble oscillation changes and the bubble behavior approaches that of an empty Rayleigh cavity. Experimental verification of the proposed model was conducted using an acoustic calorimeter with a set of barbell horns. The maximum amplitude of the oscillatory velocity of the horns' radiating surfaces was 17 m/s. Static pressure in the calorimeter was varied in the range from 1 to 5 bars. The experimental data and the results of the calculations according to the proposed model were in good agreement. Simple algebraic expressions that follow from the model can be used for engineering calculations of the energy parameters of the ultrasonic radiators used in sonochemical reactors. PMID:17869158

Peshkovsky, Sergei L; Peshkovsky, Alexey S

2007-08-07

263

Experimental characterization of aviation-fuel cavitation  

NASA Astrophysics Data System (ADS)

The results of an experimental investigation of the gaseous cavitation of JP-8 aviation fuel in a converging-diverging nozzle are presented. Fuel cavitation is experimentally characterized by high-speed digital imaging, static pressure distributions, and nonintrusive void fraction and bubble velocity measurements. For comparative purposes, experiments were performed using distilled water and dodecane for the same nozzle and nozzle pressure ratios. Dodecane, the largest component of JP-8 by weight, served as its single-component surrogate. For each working fluid, the experiments examined two different flow regimes: an initially single-phase liquid flow in which no cavitation occurred and another that evolved into two-phase cavitating flow. Additional experiments were performed to study the effect of air bubbles injected into either water or JP-8 at the nozzle inlet. For a sufficiently low range of imposed back pressures, gaseous cavitation led to choked flow for each working fluid. The character of the cavitation in the three fluids was different. These differences are highlighted and plausible mechanisms responsible for the observed behavior are discussed.

Dunn, Patrick F.; Thomas, Flint O.; Davis, Michael P.; Dorofeeva, Irina E.

2010-11-01

264

Acoustic cavitation generated by an extracorporeal shockwave lithotripter.  

PubMed

Evidence is presented of acoustic cavitation generated by a Dornier extracorporeal shockwave lithotripter. Using x-ray film, thin aluminum sheets, and relatively thick metal plates as targets, evidence of liquid jet impacts associated with cavitation bubble collapse was observed. The jet impact was violent enough to puncture thin foils and deform metal plates. Furthermore, numerous jet impacts were generated over a volume of greater than 200 cm3. It is likely that such violent cavitation will also occur in tissue, and observed biological effects (e.g. renal calculus disintegration and tissue trauma) may be related to cavitation damage. PMID:3590362

Coleman, A J; Saunders, J E; Crum, L A; Dyson, M

1987-02-01

265

Effect of vibration amplitude on vapor cavitation in journal bearings  

NASA Astrophysics Data System (ADS)

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

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

266

Cavitation damage in blood clots under HIFU  

Microsoft Academic Search

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

Hope Weiss; Golnaz Ahadi; Thilo Hoelscher; Andrew Szeri

2010-01-01

267

Propeller Cavitation in Solutions of Polyethylene Oxide.  

National Technical Information Service (NTIS)

The inception and formation rates of bubble cavitation on a 14.8-cm diameter, two-bladed propeller were measured in homogeneous aqueous solutions of polyethylene oxide. If the results can be extended to full size propellers, ships can increase their prope...

R. J. White

1971-01-01

268

The Role of Cavitation in Liposome Formation  

Microsoft Academic Search

Liposome size is a vital parameter of many quantitative biophysical studies. Sonication, or exposure to ultrasound, is used widely to manufacture artificial liposomes, yet little is known about the mechanism by which liposomes are affected by ultrasound. Cavitation, or the oscillation of small gas bubbles in a pressure-varying field, has been shown to be responsible for many biophysical effects of

Eric S. Richardson; William G. Pitt; Dixon J. Woodbury

2007-01-01

269

Improved light-scattering cavitation nuclei classifier  

Microsoft Academic Search

The scattered light approach to classification of cavitation nuclei provides speed and resolution advantages over holographic direct observation methods, but the conventional light-scattering system has been unable to discriminate between bubbles and dirt particles. A two-channel classification system has been developed to process information carried in bursts of light scattered along two different paths by candidate nuclei passing through an

William W. Moyer

1983-01-01

270

Bubble dynamics in an acoustic flow field  

Microsoft Academic Search

Dynamics of interaction between cavitational bubbles is investigated when a complex of a compression and a rarefaction pulse passes through a liquid with pre-existing micro bubbles. Cavitation was generated experimentally with the help of electromagnetic generator of a flat and a convergent acoustic pulse (2-mus duration, 1-20 MPa) having the form of a hollow sphere segment. A modeling was performed

Dmitry V. Voronin; Georgij N. Sankin; Robert Mettin; Vyacheslav S. Teslenko; Werner Lauterborn

2002-01-01

271

Studies of a novel sensor for assessing the spatial distribution of cavitation activity within ultrasonic cleaning vessels  

Microsoft Academic Search

This paper describes investigations of the spatial distribution of cavitation activity generated within an ultrasonic cleaning vessel, undertaken using a novel cavitation sensor concept. The new sensor monitors high frequency acoustic emissions (>1MHz) generated by micron-sized bubbles driven into acoustic cavitation by the applied acoustic field. Novel design features of the sensor, including its hollow, cylindrical shape, provide the sensor

Bajram Zeqiri; Mark Hodnett; Anthony J. Carroll

2006-01-01

272

The sonically induced cavitation of liquid helium  

NASA Astrophysics Data System (ADS)

The onset of sonically induced cavitation in liquid helium at frequencies between 30 and 40 kHz has been studied. In helium II, two types of cavitation activity were identified: acoustic cavitation whose characteristic noise can be detected, and visible cavitation in which vaporous cavities grow to visible size. The onset of acoustic cavitation is statistical in nature with increasing event rates as the sound pressure amplitude is increased and whose threshold depends on the waiting time at that particular amplitude. The acoustic threshold sound pressure amplitude in helium II between 1.8° K and T ? was found to lie within 0.15 mb of 0.3 mb, the variation of ±0.15 mb occurring from one determination to another, whereas the sound pressure amplitude corresponding to the visible threshold was about a hundred times larger. These two distinct types of sonically induced cavitation appear to be unique to liquid helium. However, above T ? the two thresholds were found to coincide at a sound pressure amplitude within 0.4 mb of 0.8 mb. The characteristics of the onset of acoustic cavitation were found to be independent of applied static pressure of up to 1.5 atm above and below T ? and in helium II they were unaffected by filtering, heat flushing, or rotating the liquid. The results suggest that liquid helium is nucleated by random events initiated by the ambient cosmic radiation or by vortices generated in the liquid, and they imply that at ultrasonic frequencies this liquid cannot withstand a tensile stress and behaves in this respect like water saturated with gas and containing dust motes. Attempts to determine the onset of acoustic cavitation by scattering light off the bubbles or by detecting sonoluminescence were not successful: The upper limit to the size of these bubbles was shown to be about 30 µm and the intensity of any sonoluminescence must have been less than 10-4 of that from cavitating water. The possibilities of exploiting the two types of cavitation activity in liquid helium in the construction of a posttriggerable ultrasonic bubble chamber for visualizing the tracks of ionizing particles are discussed, as are the theoretical background and future development of the work presented in this paper.

Jarman, P. D.; Taylor, K. J.

1970-05-01

273

Regulating Ultrasound Cavitation in order to Induce Reproducible Sonoporation  

NASA Astrophysics Data System (ADS)

Sonoporation would be linked to cavitation, which generally appears to be a non reproducible and unstationary phenomenon. In order to obtain an acceptable trade-off between cell mortality and transfection, a regulated cavitation generator based on an acoustical cavitation measurement was developed and tested. The medium to be sonicated is placed in a sample tray. This tray is immersed in in degassed water and positioned above the face of a flat ultrasonic transducer (frequency: 445 kHz; intensity range: 0.08-1.09 W/cm2). This technical configuration was admitted to be conducive to standing-wave generation through reflection at the air/medium interface in the well thus enhancing the cavitation phenomenon. Laterally to the transducer, a homemade hydrophone was oriented to receive the acoustical signal from the bubbles. From this spectral signal recorded at intervals of 5 ms, a cavitation index was calculated as the mean of the cavitation spectrum integration in a logarithmic scale, and the excitation power is automatically corrected. The device generates stable and reproducible cavitation level for a wide range of cavitation setpoint from stable cavitation condition up to full-developed inertial cavitation. For the ultrasound intensity range used, the time delay of the response is lower than 200 ms. The cavitation regulation device was evaluated in terms of chemical bubble collapse effect. Hydroxyl radical production was measured on terephthalic acid solutions. In open loop, the results present a great variability whatever the excitation power. On the contrary the closed loop allows a great reproducibility. This device was implemented for study of sonodynamic effect. The regulation provides more reproducible results independent of cell medium and experimental conditions (temperature, pressure). Other applications of this regulated cavitation device concern internalization of different particles (Quantum Dot) molecules (SiRNA) or plasmids (GFP, DsRed) into different types of cells (AT2, RL, LLC...). Preliminary results are presented.

Mestas, J.-L.; Alberti, L.; El Maalouf, J.; Béra, J.-C.; Gilles, B.

2010-03-01

274

Nonequilibrium thermodynamics of transport through moving interfaces with application to bubble growth and collapse.  

PubMed

We develop the general equation for the nonequilibrium reversible-irreversible coupling framework of thermodynamics to handle moving interfaces in the context of a gas that can be dissolved in a surrounding liquid. The key innovation is a "moving interface normal transfer" term required for consistency between the thermodynamic evolution equation and the chain rule of functional calculus. The freedom of atomistic displacements of the interface leads to gauge transformations under which the thermodynamic theory should be invariant. The thermodynamic framework provides a complete set of evolution equations and boundary conditions, as we illustrate for the example of bubble growth and collapse. PMID:19792138

Ottinger, Hans Christian; Bedeaux, Dick; Venerus, David C

2009-08-21

275

Electric discharge-induced cavitation: a competing approach to pulsed lasers for performing microsurgery in liquid media  

Microsoft Academic Search

Cavitation bubbles generated by fast overheating of water during pulsed laser applications in liquid medium have been shown to be a driving force of the soft tissue cutting. An alternative approach proposed in this paper is the generation of cavitation bubbles by fast overheating of liquid conductive medium by a short pulse of electric current. An electrical system based on

Daniel Palanker; Igor Turovets; Aaron Lewis

1997-01-01

276

The Influence of Surface Tension on the Diffusion-Controlled Growth or Dissolution of Spherical Gas Bubbles  

Microsoft Academic Search

Surface tension can markedly affect the growth or dissolution of small gas bubbles but, even when spherical symmetry is maintained and the interfacial concentration assumed constant, generally valid analytical solutions for the change of size with time cannot be obtained; approximations of limited validity are therefore often used. However, accurate and efficient methods for computing the diffusion-controlled growth or dissolution

M. Cable; J. R. Frade

1988-01-01

277

Growth of a Gas Bubble in a Supersaturated Liquid Under the Effect of Variant Cases of Surface Tension  

Microsoft Academic Search

In this paper, the growth of a gas bubble in a supersaturated liquid is discussed for a constant and variable cases of surface tension effect. The mathematical model is solved analytically by using the method of Plesset and Zwick18 after modified it. The growth process is affected by: diffusion coefficient D, Jacob number Ja, surface tension sigma, adjustment factor b

S. A. Mohammadein; K. G. Mohamed

2011-01-01

278

Cavitation dynamics of mechanical heart valve prostheses.  

PubMed

Nine different mechanical mitral heart valves were chosen in order to study cavitation dynamics in detail in an in vitro flow system simulating a single event of mitral valve closure. The transvalvular pressure (ventricular minus atrial pressure) rise rate averaged during the valve closing period was used as an index of the loading rate. A series of photographs in the vicinity of the inflow surface of the valve were attempted during the bubble appearance period using a stroboscopic visualization technique. The in vitro study revealed three sources of cavitation initiation in the design of the mechanical heart valves tested: stop (seat stop or seating lip), inflow strut, and clearance (gap formed between the occluder and the housing or between the two occluders in the closed position). Among these, the occluder stop design was the most critical to cavitation since all valves having the stop at the edge of the major orifice area showed a higher intensity of cavitation and threshold loading rates below the estimated normal physiological value. The analysis of bubble locations and dynamics led us to propose that the fluid squeezing effect between the occluder and the stop in the housing and the streamline contraction effect along the clearance are factors responsible for cavitation incipience. PMID:7832658

Lee, C S; Chandran, K B; Chen, L D

1994-10-01

279

Micronecking and fracture in cavitated superplastic materials  

SciTech Connect

A model of cavity growth is used to describe neck development in the ligament between voids and fracture strain of cavitated superplastic materials. The results show that the strain-rate sensitivity index has an important effect on fracture strain only at low values of cavity growth rate. This is more appreciable for a lesser initial cavitation level. The initial cavitation level weakly influences the fracture strain, in contrast to the result for the cavity growth rate. It is seen that the present fracture criterion fits well the experimental results for several superplastic materials.

Zaki, M. [Cairo Univ., Giza (Egypt). Dept. of Mechanical Design and Production

1996-04-01

280

Evaporation-induced cavitation in nanofluidic channels  

PubMed Central

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.

Duan, Chuanhua; Karnik, Rohit; Lu, Ming-Chang; Majumdar, Arun

2012-01-01

281

Thermodynamics of interleaflet cavitation in lipid bilayer membranes.  

PubMed

Interleaflet cavitation in lipid bilayer membranes, or, shortly, intramembrane cavitation (IMC), is the formation of gas bubbles between the two leaflets of the membrane. The present paper focuses on the thermodynamics of IMC, namely, on the minimum work required to form an intramembrane cavity. The minimum work can be separated into two parts, one that depends on the volume and number of gas molecules in the bubble and another that depends on the bubble geometry. Minimization of the second part at a fixed bubble volume determines the optimized bubble shape. In homogeneous cavitation this part is proportional to the bubble surface area and therefore the bubble is spherical. In contrast, in IMC the second part is no longer a simple function of the bubble area and the optimized cavity is not spherical because of the finite elasticity of the membrane. Using a simplified assumption about the cavity shape, the geometry-dependent term is derived and minimized at a fixed cavity volume. It is found that the optimized cavity is almost spherical at large bubble volumes, while at small volumes the cavity has a lenslike shape. The optimized shape is used to analyze the minimum work of IMC. PMID:23496556

Rappaport, Shay M; Berezhkovskii, Alexander M; Zimmerberg, Joshua; Bezrukov, Sergey M

2013-02-21

282

The effects of fluid properties on cavitation in a micro domain  

NASA Astrophysics Data System (ADS)

The cavitation of ethanol inside a 40 µm wide micro-orifice entrenched inside a 200 µm microchannel was experimentally studied. Experiments were conducted at inlet pressures ranging from 60 Psi to 100 Psi and cavitation numbers from ~0.1 to 1. Flow patterns along the axial position downstream from the orifice at various cavitation numbers were visualized and mapped. Cavitation inception and choking indices are reported and compared to the corresponding values of water in a similar configuration. In contrast with water cavitation, the presence of a bubbly flow pattern in the immediate vicinity of the orifice was very notable. The cavitation inception values were higher than those for water, but much lower than the values reported for large-scale orifices. Unlike for water, choking cavitation was observed only after significant reduction in the cavitation number past the inception value.

Singh, Randip; Peles, Yoav

2009-02-01

283

Cavitation dynamics and directional microbubble ejection induced by intense femtosecond laser pulses in liquids.  

PubMed

We study cavitation dynamics when focusing ring-shaped femtosecond laser beams in water. This focusing geometry reduces detrimental nonlinear beam distortions and enhances energy deposition within the medium, localized at the focal spot. We observe remarkable postcollapse dynamics of elongated cavitation bubbles with high-speed ejection of microbubbles out of the laser focal region. Bubbles are ejected along the laser axis in both directions (away and towards the laser). The initial shape of the cavitation bubble is also seen to either enhance or completely suppress jet formation during collapse. In the absence of jetting, microbubble ejection occurs orthogonal to the laser propagation axis. PMID:23031010

Faccio, D; Tamošauskas, G; Rubino, E; Darginavi?ius, J; Papazoglou, D G; Tzortzakis, S; Couairon, A; Dubietis, A

2012-09-05

284

Observations on the Role of Cavitation in Electric Spark Rock Drilling.  

National Technical Information Service (NTIS)

The cavity or bubble formed by an electric spark is nearly identical to that of cavitation caused by variation of pressure as far as bubble dynamics are concerned. For application to rock fragmentation, all three aspects of spark bubble generation are des...

A. T. Ellis J. E. Starrett

1975-01-01

285

Bursting Bubbles and Bilayers  

PubMed Central

This paper discusses various interactions between ultrasound, phospholipid monolayer-coated gas bubbles, phospholipid bilayer vesicles, and cells. The paper begins with a review of microbubble physics models, developed to describe microbubble dynamic behavior in the presence of ultrasound, and follows this with a discussion of how such models can be used to predict inertial cavitation profiles. Predicted sensitivities of inertial cavitation to changes in the values of membrane properties, including surface tension, surface dilatational viscosity, and area expansion modulus, indicate that area expansion modulus exerts the greatest relative influence on inertial cavitation. Accordingly, the theoretical dependence of area expansion modulus on chemical composition - in particular, poly (ethylene glyclol) (PEG) - is reviewed, and predictions of inertial cavitation for different PEG molecular weights and compositions are compared with experiment. Noteworthy is the predicted dependence, or lack thereof, of inertial cavitation on PEG molecular weight and mole fraction. Specifically, inertial cavitation is predicted to be independent of PEG molecular weight and mole fraction in the so-called mushroom regime. In the “brush” regime, however, inertial cavitation is predicted to increase with PEG mole fraction but to decrease (to the inverse 3/5 power) with PEG molecular weight. While excellent agreement between experiment and theory can be achieved, it is shown that the calculated inertial cavitation profiles depend strongly on the criterion used to predict inertial cavitation. This is followed by a discussion of nesting microbubbles inside the aqueous core of microcapsules and how this significantly increases the inertial cavitation threshold. Nesting thus offers a means for avoiding unwanted inertial cavitation and cell death during imaging and other applications such as sonoporation. A review of putative sonoporation mechanisms is then presented, including those involving microbubbles to deliver cargo into a cell, and those - not necessarily involving microubbles - to release cargo from a phospholipid vesicle (or reverse sonoporation). It is shown that the rate of (reverse) sonoporation from liposomes correlates with phospholipid bilayer phase behavior, liquid-disordered phases giving appreciably faster release than liquid-ordered phases. Moreover, liquid-disordered phases exhibit evidence of two release mechanisms, which are described well mathematically by enhanced diffusion (possibly via dilation of membrane phospholipids) and irreversible membrane disruption, whereas liquid-ordered phases are described by a single mechanism, which has yet to be positively identified. The ability to tune release kinetics with bilayer composition makes reverse sonoporation of phospholipid vesicles a promising methodology for controlled drug delivery. Moreover, nesting of microbubbles inside vesicles constitutes a truly “theranostic” vehicle, one that can be used for both long-lasting, safe imaging and for controlled drug delivery.

