Sample records for hydrodynamic cavitation acoustic

  1. Taming Acoustic Cavitation

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


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

  2. Superhigh Temperatures and Acoustic Cavitation

    Belyaev, V B; Miller, M B; Sermyagin, A V; Topolnikov, A S


    The experimental results on thermonuclear synthesis under acoustic cavitation have been analyzed with the account of the latest data and their discussion. The analysis testifies that this avenue of research is a very promising one. The numerical calculations of the D(d, n)^{3}He reaction rate in the deuterated acetone (C_{3}D_{6}O) under the influence of ultrasound depending on T environment temperature within the range T=249-295 K have been carried out within the framework of hydrodynamic model. The results show that it is possible to improve substantially the effect/background relationship in experiments by decreasing the fluid temperature twenty-thirty degrees below zero.

  3. Biological Effects of Acoustic Cavitation


    rectified diffusion. 56 III. STABLE CAVITATION A. Introduction There are manv areas associated with the biological effects of ultrasound in which the...used said as cavitation indicators. Further, if clinical ultrasound systems are found to be inducing cavitation , either stable or transient, it will...O BIOLOGICAL EFFECTS OF ACOUSTIC CAVITATION by Lawrence A. Crum -- Physical Acoustics Research Laboratory Department of Physics and Astronomy ’ CTE

  4. Acoustic cavitation movies

    Crum, Lawrence A.


    Acoustic cavitation is a phenomenon that occurs on microsecond time scales and micron length scales, yet, it has many macroscopic manifestations. Accordingly, it is often difficult, at least for the author, to form realistic physical descriptions of the specific mechanisms through which it expresses itself in our macroscopic world. For example, there are still many who believe that cavitation erosion is due to the shock wave that is emitted by bubble implosion, rather than the liquid jet created on asymmetric collapse...and they may be right. Over the years, the author has accumulated a number of movies and high-speed photographs of cavitation activity, which he uses to form his own visual references. In the time allotted, he will show a number of these movies and photographs and discuss their relevance to existing technological problems. A limited number of CDs containing the presented materials will be available to interested individuals. [Work supported in part by the NIH, USAMRMC, and the ONR.

  5. Acoustic cavitation and sonochemistry

    Stricker, L.


    Sonochemistry is the use of cavitation for achieving a chemical conversion. When microbubbles are driven in the nonlinear regime, localized extreme temperatures (up to 10000 K) and pressures (up to 1000 bar) can be reached upon collapse, the surrounding liquid remaining ambient,thus giving origin to

  6. Memory-Effect on Acoustic Cavitation

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


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

  7. Correlating Inertial Acoustic Cavitation Emissions with Material Erosion Resistance

    Ibanez, I.; Hodnett, M.; Zeqiri, B.; Frota, M. N.

    The standard ASTM G32-10 concerns the hydrodynamic cavitation erosion resistance of materials by subjecting them to acoustic cavitation generated by a sonotrode. The work reported extends this technique by detecting and monitoring the ultrasonic cavitation, considered responsible for the erosion process, specifically for coupons of aluminium-bronze alloy. The study uses a 65 mm diameter variant of NPL's cavitation sensor, which detects broadband acoustic emissions, and logs acoustic signals generated in the MHz frequency range, using NPL's Cavimeter. Cavitation readings were made throughout the exposure duration, which was carried out at discrete intervals (900 to 3600 s), allowing periodic mass measurements to be made to assess erosion loss under a strict protocol. Cavitation measurements and erosion were compared for different separations of the sonotrode tip from the material under test. The maximum variation associated with measurement of cavitation level was between 2.2% and 3.3% when the separation (λ) between the transducer horn and the specimen increased from 0.5 to 1.0 mm, for a transducer (sonotrode) displacement amplitude of 43.5 μm. Experiments conducted at the same transducer displacement amplitude show that the mass loss of the specimen -a measure of erosion- was 67.0 mg (λ = 0.5 mm) and 66.0 mg (λ = 1.0 mm).

  8. Effect of hydrodynamic cavitation on zooplankton: A tool for disinfection

    Sawant, S.S.; Anil, A.C.; Venkat, K.; Gaonkar, C.; Kolwalkar, J.; Khandeparker, L.; Desai, D.V.; Mahulkar, A.V.; Ranade, V.V.; Pandit, A.B.

    Application of hydrodynamic cavitation for disinfection of water is gaining momentum, as it provides environmentally and economically sound options. In this effort, the effect of cavitating conditions created by differential pump valve opening...

  9. Sonic effervescence: A tutorial on acoustic cavitation

    Apfel, R.E. [Yale University, New Haven, Connecticut 06520-8286 (United States)


    This article on acoustic cavitation is a revision of a tutorial lecture presented at the Acoustical Society of America meeting in Austin, Texas, on 28 November 1994. The general approach adopted here differs from a review article in stressing the overarching themes that come under the category of acoustic cavitation, rather than being an encyclopedic reference on the topic. When possible, specific order-of-magnitude estimates have been given so that the reader can better understand the particular phenomena being described. The basic physics is discussed, and applications are reviewed with the goal of putting them in a useful context. {copyright} {ital 1997 Acoustical Society of America.}

  10. VibroCav: Hydrodynamic Vibration and Cavitation Technology

    Bakker, T.W.


    Vibration and cavitation can be generated in many ways and serve many useful purposes. This study describes physical aspects of useful vibration and cavitation for a broad spectrum of applications at atmospheric or elevated pressures. After a review of available devices, hydrodynamic vibrating-body

  11. VibroCav: Hydrodynamic Vibration and Cavitation Technology

    Bakker, T.W.


    Vibration and cavitation can be generated in many ways and serve many useful purposes. This study describes physical aspects of useful vibration and cavitation for a broad spectrum of applications at atmospheric or elevated pressures. After a review of available devices, hydrodynamic vibrating-body

  12. Acoustic Cavitation and Bubble Dynamics.


    Achilles tendon of a cow. Presently ceramic piezoelectrics are widely used to generate ultrasonic signals, as they are relatively inexpensive and can...the application of a negative pressure could result in a rupture of the liquid while d’Alembert refused to accept this view. The rise of cavitation as a...contraction resulted in the liquid undergoing a tensile stress, eventually ending in the rupture of the liquid. The temperature at which rupture occurred was

  13. Laser-nucleated acoustic cavitation in focused ultrasound.

    Gerold, Bjoern; Kotopoulis, Spiros; McDougall, Craig; McGloin, David; Postema, Michiel; Prentice, Paul


    Acoustic cavitation can occur in therapeutic applications of high-amplitude focused ultrasound. Studying acoustic cavitation has been challenging, because the onset of nucleation is unpredictable. We hypothesized that acoustic cavitation can be forced to occur at a specific location using a laser to nucleate a microcavity in a pre-established ultrasound field. In this paper we describe a scientific instrument that is dedicated to this outcome, combining a focused ultrasound transducer with a pulsed laser. We present high-speed photographic observations of laser-induced cavitation and laser-nucleated acoustic cavitation, at frame rates of 0.5×10(6) frames per second, from laser pulses of energy above and below the optical breakdown threshold, respectively. Acoustic recordings demonstrated inertial cavitation can be controllably introduced to the ultrasound focus. This technique will contribute to the understanding of cavitation evolution in focused ultrasound including for potential therapeutic applications.

  14. Metal of cavitation erosion of a hydrodynamic reactor

    Zakirzakov, A. G.; Brand, A. E.; Petryakov, V. A.; Gordievskaya, E. F.


    Cavitation erosion is a major cause of the petroleum equipment hydraulic erosion, which leads to the metal weight loss of the equipment and its breakdown, which can be followed by the full stop of the plant or company work. The probability of the metal weight loss and equipment failure can be reduced by the use of special protective coatings or rivets, made of the sacrificial metals, the use of which significantly increases the service life and the production equipment reliability. The article investigates the cavitation erosion effect, occurred under the condition of the advanced hydrodynamic cavitation on the hydrodynamic cavitation reactor. This article presents the results of the experiments and recommendations for increasing the operational resource.

  15. Impact of acoustic cavitation on food emulsions.

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


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

  16. Prevention of Pressure Oscillations in Modeling a Cavitating Acoustic Fluid

    B. Klenow


    Full Text Available Cavitation effects play an important role in the UNDEX loading of a structure. For far-field UNDEX, the structural loading is affected by the formation of local and bulk cavitation regions, and the pressure pulses resulting from the closure of the cavitation regions. A common approach to numerically modeling cavitation in far-field underwater explosions is Cavitating Acoustic Finite Elements (CAFE and more recently Cavitating Acoustic Spectral Elements (CASE. Treatment of cavitation in this manner causes spurious pressure oscillations which must be treated by a numerical damping scheme. The focus of this paper is to investigate the severity of these oscillations on the structural response and a possible improvement to CAFE, based on the original Boris and Book Flux-Corrected Transport algorithm on structured meshes [6], to limit oscillations without the energy loss associated with the current damping schemes.

  17. Principles and effects of acoustic cavitation - A review



    Full Text Available In the recent years, food industry has shown a real interest in ultrasound use because of its effect on physical, biochemical and microbial properties of food systems. In order to better understand how the acoustic cavity effects could be best applied in food industry, a review on acoustic cavitation and its effects was done. The present paper describes in detail the basic principles underlying the effects of ultrasounds on food processing applications. It also provides theoretical background on acoustic cavitation and ultrasound production method. Moreover, harnessing mechanic, optic, chemical and biological effects of acoustic cavitation in food industry were briefly highlighted.

  18. Effect of hydrodynamic cavitation in the tissue erosion by pulsed high-intensity focused ultrasound (pHIFU)

    Zhou, Yufeng; Gao, Xiaobin Wilson


    High-intensity focused ultrasound (HIFU) is emerging as an effective therapeutic modality in clinics. Besides the thermal ablation, tissue disintegration is also possible because of the interaction between the distorted HIFU bursts and either bubble cloud or boiling bubble. Hydrodynamic cavitation is another type of cavitation and has been employed widely in industry, but its role in mechanical erosion to tissue is not clearly known. In this study, the bubble dynamics immediately after the termination of HIFU exposure in the transparent gel phantom was captured by high-speed photography, from which the bubble displacement towards the transducer and the changes of bubble size was quantitatively determined. The characteristics of hydrodynamic cavitation due to the release of the acoustic radiation force and relaxation of compressed surrounding medium were found to associate with the number of pulses delivered and HIFU parameters (i.e. pulse duration and pulse repetition frequency). Because of the initial big bubble (~1 mm), large bubble expansion (up to 1.76 folds), and quick bubble motion (up to ~1 m s-1) hydrodynamic cavitation is significant after HIFU exposure and may lead to mechanical erosion. The shielding effect of residual tiny bubbles would reduce the acoustic energy delivered to the pre-existing bubble at the focus and, subsequently, the hydrodynamic cavitation effect. Tadpole shape of mechanical erosion in ex vivo porcine kidney samples was similar to the contour of bubble dynamics in the gel. Liquefied tissue was observed to emit towards the transducer through the punctured tissue after HIFU exposure in the sonography. In summary, the release of HIFU exposure-induced hydrodynamic cavitation produces significant bubble expansion and motion, which may be another important mechanism of tissue erosion. Understanding its mechanism and optimizing the outcome would broaden and enhance HIFU applications.

  19. Mechanoluminescence and sonoluminescence from acoustic cavitation

    Eddingsaas, Nathan C.

    The intense shock wave launched from collapsing bubbles during the sonication of slurries allows for the study of chemical and physical events that occur when a solid is stressed or fractured. One such event is mechanoluminescence (ML): light produced by any mechanical action on a solid. ML has been studied for over 400 years, but much is still not known about it because the emission is inherently weak. Sonicating slurries of mechanoluminescent crystals (such as sucrose, sodium chloride, resorcinol, m-aminophenol, or coumarin) in long chain alkanes has produced very bright ML, up to 1,000 fold more intense than from manual grinding. The large increase in intensity has revealed a number of new emitting species including C2, CH, CO, CO+, CO2+, H, and He+, many of which have not been reported from ML before. In addition, the emission products show that gas phase reactions are occurring within the plasma generated from the ML discharge. The intense ML induced by acoustic cavitation allowed the plasma to be characterized in terms of heavy atom temperature of ˜400 K, electron density of 1014 cm-1, and electron energy of ˜3.5 eV. These conditions are very similar to other highly reactive microdischarges. To further extend the knowledge of the conditions generated within a cloud of cavitating bubbles, multi-bubble sonoluminescence (MBSL) of sulfuric acid has been studied. The MBSL spectrum from 95 wt % H2SO 4 consists of a broad continuum extending into the UV with SO and Ar emission lines also observed. The Ar lines were used to determine an effective emission temperature of ˜8,000 K, which is substantially greater than in other low vapor pressure systems (e.g., silicone oil, where MBSL emission temperature is only ˜5,000 K). The observation of Ar lines at this temperature also indicates that a hot plasma core is probably generated during multi-bubble cavitation in sulfuric acid. In addition, the effect of solution composition was studied by varying the acid

  20. Detecting Inception of Hydrodynamic Cavitation Noise of Ships using Quadratic Phase Coupling Index as an Indicator

    M. Sandhya


    Full Text Available There is ever increasing interest in underwater noise control onboard ships as part of concerted efforts to reduce ship’s radiated noise. Reduction of radiated noise is considered important as it will affect the performance of hydro-acoustic systems such as sonars, echo sounders, towed systems, etc. Out of three major sources of noise onboard ships, viz., machinery, propeller, and hydrodynamic noise, propeller noise is considered a major source beyond certain speed at which propellers cavitate produces cavitation noise. The inception speed of propeller cavitation is generally accompanied by sudden increase in radiated noise level of 8-15 dB when measured using a hydrophone placed on the seabed. This paper attempts to establish the concept of quadratic phase coupling index as an indicator to detect inception of cavitation of ship propellers. This concept was tested on actual ship radiated noise data measured at sea for evaluating its effectiveness.Defence Science Journal, Vol. 65, No. 1, January 2015, pp.53-62, DOI:

  1. A novel brewing process via controlled hydrodynamic cavitation

    Albanese, Lorenzo; Meneguzzo, Francesco; Pagliaro, Mario


    This paper describes a completely new brewing equipment and process based upon controlled hydrodynamic cavitation, providing significant advantages in terms of lowered capital cost, reduced production time, enhanced energy and production efficiency, food safety, while preserving beer organoleptic qualities. Experiments carried out on real microbrewery volume scale using the new and conventional technology unquestionably confirm the relevance of the new findings. Impacts of these discoveries are potentially far reaching, as beer is the worldwide most widely consumed alcoholic beverage, therefore highly relevant to health, environment the economy and even to local identities.

  2. Cavitating vortex characterization based on acoustic signal detection

    Digulescu, A.; Murgan, I.; Candel, I.; Bunea, F.; Ciocan, G.; Bucur, D. M.; Dunca, G.; Ioana, C.; Vasile, G.; Serbanescu, A.