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

2012-01-01

286

Observation of cavitation in a mechanical heart valve in a total artificial heart.  

PubMed

Recently, cavitation on the surface of mechanical heart valves has been studied as a cause of fractures occurring in implanted mechanical heart valves. The cause of cavitation in mechanical heart valves was investigated using the 25 mm Medtronic Hall valve and the 23 mm Omnicarbon valve. Closing of these valves in the mitral position was simulated in an electrohydraulic totally artificial heart. Tests were conducted under physiologic pressures at heart rates from 60 to 100 beats per minute with cardiac outputs from 4.8 to 7.7 L/min. The disk closing motion was measured by a laser displacement sensor. A high-speed video camera was used to observe the cavitation bubbles in the mechanical heart valves. The maximum closing velocity of the Omnicarbon valve was faster than that of the Medtronic Hall valve. In both valves, the closing velocity of the leaflet, used as the cavitation threshold, was approximately 1.3-1.5 m/s. In the case of the Medtronic Hall valve, cavitation bubbles were generated by the squeeze flow and by the effects of the venturi and the water hammer. With the Omnicarbon valve, the cavitation bubbles were generated by the squeeze flow and the water hammer. The mechanism leading to the development of cavitation bubbles depended on the valve closing velocity and the valve stop geometry. Most of the cavitation bubbles were observed around the valve stop and were generated by the squeeze flow. PMID:15171470

Lee, Hwansung; Tsukiya, Tomonori; Homma, Akihiko; Kamimura, Tadayuki; Takewa, Yoshiaki; Nishinaka, Tomohiro; Tatsumi, Eisuke; Taenaka, Yoshiyuki; Takano, Hisateru; Kitamura, Soichiro

287

Diagnostics of gas bubbles using wavelet transform  

Microsoft Academic Search

Detection of gas bubbles is an important indicator of the process quality in the industrial applications. Gas bubbles in the liquid not only falsify the measurement of the flow rate, but indicate problems like leakage, cavitations, reactions, boiling, etc. Based on electric field simulations and measurement in the flow laboratory, a physical device model has been developed. This paper presents

Abhisek Ukil; Daniel Schrag; Kai Hencken

2010-01-01

288

A laser induced cavitation pump  

NASA Astrophysics Data System (ADS)

We demonstrate and discuss a liquid pumping effect based on the interaction between periodically generated cavitation microbubbles and a millimeter diameter tube. The bubbles are generated by the heat of laser adsorption at the tip of an optical fiber immersed in liquid. When the bubbles are generated well away from the tube, a steady streaming flow with a relatively large and energetic ring vortex is observed. Coaxial placement of the fiber within the tube, with the fiber tip near one end of the tube, results in relatively weak pumping of liquid. In contrast, placement of the fiber outside the tube with a similar fiber tip position results in a synergetic and strong pumping effect. This paper presents quantitative measures of pumping performance as a function of relevant parameters including the axial fiber tip position, fiber orientation and laser duty cycle.

Wang, G. R.; Santiago, J. G.; Mungal, M. G.; Young, B.; Papademetriou, S.

2004-07-01

289

Orbital trajectory of an acoustic bubble in a cylindrical resonator  

NASA Astrophysics Data System (ADS)

Acoustic cavitation-induced microbubbles in a cylindrical resonator filled with water tend to concentrate into ring patterns due to the cylindrical geometry of the system. The shape of these ring patterns is directly linked to the Bjerknes force distribution in the resonator. Experimental observations showed that cavitation bubbles located in the vicinity of this ring may exhibit a spiraling behavior around the pressure nodal line. This spiraling phenomenon is numerically studied, the conditions for which a single cavitation bubble follows an orbital trajectory are established, and the influences of the acoustic pressure amplitude and the initial bubble radius are investigated.

Desjouy, Cyril; Labelle, Pauline; Gilles, Bruno; Bera, Jean-Christophe; Inserra, Claude

2013-09-01

290

Dynamic behavior of bubbles during extracorporeal shock-wave lithotripsy.  

PubMed

The interaction of air bubbles attached to gelatin surfaces, extirpated livers or abdominal aortas of rats with underwater shock waves was investigated to help clarify the tissue-damage mechanism associated with cavitation bubbles induced during extracorporeal shock-wave lithotripsy. The overpressure of the shock wave was 10.2 +/- 0.5 MPa. The initial bubble radii varied from 0.12 to 3.06 mm. The subsequent collapse of the bubbles was recorded by a high-speed camera. The liver-cell damage was histochemically evaluated. The bubble attached to gelatin or rat's liver surface migrates away from the surface with an oscillatory growth/collapse behavior after the shock-wave interaction. The penetration depth of the liquid jet into the gelatin and the radius of the subsequent damage pit on the surface depend on the initial bubble radius. The elongation and split of the nuclei in the liver parenchymal cells in the direction of the liquid jet and the increase in the cell density within the circumference of the injured region are revealed histologically. PMID:9695276

Kodama, T; Takayama, K

1998-06-01

291

Helium 3 precipitation in AISI 316L stainless steel induced by radioactive decay of tritium: Growth mechanism of helium bubbles  

SciTech Connect

The growth of helium bubbles in 316L stainless steel in which helium was generated from the tritium decay is examined using image analysis of transmission electron microscopy (TEM) micrographs. The influence of temperature (1073, 1223, and 1373 K), annealing time (0.083 to 1000 hours), cold deformation (92 pct) and helium content (35 and 3.7 appm) on the bubble's density, volume fraction, and mean size is investigated. For the chosen conditions of helium precipitation and growth (high temperature and large annealing time), the experimental results suggest that the observed increase in the size of the large bubbles present after a 0.083-hour aging at 1373 K proceeds via a facet limited migration and coalescence mechanism.

Chanfreau, A. (CEA-DAM, Bruyeres Le Chatel (France)); Brass, A.M.; Haut, C.; Chene, J. (Univ. of Paris-South, Orsay (France). Lab. of Structural Metallurgy)

1994-10-01

292

Numerical study of nucleation and growth of bubbles in viscous magmas  

SciTech Connect

The nucleation and growth processes of bubbles in viscous magmas with a constant decompression rate have been numerically investigated based on a formation which accounts for effects of viscosity, as well as diffusivity, interfacial tension, and decompression rate. The numerical solutions show two regimes in the nucleation and growth process, a diffusion-controlled regime and a viscosity-controlled regime, mainly depending on the decompression rate, initial saturation pressure and viscosity. The basic mechanism common to both regimes is that growth governs nucleation through depletion of degassing components. In basaltic eruptions the vesiculation is essentially controlled by diffusion, and the viscosity-controlled regime is limited to very high decompression rate and very small water content. When andesitic magma saturated by water at 10 MPa is decompressed through the propagation of rarefraction wave induced by a landslide, as took place in the Mount St. Helens 1980 eruption, the vesiculation is controlled by the viscosity up to 100 m depth. On the other hand, in a rhyolitic magma for the same situation, vesiculation is controlled by the viscosity over the whole depth of the magma column. In the viscosity-controlled regime, the vesicularity may be 90% or less as seen in silicic pumice, whereas in the diffusion-controlled regime the vesicularity equals or exceeds 98% such as in reticulite in Hawaiian basalt. An observed variation of the number density of bubbles by several orders of magnitude in plinian eruptions and the correlation with the SiO2 content can be attributed approximately to the dependence of diffusivity of viscosity on SiO2 content and temperature, assuming the apparent correlation between SiO2 content and temperature of magma.

Toramaru, A. [Kanazawa Univ., Kanazawa, Ishikawa (Japan)

1995-02-01

293

Calcium is a major determinant of xylem vulnerability to cavitation.  

PubMed

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 (NaPO(4)) were found to be more vulnerable to cavitation. The NaPO(4)-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 NaPO(4) 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

Herbette, Stephane; Cochard, Herve

2010-06-14

294

Calcium Is a Major Determinant of Xylem Vulnerability to Cavitation  

PubMed Central

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.

Herbette, Stephane; Cochard, Herve

2010-01-01

295

Mechanism for cavitation phenomenon in mechanical heart valves  

Microsoft Academic Search

Recently, cavitation on the surface of mechanical heart valve has been studied as a cause of fractures occurring in implanted\\u000a Mechanical Heart Valves (MHVs). It has been conceived that the MHVs mounted in an artificial heart close much faster than\\u000a in vivo sue, resulting in cavitation bubbles formation. In this study, six different kinds of monoleaflet and bileaflet valves\\u000a were

Hwansung Lee; Yoshiyuki Taenaka

2006-01-01

296

Enhancement of cavitation inception by second-harmonic superimposition  

NASA Astrophysics Data System (ADS)

High-intensity focused ultrasound (HIFU) treatment with cavitation bubbles has attracted much attention because they enhance the therapeutic efficacy of HIFU. Negative acoustic pressure is known to primarily determine the cavitation threshold. However, it is hard to generate highly negative acoustic pressure over the cavitation threshold by ultrasonic focusing because of the nonlinear propagation. The sequence, starting with the second-harmonic superimposed pulse waves enhancing the peak negative pressure, and followed by those enhancing the peak positive pressure, demonstrated the highest efficiency in cavitation inception. A high speed camera showed that the negative-pressure enhanced pulse waves produced a small cloud of cavitated microbubbles at the first stage and that the positive-pressure enhanced pulse waves expanded the microbubble cloud at the second stage.

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

2012-09-01

297

Microbubble cavitation imaging.  

PubMed

Ultrasound cavitation of microbubble contrast agents has a potential for therapeutic applications such as sonothrombolysis (STL) in acute ischemic stroke. For safety, efficacy, and reproducibility of treatment, it is critical to evaluate the cavitation state (moderate oscillations, stable cavitation, and inertial cavitation) and activity level in and around a treatment area. Acoustic passive cavitation detectors (PCDs) have been used to this end but do not provide spatial information. This paper presents a prototype of a 2-D cavitation imager capable of producing images of the dominant cavitation state and activity level in a region of interest. Similar to PCDs, the cavitation imaging described here is based on the spectral analysis of the acoustic signal radiated by the cavitating microbubbles: ultraharmonics of the excitation frequency indicate stable cavitation, whereas elevated noise bands indicate inertial cavitation; the absence of both indicates moderate oscillations. The prototype system is a modified commercially available ultrasound scanner with a sector imaging probe. The lateral resolution of the system is 1.5 mm at a focal depth of 3 cm, and the axial resolution is 3 cm for a therapy pulse length of 20 ?s. The maximum frame rate of the prototype is 2 Hz. The system has been used for assessing and mapping the relative importance of the different cavitation states of a microbubble contrast agent. In vitro (tissue-mimicking flow phantom) and in vivo (heart, liver, and brain of two swine) results for cavitation states and their changes as a function of acoustic amplitude are presented. PMID:23549527

Vignon, Francois; Shi, William T; Powers, Jeffry E; Everbach, E Carr; Liu, Jinjin; Gao, Shunji; Xie, Feng; Porter, Thomas R

2013-04-01

298

Formation and Growth Mechanism of Calcium Carbonate Nanoparticles via a Bubbling Method  

NASA Astrophysics Data System (ADS)

The mechanism of formation and growth of calcium carbonate (CaCO3) nanoparticles by bubbling carbon dioxide in aqueous suspensions of calcium hydroxide was investigated using time-resolved in situ synchrotron small-angle X-ray scattering (SAXS) and transmission electron microscopey (TEM). In situ SAXS showed a significant change in the particles size in the primary reaction. This suggests that the nucleus forms CaCO3 at in this period. After the nucleation, the crystal grow with the reaction time to yield 40 nm CaCO3 nanoparticles. TEM showed fibrous or chain-like intermediates formed by aggregation of fine particles of CaCO3 as calcite. We propose that CaCO3 crystal nuclei generated in the primary reaction grow to yield fibrous or chain-like CaCO3 which then separates into individual particles to form CaCO3 nanoparticles.

Eguchi, K.; Satake, T.; Tajika, M.; Kuwamoto, S.; Yokoyama, K.; Matsui, J.; Issiki, T.; Umesaki, N.

2011-10-01

299

Monitoring bubble growth in supersaturated blood and tissue ex vivo and the relevance to marine mammal bioeffects  

Microsoft Academic Search

There have been several recent reports that active sonar systems can lead to serious bioeffects in marine mammals, particularly beaked whales, resulting in strandings, and in some cases, to their deaths. We have devised a series of experiments to determine the potential role of low-frequency acous- tic sources as a means to induce bubble nucleation and growth in supersatu- rated

Lawrence A. Crum; Michael R. Bailey; Jingfeng Guan; Paul R. Hilmo; Steven G. Kargl; Thomas J. Matula; Oleg A. Sapozhnikov

2005-01-01

300

Ultrasound imaging for cavitation detection during HIFU ablation in brain  

NASA Astrophysics Data System (ADS)

High intensity focused ultrasound (abbreviated as HIFU) has its potential in tumor treatment due to its non-invasive benefits. During HIFU exposure, cavitation (generation of gas bubbles) is often observed, which can be an indication of potential lesion created by HIFU power. Due to a large difference in ultrasound acoustic properties between the gas bubble and surrounding tissues, ultrasonic energy is reflected and scattered at the HIFU focus, thus indicating activity around the focal area and often interfering HIFU dosage delivery. A good understanding and control of cavitation phenomenon could potentially enhance the HIFU delivery and treatment outcomes. Quantifying the onset timing and extent of the cavitation could be potentially used for detecting HIFU effects and therapy guidance. In this paper, we study the relationships among HIFU parameters, the characteristics of cavitation quantified from ultrasound imaging, and characteristics of the final tissue lesion created by HIFU. In our study, we used 12 freshly excised pig brains in vitro for observation and analysis of cavitation activities during HIFU exposure with different HIFU parameters. Final lesions were examined by slicing the brain tissues into thin slices and 3D volume was constructed with segmentation of the lesion. HIFU parameters, cavitation activities through image processing and lesion characterization were correlated. We also present our initial understanding of the process of cavitation activities under certain HIFU parameters and control of such activities that could lead to optimal lesion

Long, Tao; Amin, Viren; McClure, Scott; Roberts, Ronald; Wu, Liangshou; Heise, Matthew; Ryken, Timothy

2007-03-01

301

Characteristics of mechanical heart valve cavitation in a pneumatic ventricular assist device.  

PubMed

In previous studies, we investigated the mechanism of mechanical heart valve (MHV) cavitation and cavitation intensity with a nonsynchronized experiment system. Our group is currently developing a pneumatic ventricular assist device (PVAD), and in this study we investigated MHV cavitation intensity in the PVAD using a synchronized analysis of the cavitation images and the acoustic signal of cavitation bubbles. A 23-mm Medtronic Hall valve with an opening angle of 70 degrees was mounted in the mitral position of the PVAD after removing the sewing ring. A function generator provided a square signal, which used the trigger signal of the electrocardiogram R wave (ECG-R) mode of the control-drive console for circulatory support. This square signal was delayed by a delay circuit and was then used as the trigger signal for a pressure sensor and a high-speed video camera. The data were stored using a digital oscilloscope at a 1-MHz sampling rate, and then the pressure signal was band-pass filtered between 35 and 200 kHz using a digital filter. The band-pass filtered root mean squared (RMS) pressure and cavitation cycle duration were used as an index of cavitation intensity. The cavitation bubbles were concentrated at the valve stop, and the cavitation cycle duration and RMS pressure increased as the heart rate and driving pressure increased. At the low valve-closing velocity, bubble cavitation was observed near the valve stop. However, at the fast valve-closing velocity, cloud cavitation was observed. A high-frequency signal wave was generated when the bubbles collapsed. The cavitation cycle duration and RMS pressure increased as the valve-closing velocity increased linearly. PMID:18422801

Lee, Hwansung; Taenaka, Yoshiyuki

2008-04-16

302

Gauging the likelihood of stable cavitation from ultrasound contrast agents  

NASA Astrophysics Data System (ADS)

The mechanical index (MI) was formulated to gauge the likelihood of adverse bioeffects from inertial cavitation. However, the MI formulation did not consider bubble activity from stable cavitation. This type of bubble activity can be readily nucleated from ultrasound contrast agents (UCAs) and has the potential to promote beneficial bioeffects. Here, the presence of stable cavitation is determined numerically by tracking the onset of subharmonic oscillations within a population of bubbles for frequencies up to 7 MHz and peak rarefactional pressures up to 3 MPa. In addition, the acoustic pressure rupture threshold of an UCA population was determined using the Marmottant model. The threshold for subharmonic emissions of optimally sized bubbles was found to be lower than the inertial cavitation threshold for all frequencies studied. The rupture thresholds of optimally sized UCAs were found to be lower than the threshold for subharmonic emissions for either single cycle or steady state acoustic excitations. Because the thresholds of both subharmonic emissions and UCA rupture are linearly dependent on frequency, an index of the form ICAV = Pr/f (where Pr is the peak rarefactional pressure in MPa and f is the frequency in MHz) was derived to gauge the likelihood of subharmonic emissions due to stable cavitation activity nucleated from UCAs.

Bader, Kenneth B.; Holland, Christy K.

2013-01-01

303

Submicrocavity Structure of Water between Hydrophobic and Hydrophilic Walls as Revealed by Optical Cavitation  

Microsoft Academic Search

Laser-induced cavitation in a thin water layer bounded by hydrophobic and hydrophilic surfaces has been explored. For hydrophobic surfaces, the cavitation probability is enhanced and its threshold lowered. For hydrophilic walls, the formation of a macroscopic gas bubble during the laser pulse is consistent with earlier work on the existence of submicrobubble (bubston) clusters in bulk water (Bunkin et al.,

O. I. Vinogradova; N. F. Bunkin; N. V. Churaev; O. A. Kiseleva; A. V. Lobeyev; B. W. Ninham

1995-01-01

304

Effect of shaft frequency on cavitation in a journal bearing for noncentered circular whirl  

Microsoft Academic Search

The effect of shaft frequency on the performance of a submerged journal undergoing noncentered circular whirl is examined. The main emphasis of the paper is on the behavior of the vapor cavitation bubble and its effect on the bearing performance as a function of frequency. A cavitation algorithm due to Elrod was implemented in a computer program which solves a

David E. Brewe; M. M. Khonsari

1987-01-01

305

Effect of Shaft Frequency on Cavitation in a Journal Bearing for Noncentered Circular Whirl  

Microsoft Academic Search

This paper deals with the effect of shaft frequency on the performance of a submerged journal undergoing noncentered circular whirl. The main emphasis of the paper is on the behavior of the vapor cavitation bubble and its effect on the bearing performance as a function of frequency. A cavitation algorithm due to Elrod was implemented in a computer program which

David E. Brewe; M. M. Khonsari

1988-01-01

306

A numerical study on the effects of cavitation on orifice flow  

Microsoft Academic Search

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

S. Dabiri; W. A. Sirignano; D. D. Joseph

2010-01-01

307

A Fracture Mechanics Model for Cavitation Damage in Mechanical Heart Valve Prostheses  

Microsoft Academic Search

In the 1994 Replacement Heart Valve Guidance of the Food and Drug Administration (FDA), both cavitation and damage tolerance analyses are required for mechanical heart valves (MHV). Cavitation results from a sequence of events. First, vaporous bubbles are generated in the blood flow. They then collapse to form high-speed micro liquid jets, striking against the solid valve boundary, and subsequently

Changfu Wu; Ned H. C. Hwang; Y. K. Lin

2001-01-01

308

Cavitation limits for valves  

Microsoft Academic Search

Valves are used in piping systems to control flow rates and to regulate pressures. Whenever a large pressure drop occurs across a valve, the possibility of cavitation exists. A system can be subject to noise, vibration, and erosion damage when operating in a cavitating flow range. To quantify these effects in terms of different stages of cavitation, this paper presents

William J. Rahmeyer

1981-01-01

309

Impact of propagating and standing waves on cavitation appearance.  

PubMed

Standing waves play a significant role in the appearance of cavitation phenomena. The goal of this study was to investigate the effect that the relation between standing and propagating waves in a focused field has on acoustic bubble cloud formation. Measurements of the cavitation signals were performed on five different configurations of a hemispheric phased array transducer (230 kHz) representing a wide range of relations between propagating and standing waves. The results show that configurations with a larger propagating component induce bubble clouds at lower pressures than configurations with a larger standing component. PMID:22104538

Kenis, Alexander M; Grinfeld, Javier; Zadicario, Eyal; Vitek, Shuki

2011-11-21

310

A novel instrumentation of study cavitation maximum radii  

NASA Astrophysics Data System (ADS)

Based on the optical beam deflection (OBD) technique, a fiber-optic diagnostic technique is applied to investigate the pulsation of a laser-induced cavitation bubble on the vicinity of an aluminum target in water. The sequence waveforms induced by the bubble pulsation is presented and analyzed in detail. The maximum radii corresponding to each pulsation are determined. Furthermore, by varying the acting laser energy, the variation of the maximum bubble radius and bubble energy with respect to acting laser energy is obtained. The theoretical and experimental results are in good agreement within a relative error.

Zhao, Rui; Xu, Rong-qing; Chen, Xiao; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

2005-02-01

311

Numerical simulation of bubble growth in film boiling using a coupled level-set and volume-of-fluid method  

NASA Astrophysics Data System (ADS)

A coupled level-set and volume-of-fluid method is presented for modeling incompressible two-phase flows with surface tension. The coupled algorithm conserves mass and captures the complicated interfaces very accurately. A planar simulation of bubble growth is performed in water at near critical pressure for different degrees of superheat. The effect of superheat on the frequency of bubble formation has been analyzed. In addition, simulation of film boiling and bubble formation is performed in refrigerant R134a at near critical and far critical pressures. The effect of saturation pressure on the frequency of bubble formation has also been studied. A deviation from the periodic bubble release is observed in the case of superheat beyond 15 K in water. The effect of heat flux on the instability has also been analyzed. It is found that for water at near critical condition, a decrease in superheat from 15 to 10 K leads to oscillations with subharmonics influencing the time period of the ebullition cycle.

Tomar, G.; Biswas, G.; Sharma, A.; Agrawal, A.

2005-11-01

312

Bubble nucleation, growth and coalescence during the 1997 Vulcanian explosions of Soufrière Hills Volcano, Montserrat  

NASA Astrophysics Data System (ADS)

Soufrière Hills Volcano had two periods of repetitive Vulcanian activity in 1997, during which 88 explosions occurred. Each explosion discharged the contents of the upper 0.5-2 km of the conduit, two thirds as pyroclastic flows and the rest as fallout from 3-15-km-high buoyant plumes: frothy pumices from a deep, gas-rich zone, lava and breadcrust bombs from a degassed lava plug, and dense pumices from a transition zone. Vesicles constitute 1-66 vol% of breadcrust bombs and 24-79 % of pumices, all those larger than a few tens of µm being interconnected. Small vesicles (< few tens of µm) in all pyroclasts are interpreted as having formed syn-explosively because they are present in breadcrust bombs formed from originally non-vesicular magma. Most large vesicles (> few hundreds of µm) in pumices are interpreted as pre-dating explosion, implying pre-explosive conduit porosities of up to 55%. About 15% of large vesicles in pumices, and all those in breadcrust bombs, are angular voids formed by syn-explosive fracturing of amphibole phenocrysts. An intermediate-sized vesicle population formed by coalescence of the small syn-explosive bubbles. Nucleation took place heterogeneously on titanomagnetite, number densities of which greatly exceed those of vesicles. Bubble growth took place under disequilibrium conditions, largely by decompression-driven expansion; diffusive outgassing of melt was limited by the short timescale of the explosions, accounting for high water contents preserved in matrix glasses. Development of vesicle textures was controlled by the time interval between magma decompression and the onset of clast-surface cooling. Plug-derived fragments entered the air quickly after fragmentation (~10 s), so interiors continued to vesiculate once the rinds had quenched. A larger time interval for deep-derived pumices (~50 s) allowed complete vesiculation of the entire clast prior to surface quench, accounting for the lack of breadcrusting, as well as for the textural similarity between flow and fall pumices, despite different thermal histories after leaving the vent. This also allowed syn-explosive coalescence to proceed further in pumices than in the breadcrust bombs. Vesiculation of pumices was therefore largely confined to the conduit; indeed, uniaxial boudinage of some amphiboles implies that significant syn-explosive vesiculation of pumices took place even prior to magma fragmentation. Syn-explosive decompression rates estimated from vesicle number densities (> 0.3-6.5 MPa/s) are consistent with those predicted by numerical models. They are also consistent with the idea that syn-explosive bubble nucleation during the 1997 explosions was initiated during rapid decompression of conduit magma in a zone of steep pressure gradient beneath the descending fragmentation level.

Druitt, T. H.; Giachetti, T.; Burgisser, A.; Arbaret, L.

2009-12-01

313

Parallel computing of the underwater explosion cavitation effects on full-scale ship structures  

NASA Astrophysics Data System (ADS)

As well as shock wave and bubble pulse loading, cavitation also has very significant influences on the dynamic response of surface ships and other near-surface marine structures to underwater explosive loadings. In this paper, the acoustic-structure coupling method embedded in ABAQUS is adopted to do numerical analysis of underwater explosion considering cavitation. Both the shape of bulk cavitation region and local cavitation region are obtained, and they are in good agreement with analytical results. The duration of reloading is several times longer than that of a shock wave. In the end, both the single computation and parallel computation of the cavitation effect on the dynamic responses of a full-scale ship are presented, which proved that reloading caused by cavitation is non-ignorable. All these results are helpful in understanding underwater explosion cavitation effects.

Zong, Zhi; Zhao, Yanjie; Ye, Fan; Li, Haitao; Chen, Gang

2012-12-01

314

Cavitation guide for control valves  

Microsoft Academic Search

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

Tullis

1993-01-01

315

P3C-12 Combining Spectral and Intensity Data to Identify Regions of Cavitation in Ultrasound Images; Application to HIFU  

Microsoft Academic Search

The high power intensities in HIFU often result in bubble production, either through cavitation or boiling, which are believed to be a primary contributor to tissue necrosis Bubbles are associated with the appearance of bright hyperechoic regions in ultrasound B-mode images are observed from the bubbles. As they are often the only changes observed during treatment on tissue, some HIFU

Chang-yu Hsieh; Penny Probert Smith; Tom Leslie; James Kennedy; Guoliang Ye; Fares Mayia

2007-01-01

316

Influence of electric field on single gas-bubble growth and detachment in microgravity  

Microsoft Academic Search

The effect of electric and gravitational field on detachment and motion of gas bubbles was studied by injecting nitrogen in a fluoroinert liquid (FC-72) at ambient temperature and pressure through an orifice (about 0.1 mm diameter) drilled in a horizontal tube. In such a way, it was possible to investigate the mechanical effects in bubble dynamics separately from the thermal

P Di Marco; W Grassi; G Memoli; T Takamasa; A Tomiyama; S Hosokawa

2003-01-01

317

Bubble dynamics in N dimensions  

NASA Astrophysics Data System (ADS)

Cavitation and bubble dynamics are central concepts in engineering, the natural sciences, and the mathematics of fluid mechanics. Due to the nonlinear nature of their dynamics, the governing equations are not fully solvable. Here, the dynamics of a spherical bubble in an N-dimensional fluid are discussed in the hope that examining bubble behavior in N dimensions will add insight to their behavior in three dimensions. Several canonical results in bubble dynamics are re-derived, including the Rayleigh collapse time, the Rayleigh-Plesset equation, and the Minnaert frequency. Recent analytical approximations to the Rayleigh collapse are discussed, and the N-dimensional generalization is used to resolve a known discrepancy. Numerical simulations are used to examine the onset of nonlinear behavior. Overall, the dynamics of bubbles are faster at higher dimensions, with nonlinear behavior occurring at lower strain. Several features are found to be unique to three dimensions, including the trend of nonlinear behavior and apparent coincidences in timescales.

Klotz, Alexander R.

2013-08-01

318

A Study on the Mechanism for Cavitation in the Mechanical Heart Valves with an Electrohydraulic Total Artificial Heart  

NASA Astrophysics Data System (ADS)

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.

Lee, Hwansung; Tsukiya, Tomonori; Homma, Akihiko; Kamimura, Tadayuki; Tatsumi, Eisuke; Taenaka, Yoshiyuki; Kitamura, Soichiro

319

Cavitating Flow over a Mini Hydrofoil  

NASA Astrophysics Data System (ADS)

We consider a cavitating flow over a mini hydrofoil (foil profile: Clark-Y-11.7) having a 14 mm chord length in a cavitation tunnel at various cavitation numbers. Experimental observations show that cavitating flows over a miniature hydrofoil display several types of cavitation behavior, such as cavitation inception, sheet cavitation, cloud cavitation and super cavitation with the decreasing cavitation number. Under the same cavitation conditions, cavitation over a mini hydrofoil would be suppressed in comparison to cavitation over an ordinary hydrofoil. This cavitation scale effect is suspected to be caused by the Reynolds number.

Luo, Xian-Wu; Ji, Bin; Zhang, Yao; Xu, Hong-Yuan

2012-01-01

320

Experimental study and modeling of swelling and bubble growth in carbon nanofiber filled mesophase pitch during carbonization  

NASA Astrophysics Data System (ADS)

Graphite and all carbon bipolar plates show corrosion resistance in fuel cells and provide good electrical conductivity. These materials typically need to be individually machined, a time consuming and costly process. Mesophase pitch is used to manufacture carbon fibers and carbon-carbon composites. This material provides a good starting point for the production of a moldable, all carbon bipolar plate. However, processing of mesophase pitch to produce all carbon materials requires a time intensive oxidation step to prevent swelling during carbonization. In this work, carbon nanofibers were used to reduce swelling in mesophase pitch. It was found that the increase in viscosity with the addition of carbon nanofibers was responsible for the reduction in swelling. The influence of the filler became apparent above the percolation threshold. At loadings below the percolation threshold, the swelling of the mesophase pitch was not reduced after carbonization. The swelling of the mesophase pitch at a given carbon nanofiber loading was also dependent on the length of the carbon nanofibers. Longer carbon nanofibers led to greater increases in the viscosity of the melt and thus led to greater reduction in swelling. The final carbon product was evaluated for use as a low temperature fuel cell bipolar plate material. Constraining the mesophase pitch during carbonization led to a final product with strength and electrical conductivity comparable to current composite bipolar plate materials. The addition of micron size chopped glass fibers with a softening point near 850°C and carbon nanofibers led to a final product with air permeability less than that of graphite. A spherically symmetric, single bubble growth model was also developed. The model included temperature dependence, liquid to bubble mass transfer and reactions in the system. Results from simulations showed that that the increase in viscosity due to the addition of carbon nanofibers slows the growth of bubbles, but that the time scale of single bubble growth is much shorter than the time over which the foam grows. The single bubble growth model was deemed to be applicable to low loadings of carbon nanofiber, where the bubble size distribution in the final foam is narrow.

Calebrese, Christopher

321

Time-frequency analysis of transient pressure signals for a mechanical heart valve cavitation study.  

PubMed

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

Yu, A A; White, J A; Hwang, N H

322

CINEMATOGRAPHIC ANALYSIS OF A SINGLE BUBBLE COLLAPSE FLOW INDUCED BY PRESSURE WAVE  

Microsoft Academic Search

In this study, a single cavitation bubble is generated by rotating a U-tube filled with water. A series of bubble collapse flows induced by pressure waves of different strengths are investigated by positioning the cavitation bubble at different stand-off distances to the solid boundary. It is found that the Kelvin-Helmholtz vortices are formed when the liquid jet induced by the

Shenq-Yuh Jaw; Whey-Fone Tsai; Robert R. Hwang

323

Cavitational hydrothermal oxidation: A new remediation process. Annual progress report, September 1996--August 1997  

SciTech Connect

'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.'

Suslick, K.S.

1997-11-21

324

Cavitational hydrothermal oxidation: A new remediation process. 1998 annual progress report  

SciTech Connect

'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.'

Suslick, K.S.

1998-06-01

325

Effect of micro/nano-particles in cavitation erosion.  

PubMed

The tests in de-ionized water with micro/nano CeO2 particles are carried out to study the effect of the micro/nano particles in inception of cavitation erosion. The existence of micro/nano particles is found to be the requisite factor and the degree of cavitation erosion is related to the sizes of the particles. Particles in the micro/nano scale may act as the transporters of micro bubbles to keep or get close to the solid surface together and the pressure fluctuation induced by the surface roughness causes the collapse of bubbles and erosion of the surface. Discrete phase models are employed to simulation the moving tracks of the particles. The sizes of the particles affect their capabilities of keeping and getting close to the surface. The effect of the particles of a certain size in cavitation erosion is determined by the combinational action of the two. PMID:19441392

Li, Y J; Chen, H S; Chen, D R; Wang, J D

2009-02-01

326

Experimental and numerical analysis of cavitating flow around a hydrofoil  

NASA Astrophysics Data System (ADS)

The paper describes experiments carried out in the cavitation tunnel with the rectangular test section of 150 × 150 × 500 mm and the maximum test section inlet velocity of 25 m/s. These experiments have been aimed to visualize the cavitation phenomena as well as to quantify the erosion potential using pitting tests evaluated during the incubation period for the cast-iron prismatic hydrofoil with the modified NACA profile. A bypass section installed in the tunnel has allowed to measure the nuclei content in the inlet flow to the test section using the acoustic spectrometer. The measured data have been compared with the CFD analysis of the cavitation phenomena on the hydrofoil as well as the numerically determined location and magnitude of the first calculated collapses of the cavitating bubbles with a good agreement.

Sedlá?, Milan; Komárek, Martin; Vyroubal, Michal; Müller, Miloš

2012-04-01

327

Cavitation damage in blood clots under HIFU  

NASA Astrophysics Data System (ADS)

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.