    In hydraulic turbines operating at part loads, a cavitating vortex structure appears at runner outlet. This helical vortex, called vortex rope, can be cavitating in its core if the local pressure is lower that the vaporization pressure. An actual concern is the detection of the cavitation apparition and the characterization of its level. This paper presents a potentially innovative method for the detection of the cavitating vortex presence based on acoustic methods. The method is tested on a reduced scale facility using two acoustic transceivers positioned in ”V” configuration. The received signals were continuously recorded and their frequency content was chosen to fit the flow and the cavitating vortex. Experimental results showed that due to the increasing flow rate, the signal - vortex interaction is observed as modifications on the received signal's high order statistics and bandwidth. Also, the signal processing results were correlated with the data measured with a pressure sensor mounted in the cavitating vortex section. Finally it is shown that this non-intrusive acoustic approach can indicate the apparition, development and the damping of the cavitating vortex. For real scale facilities, applying this method is a work in progress.

  3. Intensification of biogas production using pretreatment based on hydrodynamic cavitation.

    Patil, Pankaj N; Gogate, Parag R; Csoka, Levente; Dregelyi-Kiss, Agota; Horvath, Miklos


    The present work investigates the application of hydrodynamic cavitation (HC) for the pretreatment of wheat straw with an objective of enhancing the biogas production. The hydrodynamic cavitation reactor is based on a stator and rotor assembly. The effect of three different speeds of rotor (2300, 2500, 2700 rpm), wheat straw to water ratios (0.5%, 1% and 1.5% wt/wt) and also treatment times as 2, 4 and 6 min have been investigated in the work using the design of experiments (DOE) approach. It was observed that the methane yield of 31.8 ml was obtained with untreated wheat straw whereas 77.9 ml was obtained with HC pre-treated wheat straw confirming the favourable changes during the pre-treatment. The combined pre-treatment using KOH and HC gave maximum yield of biogas as 172.3 ml. Overall, it has been established that significant enhancement in the biogas production can be obtained due to the pretreatment using HC which can also be further intensified by combination with chemical treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Bulk Viscosity and Cavitation in Boost-Invariant Hydrodynamic Expansion

    Rajagopal, Krishna


    We solve second order relativistic hydrodynamics equations for a boost-invariant 1+1-dimensional expanding fluid with an equation of state taken from lattice calculations of the thermodynamics of strongly coupled quark-gluon plasma. We investigate the dependence of the energy density as a function of proper time on the values of the shear viscosity, the bulk viscosity, and second order coefficients, confirming that large changes in the values of the latter have negligible effects. Varying the shear viscosity between zero and a few times s/(4 pi), with s the entropy density, has significant effects, as expected based on other studies. Introducing a nonzero bulk viscosity also has significant effects. In fact, if the bulk viscosity peaks near the crossover temperature Tc to the degree indicated by recent lattice calculations in QCD without quarks, it can make the fluid cavitate -- falling apart into droplets. It is interesting to see a hydrodynamic calculation predicting its own breakdown, via cavitation, at th...

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

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


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

  6. Experimental and simulation investigations of acoustic cavitation in megasonic cleaning

    Muralidharan, Krishna; Keswani, Manish; Shende, Hrishikesh; Deymier, Pierre; Raghavan, Srini; Eschbach, Florence; Sengupta, Archita


    Extreme ultra-violet (EUV) lithography has become the technique of choice to print the ever-shrinking nanoscale features on the silicon wafer. For successful transfer of patterns on to the wafer, the EUV photomask cannot contain defects greater than 30 nm. Megasonic cleaning is a very successful cleaning technique for removal of particles on photomasks, but also causes a relatively high amount of damage to the fragile EUV photomasks thin film structures. Though it is believed that acoustic cavitation is the primary phenomenon responsible for cleaning as well as pattern damage, a fundamental picture of the acoustic cavitation mechanisms in play during megasonic cleaning has not yet clearly emerged. In this study, we characterize the role of acoustic cavitation in megasonic cleaning by examining the effects of acoustic power densities, cleaning solution properties, and dissolved gas content on cavitation via experiments and molecular dynamics (MD) simulations. MD is an atomistic computation technique capable of modeling atomic-level and nanoscale processes accurately making it well suited to study the effect of cavitation on nano-sized particles and patterns.

  7. Mass Transfer During Osmotic Dehydration Using Acoustic Cavitation

    孙宝芝; 淮秀兰; 姜任秋; 刘登瀛


    An experimental study on intensifying osmotic dehydration was carried out in a state of nature and with acoustic cavitation of different cavitating intensity (0.5A, 0.TA and 0.9A) respectively, in which the material is apple slice of 5 mm thickness. The result showed that acoustic cavitation remarkably enhanced the osmotic dehydration, and the water loss was accelerated with the increase of cavitating intensity. The water diffusivity coefficients ranged from 1.8 × 10-10 m2.s-1 at 0.5A to 2.6 × 10-10 m2.s-1 at 0.9A, and solute diffusivity coefficients ranged from 3.5×10-11 m2.s-1 at 0.5A to 4.6×10-11 m2.s-1 at 0.9A. On the basis of experiments, a mathematical model was established about mass transfer during osmotic dehydration, and the numerical simulation was carried out. The calculated results agree well with experimental data, and represent the rule of mass transfer during osmotic dehydration intensified by acoustic cavitation.

  8. Acoustic and Cavitation Fields of Shock Wave Therapy Devices

    Chitnis, Parag V.; Cleveland, Robin O.


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

  9. Thermo-Hydrodynamic Analysis of a Plain Journal Bearing on the Basis of a New Mass Conserving Cavitation Algorithm

    Alakhramsing, S.; Van Ostayen, R.A.J.; Eling, R.P.T.


    Accurate prediction of cavitation is an important feature in hydrodynamic bearing modeling. Especially for thermo-hydrodynamic modeling, it is crucial to use a mass-conservative cavitation algorithm. This paper introduces a new mass-conserving Reynolds cavitation algorithm, which provides fast conve

  10. Dynamical behaviors of hydrodynamic cavitation bubble under ultrasound field%声场中水力空化泡的动力学特性

    沈壮志; 林书玉


    以水为工作介质,考虑了液体黏性、表面张力、可压缩性及湍流作用等情况,对文丘里管反应器中空化泡在声场作用下的动力学行为特性进行了数值研究.分析了超声波频率、声压及喉径比对空化泡运动特性以及空化泡崩溃时所形成泡温以及压力脉冲的影响.结果表明,超声将水力空化泡运动调制成稳态空化,有利于增强空化效果.%Considering liquid viscosity,surface tension,liquid compressibility and turbulence,the dynamical behaviors of cavitation bubble in venturi cavitation reactor are numerically investigated with using acoustic field regarding water as a work medium.The effects of acoustic frequency,acoustic pressure and ratio of throat to pipe diameter on cavitation bubble dynamics,bubble temperature and pressure pulse by rapid collapse of cavitation bubble are analysed.The results show that bubble motion of hydrodynamic cavitation modulated by ultrasound,becomes the high energy stable cavitation.It is favorable for enhancing the cavitation effect.

  11. Effect of geometry of hydrodynamically cavitating device on degradation of orange-G.

    Saharan, Virendra Kumar; Rizwani, Manav A; Malani, Aqeel A; Pandit, Aniruddha B


    In this research work, we have carried out geometric optimization of different cavitating devices using degradation of orange-G dye [OG] as a model pollutant. Three different cavitating devices viz. orifice plate, circular venturi and slit venturi were optimized and the degradation of orange-G dye was studied. The optimization of all three cavitating devices was done in terms of fluid inlet pressure to the cavitating devices and cavitation number. The effect of pH and initial concentration of the dye on the degradation rate was also studied. The geometry of cavitating device (flow cross sectional area, perimeter, shape, etc.) was found to be an important parameter in getting the maximum cavitational effect using hydrodynamic cavitation. The cavitational yield of all three cavitating devices were compared on the basis of mg of total organic carbon (TOC) reduction per unit energy supplied. The slit venturi gives almost 50% higher degradation rate and cavitational yield among all three cavitating devices studied for the same amount of energy supplied.

  12. Hydrodynamic cavitation in micro channels with channel sizes of 100 and 750 micrometers

    Rooze, J.; André, M.; Gulik, van der G-J.S.; Fernandez Rivas, D.; Gardeniers, J.G.E.; Rebrov, E.V.; Schouten, J.C.; Keurentjes, J.T.F.


    Decreasing the constriction size and residence time in hydrodynamic cavitation is predicted to give increased hot spot temperatures at bubble collapse and increased radical formation rate. Cavitation in a 100 × 100 μm2 rectangular micro channel and in a circular 750 μm diameter milli channel has be

  13. Enhanced decolorization of methyl orange using zero-valent copper nanoparticles under assistance of hydrodynamic cavitation.

    Li, Pan; Song, Yuan; Wang, Shuai; Tao, Zheng; Yu, Shuili; Liu, Yanan


    The rate of reduction reactions of zero-valent metal nanoparticles is restricted by their agglomeration. Hydrodynamic cavitation was used to overcome the disadvantage in this study. Experiments for decolorization of methyl orange azo dye by zero-valent copper nanoparticles were carried out in aqueous solution with and without hydrodynamic cavitation. The results showed that hydrodynamic cavitation greatly accelerated the decolorization rate of methyl orange. The size of nanoparticles was decreased after hydrodynamic cavitation treatment. The effects of important operating parameters such as discharge pressure, initial solution pH, and copper nanoparticle concentration on the degradation rates were studied. It was observed that there was an optimum discharge pressure to get best decolorization performance. Lower solution pH were favorable for the decolorization. The pseudo-first-order kinetic constant for the degradation of methyl orange increased linearly with the copper dose. UV-vis spectroscopic and Fourier transform infrared (FT-IR) analyses confirmed that many degradation intermediates were formed. The results indicated hydroxyl radicals played a key role in the decolorization process. Therefore, the enhancement of decolorization by hydrodynamic cavitation could due to the deagglomeration of nanoparticles as well as the oxidation by the in situ generated hydroxyl radicals. These findings greatly increase the potential of the Cu(0)/hydrodynamic cavitation technique for use in the field of treatment of wastewater containing hazardous materials.

  14. Acoustic Emissions to Measure Drought-Induced Cavitation in Plants

    Linus De Roo


    Full Text Available Acoustic emissions are frequently used in material sciences and engineering applications for structural health monitoring. It is known that plants also emit acoustic emissions, and their application in plant sciences is rapidly increasing, especially to investigate drought-induced plant stress. Vulnerability to drought-induced cavitation is a key trait of plant water relations, and contains valuable information about how plants may cope with drought stress. There is, however, no consensus in literature about how this is best measured. Here, we discuss detection of acoustic emissions as a measure for drought-induced cavitation. Past research and the current state of the art are reviewed. We also discuss how the acoustic emission technique can help solve some of the main issues regarding quantification of the degree of cavitation, and how it can contribute to our knowledge about plant behavior during drought stress. So far, crossbreeding in the field of material sciences proved very successful, and we therefore recommend continuing in this direction in future research.

  15. Degradation of diclofenac sodium using combined processes based on hydrodynamic cavitation and heterogeneous photocatalysis.

    Bagal, Manisha V; Gogate, Parag R


    Diclofenac sodium, a widely detected pharmaceutical drug in wastewater samples, has been selected as a model pollutant for degradation using novel combined approach of hydrodynamic cavitation and heterogeneous photocatalysis. A slit venturi has been used as cavitating device in the hydrodynamic cavitation reactor. The effect of various operating parameters such as inlet fluid pressure (2-4 bar) and initial pH of the solution (4-7.5) on the extent of degradation have been studied. The maximum extent of degradation of diclofenac sodium was obtained at inlet fluid pressure of 3 bar and initial pH as 4 using hydrodynamic cavitation alone. The loadings of TiO2 and H2O2 have been optimised to maximise the extent of degradation of diclofenac sodium. Kinetic study revealed that the degradation of diclofenac sodium fitted first order kinetics over the selected range of operating protocols. It has been observed that combination of hydrodynamic cavitation with UV, UV/TiO2 and UV/TiO2/H2O2 results in enhanced extents of degradation as compared to the individual schemes. The maximum extent of degradation as 95% with 76% reduction in TOC has been observed using hydrodynamic cavitation in conjunction with UV/TiO2/H2O2 under the optimised operating conditions. The diclofenac sodium degradation byproducts have been identified using LC/MS analysis.

  16. Effect of PSD on Acoustic Cavitation Surge in Inlet Pipe of Turbopump

    吉田, 義樹; 藤原, 徹也; 南里, 秀明; Yoshida, Yoshiki; Fujiwara, Tetsuya; Nanri, Hideaki


    To investigate the effect of PSD on acoustic cavitation surge in turbopump, we conducted analyses with the resistance of PSD as a parameter. Consequently, we found that patterns of the acoustic cavitation surge were classified into three types by the value of the resistance. (1) First (the resistance of the PSD is smaller.), when the frequency of the inertial cavitation surge between the PSD and the turbopump coincides with the acoustic natural frequencies between the tank and the PSD, the ac...

  17. Disruption of Brewers' yeast by hydrodynamic cavitation: Process variables and their influence on selective release.

    Balasundaram, B; Harrison, S T L


    Intracellular products, not secreted from the microbial cell, are released by breaking the cell envelope consisting of cytoplasmic membrane and an outer cell wall. Hydrodynamic cavitation has been reported to cause microbial cell disruption. By manipulating the operating variables involved, a wide range of intensity of cavitation can be achieved resulting in a varying extent of disruption. The effect of the process variables including cavitation number, initial cell concentration of the suspension and the number of passes across the cavitation zone on the release of enzymes from various locations of the Brewers' yeast was studied. The release profile of the enzymes studied include alpha-glucosidase (periplasmic), invertase (cell wall bound), alcohol dehydrogenase (ADH; cytoplasmic) and glucose-6-phosphate dehydrogenase (G6PDH; cytoplasmic). An optimum cavitation number Cv of 0.13 for maximum disruption was observed across the range Cv 0.09-0.99. The optimum cell concentration was found to be 0.5% (w/v, wet wt) when varying over the range 0.1%-5%. The sustained effect of cavitation on the yeast cell wall when re-circulating the suspension across the cavitation zone was found to release the cell wall bound enzyme invertase (86%) to a greater extent than the enzymes from other locations of the cell (e.g. periplasmic alpha-glucosidase at 17%). Localised damage to the cell wall could be observed using transmission electron microscopy (TEM) of cells subjected to less intense cavitation conditions. Absence of the release of cytoplasmic enzymes to a significant extent, absence of micronisation as observed by TEM and presence of a lower number of proteins bands in the culture supernatant on SDS-PAGE analysis following hydrodynamic cavitation compared to disruption by high-pressure homogenisation confirmed the selective release offered by hydrodynamic cavitation.

  18. Localization in an acoustic cavitation cloud

    Miao, Boya


    Using a nonlinear sound wave equation for a bubbly liquid in conjunction with an equation for bubble pulsation, we predict and experimentally demonstrate the appearance of a gap in the frequency spectrum of a sound wave propagating in a cavitation cloud comprising bubbles. For bubbles with an ambient radius of 100 {\\mu}m, the calculations revealed that this gap corresponds to the phenomenon of sound wave localization. For bubbles with an ambient radius of 120 {\\mu}m, this spectral gap relates to a forbidden band of the sound wave. In the experiment, we observed the predicted gap in the frequency spectrum in soda water; however, in tap water, no spectral gap was present because the bubbles were much smaller than 100 {\\mu}m.