Weiss, Hope; Ahadi, Golnaz; Hoelscher, Thilo; Szeri, Andrew

2010-11-01

328

Cavitation pressure in liquid helium  

NASA Astrophysics Data System (ADS)

Recent experiments have suggested that, at low enough temperature, the homogeneous nucleation of bubbles occurs in liquid helium near the calculated spinodal limit. This was done in pure superfluid helium 4 and in pure normal liquid helium 3. However, in such experiments, where the negative pressure is produced by focusing an acoustic wave in the bulk liquid, the local amplitude of the instantaneous pressure or density is not directly measurable. In this article, we present a series of measurements as a function of the static pressure in the experimental cell. They allowed us to obtain an upper bound for the cavitation pressure Pcav (at low temperature, Pcav<-2.4 bar in helium 3, Pcav<-8.0 bar in helium 4). From a more precise study of the acoustic transducer characteristics, we also obtained a lower bound (at low temperature, Pcav>-3.0 bar in helium 3, Pcav>-10.4 bar in helium 4). In this article we thus present quantitative evidence that cavitation occurs at low temperature near the calculated spinodal limit (-3.1 bar in helium 3 and -9.5 bar in helium 4). Further information is also obtained on the comparison between the two helium isotopes. We finally discuss the magnitude of nonlinear effects in the focusing of a sound wave in liquid helium, where the pressure dependence of the compressibility is large.

Caupin, F.; Balibar, S.

2001-08-01

329

Hyperecho in ultrasound images of HIFU therapy: involvement of cavitation.  

PubMed

High-intensity focused ultrasound (US), or HIFU, treatment of soft tissues has been shown to result in a hyperechoic region in B-mode US images. We report on detecting cavitation in vivo in correlation with the appearance of a hyperechoic region. The US system consisted of a HIFU transducer (3.3 MHz), a broadband A-mode transducer for active and passive cavitation detection and an US-imaging probe that were all confocal and synchronized. HIFU, at in situ intensities of 220 to 1710 W/cm(2), was applied for 10 s to pig muscles in vivo. Active and passive cavitation detection results showed a strong correlation between the onset of cavitation and the appearance of a hyperechoic region. Passive cavitation detection results showed that inertial cavitation typically occurred prior (within 0.5 s) to the appearance of a hyperechoic region. The observed cavitation activity confirms that bubbles are present during the formation of a hyperechoic region at the HIFU focus. PMID:15972200

Rabkin, Brian A; Zderic, Vesna; Vaezy, Shahram

2005-07-01

330

Characterization of acoustic cavitation in water and molten aluminum alloy.  

PubMed

High-intensive ultrasonic vibrations have been recognized as an attractive tool for refining the grain structure of metals in casting technology. However, the practical application of ultrasonics in this area remains rather limited. One of the reasons is a lack of data needed to optimize the ultrasonic treatment conditions, particularly those concerning characteristics of cavitation zone in molten aluminum. The main aim of the present study was to investigate the intensity and spectral characteristics of cavitation noise generated during radiation of ultrasonic waves into water and molten aluminum alloys, and to establish a measure for evaluating the cavitation intensity. The measurements were performed by using a high temperature cavitometer capable of measuring the level of cavitation noise within five frequency bands from 0.01 to 10MHz. The effect of cavitation treatment was verified by applying high-intense ultrasonic vibrations to a DC caster to refine the primary silicon grains of a model Al-17Si alloy. It was found that the level of high frequency noise components is the most adequate parameter for evaluating the cavitation intensity. Based on this finding, it was concluded that implosions of cavitation bubbles play a decisive role in refinement of the alloy structure. PMID:23141190

Komarov, Sergey; Oda, Kazuhiro; Ishiwata, Yasuo; Dezhkunov, Nikolay

2012-10-23

331

EFFECT OF A MAGNETIC FIELD ON TWO-PHASE LIQUID METAL FLOW AND CAVITATION OCCURRENCE  

Microsoft Academic Search

To clarify the effect of a magetic field on two-phase bubble flow characteristics and cavitation occurrence, an analytical study of two-phase MHD flow with low quality is developed, taking into account slip and bubble expansion. Numerical calculation shows that the application of a magnetic field causes a decrease in pressure in the diverging passage and an increase in the incipient

S. KAMIYAMA; T. YAMASAKI; T. WATAI

1984-01-01

332

Numerical modeling and simulation of laminar and transitional submerged cavitating jets  

Microsoft Academic Search

Numerical investigations on the effect of cavitation and bubble dynamics on fluid flow with applications to hydraulic valves are carried out. First, the parameter space of a previously developed quasi-one-dimensional model accounting for the coupling between the fluid flow and bubble dynamics is explored. Several flow and geometric parameters are shown to have a considerable effect on the stability of

Tao Xing

2002-01-01

333

ON THE DYNAMICS AND ACOUSTICS OF CLOUD CAVITATION ON AN OSCILLATING HYDROFOIL  

Microsoft Academic Search

Observations have been made of the growth and collapse of surface and cloud cavitation on a finite aspect ratio hydrofoil oscillating in pitch. The cavitation was recorded using both still and high-speed motion picture photography, and the variations with cavitation number and reduced frequency of oscillation were investigated. The noise generated by the cavity collapse was also measured and analyzed.

E. A. McKenney; Christopher E. Brennen

334

Temporal and Spatial Detection of HIFU-Induced Inertial and Hot-Vapor Cavitation with a Diagnostic Ultrasound System  

Microsoft Academic Search

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,

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

2009-01-01

335

Interaction of two differently sized oscillating bubbles in a free field  

NASA Astrophysics Data System (ADS)

Most real life bubble dynamics applications involve multiple bubbles, for example, in cavitation erosion prevention, ultrasonic baths, underwater warfare, and medical applications involving microbubble contrast agents. Most scientific dealings with bubble-bubble interaction focus on two similarly sized bubbles. In this study, the interaction between two oscillating differently sized bubbles (generated in tap water) is studied using high speed photography. Four types of bubble behavior were observed, namely, jetting toward each other, jetting away from each other, bubble coalescence, and a behavior termed the “catapult” effect. In-phase bubbles jet toward each other, while out-of-phase bubbles jet away from each other. There exists a critical phase difference that separates the two regimes. The behavior of the bubbles is fully characterized by their dimensionless separation distance, their phase difference, and their size ratio. It is also found that for bubbles with large size difference, the smaller bubble behaves similarly to a single bubble oscillating near a free surface.

Chew, Lup Wai; Klaseboer, Evert; Ohl, Siew-Wan; Khoo, Boo Cheong

2011-12-01

336

Porous resins as a cavitation enhancer for low-frequency sonophoresis.  

PubMed

The application of low-frequency ultrasound enhances drug transport through the skin, a phenomenon referred to as low-frequency sonophoresis. This enhancement is mediated through cavitation, the formation and collapse of gaseous bubbles. We hypothesized that the efficacy of low-frequency sonophoresis can be significantly enhanced by provision of nuclei for cavitation. In this study, we used two porous resins, Diaion HP20 and Diaion HP2MG (2MG), as cavitation nuclei. We measured the effect of these resins on cavitation using pitting of aluminum foil. 2MG showed a higher efficacy in enhancing cavitation compared with Diaion HP20. 2MG was also effective in enhancing transdermal mannitol transport. These results confirm that the addition of cavitation nuclei such as porous resins further increases the effect of low-frequency ultrasound on skin permeability. PMID:11920760

Terahara, Takaaki; Mitragotri, Samir; Langer, Robert

2002-03-01

337

Inducer Design to Avoid Cavitation Instabilities  

NASA Astrophysics Data System (ADS)

Three inducers were designed to avoid cavitation instabilities. This was accomplished by avoiding the interaction of tip cavity with the leading edge of the opposing blade. The first one applied extremely larger leading edge sweep, the second and third ones applied smaller incidence angle by reducing the inlet blade angle or increasing the design flow rate, respectively. The inducer with larger design flow rate has larger outlet blade angle to obtain sufficient pressure rise. The inducer with larger sweep could suppress the cavitation instabilities in wide ranges of cavitation number and flow rate, owing to weaker tip leakage vortex cavity with stronger disturbance by backflow vortices. The inducer with larger outlet blade angle could avoid the cavitation instabilities at higher flow rates owing to the extension of the tip cavity along the suction surface of the blade. The inducer with smaller inlet blade angle could avoid the cavitation instabilities at the flow rates larger than the design flow coefficient, owing to the occurrence of the cavity first in the blade passage and its extension upstream. The cavity shape and suction performance were reasonably simulated by three dimensional CFD computations under the steady cavitating condition, except for the backflow vortex cavity. The difference in the growth of cavity for each inducer is explained from the difference of the pressure distribution on the suction side of the blades.

Kang, Donghyuk; Watanabe, Toshifumi; Yonezawa, Koichi; Horiguchi, Hironori; Kawata, Yutaka; Tsujimoto, Yoshinobu

2010-06-01

338

Effect of Noble Gases on Sonoluminescence Temperatures during Multibubble Cavitation  

SciTech Connect

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.

Didenko, Yuri T.; McNamara, William B. III; Suslick, Kenneth S.

2000-01-24

339

A Study on the Mechanism for Cavitation in the Mechanical Heart Valves with an Electrohydraulic Total Artificial Heart  

Microsoft Academic Search

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

Hwansung Lee; Tomonori Tsukiya; Akihiko Homma; Tadayuki Kamimura; Eisuke Tatsumi; Yoshiyuki Taenaka; Soichiro Kitamura

2004-01-01

340

Can Cavitation Be Anticipated?  

Microsoft Academic Search

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.

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

1999-01-01

341

Measurement Of Gas Bubbles In Mercury Using Proton Radiography  

Microsoft Academic Search

An experiment using proton radiography on a small mercury loop for testing gas bubble injection was conducted at the Los Alamos Neutron Science Center (LANSCE) in December 2006. Small gas bubble injection is one of the approaches under development to reduce cavitation damage in the U.S. Spallation Neutron Source mercury target vessel. Several hundred radiograph images were obtained as the

Bernie Riemer; Philip R Bingham; Fesseha G Mariam; Frank E Merrill

2007-01-01

342

Vortex bubble formation in pair plasmas.  

PubMed

It is shown that delocalized vortex solitons in relativistic pair plasmas with small temperature asymmetries can be unstable for intermediate intensities of the background electromagnetic field. Instability leads to the generation of ever-expanding cavitating bubbles in which the electromagnetic fields are zero. The existence of such electromagnetic bubbles is demonstrated by qualitative arguments based on a hydrodynamic analogy, and by numerical solutions of the appropriate nonlinear Schrödinger equation with a saturating nonlinearity. PMID:23944600

Berezhiani, V I; Shatashvili, N L; Mahajan, S M; Aleksi?, B N

2013-07-18

343

Cavitation in Amorphous Solids  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations of cavitation in a Zr50Cu50 metallic glass exhibit a waiting time dependent cavitation rate. On short time scales nucleation rates and critical cavity sizes are commensurate with a classical theory of nucleation that accounts for both the plastic dissipation during cavitation and the cavity size dependence of the surface energy. All but one parameter, the Tolman length, can be extracted directly from independent calculations or estimated from physical principles. On longer time scales aging in the form of shear relaxations results in a systematic decrease of cavitation rate. The high cavitation rates that arise due to the suppression of the surface energy in small cavities provide a possible explanation for the quasi-brittle fracture observed in metallic glasses. Analogous simulations of Fe80P20 reveal that segregation of P on the nanoscale leads to qualitatively different behavior that may be attributable to the idiosyncrasies of the interatomic potential.

Falk, Michael; Guan, Pengfei; Lu, Shuo; Spector, Michael; Valavala, Pavan

2013-03-01

344

Snapping shrimp make flashing bubbles.  

PubMed

Snapping shrimp produce a loud crackling noise that is intense enough to disturb underwater communication. This sound originates from the violent collapse of a large cavitation bubble generated under the tensile forces of a high-velocity water jet formed when the shrimp's snapper-claw snaps shut (Fig. 1). Here we show that a short, intense flash of light is emitted as the bubble collapses, indicating that extreme pressures and temperatures of at least 5,000 K (ref. 4) must exist inside the bubble at the point of collapse. We have dubbed this phenomenon 'shrimpoluminescence' - the first observation, to our knowledge, of this mode of light production in any animal - because of its apparent similarity to sonoluminescence, the light emission from a bubble periodically driven by ultrasound. PMID:11586346

Lohse, D; Schmitz, B; Versluis, M

2001-10-01

345

Can Cavitation Be Anticipated?  

SciTech Connect

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.

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

1999-04-25

346

Low-Drag Cavitating Hydrofoils  

Microsoft Academic Search

Cavitation research in the naval hydrodynamics context has generally been aimed at either the avoidance of cavitation or in the investigation of supercavitating flows at very low values of the cavitation index. However, inviscid theory shows that there is a regime of partially cavitating flows where relatively high lift to drag ratios can be obtained. The design of a low-drag

Eduard Amromin; Roger E. A. Arndt; James Kopriva; Martin Wosnik

2004-01-01

347

Mechanism for cavitation in the mechanical heart valve with an artificial heart: nuclei and viscosity dependence.  

PubMed

Until now, we have estimated cavitation for mechanical heart valves (MHV) mounted in an electrohydraulic total artificial heart (EHTAH) with tap water. However, tap water at room temperature is not a proper substitute for blood at 37 degrees C. We therefore investigated fluid characterization in studies of MHV cavitation associated with the viscosity and nuclei content of a testing fluid. We used the Medtronic Hall valve mounted in the mitral position of the EHTAH. As testing fluids, tap water, distilled water, and glycerin solution were used. The valve-closing velocity, pressure-drop measurements, and a high-speed video camera were employed to determine the cavitation intensity in MHV. Most of the cavitation bubbles were observed at the edge of the valve stop. Our analysis of the results indicates that squeeze flow is the major cause of cavitation in the Medtronic Hall valve. The cavitation intensity increased with increases in the fluid viscosity and the valve-closing velocity. Even if cavitation intensity in glycerin solution was greater, the cavitation occurrence probability was less in glycerin solution than in tap water. Our results suggest that tap water contains particles that cause an increase in the cavitation occurrence probability. We conclude that cavitation intensity is greatly affected by the nuclei concentration in the fluid and the fluid viscosity. PMID:15644082

Lee, Hwansung; Taenaka, Yoshiyuki; Kitamura, Soichiro

2005-01-01

348

Development of Liposomal Bubbles with Perfluoropropane Gas as Gene Delivery Carriers  

Microsoft Academic Search

Liposomes have some advantages as drug, antigen and gene delivery carriers. Their size can be easily controlled and they can be modified to add a targeting function. Based on liposome technology, we developed novel liposomal bubbles (Bubble liposomes) containing the ultrasound imaging gas, perfluoropropane. We assessed the feasibility of Bubble liposomes as carriers for gene delivery after cavitation induced by

Kazuo Maruyama; Ryo Suzuki; Kaori Sawamura; Tomoko Takizawa; Naoki Utoguchi; Yoichi Negishi

2007-01-01

349

Concentration Evolution of Gas Species within a Collapsing Bubble in a Liquid Medium  

Microsoft Academic Search

In this study numerical methods are used to investigate the relationship between chemical concentration of gas species within a cavitating bubble, equilibrium radius of the gas bubble and pressure variations in the ambient liquid. For this purpose, governing equations are developed to describe the dynamic equilibrium of a bubble in a flowing fluid and mass transfer between gas and liquid

Wonyong Jang; Mustafa M. Aral

2003-01-01

350

Mechanism for cavitation of monoleaflet and bileaflet valves in an artificial heart.  

PubMed

It is possible that mechanical heart valves mounted in an artificial heart close much faster than those used for clinical valve replacement, resulting in the formation of cavitation bubbles. In this study, the mechanism for mechanical heart cavitation was investigated using the Medtronic Hall monoleaflet valve and the Sorin Bicarbon bileaflet valve mounted at the mitral position in an electrohydraulic total artificial heart. The valve-closing velocity was measured with a charge-coupled device (CCD) laser displacement sensor, and images of mechanical heart valve cavitation were recorded using a high-speed video camera. The valve-closing velocity of the Sorin Bicarbon bileaflet valve was lower than that of the Medtronic Hall monoleaflet valve. Most of the cavitation bubbles generated by the monoleaflet valve were observed near the valve stop; with the Sorin Bicarbon bileaflet valve, cavitation bubbles were concentrated along the leaflet tip. The cavitation density increased as the valve-closing velocity and the valve stop area increased. These results strongly indicate that squeeze flow holds the key to cavitation in the mechanical heart valve. From the perspective of squeeze flow, bileaflet valves with a low valve-closing velocity and a small valve stop area may cause less blood cell damage than monoleaflet valves. PMID:16998700

Lee, Hwansung; Tatsumi, Eisuke; Homma, Akihiko; Tsukiya, Tomonori; Taenaka, Yoshiyuki

2006-01-01

351

An experimental investigation of cavitation in JP8 jet fuel.  

NASA Astrophysics Data System (ADS)

In this experimental study flow induced cavitation in JP8 jet fuel is investigated for the first time. In internal fuel handling machinery cavitation is associated with sharp turns in the flow path. It is well known that cavitation bubble collapse leads to damage and eventual failure of pumps and valves. In this study we consider a generic flow problem that is relevant to a wide number of fuel handling applications. This consists of an axisymmetric jet of JP8 fuel that emerges from the center of a disk. The jet impinges on a second disk suspended just above the first and consequently forces the flow to turn suddenly and flow radially into a thin gap between the disks. In this manner, the initially axial flow must turn rapidly into the radial direction. The large radial dilatation acts on nuclei present to give rise to cavitation bubble formation. Detailed experiments are performed in a closed loop facility that allows the dissolved gas and contaminant particle concentration in the fuel to be controlled. The cavitation inception process is studied through high resolution imaging, pressure measurement and with a phase Doppler particle analyzer.

Iqbal, Muhammad

2005-11-01

352

Transcranial Doppler and acoustic pressure fluctuations for the assessment of cavitation and thromboembolism in patients with mechanical heart valves.  

PubMed

The formation and collapse of vapor-filled bubbles near a mechanical heart valve is called cavitation. Such microbubbles are suspected to have strong pro-coagulant effects. Therefore, cavitation may be a contributing factor to the pro-thrombotic effects of mechanical valves. Herein, we systematically review the available evidence linking cavitation and thrombosis. We also critically appraise the potential usefulness of transcranial Doppler and other new non-invasive diagnostic methods to study cavitation and cerebral embolism in mechanical valve patients. Experimental studies indicate that cavitation microbubbles cause platelet aggregation, complement-activation, fibrinolysis, release of tissue-factor, and endothelial damage. Administration of 100% oxygen to mechanical valve patients during transcranial Doppler examination can transiently decrease the counts of Doppler-detected cerebral microemboli compared with room air. This is associated with removal of most circulating gaseous emboli from cavitation. This method may therefore be applied to the study of cavitation and thromboembolism. Additionally, the analysis of high-frequency acoustic-pressure fluctuations detected from the implosion of cavitation bubbles is a promising method for assessment of cavitation in vivo; however, this requires further development. A better understanding of cavitation is important in order to adequately investigate its role in the overall pro-thrombotic effects in mechanical valve patients. Such studies may allow establishing guidelines for new valve designs. PMID:18056151

Rodriguez, Rosendo A; Ruel, Marc; Labrosse, Michel; Mesana, Thierry

2007-12-03

353

Cavitation in microscale confinement: new concept of mild brain injury.  

NASA Astrophysics Data System (ADS)

The present effort is to understand the possible damages in brain caused by the cavitation bubbles generated when the impacting shock waves passing through human head. In order to build an adequate mathematical model of this phenomenon, one should be able to model inception and dynamics of cavitation in biological liquid confined in macroscale or microscale space between solids, elastic surfaces, or membranes -- biological tissues, in general. A more in-depth understanding of the outcomes from the dynamic response of brain tissue, including the location, size, and geometry of the damage site, will be of assistance to physicians in the properly interpreting the neurodiagnostic results. In the present study it is stated that in micro scale confinement bubble collapse can not cause any damage. This is due to the fact that collapse is damped by viscous dissipation in micro channels. Otherwise, the bubble inception itself may cause damage. It is shown that cavitation inception in micro scale may happen for much higher tensions than in infinite liquid. At such a strong tension substantial amount of elastic energy is stored in liquid. This energy being released during cavitation inception generates `recoil pressure' that may be high enough to damage biological tissue.

Akhatov, Iskander; Wang, Cheng; Ziejewski, Mariusz

2007-11-01

354

Estimation of mechanical heart valve cavitation in a pneumatic ventricular assist device.  

PubMed

In this study, we investigated the possibility of estimating the mechanical heart valve (MHV) cavitation intensity using the slope of the driving pressure (DP) just before valve closure in a pneumatic ventricular assist device. We installed a 23-mm Medtronic Hall valve at the inlet of our pneumatic ventricular assist device (VAD). Tests were conducted under physiologic pressures at heart rates ranging from 60 to 90 beats/min and cardiac outputs ranging from 4.5 to 6.7 l/min. The valve-closing velocity was measured with a CCD laster displacement sensor, and the images of MHV cavitation were recorded using a high-speed video camera. The cavitation cycle time (equal to the observed duration of the cavitation bubbles) was used as the MHV cavitation intensity. The valve-closing velocity increased as the heart rate increased. Most of the cavitation bubbles were observed near the valve stop, and the cavitation intensity increased as the heart rate increased. The slope of the DP at 20 ms before valve closure was used as an index of the cavitation intensity. There were differences in the slope of the DP between low and high heart rates, but the slope of the DP had a tendency to linearly increase with increasing valve-closing velocity. PMID:17846718

Lee, Hwansung; Akagawa, Eiki; Homma, Akihiko; Tsukiya, Tomonori; Tatsumi, Eisuke; Taenaka, Yoshiyuki

2007-09-20

355

Estimation of mechanical heart valve cavitation in an electro-hydraulic total artificial heart.  

PubMed

The purpose of this study was to establish a method for estimating mechanical in vitro heart valve cavitation in an electro-hydraulic total artificial heart (EHTAH). The variations in the left driving pressure (LDP) slope of the EHTAH were used as an index of the cavitation intensity. The LDP slope was controlled by changing the stroke volume of the EHTAH. The stroke volume was changed from full-filling and full-eject to partial-filling and partial-eject conditions. A 25-mm Medtronic Hall valve was installed in the mitral position of the EHTAH. Cavitation bubbles were concentrated on the valve stop; the major cause of these cavitation bubbles was determined to be squeeze flow. The valve-closing velocity was found to be proportional to increases in the LDP slope and the stroke volume of the left blood pump. The cavitation intensity and the cavitation event rate increased with increases in the stroke volume of the EHTAH. A consistent correlation was observed between the valve-closing velocity and the cavitation intensity. The LDP slope of the EHTAH may play an important role in estimating the mechanical heart valve cavitation intensity. PMID:16409393

Lee, Hwansung; Taenaka, Yoshiyuki; Kitamura, Soichro

2006-01-01

356

Nucleation threshold and deactivation mechanisms of nanoscopic cavitation nuclei  

NASA Astrophysics Data System (ADS)

The acoustic nucleation threshold for bubbles trapped in cavities has theoretically been predicted within the crevice theory by Atchley and Prosperetti [``The crevice model of bubble nucleation,'' J. Acoust. Soc. Am. 86, 1065 (1989)]. Here, we determine this threshold experimentally, by applying a single pressure pulse to bubbles trapped in cylindrical nanoscopic pits (``artificial crevices'') with radii down to 50 nm. By decreasing the minimum pressure stepwise, we observe the threshold for which the bubbles start to nucleate. The experimental results are quantitatively in good agreement with the theoretical predictions of Atchley and Prosperetti. In addition, we provide the mechanism which explains the deactivation of cavitation nuclei: gas diffusion together with an aspherical bubble collapse. Finally, we present superhydrophobic nuclei which cannot be deactivated, unless with a high-speed liquid jet directed into the pit.

Borkent, Bram M.; Gekle, Stephan; Prosperetti, Andrea; Lohse, Detlef

2009-10-01

357

Dynamics of laser-induced cavitation in liquid  

NASA Astrophysics Data System (ADS)

This paper presents an analysis of the rate of bubble expansion and an estimate of maximum bubble diameter and bubble lifetime prior to collapse. Such data are needed for the optimization of system parameters for elemental analysis in water by laser-induced breakdown spectroscopy (LIBS). Two techniques were used for this study: pump-probe beam deflection and high-speed photography. Plasma in the water bulk was generated by a focussed laser pulse with energy of 140 mJ and pulse duration of 10 ns, operating at the fundamental Nd:YAG laser wavelength (1064 nm). Reasonable agreement on the value of maximum bubble diameter was obtained between the photographic and probe beam deflection results. Reasonable agreement for the total duration of the oscillating cavitation bubble was also obtained for the two techniques, with a mean value of ˜800 ?s. A comparison between empirical results and predictions based on the Rayleigh equation is also presented.

Peel, Christopher S.; Fang, Xiao; Ahmad, S. Rafi

2011-06-01

358

The general solution and its analyticity for growth or dissolution of a gas bubble  

Microsoft Academic Search

The isothermal diffusion of a gas bubble in an infinite liquid which is either supersaturated or undersaturated, subject to an arbitrarily prescribed initial condition and the effect of surface tension at the interface, is studied. One of the objectives of the paper is to investigate the analyticity of the solutions. For this purpose, the prescribed initial condition is considered to

L. N. Tao

1979-01-01

359

Acoustic cavitation studies  

NASA Astrophysics Data System (ADS)

The primary thrust of this study was toward a more complete understanding of general aspects of acoustic cavitation. The effect of long-chain polymer additives on the cavitation threshold was investigated to determine if they reduced the acoustic cavitation threshold in a similar manner to the observed reduction in the cavitation index in hydrodynamic cavitation. Measurements were made of the acoustic cavitation threshold as a function of polymer concentration for additives such as guar gum and polyethelene oxide. The measurements were also made as a function of dissolved gas concentration, surface tension and viscosity. It was determined that there was a significant increase in the acoustic cavitation threshold for increased concentrations of the polymer additives (measurable effects could be obtained for concentrations as low as a few parts per million). One would normally expect that an additive that reduces surface tension to decrease the pressure required to cause a cavity to grow and thus these additives, at first thought, should reduce the threshold. However, even in the hydrodynamic case, the threshold was increased. In both of the hydrodynamic cases considered, the explanation for the increased threshold was given in terms of changed fluid dynamics rather than changed physical properties of the fluid.

Crum, L. A.

1981-09-01

360

A new approach to detection of the cavitation on mechanical heart valves.  

PubMed

The cavitation on the mechanical heart valves (MHVs) is thought to be a cause of the mechanical failure of the occluder; also, the free radicals that would be generated when the cavitation bubbles implode might affect the patients chemically. These cavitation effects are attributed to the bubble collapse. Therefore, it is important to detect the bubble implosion behavior to analyze the cavitation on MHVs. The cavitation bubbles induce the generation of free radicals at their implosion, and the excited hydroxyl radicals emit the faint light. Based on this fact, we have tried to observe the faint light emission from a MHV to specifically capture the implosion of the cavitation bubbles. A highly sensitive CCD (charge coupled device) camera (C2400-35 VIM camera, Hamamatsu Photonics, Hamamatsu, Japan) was adopted in this study. This camera can observe low light down to the single photon counting range, and it gives two-dimensional mapping of the light. A 20 mm Björk-Shiley valve was submerged in the water tank of 10 L deionized water with luminol as a light enhancer, and then the pressure difference of 150 mm Hg was exerted on the valve at a rate of 60 bpm with a pulse duplicator. The camera and the water tank were settled in the lightproof configuration. After 2 hours of exposure, faint light images have been obtained successfully. The light emits mostly from the edge of the occluder on the inflow side in the major orifice of the valve. Therefore the results suggest that the bubbles would implode around this region and that free radicals caused by cavitation might be produced on MHV, which has coincided with our preliminary result by an electron spin resonance spectrometry. PMID:12790381

Takiura, Koki; Chinzei, Tsuneo; Abe, Yusuke; Isoyama, Takashi; Saito, Itsuro; Ozeki, Toshinaga; Imachi, Kou

361

HIGH-SPEED MOTION IN BUBBLY FLOWS  

Microsoft Academic Search

Supercavitating bodies can achieve very high speeds under water by virtue of reduced drag: with proper design, a cavitation bubble is generated at the nose and skin friction drag is drastically reduced. Depending on the type of supercavitating vehicle under consideration, the overall drag coefficient can be an order of magnitude less than that of a fully-wetted vehicle. However, control

John R. Grant; Ivan N. Kirschner

2003-01-01

362

Nano bubbles in liquid of a noble-gas mixture.  

PubMed

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

Yamamoto, Takenori; Ohnishi, Shuhei

2009-12-01

363

Optical observations of the growth and day-to-day variability of equatorial plasma bubbles  

Microsoft Academic Search

A new narrow-field ionospheric imaging system, the Portable Ionospheric Camera and Small-Scale Observatory, has been installed at the Cerro Tololo Inter-American Observatory near La Serena, Chile (geographic 30.17°S, 289.19°E; geomagnetic 16.72°S, 0.42°E). We present observations of the naturally occurring nightglow emission at 630.0 nm on three consecutive nights demonstrating the day-to-day variability in the occurrence of equatorial plasma bubbles or

J. J. Makela; E. S. Miller

2008-01-01

364

Optical observations of the growth and day-to-day variability of equatorial plasma bubbles  

Microsoft Academic Search

A new narrow-field ionospheric imaging system, the Portable Ionospheric Camera and Small-Scale Observatory, has been installed at the Cerro Tololo Inter-American Observatory near La Serena, Chile (geographic 30.17°S, 289.19°E geomagnetic 16.72°S, 0.42°E). We present observations of the naturally occurring nightglow emission at 630.0 nm on three consecutive nights demonstrating the day-to-day variability in the occurrence of equatorial plasma bubbles or

J. J. Makela; E. S. Miller

2008-01-01

365

Cavitating flow investigation inside centrifugal impellers for a condensate pump  

NASA Astrophysics Data System (ADS)

In order to investigate the effect of blade inlet angle on centrifugal pump cavitation performance, numerical simulation of cavitating turbulent flow is conducted for a condensate pump with different impellers based on SST k-? turbulence model and a mixture cavitation model. The results indicate that for a condensate pump having meridional section with larger area at blade leading edge compared with conventional pumps, the reverse flows inside the blade-to-blade channels are not negligible. It is noted that large incidence at blade leading edge is helpful to improve the cavitation performance for the pump. The possible reason may be the growth of cavities inside the impeller has less influence on the flow in the channel between two neighboring blades. Further, uniform incidence angle along the blade leading edge is preferable for the improvement of cavitation performance.

Wei, W.; Luo, X. W.; Ji, B.; Zhuang, B. T.; Xu, H. Y.

2012-11-01

366

Sonoporation with single bubbles in microfluidic systems  

NASA Astrophysics Data System (ADS)

When bubbles oscillate close to cells in suspension they can cause viable or permanent poration of the cell membrane. This method named as sonoporation offers potentials for novel therapeutic applications in medicine i.e., cell killing or actively induced drug uptake. Until now, the details of bubble-to-cell interactions are not clarified especially due to a lack of experimental methods. Here we show that sonoporation of cells in suspension is made possible and can be studied in details when using a microfluidic system together with laser-induced cavitation bubbles.

Le Gac, Séverine; Zwaan, Ed; van der Berg, Albert; Ohl, Claus-Dieter

2007-05-01

367

An Experimental Study of Cavitation Detection in a Centrifugal Pump Using Envelope Analysis  

NASA Astrophysics Data System (ADS)

Cavitation represents one of the most common faults in pumps and could potentially lead to a series of failure in mechanical seal, impeller, bearing, shaft, motor, etc. In this work, an experimental rig was setup to investigate cavitation detection using vibration envelope analysis method, and measured parameters included sound, pressure and flow rate for feasibility of cavitation detection. The experiment testing included 3 operating points of the centrifugal pump (B.E.P, 90% of B.E.P and 80% of B.E.P). Suction pressure of the centrifugal pump was decreased gradually until the inception point of cavitation. Vibration measurements were undertaken at various locations including casing, bearing, suction and discharge flange of the centrifugal pump. Comparisons of envelope spectrums under cavitating and non-cavitating conditions were presented. Envelope analysis was proven useful in detecting cavitation over the 3 testing conditions. During the normal operating condition, vibration peak synchronous to rotational speed was more pronounced. It was however during cavitation condition, the half order sub-harmonic vibration component was clearly evident in the envelope spectrums undertaken at all measurement locations except at the pump bearing. The possible explanation of the strong sub-harmonic (½ of BPF) during cavitation existence in the centrifugal pump was due to insufficient time for the bubbles to collapse completely before the end of the single cycle.

Tan, Chek Zin; Leong, M. Salman

368

Sonosensitive nanoparticles for controlled instigation of cavitation and drug delivery by ultrasound  

NASA Astrophysics Data System (ADS)

Reliable instigation of cavitation in-vivo during ultrasound therapy is notoriously difficult. Lowering the peak rarefractional pressure required to initiate cavitation (the cavitation threshold) has been previously addressed using ultrasound contrast agents in the form of encapsulated stabilized micron scale bubbles. These agents lack stability and are generally too large to extravasate into tumours and other target tissues. Solid nanoparticles are proposed as novel cavitation nucleation agents, which overcome these limitations. Such agents are manufactured to achieve high surface roughness and hydrophobicity, facilitating air entrapment upon drying, thus harboring an abundance of cavitation nucleation sites. These nanoparticulate nucleating agents have been found to lower the cavitation threshold significantly in aqueous biological media, enabling reproducible cavitation activity during repeated exposure to therapeutic ultrasound. This paper investigates the engineering of core-shell nanoparticles and examines their ability to initiate inertial cavitation in the context of ultrasound-enhanced localized drug delivery for cancer. Core-shell nanoparticles have been found to decrease the peak focal pressure where the probability of cavitation is greater than 0.5, by factors of five- to ten-fold, dependent on particle size, total surface area and surface morphology.

Wagstaffe, Sarah J.; Schiffter, Heiko A.; Arora, Manish; Coussios, Constantin-C.

2012-10-01

369

Bubble Tray  

NSDL National Science Digital Library

Bubble Tray from the Exploratorium is an activity about surface tension and constructive or destructive interference observed in soap bubbles. The site provides a soap bubble recipe and suggests common supplies like a coat hanger and pizza pan to produce large, long lasting bubbles. An explanation of the physics involved and other methods of making large bubbles are also supplied. This activity is part of Exploratorium's Science Snacks series.

2006-07-16

370

Mechanism for cavitation of monoleaflet and bileaflet valves in an artificial heart  

Microsoft Academic Search

It is possible that mechanical heart valves mounted in an artificial heart close much faster than those used for clinical\\u000a valve replacement, resulting in the formation of cavitation bubbles. In this study, the mechanism for mechanical heart cavitation\\u000a was investigated using the Medtronic Hall monoleaflet valve and the Sorin Bicarbon bileaflet valve mounted at the mitral position\\u000a in an electrohydraulic

Hwansung Lee; Eisuke Tatsumi; Akihiko Homma; Tomonori Tsukiya; Yoshiyuki Taenaka

2006-01-01

371

HIFU-Induced Hyperecho in Ultrasound Images, Cavitation Activity and Thermal Behavior  

NASA Astrophysics Data System (ADS)

High Intensity Focused Ultrasound (HIFU) treatment of soft tissues has been shown to result in a hyperechoic region in B-mode ultrasound (US) images. This is believed to result from bubble activity at the HIFU focus. Here we report our in vivo results of detecting inertial and stable cavitation in correlation with the appearance of a hyperechoic region, along with in vitro confirmation of these results that included measurement of the temperature at the HIFU focus. The ultrasound system consisted of a HIFU transducer (3.3 MHz), a broadband A-mode transducer for active and passive cavitation detection (ACD and PCD), and an US-imaging probe that were all co-focal and synchronized. HIFU, at in situ intensities of 220- 1,710 W/cm2, was applied for 10 s to pig muscles in vivo or polyacrylamide in vitro at a focal depth of 2 cm. A thermocouple placed at the HIFU focus was added to the above system during the in vitro portion of this study. ACD and PCD results showed a strong correlation between the onset of cavitation and the appearance of a hyperechoic region. In vivo PCD results showed that inertial cavitation typically occurred prior (within 0.5 s) to the appearance of a hyperechoic region. In vitro PCD results show that inertial cavitation occurred at or within 1-2 pulses prior to the appearance of a hyperechoic region and typically preceded rapid heating up to 110 °C at the HIFU focus within 1-2 pulses. The observed cavitation activity suggests that bubbles are present during the formation of a hyperechoic region at the HIFU focus and that boiling occurs rapidly after the onset of cavitation. Further investigation is needed to determine if the hyperechoic region in the US image originates from bubbles formed during cavitation alone or during cavitation-induced boiling.