  19. Influences of hydrodynamic conditions, nozzle geometry on appearance of high submerged cavitating jets

    Hutli Ezddin


    Full Text Available Based on visualization results of highly-submerged cavitating water jet obtained with digital camera, the influences of related parameters such as: injection pressure, nozzle diameter and geometry, nozzle mounting (for convergent / divergent flow, cavitation number and exit jet velocity, were investigated. In addition, the influence of visualization system position was also studied. All the parameters have been found to be of strong influence on the jet appearance and performance. Both hydro-dynamical and geometrical parameters are playing the main role in behavior and intensity of cavitation phenomenon produced by cavitating jet generator. Based on our considerable previous experience in working with cavitating jet generator, the working conditions were chosen in order to obtain measurable phenomenon. [Projekat Ministarstva nauke Republike Srbije, br. TR35046

  20. Hydrodynamic Nuclei Concentration Technique in Cavitation Research and Comparison to Phase-Doppler Measurements

    Ebert, Eric; Kröger, Willfried; Damaschke, Nils


    Small particles, especially bubbles in the micro-meter range, influence the cavitation of the propellers. The prediction of cavitation inception and water quality measurements are important in cavitation research. The Hydrodynamic Nuclei Concentration (HDNC) technique can be used for reliable bubble concentration measurements in fluid flows. The HDNC technique bases on the analysis of scattered light from the cavitation nuclei in the water. The HDNC technique can distinguish between bubbles and solid particles. The particle type classification is important, because the number concentration of solid particles is often much higher than the nuclei concentration in cavitation tunnels and in seawater. Verification experiments show, that the HDNC technique reaches similar capabilities in number concentration estimation as Phase Doppler (PD) technique in much shorter acquisition time.

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

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


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

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

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


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

  3. Visualization of fluid turbulence and acoustic cavitation during phacoemulsification.

    Tognetto, Daniele; Sanguinetti, Giorgia; Sirotti, Paolo; Brezar, Edoardo; Ravalico, Giuseppe


    To describe a technique for visualizing fluid turbulence and cavitational energy created by ultrasonic phaco tips. University Eye Clinic of Trieste, Trieste, Italy. Generation of cavitational energy by the phaco tip was visualized using an optical test bench comprising several components. The technique uses a telescope system to expand a laser light source into a coherent, collimated beam of light with a diameter of approximately 50.0 mm. The expanded laser beam shines on the test tube containing the tip activated in a medium of water or ophthalmic viscosurgical device (OVD). Two precision optical collimators complete the optical test bench and form the system used to focus data onto a charge-coupled device television camera connected to a recorder. Images of irrigation, irrigation combined with aspiration, irrigation/aspiration, and phacosonication were obtained with the tip immersed in a tube containing water or OVD. Optical image processing enabled acoustic cavitation to be visualized during phacosonication. The system is a possible means of evaluating a single phaco apparatus power setting and comparing phaco machines and techniques.

  4. Processing of Microalgae: Acoustic Cavitation and Hydrothermal Conversion

    Greenly, Justin Michael

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


    孙宝芝; 姜任秋; 淮秀兰; 李斌; 刘登瀛


    An experimental study was carried out to enhance osmotic dehydration of fruits--apples using acoustic cavitation. The variation in water losses and dry matter gain rates of materials with solute concentration, cavitation intensity, the thickness of materials and treating time segment during osmotic dehydration was discussed, at the same time, the influence of different materials on mass transfer during osmotic dehydration using acoustic cavitation was investigated. The results showed that water losses rates of materials were remarkably increased during osmotic dehydration using acoustic cavitation, but dry matter gain rates increased very little. Meanwhile the physical mechanism of enhanced mass transfer during osmotic dehydration with acoustic cavitation was clarified on the basis of analyzing the experimental results.

  6. Correlation between microbubble-induced acoustic cavitation and hemolysis in vitro

    Zhang Chun-Bing; Liu Zheng; Guo Xia-Sheng; Zhang Dong


    Microbubbles promise to enhance the efficiency of ultrasound-mediated drug delivery and gene therapy by taking advantage of artificial cavitation nuclei. The purpose of this study is to examine the ultrasound-induced hemolysis in the application of drug delivery in the presence of microbubbles. To achieve this goal, human red blood cells mixed with microbubbles were exposed to 1-MHz pulsed ultrasound. The hemolysis level was measured by a flow cytometry, and the cavitation dose was detected by a passive cavitation detecting system. The results demonstrate that larger cavitation dose would be generated with the increase of acoustic pressure, which might give rise to the enhancement of hemolysis. Besides the experimental observations, the acoustic pressure dependence of the radial oscillation of microbubble was theoretically estimated. The comparison between the experimental and calculation results indicates that the hemolysis should be highly correlated to the acoustic cavitation.

  7. Precise measurement technique for the stable acoustic cavitation bubble

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


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

  8. Multi-focal laser surgery: cutting enhancement by hydrodynamic interactions between cavitation bubbles

    Toytman, Ilya; Simanovski, Dmitri; Palanker, Daniel


    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 time...

  9. Optimization of biodiesel production in a hydrodynamic cavitation reactor using used frying oil.

    Ghayal, Dyneshwar; Pandit, Aniruddha B; Rathod, Virendra K


    The present work demonstrates the application of a hydrodynamic cavitation reactor for the synthesis of biodiesel with used frying oil as a feedstock. The synthesis involved the transesterification of used frying oil (UFO) with methanol in the presence of potassium hydroxide as a catalyst. The effect of geometry and upstream pressure of a cavitating orifice plate on the rate of transesterification reaction has been studied. It is observed that the micro level turbulence created by hydrodynamic cavitation somewhat overcomes the mass transfer limitations for triphasic transesterification reaction. The significant effects of upstream pressure on the rate of formation of methyl esters have been seen. It has been observed that flow geometry of orifice plate plays a crucial role in process intensification. With an optimized plate geometry of 2mm hole diameter and 25 holes, more than 95% of triglycerides have been converted to methyl esters in 10 min of reaction time with cavitational yield of 1.28 × 10(-3) (Grams of methyl esters produced per Joule of energy supplied). The potential of UFO to produce good quality methyl esters has been demonstrated.

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

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


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

  11. Hydrodynamic cavitation as an efficient method for the formation of sub-100 nm O/W emulsions with high stability

    Zhiliang Zhang; Guangquan Wang; Yong Nie; Jianbing Ji


    Hydrodynamic cavitation, a newly developed process intensification technique, has demonstrated immense po-tential for intensifying diverse physical and chemical processes. In this study, hydrodynamic cavitation was ex-plored as an efficient method for the formation of sub-100 nm oil-in-water (O/W) emulsions with high stability. O/W emulsion with an average droplet size of 27 nm was successful y prepared. The average droplet size of O/W emulsions decreased with the increase of the inlet pressure, number of cavitation passes and surfac-tant concentration. The formed emulsion exhibited admirable physical stability during 8 months. Moreover, the hydrodynamic cavitation method can be generalized to fabricate large varieties of O/W emulsions, which showed great potential for large-scale formation of O/W emulsions with lower energy consumption.

  12. A viable method to predict acoustic streaming in presence of cavitation.

    Louisnard, O


    The steady liquid flow observed under ultrasonic emitters generating acoustic cavitation can be successfully predicted by a standard turbulent flow calculation. The flow is driven by the classical averaged volumetric force density calculated from the acoustic field, but the inertial term in Navier-Stokes equations must be kept, and a turbulent solution must be sought. The acoustic field must be computed with a realistic model, properly accounting for dissipation by the cavitation bubbles [Louisnard, Ultrason. Sonochem., 19, (2012) 56-65]. Comparison with 20kHz experiments, involving the combination of acoustic streaming and a perpendicular forced flow in a duct, shows reasonably good agreement. Moreover, the persistence of the cavitation effects on the wall facing the emitter, in spite of the deflection of the streaming jet, is correctly reproduced by the model. It is also shown that predictions based either on linear acoustics with the correct turbulent solution, or with Louisnard's model with Eckart-Nyborg's theory yields unrealistic results.

  13. Degradation of imidacloprid using combined advanced oxidation processes based on hydrodynamic cavitation.

    Patil, Pankaj N; Bote, Sayli D; Gogate, Parag R


    The harmful effects of wastewaters containing pesticides or insecticides on human and aquatic life impart the need of effectively treating the wastewater streams containing these contaminants. In the present work, hydrodynamic cavitation reactors have been applied for the degradation of imidacloprid with process intensification studies based on different additives and combination with other similar processes. Effect of different operating parameters viz. concentration (20-60 ppm), pressure (1-8 bar), temperature (34 °C, 39 °C and 42 °C) and initial pH (2.5-8.3) has been investigated initially using orifice plate as cavitating device. It has been observed that 23.85% degradation of imidacloprid is obtained at optimized set of operating parameters. The efficacy of different process intensifying approaches based on the use of hydrogen peroxide (20-80 ppm), Fenton's reagent (H2O2:FeSO4 ratio as 1:1, 1:2, 2:1, 2:2, 4:1 and 4:2), advanced Fenton process (H2O2:Iron Powder ratio as 1:1, 2:1 and 4:1) and combination of Na2S2O8 and FeSO4 (FeSO4:Na2S2O8 ratio as 1:1, 1:2, 1:3 and 1:4) on the extent of degradation has been investigated. It was observed that near complete degradation of imidacloprid was achieved in all the cases at optimized values of process intensifying parameters. The time required for complete degradation of imidacloprid for approach based on hydrogen peroxide was 120 min where as for the Fenton and advance Fenton process, the required time was only 60 min. To check the effectiveness of hydrodynamic cavitation with different cavitating devices, few experiments were also performed with the help of slit venturi as a cavitating device at already optimized values of parameters. The present work has conclusively established that combined processes based on hydrodynamic cavitation can be effectively used for complete degradation of imidacloprid.

  14. A novel sensor for monitoring acoustic cavitation. Part II: Prototype performance evaluation.

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


    This paper describes a series of experimental studies to evaluate the performance of newly developed sensors for monitoring broadband acoustic emissions generated by acoustic cavitation. The prototype sensors are fabricated in the form of hollow, open-ended cylinders, whose inner surface is made from a thin film of piezoelectric polymer acting as a passive acoustic receiver of bandwidth greater than 10 MHz. A 4-mm thick coating of special acoustical absorber forms the outer surface of the sensor. The layer functions as a shield to cavitation events occurring outside the hollow sensor body, allowing megahertz acoustic emissions emanating from within the liquid contained in the sensor to be monitored. Testing of the new sensor concept has been carried out within the cavitating field provided by a commercial ultrasonic cleaning vessel operating at 40 kHz whose power output is rated at 1 kW. It is demonstrated that the prototype cavitation sensors are able to record a systematic increase in the level of the high-frequency acoustic spectrum (> 1 MHz) as electrical power to the cleaning vessel is increased. Through careful control of the experimental conditions, reproducibility of the high frequency "energy" associated with the cavitation spectrum was found to be typically +25%.

  15. Cavitation

    Young, F Ronald


    First published by McGraw-Hill in 1989, this book provides a unified treatment of cavitation, a phenomenon which extends across the boundaries of many fields. The approach is wide-ranging and the aim is to give due consideration to the many aspects of cavitation in proportion to their importance. Particular attention is paid to the diverse situations in which cavitation occurs and to its practical applications.

  16. Hydrodynamic cavitation applied to industrial wastewater; Tratamiento de efluentes industriales mediante cavitacion hidrodinamica

    Benito, Y.; Arrojo, S.


    The use environmental technology of the phenomenon known as cavitation has opened in the last new years alternatives for the treatment especially for industrial effluents. CIEMAT has designed and constructed a plant of cavitation hydrodynamics to take to end experiments that it allows us to show the possibilities of this technology as process of advanced oxidation of low cost. The experimentation has been made with water contaminated by substances like toluene and some derivatives, chloride organic compounds, xylenes, ammonia, wastewater from the ended of leather sector, there being achieved important reductions of the DQO (of the order of 60%) in short times. This work shows the results obtained in the experimentation of waters contaminated with toluene and p-nitrophenol. (Author)

  17. Single-transducer dual-frequency ultrasound generation to enhance acoustic cavitation.

    Liu, Hao-Li; Hsieh, Chao-Ming


    Dual- or multiple-frequency ultrasound stimulation is capable of effectively enhancing the acoustic cavitation effect over single-frequency ultrasound. Potential application of this sonoreactor design has been widely proposed such as on sonoluminescence, sonochemistry enhancement, and transdermal drug release enhancement. All currently available sonoreactor designs employed multiple piezoelectric transducers for generating single-frequency ultrasonic waves separately and then these waves were mixed and interfered in solutions. The purpose of this research is to propose a novel design of generating dual-frequency ultrasonic waves with single piezoelectric elements, thereby enhancing acoustic cavitation. Macroscopic bubbles were detected optically, and they were quantified at either a single-frequency or for different frequency combinations for determining their efficiency for enhancing acoustic cavitation. Visible bubbles were optically detected and hydrogen peroxide was measured to quantify acoustic cavitation. Test water samples with different gas concentrations and different power levels were used to determine the efficacy of enhancing acoustic cavitation of this design. The spectrum obtained from the backscattered signals was also recorded and examined to confirm the occurrence of stable cavitation. The results confirmed that single-element dual-frequency ultrasound stimulation can enhance acoustic cavitation. Under certain testing conditions, the generation of bubbles can be enhanced up to a level of five times higher than the generation of bubbles in single-frequency stimulation, and can increase the hydrogen peroxide production up to an increase of one fold. This design may serve as a useful alternative for future sonoreactor design owing to its simplicity to produce dual- or multiple-frequency ultrasound.

  18. Natural and laser-induced cavitation in corn stems: On the mechanisms of acoustic emissions

    Gabriel Mario Bilmes


    Full Text Available Water in plant xylem is often superheated, and therefore in a meta-stable state. Under certain conditions, it may suddenly turn from the liquid to the vapor state. This cavitation process produces acoustic emissions. We report the measurement of ultrasonic acoustic emissions (UAE produced by natural and induced cavitation in corn stems. We induced cavitation and UAE in vivo, in well controlled and reproducible experiments, by irradiating the bare stem of the plants with a continuous-wave laser beam. By tracing the source of UAE, we were able to detect absorption and frequency filtering of the UAE propagating through the stem. This technique allows the unique possibility of studying localized embolism of plant conduits, and thus to test hypotheses on the hydraulic architecture of plants. Based on our results, we postulate that the source of UAE is a transient "cavity oscillation"' triggered by the disruptive effect of cavitation inception.

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

    Coussios, Constantin C.; Roy, Ronald A.