Rabkin, Brian A.; Zderic, Vesna; Vaezy, Shahram

2005-03-01

372

A Study of Bubble Activity Generated in Ex Vivo Tissue by High Intensity Focused Ultrasound  

Microsoft Academic Search

Cancer treatment by extracorporeal high-intensity focused ultrasound (HIFU) is constrained by the time required to ablate clinically relevant tumour volumes. Although cavitation may be used to optimize HIFU treatments, its role during lesion formation is ambiguous. Clear differentiation is required between acoustic cavitation (noninertial and inertial) effects and bubble formation arising from two thermally-driven effects (the vapourization of liquid into

James McLaughlan; Ian Rivens; Timothy Leighton; Gail ter Haar

2010-01-01

373

Cavitation guide for control valves  

SciTech Connect

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.

Tullis, J.P. [Tullis Engineering Consultants, Logan, UT (United States)

1993-04-01

374

Possibility of quantitative prediction of cavitation erosion without model test  

SciTech Connect

A scenario for quantitative prediction of cavitation erosion was proposed. The key value is the impact force/pressure spectrum on a solid surface caused by cavitation bubble collapse. As the first step of prediction, the authors constructed the scenario from an estimation of the cavity generation rate to the prediction of impact force spectrum, including the estimations of collapsing cavity number and impact pressure. The prediction was compared with measurements of impact force spectra on a partially cavitating hydrofoil. A good quantitative agreement was obtained between the prediction and the experiment. However, the present method predicted a larger effect of main flow velocity than that observed. The present scenario is promising as a method of predicting erosion without using a model test.

Kato, Hiroharu; Konno, Akihisa; Maeda, Masatsugu; Yamaguchi, Hajime [Univ. of Tokyo (Japan). Dept. of Naval Architecture and Ocean Engineering

1996-09-01

375

On the role of shear viscosity in mediating inertial cavitation from short-pulse, megahertz-frequency ultrasound  

Microsoft Academic Search

Pressure thresholds for inertial cavitation in water and biological media modeled as a viscous fluid are calculated using a numerical implementation of the Gilmore equation for adiabatic bubble oscillations. The threshold criterion is chosen to be a bubble collapse temperature of 5000 K in order to facilitate comparison with the analytical theory of others. There is a trend toward increasing

John S. Allen; Ronald A. Roy; Charles C. Church

1997-01-01

376

The use of transparent aqueous gels for observing and recording cavitation activity produced by high intensity focused ultrasound  

Microsoft Academic Search

Low gelling temperature agarose gels are exceptionally clear and owe their rigidity to the formation of a homogenous lattice of polymer molecules. We have observed cavitation bubbles moving though these gels leaving visible tunnel-like tracks whose walls can be visualized at high magnification, especially with phase contrast illumination. These tracks provide a record of the limits of each individual bubble's

Alun R. Williams; Douglas L. Miller

2003-01-01

377

Theoretical investigation of bubble heating in soft tissue  

NASA Astrophysics Data System (ADS)

Cavitation bubbles in soft tissue during therapeutic ultrasound seem to be unavoidable. Therefore, to understand the behavior of these bubbles is of special interest during high intensity focused ultrasound (HIFU). Results have shown that cavitation bubbles can increase heating rates, which is desired for therapeutic purposes. Previous modeling efforts employing a Newtonian nonlinear bubble model identified two primary mechanisms for bubble-enhanced heating, viscous heating and radiation heating, which are strongly dependent on both viscosity and bubble size. We have extended this work using our recently developed viscoelastic bubble model describing the nonlinear behavior of bubbles in soft tissue. Results obtained for different driving frequencies and pressures in several kinds of soft tissue (blood, liver, muscle, etc.) suggest that the presence of elasticity reduces the nonlinearity of bubble oscillations, and the deposited power due to viscosity and radiation are both reduced in the small bubble region (generally Ro < 2 ?m) but increased for larger bubbles. The effects of viscosity, driving frequency and driving pressure are also discussed.

Yang, Xinmai; Church, Charles C.

2006-05-01

378

Parametric study of acoustically-driven microbubble cavitations in a sonochemical reactor.  

PubMed

The bubble cavitation along a solid wall is investigated with a three-dimensional model based on the indirect boundary element method. Kinetic energy and Kelvin impulse are calculated in order to quantify the strength of cavitation. The influences of acoustic wave amplitude and frequency and liquid properties on the strength of cavitation are investigated. This study was carried out in order to better understand the relation between microscale processes and macroscale parameters in a sonochemical reactor used for impregnation of fabrics with nanoparticles. PMID:23958355

Fu, Zhiwei; Popov, Viktor

2013-07-23

379

Work in progress report - Valves Transcranial Doppler and acoustic pressure fluctuations for the assessment of cavitation and thromboembolism in patients with mechanical heart valves  

Microsoft Academic Search

The formation and collapse of vapor-filled bubbles near a mechanical heart valve is called cavitation. Such microbubbles are suspected to have strong pro-coagulant effects. Therefore, cavitation may be a contributing factor to the pro-thrombotic effects of mechanical valves. Herein, we systematically review the available evidence linking cavitation and thrombosis. We also critically appraise the potential usefulness of transcranial Doppler and

Rosendo A. Rodriguez; Marc Ruel; Michel Labrosse; Thierry Mesana

2010-01-01

380

Interaction of Two Differently Sized Bubbles in a Free Field  

NASA Astrophysics Data System (ADS)

The interaction between two different sized (spark created, non-equilibrium) bubbles is studied by using high speed photography. The bubble size ranges from 2 to 7 mm. The experimental results are compared to that of the similar sized bubbles reported in the literature. Interestingly, all the four major behaviors of bubble-bubble interactions (i.e. 'bubble-collapsed' induced liquid jets directed away from each other, liquid jets directed towards each other, bubble coalescence and the 'catapult' effect) are observed which bear much similarity to that found for similar sized bubbles' interaction. The main parameters studied/varied are the size of the bubbles, the dimensionless separation distance and the phase difference between the two bubbles. The results obtained are consistent with the cases of similar sized bubbles reported in the literature, with each type of behavior occupying a distinct region in the graphical plot. This indicates that the results for the (special) similar sized bubbles can be generalized to cases with different sized bubbles. Many of the real life applications such as cavitations corrosions often involve bubbles with significant size difference, thus the present findings are useful in predicting the behavior of multiple bubbles in many situations.

Chew, Lup Wai; Khoo, Boo Cheong; Klaseboer, Evert; Ohl, Siew-Wan

381

High-speed observation of bubble cloud generation near a rigid wall by second-harmonic superimposed ultrasound.  

PubMed

Cavitation bubbles are known to accelerate therapeutic effects of ultrasound. Although negative acoustic pressure is the principle factor of cavitation, positive acoustic pressure has a role for bubble cloud formation at a high intensity of focused ultrasound when cavitation bubbles provide pressure release surfaces converting the pressure from highly positive to negative. In this study, the second-harmonic was superimposed onto the fundamental acoustic pressure to emphasize either peak positive or negative pressure. The peak negative and positive pressure emphasized waves were focused on a surface of an aluminum block. Cavitation bubbles induced near the block were observed with a high-speed camera by backlight and the size of the cavitation generation region was measured from the high-speed images. The negative pressure emphasized waves showed an advantage in cavitation inception over the positive pressure emphasized waves. In the sequence of the negative pressure emphasized waves immediately followed by the positive pressure emphasized waves, cavitation bubbles were generated on the block by the former waves and the cavitation region were expanded toward the transducer in the latter waves with high reproducibility. The sequence demonstrated its potential usefulness in enhancing the effects of therapeutic ultrasound at a high acoustic intensity. PMID:23927191

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

2013-08-01

382

Cavitation luminescence in a water hammer: Upscaling sonoluminescence  

NASA Astrophysics Data System (ADS)

Oscillatory acceleration and deceleration of a column of water leads to a pipe hammer as well as cavitation. With a small amount of xenon gas dissolved in the water, we can detect a stream of predominantly ultraviolet subnanosecond flashes of light which are attributed to collapsing bubbles. The observed emission can exceed 108 photons for a single collapse and has a peak power over 0.4 W.

Su, C.-K.; Camara, C.; Kappus, B.; Putterman, S. J.

2003-06-01

383

Laser interactions in fluid materials: laser-induced cavitation in liquid nitrogen and the possibility of environmental gas decomposition by laser  

NASA Astrophysics Data System (ADS)

Studies on some laser interactions to fluid materials are presented. Firstly, pulsed-laser-induced cavitation bubble in liquid nitrogen is investigated by YAG laser irradiation. High speed schlieren photographs by Imacon-790 are taken to observe the laser-induced bubble dynamics. Bubble and solid wall interactions are also investigated. Based on the results obtained, a novel laser surface processing technology using the pulse-laser-induced cavitation bubbles is secondly proposed. Furthermore, discussing by the fundamental results of the experiment of laser-gas molecular absorption, the possibility of decomposition of environmental gases by CW CO2 laser irradiation is also studied.

Maeno, Kazuo; Sato, Hitoshi; Prat, Christophe; Endo, Seiichi

1998-12-01

384

Luminescence mechanism of acoustic and laser-induced cavitation  

NASA Astrophysics Data System (ADS)

A new approach is proposed for explaining the experimental data on sonoluminescence of acoustic and laser-induced cavitation bubbles. It is suggested that two different sonoluminescence mechanisms, namely, thermal and electric ones, are possible and that they manifest themselves depending on the bubble dynamics. An intense thermal luminescence occurs as a result of compression of an individual stationary spherical bubble; a weak electric luminescence accompanies the deformation and splitting of the bubble when thermal luminescence is suppressed (for example, in the case of multibubble sonoluminescence). It is shown that, when an individual bubble loses its spherical shape under the effect of different actions (change in the acoustic pressure, artificial deformation, translatory motion, etc.) or when a laser-induced bubble undergoes fragmentation, the sonoluminescence spectrum exhibits specific bands that are similar to the bands in the multibubble sonoluminescence spectrum. The appearance of these bands is attributed to the suppression of the thermal sonoluminescence mechanism and the manifestation of the electric mechanism. It is shown that the maximum temperature T max characterizing the compression of a laser-induced bubble is primarily determined by the temperature of the plasma at the instant of the laser-induced breakdown, whereas, for an acoustic bubble, T max is primarily determined by the acoustic and hydrostatic pressures and by the saturation vapor pressure of the liquid.

Margulis, M. A.; Margulis, I. M.

2006-05-01

385

Assessment of shock wave lithotripters via cavitation potential  

PubMed Central

A method to characterize shock wave lithotripters by examining the potential for cavitation associated with the lithotripter shock wave (LSW) has been developed. The method uses the maximum radius achieved by a bubble subjected to a LSW as a representation of the cavitation potential for that region in the lithotripter. It is found that the maximum radius is determined by the work done on a bubble by the LSW. The method is used to characterize two reflectors: an ellipsoidal reflector and an ellipsoidal reflector with an insert. The results show that the use of an insert reduced the ?6 dB volume (with respect to peak positive pressure) from 1.6 to 0.4 cm3, the ?6 dB volume (with respect to peak negative pressure) from 14.5 to 8.3 cm3, and reduced the volume characterized by high cavitation potential (i.e., regions characterized by bubbles with radii larger than 429 µm) from 103 to 26 cm3. Thus, the insert is an effective way to localize the potentially damaging effects of shock wave lithotripsy, and suggests an approach to optimize the shape of the reflector.

Iloreta, Jonathan I.; Zhou, Yufeng; Sankin, Georgy N.; Zhong, Pei; Szeri, Andrew J.

2008-01-01

386

Tandem shock wave cavitation enhancement for extracorporeal lithotripsy.  

PubMed

Extracorporeal shock wave lithotripsy (ESWL) has been successful for more than twenty years in treating patients with kidney stones. Hundreds of underwater shock waves are generated outside the patient's body and focused on the kidney stone. Stones fracture mainly due to spalling, cavitation and layer separation. Cavitation bubbles are produced in the vicinity of the stone by the tensile phase of each shock wave. Bubbles expand, stabilize and finally collapse violently, creating stone-damaging secondary shock waves and microjets. Bubble collapse can be intensified by sending a second shock wave a few hundred microseconds after the first. A novel method of generating two piezoelectrically generated shock waves with an adjustable time delay between 50 and 950 micros is described and tested. The objective is to enhance cavitation-induced damage to kidney stones during ESWL in order to reduce treatment time. In vitro kidney stone model fragmentation efficiency and pressure measurements were compared with those for a standard ESWL system. Results indicate that fragmentation efficiency was significantly enhanced at a shock wave delay of about 400 and 250 micros using rectangular and spherical stone phantoms, respectively. The system presented here could be installed in clinical devices at relatively low cost, without the need for a second shock wave generator. PMID:12476975

Loske, Achim M; Prieto, Fernando E; Fernandez, Francisco; van Cauwelaert, Javier

2002-11-21

387

Tandem shock wave cavitation enhancement for extracorporeal lithotripsy  

NASA Astrophysics Data System (ADS)

Extracorporeal shock wave lithotripsy (ESWL) has been successful for more than twenty years in treating patients with kidney stones. Hundreds of underwater shock waves are generated outside the patient's body and focused on the kidney stone. Stones fracture mainly due to spalling, cavitation and layer separation. Cavitation bubbles are produced in the vicinity of the stone by the tensile phase of each shock wave. Bubbles expand, stabilize and finally collapse violently, creating stone-damaging secondary shock waves and microjets. Bubble collapse can be intensified by sending a second shock wave a few hundred microseconds after the first. A novel method of generating two piezoelectrically generated shock waves with an adjustable time delay between 50 and 950 µs is described and tested. The objective is to enhance cavitation-induced damage to kidney stones during ESWL in order to reduce treatment time. In vitro kidney stone model fragmentation efficiency and pressure measurements were compared with those for a standard ESWL system. Results indicate that fragmentation efficiency was significantly enhanced at a shock wave delay of about 400 and 250 µs using rectangular and spherical stone phantoms, respectively. The system presented here could be installed in clinical devices at relatively low cost, without the need for a second shock wave generator.

Loske, Achim M.; Prieto, Fernando E.; Fernández, Francisco; van Cauwelaert, Javier

2002-11-01

388

Soap Bubbles  

NSDL National Science Digital Library

Learners explore three-dimensional geometric frames including cubes and tetrahedrons, as they create bubble wands with pipe cleaners and drinking straws. Then they investigate how soap film flows into a state of minimum energy when they lift the wand up from the bubble solution. Learners also see how light reflection and interference create shimmering colors in the bubbles.

Exploratorium, The

2011-12-07

389

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

NASA Astrophysics Data System (ADS)

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.

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

2006-05-01

390

Multi million-to-Billion Atom Molecular Dynamics Simulations of Cavitation-Induced Damage on a Silica Slab  

NASA Astrophysics Data System (ADS)

Cavitation bubble collapse causes severe damage to materials. For example, cavitation erosion is a major threat to the safety of nuclear power plants. The cavitation bubbles may also be utilized for preventing stress corrosion cracking with water jet peening technology. We have performed multi million-to-billion atoms molecular dynamics simulations to investigate the shock-induced cavitation damage mechanism on an amorphous silica slab in water. The system consists of a 60nm thick silica slab immersed in water in an MD box of dimension 285 x 200 x 200 nm3. A nanobubble is created by removing water molecules within a sphere of radius 100 nm. To apply a planar shock, we assign a uniform particle velocity vp on the entire system towards a planar momentum mirror. We have performed the simulation with two kinds of bubbles, an empty bubble and a bubble filled with inert gas. The simulation results reveal nanojet formation during bubble collapse causing damage on the silica surface; however, the damage was significantly reduced in the case of the filled bubble. We will discuss the effect of the presence of inter gas inside the nanobubble on the pressure distribution, the extent of damage, and collapse behavior corresponding the shock front.

Shekhar, Adarsh; Nomura, Ken-Ichi; Kalia, Rajiv; Nakano, Aiichiro; Vashishta, Priya

2012-02-01

391

Investigation of cavitation as a possible damage mechanism in blast-induced traumatic brain injury.  

PubMed

Cavitation was investigated as a possible damage mechanism for war-related traumatic brain injury (TBI) due to an improvised explosive device (IED) blast. When a frontal blast wave encounters the head, a shock wave is transmitted through the skull, cerebrospinal fluid (CSF), and tissue, causing negative pressure at the contrecoup that may result in cavitation. Numerical simulations and shock tube experiments were conducted to determine the possibility of cranial cavitation from realistic IED non-impact blast loading. Simplified surrogate models of the head consisted of a transparent polycarbonate ellipsoid. The first series of tests in the 18-inch-diameter shock tube were conducted on an ellipsoid filled with degassed water to simulate CSF and tissue. In the second series, Sylgard gel, surrounded by a layer of degassed water, was used to represent the tissue and CSF, respectively. Simulated blast overpressure in the shock tube tests ranged from a nominal 10-25 pounds per square inch gauge (psig; 69-170?kPa). Pressure in the simulated CSF was determined by Kulite thin line pressure sensors at the coup, center, and contrecoup positions. Using video taken at 10,000 frames/sec, we verified the presence of cavitation bubbles at the contrecoup in both ellipsoid models. In all tests, cavitation at the contrecoup was observed to coincide temporally with periods of negative pressure. Collapse of the cavitation bubbles caused by the surrounding pressure and elastic rebound of the skull resulted in significant pressure spikes in the simulated CSF. Numerical simulations using the DYSMAS hydrocode to predict onset of cavitation and pressure spikes during cavity collapse were in good agreement with the tests. The numerical simulations and experiments indicate that skull deformation is a significant factor causing cavitation. These results suggest that cavitation may be a damage mechanism contributing to TBI that requires future study. PMID:22489674

Goeller, Jacques; Wardlaw, Andrew; Treichler, Derrick; O'Bruba, Joseph; Weiss, Greg

2012-05-14

392

Vibration of Cavitating Hydrofoils.  