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

  20. Natural and laser-induced cavitation in corn stems: On the mechanisms of acoustic emissions

    Fernández, E; Bilmes, G M; 10.4279/PIP.040003


    Water in plant xylem is often superheated, and therefore in a meta-stable state. Under certain conditions, it may suddenly turn from the liquid to the vapor state. This cavitation process produces acoustic emissions. We report the measurement of ultrasonic acoustic emissions (UAE) produced by natural and induced cavitation in corn stems. We induced cavitation and UAE in vivo, in well controlled and reproducible experiments, by irradiating the bare stem of the plants with a continuous-wave laser beam. By tracing the source of UAE, we were able to detect absorption and frequency filtering of the UAE propagating through the stem. This technique allows the unique possibility of studying localized embolism of plant conduits, and thus to test hypotheses on the hydraulic architecture of plants. Based on our results, we postulate that the source of UAE is a transient "cavity oscillation" triggered by the disruptive effect of cavitation inception.

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

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


    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.

  2. Quantification of Acoustic Cavitation Produced by a Clinical Extracorporeal Shock Wave Therapy System Using a Passive Cylindrical Detector

    Choi, M. J.; Cho, S. C.; Kang, G. S.; Paeng, D. G.; Lee, K. I.; Hodnett, M.; Zeqiri, B.; Coleman, A. J.

    Acoustic cavitation is regarded to play an important role in extracorporeal shock wave therapy (ESWT). However it is not yet well characterized the cavitation in ESWT due to difficulty in its measurement. This study tests NPL cavitation sensor to discuss its potential to quantify cavitation activities produced by a clinical shock wave field. In the present experiment, the sensor was located at the focus of an electromagentic shock wave generator (HnT Medical System, Korea). Measurements were repeated 15 times as varying setting numbers. It was observed that the acoustic signals recorded by the sensor contain characteristic features of broadband spikes representing cavitation. Spectral band magnitude (SBM), used as a cavitation measure, rose with the setting number. There was a threshold above which SBM soared up and had its uncertainty greately increased. The results prove the potential of the sensor in characterizing the cavitation produced by shock wave fields.

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

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


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

  4. The Relationship of Cavitation to the Negative Acoustic Pressure Amplitude in Ultrasonic Therapy

    Ting-Bo Fan; Juan Tu; Lin-Jiao Luo; Xia-Sheng Guo; Pin-Tong Huang; Dong Zhang


    The relationship between the cavitation and acoustic peak negative pressure in the high-intensity focused ultrasound (HIFU) field is analyzed in water and tissue phantom.The peak negative pressure at the focus is determined by a hybrid approach combining the measurement with the simulation.The spheroidal beam equation is utilized to describe the nonlinear acoustic propagation.The waveform at the focus is measured by a fiber optic probe hydrophone in water.The relationship between the source pressure amplitude and the excitation voltage is determined by fitting the measured ratio of the second harmonic to the fundamental component at the focus,based on the model simulation.Then the focal negative pressure is calculated for arbitrary voltage excitation in water and tissue phantom.A portable B-mode ultrasound scanner is applied to monitor HIFU-induced cavitation in real time,and a passive cavitation detection (PCD) system is used to acquire the bubble scattering signals in the HIFU focal volume for the cavitation quantification.The results show that:(1) unstable cavitation starts to appear in degassed water when the peak negative pressure of HIFU signals reaches 13.5 MPa;and (2) the cavitation activity can be detected in tissue phantom by B-mode images and in the PCD system with HIFU peak negative pressures of 9.0 MPa and 7.8 MPa,respectively,which suggests that real-time B-mode images could be used to monitor the cavitation activity in two dimensions,while PCD systems are more sensitive to detect scattering and emission signals from cavitation bubbles.

  5. Can Cavitation Be Anticipated?

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


    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.

  6. Evaluation of Acoustic Cavitation in Terephthalic Acid Solutions Containing Gold Nanoparticles by the Spectrofluorometry Method

    Ameneh Sazgarnia


    Full Text Available Background. When a liquid is irradiated with high intensity and low-frequency ultrasound, acoustic cavitation occurs. The existence of particles in a liquid provides nucleation sites for cavitation bubbles and leads to a decrease in the ultrasonic intensity threshold needed for cavitation onset. Materials and Methods. The study was designed to measure hydroxyl radicals in terephthalic acid solutions containing gold nanoparticles in a near field of a 1 MHz sonotherapy probe. The effect of ultrasound irradiation parameters containing mode of sonication and ultrasound intensity in hydroxyl radicals production have been investigated by the spectrofluorometry method. Results. Recorded fluorescence signal in terephthalic acid solution containing gold nanoparticles was higher than the terephthalic acid solution without gold nanoparticles. Also, the results showed that any increase in intensity of the sonication would be associated with an increase in the fluorescence intensity. Conclusion. Acoustic cavitation in the presence of gold nanoparticles has been introduced as a way for improving therapeutic effects on the tumors in sonodynamic therapy. Also, the terephthalic acid dosimetry is suitable for detecting and quantifying free hydroxyl radicals as a criterion of cavitation production over a certain range of conditions in medical ultrasound fields.

  7. Biodiesel production process intensification using a rotor-stator type generator of hydrodynamic cavitation.

    Crudo, Daniele; Bosco, Valentina; Cavaglià, Giuliano; Grillo, Giorgio; Mantegna, Stefano; Cravotto, Giancarlo


    Triglyceride transesterification for biodiesel production is a model reaction which is used to compare the conversion efficiency, yield, reaction time, energy consumption, scalability and cost estimation of different reactor technology and energy source. This work describes an efficient, fast and cost-effective procedure for biodiesel preparation using a rotating generator of hydrodynamic cavitation (HC). The base-catalyzed transesterification (methanol/sodium hydroxide) has been carried out using refined and bleached palm oil and waste vegetable cooking oil. The novel HC unit is a continuous rotor-stator type reactor in which reagents are directly fed into the controlled cavitation chamber. The high-speed rotation of the reactor creates micron-sized droplets of the immiscible reacting mixture leading to outstanding mass and heat transfer and enhancing the kinetics of the transesterification reaction which completes much more quickly than traditional methods. All the biodiesel samples obtained respect the ASTM standard and present fatty acid methyl ester contents of >99% m/m in both feedstocks. The electrical energy consumption of the HC reactor is 0.030kWh per L of produced crude biodiesel, making this innovative technology really quite competitive. The reactor can be easily scaled-up, from producing a few hundred to thousands of liters of biodiesel per hour while avoiding the risk of orifices clogging with oil impurities, which may occur in conventional HC reactors. Furthermore it requires minimal installation space due to its compact design, which enhances overall security.

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

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


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

  9. Degradation of 4-chloro 2-aminophenol using a novel combined process based on hydrodynamic cavitation, UV photolysis and ozone.

    Barik, Arati J; Gogate, Parag R


    The degradation of 4-chloro 2-aminophenol (4C2AP), an acute toxic organic compound, has been studied using different approaches based on the hydrodynamic cavitation (HC) with orifice plate as cavitating device, photolysis (UV) and ozonation (O3). The dependency of extent of degradation on operating parameters like operating pressure (2-5 bar), initial pH (3-8) and temperature (30-38 °C) have been established initially to maximize the efficacy of hydrodynamic cavitation. Subsequently the degradation has been studied using combined treatment strategies as HC+UV, HC+O3, UV+O3 and HC+UV+O3 at the established optimum parameters of operating temperature as 30 °C, initial pH of 6 and inlet pressure of 4 bar. The maximum extent of degradation as 96.85% and 73.6% reduction in TOC has been obtained using hydrodynamic cavitation in combination with UV photolysis and ozonation under the optimized operating conditions. The degradation products of 4C2AP have been identified using GC-MS. The present work has clearly established the efficacy of combined treatment approach (HC+UV+O3) for the removal of organic pollutant for the first time.

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

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


    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 coolant vaporization at the sphere surface. The growth of the cavitation vapor nuclei inside the hot drop is shown to be influenced by the subsequent long duration surface pressure pulses. The variation of the amplitude of these surface pulses with experimental variables is shown to exhibit the same trends with these variables as does the variation in extent of fragmentation.

  11. 声空强化渗透脱水过程质扩散研究%Mass Transfer During Osmotic Dehydration Using Acoustic Cavitation

    孙宝芝; 淮秀兰; 姜任秋; 刘登瀛


    An experimental study on intensifying osmotic dehydration was carried out in a state of nature and with acoustic cavitation of different cavitating intensity (0.5A, 0.TA and 0.9A) respectively, in which the material is apple slice of 5 mm thickness. The result showed that acoustic cavitation remarkably enhanced the osmotic dehydration, and the water loss was accelerated with the increase of cavitating intensity. The water diffusivitymodel was established about mass transfer during osmotic dehydration, and the numerical simulation was carried out. The calculated results agree well with experimental data, and represent the rule of mass transfer during osmotic dehydration intensified by acoustic cavitation.

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

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


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

  13. Evaluation of correlation between chemical dosimetry and subharmonic spectrum analysis to examine the acoustic cavitation.

    Hasanzadeh, Hadi; Mokhtari-Dizaji, Manijhe; Bathaie, S Zahra; Hassan, Zuhair M


    Currently several therapeutic applications of ultrasound in cancer treatment are under progress which uses cavitation phenomena to deliver their effects. There are several methods to evaluate cavitation activity such as chemical dosimetry and measurement of subharmonic signals. In this study, the cavitation activity induced by the ultrasound irradiation on exposure parameters has been measured by terephthalic acid chemical dosimetry and subharmonic analysis. Experiments were performed in the near 1 MHz fields in the progressive wave mode and effect of duty cycles changes with 2 W/cm(2) intensity (I(SATA)) and acoustic intensity changes in continuous mode on both fluorescence intensity and subharmonic intensity were measured. The dependence between fluorescence intensity of terephthalic acid chemical dosimetry and subharmonic intensity analysis were analyzed by Pearson correlation (p-value subharmonic intensity and the fluorescence intensity for continuous mode is higher than for pulsing mode (p-value subharmonic intensity and the fluorescence intensity with sonication intensity (p-value subharmonic intensity at different duty cycles (R=0.997, p-value subharmonic intensity (microW/cm(2)) significantly correlated with the fluorescence intensity (count) (R=0.901; psubharmonic intensity due to subharmonic spectrum analysis. It is concluded that there is dependence between terephthalic acid chemical dosimetry and subharmonic spectrum analysis to examine the acoustic cavitation activity.

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

    Wang, Qi

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

  15. Effect of acoustic parameters on the cavitation behavior of SonoVue microbubbles induced by pulsed ultrasound.

    Lin, Yutong; Lin, Lizhou; Cheng, Mouwen; Jin, Lifang; Du, Lianfang; Han, Tao; Xu, Lin; Yu, Alfred C H; Qin, Peng


    SonoVue microbubbles could serve as artificial nuclei for ultrasound-triggered stable and inertial cavitation, resulting in beneficial biological effects for future therapeutic applications. To optimize and control the use of the cavitation of SonoVue bubbles in therapy while ensuring safety, it is important to comprehensively understand the relationship between the acoustic parameters and the cavitation behavior of the SonoVue bubbles. An agarose-gel tissue phantom was fabricated to hold the SonoVue bubble suspension. 1-MHz transmitting transducer calibrated by a hydrophone was used to trigger the cavitation of SonoVue bubbles under different ultrasonic parameters (i.e., peak rarefactional pressure (PRP), pulse repetition frequency (PRF), and pulse duration (PD)). Another 7.5-MHz focused transducer was employed to passively receive acoustic signals from the exposed bubbles. The ultraharmonics and broadband intensities in the acoustic emission spectra were measured to quantify the extent of stable and inertial cavitation of SonoVue bubbles, respectively. We found that the onset of both stable and inertial cavitation exhibited a strong dependence on the PRP and PD and a relatively weak dependence on the PRF. Approximate 0.25MPa PRP with more than 20μs PD was considered to be necessary for ultraharmonics emission of SonoVue bubbles, and obvious broadband signals started to appear when the PRP exceeded 0.40MPa. Moreover, the doses of stable and inertial cavitation varied with the PRP. The stable cavitation dose initially increased with increasing PRP, and then decreased rapidly after 0.5MPa. By contrast, the inertial cavitation dose continuously increased with increasing PRP. Finally, the doses of both stable and inertial cavitation were positively correlated with PRF and PD. These results could provide instructive information for optimizing future therapeutic applications of SonoVue bubbles.

  16. Disinfection of bore well water with chlorine dioxide/sodium hypochlorite and hydrodynamic cavitation.

    Wang, Yifei; Jia, Aiyin; Wu, Yue; Wu, Chunde; Chen, Lijun


    The effect of hydrodynamic cavitation (HC) on potable water disinfection of chemicals was investigated. The bore well water was introduced into HC set-up to examine the effect of HC alone and combination of HC and chemicals such as chlorine dioxide and sodium hypochlorite. The effect of inlet pressure and geometrical parameters on disinfection was studied using HC alone and the results showed that increasing inlet pressure and using more and bigger holes of orifice plates can result in a higher disinfection rates. When HC was combined with chemicals, HC can reduce the doses of the chemicals and shorten the time of disinfection. It was also found that the decrease in bacteria concentration followed a first-order kinetic model. As for the experiment of combination of HC and sodium hypochlorite for disinfection, HC not only improves the disinfection rate but also degrades natural organic matter and chloroform. Compared with only sodium hypochlorite disinfection, combined processes get higher disinfection rate and lower production of chloroform, particularly the pretreatment with HC enhances the disinfection rate by 32% and there is a simultaneous reduction in production of chloroform by 39%.

  17. Sonochemical and hydrodynamic cavitation reactors for laccase/hydrogen peroxide cotton bleaching.

    Gonçalves, Idalina; Martins, Madalena; Loureiro, Ana; Gomes, Andreia; Cavaco-Paulo, Artur; Silva, Carla


    The main goal of this work is to develop a novel and environmental-friendly technology for cotton bleaching with reduced processing costs. This work exploits a combined laccase-hydrogen peroxide process assisted by ultrasound. For this purpose, specific reactors were studied, namely ultrasonic power generator type K8 (850 kHz) and ultrasonic bath equipment Ultrasonic cleaner USC600TH (45 kHz). The optimal operating conditions for bleaching were chosen considering the highest levels of hydroxyl radical production and the lowest energy input. The capacity to produce hydroxyl radicals by hydrodynamic cavitation was also assessed in two homogenizers, EmulsiFlex®-C3 and APV-2000. Laccase nanoemulsions were produced by high pressure homogenization using BSA (bovine serum albumin) as emulsifier. The bleaching efficiency of these formulations was tested and the results showed higher whiteness values when compared to free laccase. The combination of laccase-hydrogen peroxide process with ultrasound energy produced higher whiteness levels than those obtained by conventional methods. The amount of hydrogen peroxide was reduced 50% as well as the energy consumption in terms of temperature (reduction of 40 °C) and operating time (reduction of 90 min).

  18. Degradation of 2,4-dinitrophenol using a combination of hydrodynamic cavitation, chemical and advanced oxidation processes.

    Bagal, Manisha V; Gogate, Parag R


    In the present work, degradation of 2,4-dinitrophenol (DNP), a persistent organic contaminant with high toxicity and very low biodegradability has been investigated using combination of hydrodynamic cavitation (HC) and chemical/advanced oxidation. The cavitating conditions have been generated using orifice plate as a cavitating device. Initially, the optimization of basic operating parameters have been done by performing experiments over varying inlet pressure (over the range of 3-6 bar), temperature (30 °C, 35 °C and 40 °C) and solution pH (over the range of 3-11). Subsequently, combined treatment strategies have been investigated for process intensification of the degradation process. The effect of HC combined with chemical oxidation processes such as hydrogen peroxide (HC/H2O2), ferrous activated persulfate (HC/Na2S2O8/FeSO4) and HC coupled with advanced oxidation processes such as conventional Fenton (HC/FeSO4/H2O2), advanced Fenton (HC/Fe/H2O2) and Fenton-like process (HC/CuO/H2O2) on the extent of degradation of DNP have also been investigated at optimized conditions of pH 4, temperature of 35 °C and inlet pressure of 4 bar. Kinetic study revealed that degradation of DNP fitted first order kinetics for all the approaches under investigation. Complete degradation with maximum rate of DNP degradation has been observed for the combined HC/Fenton process. The energy consumption analysis for hydrodynamic cavitation based process has been done on the basis of cavitational yield. Degradation intermediates have also been identified and quantified in the current work. The synergistic index calculated for all the combined processes indicates HC/Fenton process is more feasible than the combination of HC with other Fenton like processes.

  19. Detection of acoustic cavitation in the heart with microbubble contrast agents in vivo: a mechanism for ultrasound-induced arrhythmias.

    Rota, Claudio; Raeman, Carol H; Child, Sally Z; Dalecki, Diane


    Ultrasound fields can produce premature cardiac contractions under appropriate exposure conditions. The pressure threshold for ultrasound-induced premature contractions is significantly lowered when microbubble contrast agents are present in the vasculature. The objective of this study was to measure directly ultrasound-induced cavitation in the murine heart in vivo and correlate the occurrence of cavitation with the production of premature cardiac contractions. A passive cavitation detection technique was used to quantify cavitation activity in the heart. Experiments were performed with anesthetized, adult mice given intravenous injections of either a contrast agent (Optison) or saline. Murine hearts were exposed to ultrasound pulses (200 kHz, 1 ms, 0.1-0.25 MPa). Premature beats were produced in mice injected with Optison and the likelihood of producing a premature beat increased with increasing pressure amplitude. Similarly, cavitation was detected in mice injected with Optison and the amplitude of the passive cavitation detector signal increased with increasing exposure amplitude. Furthermore, there was a direct correlation between the extent of cavitation and the likelihood of ultrasound producing a premature beat. Neither premature beats nor cavitation activity were observed in animals injected with saline and exposed to ultrasound. These results are consistent with acoustic cavitation as a mechanism for this bioeffect.


    SHI Honghui; KUME Makoto


    The fluid mechanics of water entry is studied through investigating the underwater acoustics and the supercavitation. Underwater acoustic signals in water entry are extensively measured at about 30 different positions by using a PVDF needle hydrophone. From the measurements we obtain (1) the primary shock wave caused by the impact of the blunt body on free surface; (2) the vapor pressure inside the cavity; (3) the secondary shock wave caused by pulling away of the cavity from free surface; and so on. The supercavitation induced by the blunt body is observed by using a digital high-speed video camera as well as the single shot photography. The periodic and 3 dimensional motion of the supercavitation is revealed. The experiment is carried out at room temperature.

  1. 局部空泡水翼性能研究%Research on the Hydrodynamic Performance of Partially Cavitating Hydrofoils

    谭睿博; 许劲松


    空泡对水翼的水动力特性具有重要的影响,使用数值模拟方法研究空泡特性及其机理有着广泛的工程应用价值.对二维NACA翼型的模拟结果表明,基于势流理论的边界元积分方法适用于局部空泡水翼的性能研究,翼型几何参数变化对空泡长度和升力性能均有显著影响,在水翼设计与使用过程中必须对空泡发生与变化给予充分关注.%Cavitation has extremely important influence on hydrodynamic performance of the hydrofoils.Numerical simulation is valuable for study on the characteristics and mechanism of cavitating flow.Application of a non-linear boundary element method on the partially cavitating hydrofoil shows that the lift performance of hydrofoils changes considerably with the occurrence and development of the partial cavitation.It must be completely concerned during hydrofoil design and operation.

  2. Generation of abnormal acoustic noise: Singing of a cavitating tip vortex

    Peng, Xiaoxing; Wang, Benlong; Li, Haoyu; Xu, Lianghao; Song, Mingtai


    We present experimental results and a theoretical analysis for the singing of a cavitating tip vortex (SCTV), which has been occasionally observed under special conditions in a few experimental facilities around the world since the 1990s. Due to lack of repeatability, little is known about the generation mechanism of SCTV [R. E. A. Arndt, Annu. Rev. Fluid Mech. 34, 143 (2002), 10.1146/annurev.fluid.34.082301.114957]. In the present work we propose an experimental procedure to produce the SCTV phenomenon at selected flow conditions in the China Ship Scientific Research Center cavitation mechanism tunnel. By analyzing the frequency characteristics of the acoustical signal and the bubble dynamics, it is found that the tone of SCTV matches the natural frequency of radial oscillation of the cylinder bubble and a formulation to predict SCTV is developed. Good agreement is obtained between the proposed formulation and the experimental data from different facilities.

  3. Periodic shock-emission from acoustically driven cavitation clouds: a source of the subharmonic signal.

    Johnston, Keith; Tapia-Siles, Cecilia; Gerold, Bjoern; Postema, Michiel; Cochran, Sandy; Cuschieri, Alfred; Prentice, Paul


    Single clouds of cavitation bubbles, driven by 254kHz focused ultrasound at pressure amplitudes in the range of 0.48-1.22MPa, have been observed via high-speed shadowgraphic imaging at 1×10(6) frames per second. Clouds underwent repetitive growth, oscillation and collapse (GOC) cycles, with shock-waves emitted periodically at the instant of collapse during each cycle. The frequency of cloud collapse, and coincident shock-emission, was primarily dependent on the intensity of the focused ultrasound driving the activity. The lowest peak-to-peak pressure amplitude of 0.48MPa generated shock-waves with an average period of 7.9±0.5μs, corresponding to a frequency of f0/2, half-harmonic to the fundamental driving. Increasing the intensity gave rise to GOC cycles and shock-emission periods of 11.8±0.3, 15.8±0.3, 19.8±0.2μs, at pressure amplitudes of 0.64, 0.92 and 1.22MPa, corresponding to the higher-order subharmonics of f0/3, f0/4 and f0/5, respectively. Parallel passive acoustic detection, filtered for the fundamental driving, revealed features that correlated temporally to the shock-emissions observed via high-speed imaging, p(two-tailed) subharmonic spectral peaks, in the frequency domain. The larger cavitation clouds (>200μm diameter, at maximum inflation), that developed under insonations of peak-to-peak pressure amplitudes >1.0MPa, emitted shock-waves with two or more fronts suggesting non-uniform collapse of the cloud. The observations indicate that periodic shock-emissions from acoustically driven cavitation clouds provide a source for the cavitation subharmonic signal, and that shock structure may be used to study intra-cloud dynamics at sub-microsecond timescales.

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

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


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

  5. The Evaluation of Efficacy of the Combination of Acoustic Cavitation and Radiofrequency Lipolysis in Body Sculpturing

    Seval Dogruk Kacar


    Full Text Available Aim: There is widespread use of noninvasive body sculpturing methods with the emerging new technologies in the field of aesthethic dermatology. However scientific data about these methods is limited. In our study the efficacy of the combination of acoustic cavitation and radiofrequency in body sculpturing is retrospectively evaluated. Material and Method: We retrospectively evaluated the patients who underwent body contouring treatment for belly and waist area in Dermatocosmetology unit of Afyon Kocatepe University Hospital between September 2012 and September 2013. The combination of acoustic cavitation and radiofrequency is applied 2 times a week for 10 sessions for body contouring of waist and belly. Before treatment and after each session the height, weight and perimetric measurements are recorded. Patients satisfaction level is assessed by visual analogue scale (VAS between 0 (dissatisfied, no effect and 5 (very satisfied, very effective. Results: The mean age of 15 female patients were 36,4±10,2 (23-52. There were statistically significant difference in weight and perimetric measurements of waist (superior waist, waist circumference, inferior waist between the beginning and end of treatment (respectively, p=0.002 and p=0.001 for the remaining three. Sixty percent of patients described the treatment as satisfactory according to VAS. The remaining were not satisfied although the treatments produced a change. No adverse effects reported other than a transient erythema during treatment. Discussion: Diet and exercise are still the most relevant ways to achieve optimal body shape and tone. Besides it is possible to eliminate excess fat and skin in appropriate patients by body sculpturing methods such as invasive and noninvasive liposuction and lipolysis. We found the combination of acoustic cavitation and radiofrequency effective in body shaping.

  6. The efficiency of a new hydrodynamic cavitation pilot system on Artemia salina cysts and natural population of copepods and bacteria under controlled mesocosm conditions.

    Cvetković, Martina; Grego, Mateja; Turk, Valentina


    A study of the efficiency of hydrodynamic cavitation and separation was carried out to evaluate an innovative, environmentally safe and acceptable system for ballast water treatment for reducing the risk of introducing non-native species worldwide. Mesocosm experiments were performed to assess the morphological changes and viability of zooplankton (copepods), Artemia salina cysts, and the growth potential of marine bacteria after the hydrodynamic cavitation treatment with a different number of cycles. Our preliminary results confirmed the significant efficiency of the treatment since more than 98% of the copepods and A. salina cysts were damaged, in comparison with the initial population. The efficiency increased with the number of the hydrodynamic cavitation cycles, or in combination with a separation technique for cysts. There was also a significant decrease in bacterial abundance and growth rate, compared to the initial number and growth potential.

  7. Real-time monitoring of controllable cavitation erosion in a vessel phantom with passive acoustic mapping.

    Lu, Shukuan; Shi, Aiwei; Jing, Bowen; Du, Xuan; Wan, Mingxi


    Cavitation erosion in blood vessel plays an important role in ultrasound thrombolysis, drug delivery, and other clinical applications. The controllable superficial vessel erosion based on ultrasonic standing wave (USW) has been used to effectively prevent vessel ruptures and haemorrhages, and optical method is used to observe the experiments. But optical method can only work in transparent media. Compared with standard B-mode imaging, passive acoustic mapping (PAM) can monitor erosion in real time and has better sensitivity of cavitation detection. However, the conventionally used PAM has limitations in imaging resolution and artifacts. In this study, a unique PAM method that combined the robust Capon beamformer (RCB) with the sign coherence factor (SCF) was proposed to monitor the superficial vessel erosion in real time. The performance of the proposed method was validated by simulations. In vitro experiments showed that the lateral (axial) resolution of the proposed PAM was 2.31±0.51 (3.19±0.38) times higher than time exposure acoustics (TEA)-based PAM and 1.73±0.38 (1.76±0.48) times higher than RCB-based PAM, and the cavitation-to-artifact ratio (CAR) of the proposed PAM could be improved by 22.5±3.2dB and 7.1±1.2dB compared with TEA and RCB-based PAM. These results showed that the proposed PAM can precisely monitor the superficial vessel erosion and the erosion shift after USW modulation. This work may have the potential of developing a useful tool for precise spatial control and real-time monitoring of the superficial vessel erosion. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Application of Technology of Hydrodynamic Cavitation Processing High-Viscosity Oils for the Purpose of Improving the Rheological Characteristics of Oils

    Zemenkov, Y. D.; Zemenkova, M. Y.; Vengerov, A. A.; Brand, A. E.


    There is investigated the technology of hydrodynamic cavitational processing viscous and high-viscosity oils and the possibility of its application in the pipeline transport system for the purpose of increasing of rheological properties of the transported oils, including dynamic viscosity shear stress in the article. It is considered the possibility of application of the combined hydrodynamic cavitational processing with addition of depressor additive for identification of effect of a synergism. It is developed the laboratory bench and they are presented results of modeling and laboratory researches. It is developed the hardware and technological scheme of application of the developed equipment at industrial objects of pipeline transport.

  9. Early-age acoustic emission measurements in hydrating cement paste: Evidence for cavitation during solidification due to self-desiccation

    Lura, Pietro; Couch, J.; Jensen, Ole Mejlhede


    In this study, the acoustic emission activity of cement pastes was investigated during the first day of hydration. Deaired, fresh cement pastes were cast in sealed sample holders designed to minimize friction and restraint. The majority of acoustic emission events occurred in lower water to cement....... According to these experimental results, the acoustic emission measured around setting time was attributed to cavitation events occurring in the pores of the cement paste due to self-desiccation. This paper shows how acoustic emission might be used to indicate the time when the fluid–solid transition occurs...

  10. Synergetic effect of combination of AOP's (hydrodynamic cavitation and H{sub 2}O{sub 2}) on the degradation of neonicotinoid class of insecticide

    Raut-Jadhav, Sunita [Vishwakarma Institute of Technology, Pune 411037 (India); Saharan, Virendra Kumar [Chemical Engineering Department, M. N. I. T, Jaipur, Rajasthan, 302001 (India); Pinjari, Dipak [Chemical Engineering Department, Institute of Chemical Technology, (ICT), Matunga, Mumbai, 400019 (India); Sonawane, Shirish, E-mail: [Chemical Engineering Department, N. I. T Warangal, Andhra Pradesh 506004 (India); Saini, Daulat, E-mail: [National Chemical Laboratory, Pune, 411008 (India); Pandit, Aniruddha, E-mail: [Chemical Engineering Department, Institute of Chemical Technology, (ICT), Matunga, Mumbai, 400019 (India)


    Highlights: • Degradation of imidacloprid using hydrodynamic cavitation based techniques. • Combination of hydrodynamic cavitation and H{sub 2}O{sub 2} shows substantial synergetic effect. • Synergetic coefficient of combined process is 22.79. • Degradation mechanism of imidacloprid has been proposed. -- Abstract: In the present work, degradation of imidacloprid (neonicotinoid class of insecticide) in aqueous solution has been systematically investigated using hydrodynamic cavitation and combination of hydrodynamic cavitation (HC) and H{sub 2}O{sub 2}. Initially, effect of different operating parameters such as inlet pressure to the cavitating device (5–20 bar) and operating pH (2–7.5) has been investigated. Optimization of process parameters was followed by the study of effect of combination of HC and H{sub 2}O{sub 2} process on the rate of degradation of imidacloprid. Significant enhancement in the rate of degradation of imidacloprid has been observed using HC + H{sub 2}O{sub 2} process which lead to a complete degradation of imidacloprid in 45 min of operation using optimal molar ratio of imidacloprid:H{sub 2}O{sub 2} as 1:40. Substantial synergetic effect has been observed using HC + H{sub 2}O{sub 2} process which confer the synergetic coefficient of 22.79. An attempt has been made to investigate and compare the energy efficiency and extent of mineralization of individual and combined processes applied in the present work. Identification of the byproducts formed during degradation of imidacloprid has also been done using LC–MS analysis. The present work has established a fact that hydrodynamic cavitation in combination with H{sub 2}O{sub 2} can be effectively used for degradation of imidacloprid.