National Technical Information Service (NTIS)

A primarily experimental research program was carried out using a free-jet water tunnel for the purpose of studying force and moment fluctuations on cavitating two-dimensional hydrofoils. Both a symmetrical wedge and a non-symmetrical wedge were tested fo...

C. C. S. Song

1969-01-01

393

Combination of ultrasound and bubble liposome enhance the effect of doxorubicin and inhibit murine osteosarcoma growth.  

PubMed

If ultrasound (US) is applied to cells, permeability across the cell membrane temporarily increases, making it easier for drugs to be taken into the cells from around the cell membrane. Moreover, when used in combination with Bubble liposome (BL: liposomes which entrap an ultrasound imaging gas), even low-power ultrasound can facilitate drug delivery into cells. In the present study, we constructed a new drug delivery system (DDS) involving concomitant use of US and BL with doxorubicin (DOX), a key drug in the chemotherapy of osteosarcoma, and demonstrated both in vitro and in vivo that it markedly inhibited the proliferation of osteosarcoma cells. Furthermore, this system achieved an equivalent antitumor effect at about 1/5 the dose of antitumor agent employed in monotherapy with DOX. These findings suggest the possibility of reduction of adverse events. In this experiment, US and liposomes were tested, both of which are already in use in clinical practice. US and liposomes are both very safe in the body. The DDS composed of these elements we designed can be applied in simple and site-specific fashion and is therefore promising as a new, clinically feasible method of treatment. PMID:21613828

Ueno, Yoshinori; Sonoda, Shozo; Suzuki, Ryo; Yokouchi, Masahiro; Kawasoe, Yasuomi; Tachibana, Katsuro; Maruyama, Kazuo; Sakamoto, Taiji; Komiya, Setsuro

2011-08-15

394

Study on cavitated bifurcation problems for spheres composed of hyper-elastic materials  

Microsoft Academic Search

In this paper, spherical cavitated bifurcation problems are examined for incompressible hyper-elastic materials and compressible\\u000a hyper-elastic materials, respectively. For incompressible hyper-elastic materials, a cavitated bifurcation equation that describes\\u000a cavity formation and growth for a solid sphere, composed of a class of transversely isotropic incompressible hyper-elastic\\u000a materials, is obtained. Some qualitative properties of the solutions of the cavitated bifurcation equation are

Xue-Gang Yuan; Zheng-You Zhu; Chang-Jun Cheng

2005-01-01

395

Cavitation modeling and diesel engine cylinder liners  

NASA Astrophysics Data System (ADS)

A common occurrence of cavitation damage is the waterside pitting of a wet sleeve liner in a diesel engine. The automotive industry utilizes an ultrasonic test of 20 kHz according to ASTM standards to quantify the effectiveness of engine coolant additives to prevent damage. However, recent tests indicate a mismatch between the ultrasonic test results and actual engine test runs. The focus of this study is to generate numerical models of bubble dynamics using already published literature. In most of the published papers higher-range frequencies (ultrasonic >15 kHz) are used. It is useful to explore the results of lower excitation frequencies as the vibrating frequencies of a diesel engine liner are between 500-9000 Hz. A Rayleigh-Plesset equation, nonlinear in nature, is used to plot the relation between bubble radius and time. Plots of the numerical solution from MATLAB are compared with plots published in the literature. Results from when the frequency of excitation is changed to the liner wall frequency and the fluid properties are changed to approximate engine conditions will be presented. Future work will examine the energy released by the bubble collapse and its correlation with erosion measured as mass change in a standard test button.

Chandekar, Gautam; Pardue, Sally

2003-10-01

396

Development of an Acoustic Localization Method for Cavitation Experiments in Reverberant Environments  

NASA Astrophysics Data System (ADS)

Cavitation is a major concern for the US Navy since it can cause ship damage and produce unwanted noise. The ability to precisely locate cavitation onset in laboratory scale experiments is essential for proper design that will minimize this undesired phenomenon. Measuring the cavitation onset is more accurately determined acoustically than visually. However, if other parts of the model begin to cavitate prior to the component of interest the acoustic data is contaminated with spurious noise. Consequently, cavitation onset is widely determined by optically locating the event of interest. The current research effort aims at developing an acoustic localization scheme for reverberant environments such as water tunnels. Currently cavitation bubbles are being induced in a static water tank with a laser, allowing the localization techniques to be refined with the bubble at a known location. The source is located with the use of acoustic data collected with hydrophones and analyzed using signal processing techniques. To verify the accuracy of the acoustic scheme, the events are simultaneously monitored visually with the use of a high speed camera. Once refined testing will be conducted in a water tunnel. This research was sponsored by the Naval Engineering Education Center (NEEC).

Ranjeva, Minna; Thompson, Lee; Perlitz, Daniel; Bonness, William; Capone, Dean; Elbing, Brian

2011-11-01

397

Cavitation behavior observed in three monoleaflet mechanical heart valves under accelerated testing conditions.  

PubMed

Accelerated testing provides a substantial amount of data on mechanical heart valve durability in a short period of time, but such conditions may not accurately reflect in vivo performance. Cavitation, which occurs during mechanical heart valve closure when local flow field pressure decreases below vapor pressure, is thought to play a role in valve damage under accelerated conditions. The underlying flow dynamics and mechanisms behind cavitation bubble formation are poorly understood. Under physiologic conditions, random perivalvular cavitation is difficult to capture. We applied accelerated testing at a pulse rate of 600 bpm and transvalvular pressure of 120 mm Hg, with synchronized videographs and high-frequency pressure measurements, to study cavitation of the Medtronic Hall Standard (MHS), Medtronic Hall D-16 (MHD), and Omni Carbon (OC) valves. Results showed cavitation bubbles between 340 and 360 micros after leaflet/housing impact of the MHS, MHD, and OC valves, intensified by significant leaflet rebound. Squeeze flow, Venturi, and water hammer effects each contributed to cavitation, depending on valve design. PMID:18356649

Lo, Chi-Wen; Liu, Jia-Shing; Li, Chi-Pei; Lu, Po-Chien; Hwang, Ned H

398

Bubble Puzzles  

NASA Astrophysics Data System (ADS)

Bubbles are fascinating. With their ubiquitous occurrence in a multitude of fluid systems bubbles occupy a very important place in contemporary science and technology. In many applications, bubble control is crucial. I will demonstrate that bubble nucleation at surfaces, which always has been associated with randomness, can be perfectly controlled both in space and time. This new technique allows to quantitatively study bubble-bubble and bubble-surface interaction and reveals a shielding effect in bubble clusters [1]. -- In a second example for the importance of bubble control I will discuss their disturbing effect in piezo-acoustic ink-jet printing: I will show how bubbles are entrained, grow by rectified diffusion, and finally seriously disturb the jetting process by counteracting the pressure build-up at the nozzle [2]. [1] N. Bremond, M. Arora, C. D. Ohl, and D. Lohse, Phys. Rev. Lett. 96, 224501 (2006). [2] J. de Jong, H. Reinten, M. van den Berg, H. Wijshoff, M. Versluis, G. de Bruin, and D. Lohse, J. Acoust. Soc. Am., (August 2006).

Lohse, Detlef

2006-11-01

399

Cavitational effects during creep in polycrystalline alumina  

SciTech Connect

Cavitation in deformed fine-grained Al/sub 2/O/sub 3/ was studied as a function of deformation temperature and strain rate. Three distinct cavity profiles were observed in varying proportions depending on the temperature and loading rate. Symmetrically shaped equilibrium cavities were observed at low stress and temperature. Crack-like (nonequilibrium) cavities were observed at higher stress and temperature. Full-facet cavities were observed as the end product of crack-like cavity growth and as a precursor to coalescence. These observations provide strong support for the cavity growth model developed by Chuang, et al. and establish cavitation as an important deformation and failure mechanism in ceramic materials.

Blumenthal, W.R.

1980-11-01

400

Laser applications to fluid materials: laser-induced cavitation in cryogenic liquid and gas decomposition by laser  

NASA Astrophysics Data System (ADS)

In this paper laser applications to fluid dynamical problems are presented. Firstly as for the recent research on cavitations, pulsed-laser-induced cavitation bubble in liquid nitrogen is studied. The bubble is produced by focused and pulsed irradiation of second harmonics of YAG laser in the cryostat. The dynamics of laser-induced bubble is visualized by high-speed shadowgraphs and schlieren photographs by an image-converter camera (Imacon-790). Bubble and solid wall interactions are also investigated. Based on the results obtained, a novel laser surface processing technology using the pulse-laser-induced cavitation bubbles is secondly proposed. The possibility of cold material surface processing by produced cavitation bubble is discussed including the cryogenic range. Furthermore, discussing by the fundamental results of the experiment of laser-gas molecular absorption, the possibility of decomposition of environmental gases by strong CW CO2 laser irradiation is also studied. Freon 12, 113, and other environmental gases including SF6 are very tough to be decomposed, and they break effectively the ozone molecules at high altitude above the Earth, or they heat up the earth. The wavelength range of the infrared laser is suitable for the molecular absorption to increase their temperature to be ionized. The possibility and trial experiments are discussed.

Maeno, Kazuo; Sato, Hitoshi; Endo, Seiichi

1999-05-01

401

HIFU-Induced Hyperecho in Ultrasound Images, Cavitation Activity and Thermal Behavior  

Microsoft Academic Search

High Intensity Focused Ultrasound (HIFU) treatment of soft tissues has been shown to result in a hyperechoic region in B-mode ultrasound (US) images. This is believed to result from bubble activity at the HIFU focus. Here we report our in vivo results of detecting inertial and stable cavitation in correlation with the appearance of a hyperechoic region, along with in

Brian A. Rabkin; Vesna Zderic; Shahram Vaezy

2005-01-01

402

A new cavitation suppression technique for local ablation using high-intensity focused ultrasound  

Microsoft Academic Search

When soft tissues are coagulated instantaneously during a high temperature local heating therapy for cancer using high-intensity focused ultrasound, it is extremely important to have good control over the heated area. However, scattering of the ultrasonic energy by cavitation bubbles generated by sonication degrades the heating performance at the focal spot, and there is an undesirable rise in temperature along

K. Fujimoto; Y. Ishibashi; M. Shibata; T. Suzuki; S. Aida; N. Ioritani; S. Shirai; S. Orikasa

1995-01-01

403

High-speed observation of acoustic cavitation erosion in multibubble systems  

Microsoft Academic Search

Cleaning and erosion of objects by ultrasound in liquids are caused by the action of acoustic cavitation bubbles. Experiments have been performed with respect to the erosive effect of multibubble structures on painted glass surfaces and on aluminium foils in an ultrasonic standing wave field at 40 kHz. High-speed imaging techniques have been employed to investigate the mechanisms at work,

D. Krefting; R. Mettin; W. Lauterborn

2004-01-01

404

Cavitation damage experiments for mercury spallation targets at the LANSCE – WNR in 2005  

Microsoft Academic Search

In-beam experiments investigating cavitation damage in short pulse mercury spallation targets were performed at the Los Alamos Neutron Science Center – Weapons Neutron Research (LANSCE – WNR) facility in 2005. Two main areas were investigated. First, damage dependence on three mercury conditions – stagnant, flowing, and flowing with bubble injection – was investigated by employing a small mercury target loop

Bernie Riemer; John R Haines; Mark W Wendel; Guenter Bauer; Masatoshi Futakawa; Shoichi Hasegawa; Hiroyuki Kogawa

2008-01-01

405

Big Bubbles  

NSDL National Science Digital Library

How do you measure a bubble when it's floating? You can't really, but in this activity, learners can measure the diameter of the ring of suds a bubble leaves on a flat surface. The fun is blowing up the bubbles as big as possible with a straw. Then comes the measuring. This activity can be used to connect science and math, and makes a great rainy day or indoor lunch activity.

Science, Lawrence H.

2010-01-01

406

Cancer gene therapy by IL-12 gene delivery using liposomal bubbles and tumoral ultrasound exposure.  

PubMed

Interleukin-12 (IL-12) gene therapy is expected to be effective against cancers because it primes the immune system for cancer cells. In this therapy, it is important to induce IL-12 gene expression in the tumor tissue. Sonoporation is an attractive technique for developing non-invasive and non-viral gene delivery systems, but simple sonoporation using only ultrasound is not an effective cancer gene therapy because of the low efficiency of gene delivery. We addressed this problem by combining ultrasound and novel ultrasound-sensitive liposomes (Bubble liposomes) which contain the ultrasound imaging gas perfluoropropane. Our previous work showed that this is an effective gene delivery system, and that Bubble liposome collapse (cavitation) is induced by ultrasound exposure. In this study, we assessed the utility of this system in cancer gene therapy using IL-12 corded plasmid DNA. The combination of Bubble liposomes and ultrasound dramatically suppressed tumor growth. This therapeutic effect was T-cell dependent, requiring mainly CD8(+) T lymphocytes in the effector phase, as confirmed by a mouse in vivo depletion assay. In addition, migration of CD8(+) T cells was observed in the mice, indicating that the combination of Bubble liposomes and ultrasound is a good non-viral vector system in IL-12 cancer gene therapy. PMID:19883708

Suzuki, Ryo; Namai, Eisuke; Oda, Yusuke; Nishiie, Norihito; Otake, Shota; Koshima, Risa; Hirata, Keiichi; Taira, Yuichiro; Utoguchi, Naoki; Negishi, Yoichi; Nakagawa, Shinsaku; Maruyama, Kazuo

2009-10-31

407

Cellular Injury of Cardiomyocytes during Hepatocyte Growth Factor Gene Transfection with Ultrasound-Triggered Bubble Liposome Destruction  

PubMed Central

We transfected naked HGF plasmid DNA into cultured cardiomyocytes using a sonoporation method consisting of ultrasound-triggered bubble liposome destruction. We examined the effects on transfection efficiency of three concentrations of bubble liposome (1 × 106, 1 × 107, 1 × 108/mL), three concentrations of HGF DNA (60, 120, 180??g/mL), two insonification times (30, 60?sec), and three incubation times (15, 60, 120?min). We found that low concentrations of bubble liposome and low concentrations of DNA provided the largest amount of the HGF protein expression by the sonoporated cardiomyocytes. Variation of insonification and incubation times did not affect the amount of product. Following insonification, cardiomyocytes showed cellular injury, as determined by a dye exclusion test. The extent of injury was most severe with the highest concentration of bubble liposome. In conclusion, there are some trade-offs between gene transfection efficiency and cellular injury using ultrasound-triggered bubble liposome destruction as a method for gene transfection.

Komamura, Kazuo; Tatsumi, Rie; Tsujita-Kuroda, Yuko; Onoe, Takatoshi; Matsumoto, Kunio; Nakamura, Toshikazu; Miyazaki, Jun-ichi; Horio, Takeshi; Sugimachi, Masaru

2011-01-01

408

Model test and CFD calculation of a cavitating bulb turbine  

NASA Astrophysics Data System (ADS)

The flow in a horizontal shaft bulb turbine is calculated as a two-phase flow with a commercial Computational Fluid Dynamics (CFD-)-code including cavitation model. The results are compared with experimental results achieved at a closed loop test rig for model turbines. On the model test rig, for a certain operating point (i.e. volume flow, net head, blade angle, guide vane opening) the pressure behind the turbine is lowered (i.e. the Thoma-coefficient ? is lowered) and the efficiency of the turbine is recorded. The measured values can be depicted in a so-called ?-break curve or ?- ?-diagram. Usually, the efficiency is independent of the Thoma-coefficient up to a certain value. When lowering the Thoma-coefficient below this value the efficiency will drop rapidly. Visual observations of the different cavitation conditions complete the experiment. In analogy, several calculations are done for different Thoma-coefficients ?and the corresponding hydraulic losses of the runner are evaluated quantitatively. For a low ?-value showing in the experiment significant efficiency loss, the the change of volume flow in the experiment was simulated. Besides, the fraction of water vapour as an indication of the size of the cavitation cavity is analyzed qualitatively. The experimentally and the numerically obtained results are compared and show a good agreement. Especially the drop in efficiency can be calculated with satisfying accuracy. This drop in efficiency is of high practical importance since it is one criterion to determine the admissible cavitation in a bulb-turbine. The visual impression of the cavitation in the CFD-analysis is well in accordance with the observed cavitation bubbles recorded on sketches and/or photographs.

Necker, J.; Aschenbrenner, T.

2010-08-01

409

Etiology of gas bubble disease  

SciTech Connect

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

Bouck, G.R.

1980-11-01

410

Xylem vulnerability to cavitation varies among poplar and willow clones and correlates with yield.  