  11. Microbubble Cavitation Imaging

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


    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.

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

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


    Cavitation events seeded by microbubbles have been previously reported to be associated with MR- or fluorescent-contrast enhancement after focused ultrasound (FUS)-induced blood-brain barrier (BBB) opening. However, it is still unknown whether bubble activity can be correlated with the reversibility (the duration of opening and the likelihood of safe reinstatement) and the permeability of opened BBB, which is critical for the clinical translation of using passive cavitation detection to monitor, predict and control the opening. In this study, the dependence of acoustic cavitation on the BBB opening duration, permeability coefficient and histological damage occurrence were thus investigated. Transcranial pulsed FUS at 1.5 MHz in the presence of systemically circulating microbubbles was applied in the mouse hippocampi (n  =  60). The stable and inertial cavitation activities were monitored during sonication. Contrast-enhanced MRI was performed immediately after sonication and every 24 h up to 6 d thereafter, to assess BBB opening, brain tissue permeability and potential edema. Histological evaluations were used to assess the occurrence of neurovascular damages. It was found that stable cavitation was well correlated with: (1) the duration of the BBB opening (r(2)  =  0.77); (2) the permeability of the opened BBB (r(2)  =  0.82); (3) the likelihood of safe opening (P  cavitation dose was correlated with the resulting BBB permeability (r(2)  =  0.72). Stable cavitation was found to be more reliable than inertial cavitation at assessing the BBB opening within the pressure range used in this study. This study demonstrates that the stable cavitation response during BBB opening holds promise for predicting and controlling the restoration and pharmacokinetics of FUS-opened BBB. The stable cavitation response therefore showed great promise in predicting the BBB opening duration, enabling thus control of opening according to the drug

  13. Effect of dissolved gases in water on acoustic cavitation and bubble growth rate in 0.83 MHz megasonic of interest to wafer cleaning.

    Kang, Bong-Kyun; Kim, Min-Su; Park, Jin-Goo


    Changes in the cavitation intensity of gases dissolved in water, including H2, N2, and Ar, have been established in studies of acoustic bubble growth rates under ultrasonic fields. Variations in the acoustic properties of dissolved gases in water affect the cavitation intensity at a high frequency (0.83 MHz) due to changes in the rectified diffusion and bubble coalescence rate. It has been proposed that acoustic bubble growth rates rapidly increase when water contains a gas, such as hydrogen faster single bubble growth due to rectified diffusion, and a higher rate of coalescence under Bjerknes forces. The change of acoustic bubble growth rate in rectified diffusion has an effect on the damping constant and diffusivity of gas at the acoustic bubble and liquid interface. It has been suggested that the coalescence reaction of bubbles under Bjerknes forces is a reaction determined by the compressibility and density of dissolved gas in water associated with sound velocity and density in acoustic bubbles. High acoustic bubble growth rates also contribute to enhanced cavitation effects in terms of dissolved gas in water. On the other hand, when Ar gas dissolves into water under ultrasound field, cavitation behavior was reduced remarkably due to its lower acoustic bubble growth rate. It is shown that change of cavitation intensity in various dissolved gases were verified through cleaning experiments in the single type of cleaning tool such as particle removal and pattern damage based on numerically calculated acoustic bubble growth rates. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Simultaneous treatment (cell disruption and lipid extraction) of wet microalgae using hydrodynamic cavitation for enhancing the lipid yield.

    Lee, Ilgyu; Han, Jong-In


    Simultaneous treatment (combining with cell disruption and lipid extraction) using hydrodynamic cavitation (HC) was applied to Nannochloropsis salina to demonstrate a simple and integrated way to produce oil from wet microalgae. A high lipid yield from the HC (25.9-99.0%) was observed compared with autoclave (16.2-66.5%) and ultrasonication (5.4-26.9%) in terms of the specific energy input (500-10,000 kJ/kg). The optimal conditions for the simultaneous treatment were established using a statistical approach. The efficiency of the simultaneous method was also demonstrated by comparing each separate treatment. The maximum lipid yield (predicted: 45.9% and experimental: 45.5%) was obtained using 0.89% sulfuric acid with a cavitation number of 1.17 for a reaction time of 25.05 min via response surface methodology. Considering its comparable extractability, energy-efficiency, and potential for scale-up, HC may be a promising method to achieve industrial-scale microalgae operation.

  15. Optimisation on pretreatment of rubber seed (Hevea brasiliensis) oil via esterification reaction in a hydrodynamic cavitation reactor.

    Bokhari, Awais; Chuah, Lai Fatt; Yusup, Suzana; Klemeš, Jiří Jaromír; Kamil, Ruzaimah Nik M


    Pretreatment of the high free fatty acid rubber seed oil (RSO) via esterification reaction has been investigated by using a pilot scale hydrodynamic cavitation (HC) reactor. Four newly designed orifice plate geometries are studied. Cavities are induced by assisted double diaphragm pump in the range of 1-3.5 bar inlet pressure. An optimised plate with 21 holes of 1mm diameter and inlet pressure of 3 bar resulted in RSO acid value reduction from 72.36 to 2.64 mg KOH/g within 30 min of reaction time. Reaction parameters have been optimised by using response surface methodology and found as methanol to oil ratio of 6:1, catalyst concentration of 8 wt%, reaction time of 30 min and reaction temperature of 55°C. The reaction time and esterified efficiency of HC was three fold shorter and four fold higher than mechanical stirring. This makes the HC process more environmental friendly.

  16. Intensified depolymerization of aqueous polyacrylamide solution using combined processes based on hydrodynamic cavitation, ozone, ultraviolet light and hydrogen peroxide.

    Prajapat, Amrutlal L; Gogate, Parag R


    The present work deals with intensification of depolymerization of polyacrylamide (PAM) solution using hydrodynamic cavitation (HC) reactors based on a combination with hydrogen peroxide (H2O2), ozone (O3) and ultraviolet (UV) irradiation. Effect of inlet pressure in hydrodynamic cavitation reactor and power dissipation in the case of UV irradiation on the extent of viscosity reduction has been investigated. The combined approaches such as HC+UV, HC+O3, HC+H2O2, UV+H2O2 and UV+O3 have been subsequently investigated and found to be more efficient as compared to individual approaches. For the approach based on HC+UV+H2O2, the extent of viscosity reduction under the optimized conditions of HC (3 bar inlet pressure)+UV (8 W power)+H2O2 (0.2% loading) was 97.27% in 180 min whereas individual operations of HC (3 bar inlet pressure) and UV (8 W power) resulted in about 35.38% and 40.83% intrinsic viscosity reduction in 180 min respectively. In the case of HC (3 bar inlet pressure)+UV (8 W power)+ozone (400 mg/h flow rate) approach, the extent of viscosity reduction was 89.06% whereas individual processes of only ozone (400 mg/h flow rate), ozone (400 mg/h flow rate)+HC (3 bar inlet pressure) and ozone (400 mg/h flow rate)+UV (8 W power) resulted in lower extent of viscosity reduction as 50.34%, 60.65% and 75.31% respectively. The chemical structure of the treated PAM by all approaches was also characterized using FTIR (Fourier transform infrared) spectra and it was established that no significant chemical structure changes were obtained during the treatment. Overall, it can be said that the combination of HC+UV+H2O2 is an efficient approach for the depolymerization of PAM solution.

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

    Wu, Yulin


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

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

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


    Cavitation events seeded by microbubbles have been previously reported to be associated with MR- or fluorescent-contrast enhancement after focused ultrasound (FUS)-induced blood-brain barrier (BBB) opening. However, it is still unknown whether bubble activity can be correlated with the reversibility (the duration of opening and the likelihood of safe reinstatement) and the permeability of opened BBB, which is critical for the clinical translation of using passive cavitation detection to monitor, predict and control the opening. In this study, the dependence of acoustic cavitation on the BBB opening duration, permeability coefficient and histological damage occurrence were thus investigated. Transcranial pulsed FUS at 1.5 MHz in the presence of systemically circulating microbubbles was applied in the mouse hippocampi (n  =  60). The stable and inertial cavitation activities were monitored during sonication. Contrast-enhanced MRI was performed immediately after sonication and every 24 h up to 6 d thereafter, to assess BBB opening, brain tissue permeability and potential edema. Histological evaluations were used to assess the occurrence of neurovascular damages. It was found that stable cavitation was well correlated with: (1) the duration of the BBB opening (r2  =  0.77) (2) the permeability of the opened BBB (r2  =  0.82) (3) the likelihood of safe opening (P  drug circulation time. In addition, avoiding adverse effects in the brain and assessing the pharmacokinetics of the compounds delivered can also be achieved by monitoring and controlling the stable cavitation emissions.

  19. Optimization of a heterogeneous catalytic hydrodynamic cavitation reactor performance in decolorization of Rhodamine B: application of scrap iron sheets.

    Basiri Parsa, Jalal; Ebrahimzadeh Zonouzian, Seyyed Alireza


    A low pressure pilot scale hydrodynamic cavitation (HC) reactor with 30 L volume, using fixed scrap iron sheets, as the heterogeneous catalyst, with no external source of H2O2 was devised to investigate the effects of operating parameters of the HC reactor performance. In situ generation of Fenton reagents suggested an induced advanced Fenton process (IAFP) to explain the enhancing effect of the used catalyst in the HC process. The reactor optimization was done based upon the extent of decolorization (ED) of aqueous solution of Rhodamine B (RhB). To have a perfect study on the pertinent parameters of the heterogeneous catalyzed HC reactor, the following cases as, the effects of scrap iron sheets, inlet pressure (2.4-5.8 bar), the distance between orifice plates and catalyst sheets (submerged and inline located orifice plates), back-pressure (2-6 bar), orifice plates type (4 various orifice plates), pH (2-10) and initial RhB concentration (2-14 mg L(-1)) have been investigated. The results showed that the highest cavitational yield can be obtained at pH 3 and initial dye concentration of 10 mg L(-1). Also, an increase in the inlet pressure would lead to an increase in the ED. In addition, it was found that using the deeper holes (thicker orifice plates) would lead to lower ED, and holes with larger diameter would lead to the higher ED in the same cross-sectional area, but in the same holes' diameters, higher cross-sectional area leads to the lower ED. The submerged operation mode showed a greater cavitational effects rather than the inline mode. Also, for the inline mode, the optimum value of 3 bar was obtained for the back-pressure condition in the system. Moreover, according to the analysis of changes in the UV-Vis spectra of RhB, both degradation of RhB chromophore structure and N-deethylation were occurred during the catalyzed HC process.

  20. Microbubble cavitation imaging.

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


    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 μs. 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.

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

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


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

  2. Enhancement and control of acoustic cavitation yield by low-level dual frequency sonication: a subharmonic analysis.

    Hasanzadeh, Hadi; Mokhtari-Dizaji, Manijhe; Bathaie, S Zahra; Hassan, Zuhair M; Nilchiani, Vahid; Goudarzi, H


    Evaluation of inertial cavitation is a significant problem where this mechanism of action is responsible for therapeutic applications such as drug delivery. It has shown that using multiple frequencies one is able to enhance and control induced cavitation. In this study, we used different sonication frequencies as 28 kHz, 130 kHz, 1 MHz, 3 MHz and their dual combinations to enhance acoustic cavitation. At each frequency, two different intensities were used and the subharmonic amplitude of each frequency in combinations was measured. It was observed that in combinations which include 28 kHz, the cavitation activity is enhanced. The 28 kHz subharmonic amplitude was used to compare these protocols in their ability to enhance cavitation. Besides, the area of cavitation damage was determined using an aluminum foil. Our results showed that the inertial cavitation activity increased at higher intensities and there is a significant correlation between the subharmonic amplitude and sonication intensity at each frequency (R>0.90). In addition, simultaneous combined dual-frequency orthogonal sonication at 28 kHz with other frequencies used can significantly increase the inertial cavitation activity as compared to the algebraic sum of the individual ultrasound irradiations in 28 kHz subharmonic frequency. The 28 kHz subharmonic amplitude for 28 kHz (0.04 W/cm(2)) and 3 MHz (2 and 1 W/cm(2)) combined dual frequency were about 4.6 and 1.5 times higher than that obtained from the algebraic sum of 28 kHz and 3 MHz irradiation, respectively. Also the 28 kHz subharmonic amplitude for combination of 28 kHz (0.04 W/cm(2)) and 1 MHz (2 and 1 W/cm(2)) were about 2.4 and 1.6 times higher than that obtained with their algebraic sum. Among different combinations, the continuous mode for two ultrasound sources of 28 kHz (0.04 W/cm(2)) and 3 MHz (2 W/cm(2)) is more effective than other combinations (p-value<0.05). The results of effective irradiation area showed no damaged aluminum foil in

  3. Optimization of hydrodynamic cavitations reactor efficiency for biodiesel production by response surface methods (Case study: Sunflower oil

    H Javadikia


    Full Text Available Introduction Biofuels are considered as one of the largest sources of renewable fuels or replacement of fossil fuels. Combustion of plant-based fuels is the indirect use of solar energy. Biofuels significantly have less pollution than other fossil fuels and can easily generate from residual plant material. Waste and residues of foods and wastewater can also be a good source for biofuel production. Transesterification method (one of biodiesel production methods is the most common forms to produce mono-alkyl esters from vegetable oil and animal fats. The procedure aims are reduction the oil viscosity during the reaction between triglycerides and alcohol in the presence of a catalyst or without it. In this study, the method of transesterification with alkaline catalysts is used that it is the most common and most commercial biodiesel production method. In this study, configurations of made hydrodynamic cavitation reactor were studied to measure biodiesel fuel quality and enhanced device performance with optimum condition. The Design Expert software and response surface methodology were used to get this purpose. Materials and Methods Transesterification method was used in this study. The procedure aims were reduction of the oil viscosity during the reaction between triglycerides and alcohol in the presence of a catalyst or without it. Materials needed in the production of biodiesel transesterification method include: vegetable oil, alcohol and catalysts. The used oil in the production of biodiesel was sunflower oil, which was used 0.6 liters per each test in the production process base on titration method. Methanol with purity of 99.8 percent and the molar ratio of 6:1 to oil was used based on titration equation and according to the results of other researchers. The used catalyst in continuous production process was high-purity sodium hydroxide (99% that it is one of alkaline catalysts. Weight of hydroxide was 1% of the used oil weight in the

  4. Cavitation in Ricinus by acoustic detection: Induction in excised leaves by various factors.

    Milburn, J A


    Xylem cavitation has been studied in Ricinus plants using vibration detection to examine its induction by different factors. These observations provide considerable circumstantial evidence in justification of the new technique as already described and further developed. In general cavitation is induced only when the tissue water balance is reduced hydrostatically. Thus cavitation is promoted by intense radiation which enhances transpiration, or alternatively by the blockage of xylem conduits by suspended particles carried in the transpiration stream. In contrast a reduction in radiation, or prevention of transpiration tends to restrict cavitation. Thus cavitation can be prevented by immersing a leaf in liquid paraffin. This technique has been used to see if radioactive bombardment would trigger its induction but no detectable effect has been observed even when exposed to intense radiation.An excised leaf, losing water in air, produces a "click total". On restoration to full turgor by standing the petiole in water it recovers very slowly and subsequently its "click total" is much reduced. If however the newly wilted leaf is allowed to recover in water following gas evacuation treatment the "cavitation total" often approaches the original and the rate of recovery is extremely rapid. Apparently gas emboli develop rapidly in conduits which have cavitated, but they can be removed by vacuum injection: the conduits refill and conduction is restored.

  5. 孔板水力空化装置的数值模拟%Simulation of Hydrodynamic Cavitation Equipment with Orifice Plates

    章昱; 李育敏; 计建炳


    基于FLUENT软件,采用]k-ω模型对孔板水力空化进行数值模拟,将相同条件下模拟所得的空化区与实验空化区进行比较.结果表明,模拟计算得到的汽含率分布与实验拍摄的汽含率分布相似,k-ω模型模拟结果与实验结果吻合.采用该模型分析了不同入口压力、孔板结构参数、液体物性参数对空化强度的影响,模拟结果表明,入口压力越大,空化强度越剧烈;增加孔径和孔的数量使空化强度减弱;增大液体密度和粘度使空化强度减弱;增大液体初始含气量使空化强度先增大后减小.%Based on the software FLUENT, the hydrodynamic cavitation with orifice plates was simulated using the k-ω model. The simulation results were compared with experimental data at the same situations, which showed that the distribution of vapor fraction by simulation was similar to that of experiment. The influences of inlet pressure, structures of orifice plate and physical characters of liquid on cavitation intensity were investigated by simulation using this model. The intensity of cavitation increased with increasing of inlet pressure and the orifice diameter and number. The intensity of cavitation decreased as the increase of density and viscosity of liquid, when the initial gas holdup increased, the intensity of cavitation increased first and then weaken.

  6. Cavitation bioeffects.

    Kimmel, Eitan


    Acoustic cavitation takes place when tiny gas bubbles oscillate, grow, and collapse in liquid under the influence of ultrasonic field. This study reviews cavitation bioeffects that are found both in vivo and in vitro when exposed to either low- or high-power acoustics. Proposed mechanisms are discussed here as well based on theoretical studies, simulations and test bench experiments. Bioeffects are induced in living tissue once the gas bubble is, for instance, within a blood vessel in close vicinity to the endothelium or to the red blood cells. Conditions for inducing various bioeffects are discussed - from severe damage, such as cell necrosis, to delicate alterations, such as increased permeability of cell membrane. Present and potential applications for therapeutic purpose from stone pulverization and tissue ablation to gene transfection and transdermal delivery are reviewed including the growing use of artificial microbubbles.

  7. A novel ultrasonic cavitation enhancer

    Fernandez Rivas, David; Verhaagen, Bram; Galdamez Perez, Andres; Castro-Hernandez, Elena; Zwieten, van Ralph; Schroen, Karin


    We introduce a Cavitation Intensifying Bag as a versatile tool for acoustic cavitation control. The cavitation activity is spatially controlled by the modification of the inner surface of the bag with patterned pits of microscopic dimensions. We report on different measurements such as the transmiss

  8. A novel ultrasonic cavitation enhancer

    Rivas, Fernandez D.; Verhaagen, B.; Galdamez Perez, Andres; Castro-Hernandez, Elena; Zwieten, Van Ralph; Schroen, Karin


    We introduce a Cavitation Intensifying Bag as a versatile tool for acoustic cavitation control. The cavitation activity is spatially controlled by the modification of the inner surface of the bag with patterned pits of microscopic dimensions. We report on different measurements such as the transm

  9. Cavitation simulation on marine propellers

    Shin, Keun Woo

    is reproduced in the simulation. The overall results suggest the possibility of the cavitation model in the RANS solver to be used for practical applications in propeller design process as a complementary tool to the cavitation tunnel test and the other numerical methods. The outstanding issue for cloudy...... developed in the last decade. They show the potential for the simulation of propeller cavitation with robustness, but they are still to be more proved for practical applications. In the present work, hydrodynamic and numerical characteristics of several cavitation models developed for a viscous flow solver...... are investigated, and one of the cavitation models is verified for the cavitation simulation on marine propellers. Three cavitation models with a vapor transport equation and a cavitation model with a barotropic state law are implemented in the in-house RANS solver, EllipSys. The numerical results for cavitating...

  10. Hydrodynamic cavitation in combination with the ozone, hydrogen peroxide and the UV-based advanced oxidation processes for the removal of natural organic matter from drinking water.

    Čehovin, Matej; Medic, Alojz; Scheideler, Jens; Mielcke, Jörg; Ried, Achim; Kompare, Boris; Žgajnar Gotvajn, Andreja


    Natural organic matter in drinking water is causing concern especially due to the formation of disinfection by-products (DBPs) by chlorine, as these are proven to have adverse health effects on consumers. In this research, humic acid was used as a source of dissolved organic carbon (DOC) in drinking water (up to 3mgL(-1)). The efficiency of DOC removal was studied by applying O3, H2O2/O3, H2O2/UV and O3/UV advanced oxidation processes (AOPs) alone and combined with hybrid hydrodynamic cavitation (HC), generated by an orifice plate, as this technology recently shows promising potential for the treatment of water, containing recalcitrant organic substances. It was observed that the combined treatment by HC could significantly affect the performance of the applied AOPs, with as little as 3-9 passes through the cavitation generators. For O3 and H2O2 dosages up to 2 and 4mgL(-1), respectively, and UV dosage up to 300mJcm(-2), HC enhanced DOC removal by 5-15% in all combinations, except for O3/UV AOPs. Overall, the potential benefits of HC for DOC removal were emphasized for low ratio between applied oxidants to DOC and high UV absorbance of the sample. Investigated DBPs formation potentials require special attention for H2O2/UV AOPs and combinations with HC. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Exploring the Acoustic Parameter Space in Ultrasound Therapy: Defining the Threshold for Cavitational Effects

    Kieran, Kathleen; Hall, Timothy L.; Parsons, Jessica E.; Wolf, J. Stuart; Fowlkes, J. Brian; Cain, Charles A.; Roberts, William W.


    Focused ultrasound energy is capable of noninvasively, nonthermally ablating tissue. However, the relative contributions of thermal and cavitational effects in the therapeutic use of ultrasound are poorly understood. We sought to identify the ultrasound parameter space within which tissue can be ablated by solely mechanical means (cavitation), without a significant thermal component. Methods: Ultrasound energy (750 kHz, 20 microsecond pulses) was applied sequentially in a 3×3 grid configuration to the cortical tissue of ex vivo porcine kidneys submerged in degassed water. While maintaining constant energy density, intensity (0.11-211 kW/cm2) and duty cycle (0.04%-CW) were varied widely. A thermocouple co-localized with the center of each grid provided continuous temperature measurements. Following ablations, the kidneys were examined grossly and histologically. Results: Ablated tissue was classified into one of four discrete morphologic categories: blanched (firm, pale, desiccated tissue), disrupted (cavity containing thin, isochromatic liquid; no blanching), mixed blanched/disrupted (cavity containing pale, thick liquid; minimal blanching), and no grossly visible effect. Morphologically similar lesions clustered together within the ultrasound parameter space. Disrupted lesions had significantly lower maximal temperatures (44.2 °C) than desiccated (67.5 °C; p<0.0001) or mixed (59.4 °C; p<0.0001) lesions. Conclusions: In an ex vivo model, we have defined the ultrasound parameters within which mechanical tissue ablation, with minimal thermal components, is possible. Future research in vivo is directed toward optimizing the parameters for cavitational tissue ablation, and better understanding the impact of tissue perfusion on lesion generation and intralesional temperature rise.

  12. Apoptosis Induced by Microbubble-Assisted Acoustic Cavitation in K562 Cells: The Predominant Role of the Cyclosporin A-Dependent Mitochondrial Permeability Transition Pore.

    Zhao, Lu; Feng, Yi; Shi, Aiwei; Zong, Yujin; Wan, Mingxi


    Acoustic cavitation of microbubbles has been described as inducing tumor cell apoptosis that is partly associated with mitochondrial dysfunction; however, the exact mechanisms have not been fully characterized. Here, low-intensity pulsed ultrasound (1 MHz, 0.3-MPa peak negative pressure, 10% duty cycle and 1-kHz pulse repetition frequency) was applied to K562 chronic myelogenous leukemia cells for 1 min with 10% (v/v) SonoVue microbubbles. After ultrasound exposure, the apoptotic index was determined by flow cytometry with annexin V-fluorescein isothiocyanate/propidium iodide. In addition, mitochondrial membrane potential (ΔΨm) was determined with the JC-1 assay. Translocation of apoptosis-associated protein cytochrome c was evaluated by Western blotting. We found that microbubble-assisted acoustic cavitation can increase the cellular apoptotic index, mitochondrial depolarization and cytochrome c release in K562 cells, compared with ultrasound treatment alone. Furthermore, mitochondrial dysfunction and apoptosis were significantly inhibited by cyclosporin A, a classic inhibitor of the mitochondrial permeability transition pore; however, the inhibitor of Bax protein, Bax-inhibiting peptide, could not suppress these effects. Our results suggest that mitochondrial permeability transition pore opening is involved in mitochondrial dysfunction after exposure to microbubble-assisted acoustic cavitation. Moreover, the release of cytochrome c from the mitochondria is dependent on cyclosporin A-sensitive mitochondrial permeability transition pore opening, but not formation of the Bax-voltage dependent anion channel complex or Bax oligomeric pores. These data provide more insight into the mechanisms underlying mitochondrial dysfunction induced by acoustic cavitation and can be used as a basis for therapy. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  13. Cavitation simulation on marine propellers

    Shin, Keun Woo

    flows on a 2D hydrofoil are compared with the experimental results. In the current implementation, three models with a vapor transport equation show numerical stability and equivalently good accuracy in simulating steady and unsteady sheet cavitation. More validations for cavitating flows on 3D...... hydrofoils and conventional/highly-skewed propellers are performed with one of three cavitation models proven in 2D analysis. 3D cases also show accuracy and robustness of numerical method in simulating steady and unsteady sheet cavitation on complicated geometries. Hydrodynamic characteristics of cavitation...

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

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


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

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

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


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

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

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


    Cavitation clouds generated by short, high-amplitude, focused ultrasound pulses were previously observed to attract, trap, and erode thrombus fragments in a vessel phantom. This phenomenon may offer a noninvasive method to capture and eliminate embolic fragments flowing through the bloodstream during a cardiovascular intervention. In this article, the mechanism of embolus trapping was explored by particle image velocimetry (PIV). PIV was used to examine the fluid streaming patterns generated by ultrasound in a vessel phantom with and without crossflow of blood-mimicking fluid. Cavitation enhanced streaming, which generated fluid vortices adjacent to the focus. The focal streaming velocity, uf, was as high as 120 cm/s, while mean crossflow velocities, uc, were imposed up to 14 cm/s. When a solid particle 3-4 mm diameter was introduced into crossflow, it was trapped near the focus. Increasing uf promoted particle trapping while increasing uc promoted particle escape. The maximum crossflow Reynolds number at which particles could be trapped, Rec, was approximately linear with focal streaming number, Ref, i.e. Rec = 0.25Ref + 67.44 (R(2) = 0.76) corresponding to dimensional velocities uc = 0.084uf + 3.122 for 20 < uf < 120 cm/s. The fluidic pressure map was estimated from PIV and indicated a negative pressure gradient towards the focus, trapping the embolus near this location.

  17. Acoustic black hole in a stationary hydrodynamic flow of microcavity polaritons.

    Nguyen, H S; Gerace, D; Carusotto, I; Sanvitto, D; Galopin, E; Lemaître, A; Sagnes, I; Bloch, J; Amo, A


    We report an experimental study of superfluid hydrodynamic effects in a one-dimensional polariton fluid flowing along a laterally patterned semiconductor microcavity and hitting a micron-sized engineered defect. At high excitation power, superfluid propagation effects are observed in the polariton dynamics; in particular, a sharp acoustic horizon is formed at the defect position, separating regions of sub- and supersonic flow. Our experimental findings are quantitatively reproduced by theoretical calculations based on a generalized Gross-Pitaevskii equation. Promising perspectives to observe Hawking radiation via photon correlation measurements are illustrated.

  18. Acoustics and hydrodynamics of a drop impact on a water surface

    Chashechkin, Yu. D.; Prokhorov, V. E.


    Hydrodynamic and acoustic processes associated with a drop impact on a water surface were studied experimentally. Acoustic signals were detected underwater (with a hydrophone) and in air (with a microphone), the flow pattern was recorded with a high-speed camera, and the surface perturbation was monitored with a laser detector. The dimensionless parameters of flows (Reynolds, Froude, and Weber numbers) induced by the impact varied with fall height within the ranges of 5000 noted in a series of experiments performed at a constant fall height. The analysis of video data showed that the signal variability was induced by considerable differences in the scenarios of water entry of a drop, which assumed an ovoid shape at the end trajectory segment, in the mentioned experiments.

  19. Plasma Formation during Acoustic Cavitation: Toward a New Paradigm for Sonochemistry

    Sergey I. Nikitenko


    Full Text Available The most recent spectroscopic studies of single bubble (SBSL and multibubble (MBSL sonoluminescence reveal that the origin of extreme intrabubble conditions is related to nonequilibrium plasma formed inside the collapsing bubbles. Analysis of the relative populations of OH(A2Σ+ vibrational states observed during MBSL in water saturated with noble gases shows that in the presence of argon at low ultrasonic frequency weakly excited plasma is formed. At high-frequency ultrasound the plasma inside the collapsing bubbles exhibits Treanor behavior typical for strong vibrational excitation. Plasma formation during SBSL was observed in concentrated H2SO4 preequilibrated with Ar. The light emission spectra exhibit the lines from excited Ar atoms and ionized oxygen O2+. Formation of O2+ species is inconsistent with any thermal process. Furthermore, the SBSL spectra in H2SO4 show emission lines from Xe+, Kr+, and Ar+ in full agreement with plasma hypothesis. The photons and the “hot” particles generated by cavitation bubbles enable the excitation of nonvolatile species in solutions increasing their chemical reactivity. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble but then diffuse into the liquid phase and react with solution precursors to form a variety of products.

  20. A novel ultrasonic cavitation enhancer

    Rivas, Fernandez D.; Verhaagen, B.; Galdamez Perez, Andres; Castro-Hernandez, Elena; Zwieten, van, D.M.; Schroen, Karin


    We introduce a Cavitation Intensifying Bag as a versatile tool for acoustic cavitation control. The cavitation activity is spatially controlled by the modification of the inner surface of the bag with patterned pits of microscopic dimensions. We report on different measurements such as the transmission of ultrasound, temperature increase inside the bag during sonication. Several applications of interest to other scientific activities are also demonstrated.