PubMed

Xylem vulnerability to cavitation is a promising criterion for identifying trees with high drought tolerance, but traditional techniques for measuring cavitation resistance are unsuitable for screening large numbers of genotypes. We tested the potential of the new Cavitron technique for high throughput screening of cavitation resistance in five poplar (Populus spp.) and four willow (Salix spp.) clones. The Cavitron technique enabled the screening of three to four clones per day with sufficient accuracy to reveal significant differences between clones. Because intraspecific screening may be better carried out through the identification of correlated and more easily measured traits, we attempted to identify accessible parameters that correlate to cavitation resistance. Variability in vulnerability to cavitation across clones was poorly correlated with anatomical traits such as vessel diameter, vessel wall strength, wood density and fiber wall thickness; however, a striking correlation was established between cavitation resistance and aboveground biomass production, indicating a possible trade-off between xylem safety and growth potential. PMID:17938107

Cochard, Hervé; Casella, Eric; Mencuccini, Maurizio

2007-12-01

411

Bounds of cavitation inception in a creeping flow between eccentric cylinders rotating with a small minimum gap  

NASA Astrophysics Data System (ADS)

Bounds of cavitation inception are experimentally determined in a creeping flow between eccentric cylinders, the inner one being static and the outer rotating at a constant angular velocity, ?. The geometric configuration is additionally specified by a small minimum gap between cylinders, H, as compared with the radii of the inner and outer cylinders. For some values H and ?, cavitation bubbles are observed, which are collected on the surface of the inner cylinder and equally distributed over the line parallel to its axis near the downstream minimum gap position. Cavitation occurs for the parameters {H,?} within a region bounded on the right by the cavitation inception curve that passes through the plane origin and cannot exceed the asymptotic threshold value of the minimum gap, Ha, in whose vicinity cavitation may occur at H < Ha only for high angular rotation velocities.

Monakhov, A. A.; Chernyavski, V. M.; Shtemler, Yu.

2013-09-01

412

Passive cavitation imaging with ultrasound arrays  

PubMed Central

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.

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

2009-01-01

413

Mechanisms of mechanical heart valve cavitation in an electrohydraulic total artificial heart.  

PubMed

Until now, we have estimated cavitation for mechanical heart valves (MHV) mounted in an electrohydraulic total artificial heart (EHTAH) with tap water as a working fluid. However, tap water at room temperature is not a proper substitute for blood at 37 degrees C. We therefore investigated MHV cavitation using a glycerin solution that was identical in viscosity and vapor pressure to blood at body temperature. In this study, six different kinds of monoleaflet and bileaflet valves were mounted in the mitral position in an EHTAH, and we investigated the mechanisms for MHV cavitation. The valve closing velocity, pressure drop measurements, and a high-speed video camera were used to investigate the mechanism for MHV cavitation and to select the best MHV for our EHTAH. The closing velocity of the bileaflet valves was slower than that of the monoleaflet valves. Cavitation bubbles were concentrated on the edge of the valve stop and along the leaflet tip. It was established that squeeze flow holds the key to MHV cavitation in our study. Cavitation intensity increased with an increase in the valve closing velocity and the valve stop area. With regard to squeeze flow, the Björk-Shiley valve, because it is associated with slow squeeze flow, and the bileaflet valve with low valve closing velocity and small valve stop areas are better able to prevent blood cell damage than the monoleaflet valves. PMID:15968949

Lee, Hwansung; Taenaka, Yoshiyuki; Kitamura, Soichiro

414

The mechanisms of the formation and growth of water bubbles and associated dislocation loops in synthetic quartz  

NASA Astrophysics Data System (ADS)

The development of water bubbles in synthetic quartz has been monitored by measurements of (i) the intensity of the light scattered and (ii) the increase in volume of the crystal, both as a function of temperature and time. These macroscopic measurements have been complemented by observations of the resulting microstructures, using transmission electron microscopy (TEM). A mechanism is proposed on the assumption that hydrogen is incorporated in the quartz structure by means of (4 H)Si defects. On heating, these defects diffuse and clusters develop. A cluster of n(4 H)Si produces a water bubble of ( n-1)H2O, without any change of volume of the crystal. At any temperature T there is a critical bubble diameter above which the “steam” pressure P exceeds the pressure p for a spherical bubble in mechanical equilibrium. If P becomes greater than p, then the bubble increases in volume until P= p, the increase in volume being achieved by the pipe diffusion of Si and O away from the bubble site into a linked edge dislocation loop. This process produces the observed increase in volume of the crystal. The two diffusion processes take place virtually simultaneously and continue until all the (4 H)Si defects have been trapped in the bubbles. Values of the diffusion constant and the activation energy for the diffusion of the (4 H)Si defects are deduced. The relevance of these observations to the hydrolytic weakening of quartz is briefly discussed.

McLaren, A. C.; Cook, R. F.; Hyde, S. T.; Tobin, R. C.

1983-02-01

415

Dynamics in reactive bubbly flow  

Microsoft Academic Search

Multiphase flow in microfluidic channels encompasses a rich collection of phenomena of widespread interest in both fundamental and technological context. While studies on non reactive multiphase flow focus on the dynamics of bubble breakup, coalescence and stability, a reactive multiphase flow opens up a broader spectrum of dynamics, like nucleation, growth and detachment of bubbles as well as the secondary

Pavithra Sundararajan; Donald Koch; Abraham Stroock

2010-01-01

416

Modeling algal growth in bubble columns under sparging with CO2-enriched air.  

PubMed

A theoretical model for predicting biomass growth in semi-continuous mode under sparging with CO(2)-enriched air was developed. The model includes gas-to-liquid mass transfer, algal uptake of carbon dioxide, algal growth kinetics, and light and temperature effects. The model was validated using experimental data on growth of two microalgal species in an internally illuminated photobioreactor: Nannochloropsis salina under gas flow rates of 800 and 1200 mL min(-1) and CO(2) enrichments of 0.5, 1, and 2%; and Scenedesmus sp. at a gas flow rate of 800 mL min(-1) and CO(2) enrichments of 3 and 4%. Temporal algal concentration profiles predicted by the model under semi-continuous mode with harvesting under the different test conditions agreed well with the measured data, with r(2) values ranging from 0.817 to 0.944, p<0.001. As demonstrated, this model can be beneficial in predicting temporal variations in algal concentration and in scheduling harvesting operations under semi-continuous cultivation mode. PMID:22989642

Pegallapati, Ambica Koushik; Nirmalakhandan, Nagamany

2012-08-20

417

Magnetic Bubbles  

NASA Astrophysics Data System (ADS)

Bubbles in liquids driven by a sound field are used in many disciplines: for example bubbles clean surfaces in ultrasonic water bathes, they catalyze unique chemical reactions in sonochemistry, and under special conditions even create light. However, conventional bubbles have a major limitation when placed in an acoustic field: it is extremely hard to control their position. Here we present a new type of bubble that has permanent magnetization originating from a shell of self-assembled nanoparticles, so that magnetic fields can be used to control the bubble's position independently. We will report on the recipe and the experiment to study bubble oscillations in weak magnetic fields. The magnetic susceptibility of the bubbles is proportional to their surface area,?=(9±3x10-6m)r^2, where r is the radius. Also they are compressible in moderate acoustic fields and induce a microstreaming flow with a toroidal vortex at the upper pole of the bubble. Similar microstreaming flows have been used to transport and rupture cells at small scales. Thus we envision applications in manipulation of biological materials and in microfluidic devices using acoustic and magnetic forces.

Zhao, Xue; Quinto-Su, Pedro; Ohl, Claus-Dieter

2008-11-01

418

Comments on the evolving field of sonochemistry by a cavitation physicist  

Microsoft Academic Search

Sonochemistry is an evolving field that has shown recent rapid growth and increasing interest. Although this field concentrates on chemistry and uses acoustics principally as a tool, the basic mechanism that gives rise to sonochemistry — acoustic cavitation — is often ignored or given little attention. This paper addresses some of the relevant aspects of cavitation and physical acoustics that

Lawrence A Crum

1995-01-01

419

Real-time in vitro observation of cavitation on prosthetic heart valves  

Microsoft Academic Search

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 operating in a Penn State Electric Assist Device at physiologic conditions. For each fluid, cavity growth and collapse

C. M. Zapanta; D. R. Stinebring; S. Deutsch; D. B. Geselowitz; J. M. Tarbell

1993-01-01

420

Osmotic cavitation of elastomeric intraocular lenses.  

PubMed

In recent years, traditional rigid materials have been replaced with softer elastomers in intraocular lenses to minimize the size of the required surgical incision, thereby reducing patient recuperation time. However, water-filled cavities that may impact visual acuity are found in many of these new implants. We demonstrate that the cavitation observed in vivo can occur due to an osmotic pressure difference between the aqueous solution within the cavity and the external media in which the lens is immersed. By reducing the osmolarity of the external solution from 300 to 0mM, we observe an increase in cavity volume of almost a factor of 30. Further, we have developed a model for cavity growth assuming the controlling factor is diffusion of hydrophilic molecules from the polymer matrix into the cavity. We find that the experimental observations are consistent with the model and suggest that oligomeric species generated during polymerization are responsible for the observed cavitation. PMID:19712761

Saylor, David M; Coleman Richardson, D; Dair, Benita J; Pollack, Steven K

2009-08-25

421

Generation of underwater sound pulses, cavitation and shear waves with hydraulic hammer  

NASA Astrophysics Data System (ADS)

A hydrodynamic acoustic generator with shear waves source for seismic sea bottom profiling was developed. The principle of inversed water hammer is applied for the production of high energy pressure pulses. The mechanism of acoustic cavitation in water hammer is detailed. Homogeneous mixing of gas bubbles and fluid is numericaly modeled. Bubble dynamics is described by relations between bubble radius, pressure, nucleation, amplitude of expansion waves, and relaxation effects. A shear wave generator using inversed water hammer effects and sea water as working medium is described.

Meier, G. E. A.; Laake, A.; Rein, M.

1988-04-01

422

Bubble-Jets in Gravitational Fields (APS DFD Video V060)  

Microsoft Academic Search

We show visualizations of the gravity-induced jets formed by spherical bubbles collapsing in liquids subjected to normal gravity, micro-gravity, and hyper-gravity. These observations demonstrate that gravity can have a significant effect on cavitation bubbles. An analysis of the gravity-induced jets uncovers a scaling law between the size of bubble-induced jets and the non-dimensional parameter grad(p)*R0\\/p, where R0 is the maximal

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

2011-01-01

423

The role of cavitation microjets in the therapeutic applications of ultrasound.  

PubMed

The dynamics of a gas bubble situated in a sound-irradiated liquid and near a rigid boundary was studied theoretically to get a better understanding of the role of cavitation microjets in the therapeutic applications of ultrasound (US). The boundary integral method was adopted to simulate the temporal development of the bubble shape, jet formation during bubble collapse and bubble migration. It was found that the dynamic behaviour of the jet and the migratory characteristics of the bubble depend not only on the distance between bubble and boundary but, also, on the properties of the acoustic field. For frequencies of sound fields smaller than or equal to the resonance frequency of the bubble, jet formation and bubble migration toward the boundary are the main features of the interaction. No jet formation was observed for frequencies of sound fields larger than the resonance frequency of the bubble, and the bubble kept its initial position from the boundary throughout its motion. The pressure generated by the impact of the jet developed during bubble collapse close to the boundary may result in the fragmentation of brittle objects, such as renal calculi, dental tartar or intraocular lens. PMID:15063520

Brujan, E A

2004-03-01

424

Low-Drag Cavitating Hydrofoils  

NASA Astrophysics Data System (ADS)

Cavitation research in the naval hydrodynamics context has generally been aimed at either the avoidance of cavitation or in the investigation of supercavitating flows at very low values of the cavitation index. However, inviscid theory shows that there is a regime of partially cavitating flows where relatively high lift to drag ratios can be obtained. The design of a low-drag partially cavitating hydrofoil is based on the determination of cavity shape on some initial hydrofoil in an ideal incompressible fluid. A closed cavity scheme is employed. The contour of the designed hydrofoil is inscribed within the contour composed of the cavity surface, fictitious body and wetted surface of the initial hydrofoil. A candidate hydrofoil was designed in the framework of ideal fluid theory to provide a stable drag reduction by partial cavitation. It was determined experimentally that partial cavitation on the suction side of the blade does lead to a significant increase in the lift to drag ratio. However, if the cavitation index is lowered below the optimal value, strong oscillations in lift occur. Cavity length oscillations differ from that observed on a NACA 0015 hydrofoil with different spectral characteristics. Cavity length data are similar to that observed on the NACA foil. Supported by DARPA.

Amromin, Eduard; Arndt, Roger E. A.; Kopriva, James; Wosnik, Martin

2004-11-01

425

Flow and fracturing of viscoelastic media under diffusion-driven bubble growth: An analogue experiment for eruptive volcanic conduits  

Microsoft Academic Search

To visualize the behavior of erupting magma in volcanic conduits, we performed shock tube experiments on the ductile–brittle response of a viscoelastic medium to diffusion-driven bubble expansion. A sample of shear-thinning magma analogue is saturated by gas Ar under high pressure. On rapid decompression, Ar supersaturation causes bubbles to nucleate, grow, and coalesce in the sample, forcing it to expand,

J. Taddeucci; O. Spieler; M. Ichihara; D. B. Dingwell; P. Scarlato

2006-01-01

426

Bubble, Bubble, Toil and Trouble.  

ERIC Educational Resources Information Center

|Bubbles are a fun way to introduce the concepts of surface tension, intermolecular forces, and the use of surfactants. Presents two activities in which students add chemicals to liquid dishwashing detergent with water in order to create longer lasting bubbles. (ASK)|

Journal of Chemical Education, 2001

2001-01-01

427

Measurements of Gas Bubble Size Distributions in Flowing Liquid Mercury  

SciTech Connect

ABSTRACT Pressure waves created in liquid mercury pulsed spallation targets have been shown to induce cavitation damage on the target container. One way to mitigate such damage would be to absorb the pressure pulse energy into a dispersed population of small bubbles, however, measuring such a population in mercury is difficult since it is opaque and the mercury is involved in a turbulent flow. Ultrasonic measurements have been attempted on these types of flows, but the flow noise can interfere with the measurement, and the results are unverifiable and often unrealistic. Recently, a flow loop was built and operated at Oak Ridge National Labarotory to assess the capability of various bubbler designs to deliver an adequate population of bubbles to mitigate cavitation damage. The invented diagnostic technique involves flowing the mercury with entrained gas bubbles in a steady state through a horizontal piping section with a glass-window observation port located on the top. The mercury flow is then suddenly stopped and the bubbles are allowed to settle on the glass due to buoyancy. Using a bright-field illumination and a high-speed camera, the arriving bubbles are detected and counted, and then the images can be processed to determine the bubble populations. After using this technique to collect data on each bubbler, bubble size distributions were built for the purpose of quantifying bubbler performance, allowing the selection of the best bubbler options. This paper presents the novel procedure, photographic technique, sample visual results and some example bubble size distributions. The best bubbler options were subsequently used in proton beam irradiation tests performed at the Los Alamos National Laboratory. The cavitation damage results from the irradiated test plates in contact with the mercury are available for correlation with the bubble populations. The most effective mitigating population can now be designed into prototypical geometries for implementation into an actual SNS target.

Wendel, Mark W [ORNL; Riemer, Bernie [ORNL; Abdou, Ashraf A [ORNL

2012-01-01

428

Role of Cavitation in Bulk Ultrasound Ablation: A Histologic Study  

NASA Astrophysics Data System (ADS)

The role of cavitation in bulk ultrasound ablation has been evaluated in a series of in vitro experiments. Fresh bovine liver tissue was ablated with a 3.1 MHz ultrasound image-ablate probe at 31 W/cm2 for 20 minutes under normal and elevated ambient pressures. A 1 MHz passive cavitation detector recorded acoustic emission signals which were quantified by computation of average subharmonic, broadband, and low-frequency emission levels. After ablation, tissue was sliced and stained with 2% TTC to evaluate thermal damage. Emission levels were quantified and correlated with tissue ablation histology. The results indicate that bubble activity significantly affects heat deposition in ultrasound bulk ablation, in a manner different from high-intensity focused ultrasound (HIFU) ablation.

Karunakaran, Chandra Priya; Burgess, Mark T.; Holland, Christy K.; Mast, T. Douglas

2009-04-01

429

Cavitation erosion behavior of Inconel 690 alloy  

Microsoft Academic Search

The cavitation erosion behavior of Inconel 690 alloy was investigated using 20-kHz vibratory cavitation test equipment and analyzed by scanning electron microscopy (SEM). To clarify the development of cavitation damage with time, scanning electron photographs were recorded for various test durations, where the time was measured from the commencement of vibration. The results showed that the cavitation erosion damage in

Jie-Hao Chen; Weite Wu

2008-01-01

430

Sonochemical and high-speed optical characterization of cavitation generated by an ultrasonically oscillating dental file in root canal models.  

PubMed

Ultrasonically Activated Irrigation makes use of an ultrasonically oscillating file in order to improve the cleaning of the root canal during a root canal treatment. Cavitation has been associated with these oscillating files, but the nature and characteristics of the cavitating bubbles were not yet fully elucidated. Using sensitive equipment, the sonoluminescence (SL) and sonochemiluminescence (SCL) around these files have been measured in this study, showing that cavitation occurs even at very low power settings. Luminol photography and high-speed visualizations provided information on the spatial and temporal distribution of the cavitation bubbles. A large bubble cloud was observed at the tip of the files, but this was found not to contribute to SCL. Rather, smaller, individual bubbles observed at antinodes of the oscillating file with a smaller amplitude were leading to SCL. Confinements of the size of bovine and human root canals increased the amount of SL and SCL. The root canal models also showed the occurrence of air entrainment, resulting in the generation of stable bubbles, and of droplets, near the air-liquid interface and leading eventually to a loss of the liquid. PMID:23735893

Macedo, R G; Verhaagen, B; Fernandez Rivas, D; Gardeniers, J G E; van der Sluis, L W M; Wesselink, P R; Versluis, M

2013-04-02

431

Electric discharge-induced cavitation: a competing approach to pulsed lasers for performing microsurgery in liquid media  

NASA Astrophysics Data System (ADS)

Cavitation bubbles generated by fast overheating of water during pulsed laser applications in liquid medium have been shown to be a driving force of the soft tissue cutting. An alternative approach proposed in this paper is the generation of cavitation