  1. Stochastic equations theory and applications in acoustics, hydrodynamics, magnetohydrodynamics, and radiophysics

    Klyatskin, Valery I


    This monograph set presents a consistent and self-contained framework of stochastic dynamic systems with maximal possible completeness. Volume 1 presents the basic concepts, exact results, and asymptotic approximations of the theory of stochastic equations on the basis of the developed functional approach. This approach offers a possibility of both obtaining exact solutions to stochastic problems for a number of models of fluctuating parameters and constructing various asymptotic buildings. Ideas of statistical topography are used to discuss general issues of generating coherent structures from chaos with probability one, i.e., almost in every individual realization of random parameters. The general theory is illustrated with certain problems and applications of stochastic mathematical physics in various fields such as mechanics, hydrodynamics, magnetohydrodynamics, acoustics, optics, and radiophysics.  

  2. Cavitation-enhanced back projection for acoustic detection of attenuating structures

    Ramaekers, Pascal; de Greef, Martijn; Moonen, Chrit T. W.; Ries, Mario


    Current methodology for the detection of attenuating structures in abdominal HIFU interventions requires lengthy, elaborate image analysis, which is undesired in a clinical setting. In this work, a method for the acoustic detection of attenuating structures in the beam path of the therapeutic HIFU array is described. The proposed method is used to determine binary apodizations that can be applied to the HIFU transducer for intercostal shot positions. Such a binary apodization was determined in vivo on an anesthetized pig under controlled breathing. Validation of the proposed method was done by comparing the binary apodization based on the proposed method to a binary apodization obtained using methodology based on MR image analysis and a collision detection algorithm. The proposed acoustical method provided a binary apodization that was over 90% similar to the apodization obtained using the image analysis-based method. Additionally, the proposed method can provide a measure of the amount of attenuation that each respective transducer element encounters in its beam path towards the focus.

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

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


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

  4. An Anticipatory Model of Cavitation

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


    The Anticipatory System (AS) formalism developed by Robert Rosen provides some insight into the problem of embedding intelligent behavior in machines. AS emulates the anticipatory behavior of biological systems. AS bases its behavior on its expectations about the near future and those expectations are modified as the system gains experience. The expectation is based on an internal model that is drawn from an appeal to physical reality. To be adaptive, the model must be able to update itself. To be practical, the model must run faster than real-time. The need for a physical model and the requirement that the model execute at extreme speeds, has held back the application of AS to practical problems. Two recent advances make it possible to consider the use of AS for practical intelligent sensors. First, advances in transducer technology make it possible to obtain previously unavailable data from which a model can be derived. For example, acoustic emissions (AE) can be fed into a Bayesian system identifier that enables the separation of a weak characterizing signal, such as the signature of pump cavitation precursors, from a strong masking signal, such as a pump vibration feature. The second advance is the development of extremely fast, but inexpensive, digital signal processing hardware on which it is possible to run an adaptive Bayesian-derived model faster than real-time. This paper reports the investigation of an AS using a model of cavitation based on hydrodynamic principles and Bayesian analysis of data from high-performance AE sensors.

  5. Noise Caused by Cavitating Butterfly and Monovar Valves

    HASSIS, H.


    An experimental study of the effects of cavitation was carried out through an analysis of cavitating Butterfly and Monovar values. Focus is particularly placed on both unsteady pressure and acoustic pressure fluctuations. In this paper, the effects of cavitation on local fluctuation pressure (turbulence), acoustic propagation (damping and sound velocity), resonance frequencies and level of noise are presented.

  6. Techniques of Ultrasound Cavitation Control

    S. P. Skvortsov


    Full Text Available The control methods of ultrasonic cavitation applied now within the range from 20 kHz to 80 kHz use either control of ultrasound source parameters (amplitude, acoustic power, etc. or control of one of the cavitation effects (erosion of materials, sonoluminescence, power of acoustic noise, etc.. These methods provide effective management of technological processes, however, make it impossible to relate the estimated effect with parameters of pulsations of cavitation bubbles. This is, mainly, due to influence of a number of uncontrollable parameters, in particular, such as temperature, composition of liquid, gas content, etc. as well as because of the difficulty to establish interrelation between the estimated effect and parameters of pulsations. As a result, in most cases it is difficult to compare controlled parameters of ultrasonic cavitation among themselves, and quantitative characteristics of processes become depending on the type of ultrasonic installation and conditions of their measurement.In this regard, methods to determine parameters of bubble pulsations through sounding a cavitation area by low-intensity laser radiation or to record cavitation noise sub-harmonics reflecting dynamics of changing radius of cavitation bubbles are of interest. The method of optical sounding, via the analysis of spectral components of a scattered signal recorded by a photo-detector, allows us to define a phase of the bubbles collapse with respect to the sound wave and a moving speed of the bubbles wall, as well as to estimate a cavitation index within the light beam section.The method to record sub-harmonicas of cavitation noise allows us to define parameters of pulsations, average for cavitation areas.The above methods allow us both to study mechanisms of cavitation action and to form quantitative criteria of its efficiency based on the physical processes, rather than their consequences and are convenient for arranging a feedback in the units using

  7. Cavitation instabilities and rotordynamic effects in turbopumps and hydroturbines turbopump and inducer cavitation, experiments and design

    Salvetti, Maria


    The book provides a detailed approach to the physics, fluid dynamics, modeling, experimentation and numerical simulation of cavitation phenomena, with special emphasis on cavitation-induced instabilities and their implications on the design and operation of high performance turbopumps and hydraulic turbines. The first part covers the fundamentals (nucleation, dynamics, thermodynamic effects, erosion) and forms of cavitation (attached cavitation, cloud cavitation, supercavitation, vortex cavitation) relevant to hydraulic turbomachinery, illustrates modern experimental techniques for the characterization, visualization and analysis of cavitating flows, and introduces the main aspects of the hydrodynamic design and performance of axial inducers, centrifugal turbopumps and hydo-turbines. The second part focuses on the theoretical modeling, experimental analysis, and practical control of cavitation-induced fluid-dynamic and rotordynamic instabilities of hydraulic turbomachinery, with special emphasis on cavitating...

  8. Coupling between hydrodynamics, acoustics, and heat release in a self-excited unstable combustor

    Harvazinski, Matthew E.; Huang, Cheng; Sankaran, Venkateswaran; Feldman, Thomas W.; Anderson, William E.; Merkle, Charles L.; Talley, Douglas G.


    The unsteady gas dynamic field in a closed combustor is determined by the nonlinear interactions between chamber acoustics, hydrodynamics, and turbulent combustion that can energize these modes. These interactions are studied in detail using hybrid RANS/large eddy simulations (RANS = Reynolds Averaged Navier-Stokes) of a non-premixed, high-pressure laboratory combustor that produces self-excited longitudinal instabilities. The main variable in the study is the relative acoustic length between the combustion chamber and the tube that injects oxidizer into the combustor. Assuming a half-wave (closed-closed) combustion chamber, the tube lengths approximately correspond to quarter-, 3/8-, and half-wave resonators that serve to vary the phasing between the acoustic modes in the tube and the combustion chamber. The simulation correctly predicts the relatively stable behavior measured with the shortest tube and the very unstable behavior measured with the intermediate tube. Unstable behavior is also predicted for the longest tube, a case for which bifurcated stability behavior was measured in the experiment. In the first (stable) configuration, fuel flows into the combustor uninterrupted, and heat release is spatially continuous with a flame that remains attached to the back step. In the second (unstable) configuration, a cyclic process is apparent comprising a disruption in the fuel flow, subsequent detachment of the flame from the back step, and accumulation of fuel in the recirculation zone that ignites upon arrival of a compression wave reflected from the downstream boundary of the combustion chamber. The third case (mixed stable/unstable) shares features with both of the other cases. The major difference between the two cases predicted to be unstable is that, in the intermediate length tube, a pressure wave reflection inside the tube pushes unburnt fuel behind the back step radially outward, leading to a post-coupled reignition mechanism, while in the case of the

  9. Wastewater treatment using hybrid treatment schemes based on cavitation and Fenton chemistry: a review.

    Bagal, Manisha V; Gogate, Parag R


    Advanced oxidation processes such as cavitation and Fenton chemistry have shown considerable promise for wastewater treatment applications due to the ease of operation and simple reactor design. In this review, hybrid methods based on cavitation coupled with Fenton process for the treatment of wastewater have been discussed. The basics of individual processes (Acoustic cavitation, Hydrodynamic cavitation, Fenton chemistry) have been discussed initially highlighting the need for combined processes. The different types of reactors used for the combined processes have been discussed with some recommendations for large scale operation. The effects of important operating parameters such as solution temperature, initial pH, initial pollutant concentration and Fenton's reagent dosage have been discussed with guidelines for selection of optimum parameters. The optimization of power density is necessary for ultrasonic processes (US) and combined processes (US/Fenton) whereas the inlet pressure needs to be optimized in the case of Hydrodynamic cavitation (HC) based processes. An overview of different pollutants degraded under optimized conditions using HC/Fenton and US/Fenton process with comparison with individual processes have been presented. It has been observed that the main mechanism for the synergy of the combined process depends on the generation of additional hydroxyl radicals and its proper utilization for the degradation of the pollutant, which is strongly dependent on the loading of hydrogen peroxide. Overall, efficient wastewater treatment with high degree of energy efficiency can be achieved using combined process operating under optimized conditions, as compared to the individual process.

  10. About the Results of the Destruction of the Molecules of Liquid Hydrocarbons in the Field of Acoustic Cavitation


    Analysis was conducted of fractional composition of hydrocarbon fuel. It is found that the excitation of cavitation in the fuel leads to a change of its fractional composition. This result can be explained by the destruction of liquid hydrocarbon molecules under high intensity of the unsteady pressure field

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

    Lu-Yan Zhao


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

  12. Influence of Leading-edge Suction on Hydrodynamic and Cavitation Performance of Hydrofoil%前缘抽吸对水翼水动力及空泡性能的影响

    王超; 郭海鹏; 张立新; 郭春雨


    为了研究船用水翼前缘抽吸设置对其水动力性能及空泡性能的影响,应用数值模拟的方法进行了系统的计算分析。首先,以NACA0012为研究对象,采用两种湍流模型对翼型绕流进行模拟,通过与实验值对比,确定了合理的湍流模型。随后,计算分析了船用水翼添加前缘抽吸作用后,升力系数、阻力系数和升阻比的变化情况,及对失速角的影响,结果表明船用水翼在前缘布置吸口后可以提高失速角,扩大稳定工作攻角范围,提升翼型升阻比,起到增效的作用。最后,计算了NACA0012翼型及在其前缘加吸口水翼的定常与非定常空泡流动的数值模拟,计算结果表明:定常流动时,在翼型前缘加上吸口,可使空泡尺寸减小,改善了水翼的空泡性能;非定常流动时,加上吸口,可使空泡周期变长,空泡变化范围减小,抑制大规模空泡云的脱落,减少对水翼表面的剥蚀作用,降低空泡对水翼性能的影响。%In order to study the influence of leading-edge suction on hydrodynamic and cavitation performance of hydrofoil, the numerical simulation method is used to calculate and analyze this pro-gram. First, two different turbulence models are used to computer the characteristics of NACA0012 airfoil, and one model is confirmed for the next calculation through comparing the results with tests. Then, the variation of lift coefficient, drag coefficient, lift drag ratio and stalling angle are analyzed while suction inlet is added at leading-edge of hydrofoil. The results show that the suction inlet can increase the stalling angle, enlarge the stable working angle limit, enhance lift drag ratio and improve the efficiency of the hydrofoil. In the end, the steady and unsteady cavitation flow around the NACA0012 airfoil and leading-edge suction hydrofoil are simulated. The results show that the suction inlet can make the cavitation bubble size

  13. Cavitation in medicine.

    Brennen, Christopher Earls


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

  14. 水力空化联合臭氧氧化灭藻技术的实际应用%Practical Application of Technology Combining Ozonation With Hydrodynamic Cavitation to Algae Removal From Water

    武志林; 王伟民; 李维新; 赵诣; 汤传栋; Giancarlo Cravotto


    Based on laboratory research and pilot experiments, an industrial water treatment system combining ozonation with hydrodynamic cavitation has been developed to remove algae from eutrophicated waterbodies. A comparative study was performed to compare the technologies of"complex cavitation/ozone","extrusion cavitation/ozone","suction cavitation/ozone","ozonation alone" and "orifice plate aperture" in water treatment efficiency, relative to chlorophyll a, UV254 , COD and NH3-N contents and turbidity in treated water. Meanwhile, comparison was done between"complex cavitation/o-zone" and "ozone alone" in some economic and technological indices, such as ozone utilization rate and net purification rate per unit of ozone and energy consumed. Results show that the technology of "complex cavitation/ozone" reached 44. 5% and 88. 9% in chlorophyll removal rate and 0. 89 and 1. 78 kW·h·m-3 in per unit energy consumption, respec-tively, during the period of stable discharge, when operated at 10 or 5 m3 ·h-1 . Moreover, the indices of turbidity, UV254 and COD all dropped significantly. The two technologies were also found better than the others in the other economic and technical indices. Therefore, it is concluded that the"hydrodynamic cavitation/ozone" system can be applied to quick and effective elimination of algae and chlorophyll, suppression of algal blooms, and reduction of ecological damage and eco-nomic losses that may be caused by algal blooms and dead algae.%在小试和中试试验的基础上,研制了一套水力空化联合臭氧灭藻及净化富营养化水体的工业化水处理系统.在工程运行中,比较了优化条件下复合空化-臭氧、正压空化-臭氧、抽吸空化-臭氧和单独臭氧氧化工艺以及孔板孔径对水体中叶绿素a、浊度、UV254、COD以及氨氮等的处理效果.同时,还对复合空化-臭氧和单独臭氧氧化工艺的臭氧利用率、臭氧和单位能耗的净化效率等经济技术指标进行了比

  15. Dynamic behaviors of cavitation bubble for the steady cavitating flow

    Jun CAI; Xiulan HUAI; Xunfeng LI


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

  16. Some Cavitation Properties of Liquids

    K. D. Efremova


    Full Text Available Cavitation properties of liquid must be taken into consideration in the engineering design of hydraulic machines and hydro devices when there is a possibility that in their operation an absolute pressure in the liquid drops below atmospheric one, and for a certain time the liquid is in depression state. Cold boiling, which occurs at a comparatively low temperature under a reduced absolute pressure within or on the surface of the liquid is regarded as hydrostatic cavitation if the liquid is stationary or as hydrodynamic cavitation, if the liquid falls into conditions when in the flow cross-section there is a sharply increasing dynamic pressure and a dropping absolute pressure.In accordance with the theory of cavitation, the first phase of cavitation occurs when the absolute pressure of the degassed liquid drops to the saturated vapour pressure, and the air dissolved in the liquid, leaving the intermolecular space, is converted into micro-bubbles of combined air and becomes a generator of cavitation “nuclei”. A quantitative estimate of the minimum allowable absolute pressure in a real, fully or partially degassed liquid at which a hydrostatic cavitation occurs is of practical interest.Since the pressure of saturated vapour of a liquid is, to a certain extent, related to the forces of intermolecular interaction, it is necessary to have information on the cavitation properties of technical solutions, including air solution in a liquid, as a solute may weaken intermolecular bonds and affect the pressure value of the saturated solvent vapour. In the experiment to carry out vacuum degassing of liquids was used a hydraulic air driven vacuum pump.The paper presents hydrostatic and hydrodynamic degassing liquid processes used in the experiment.The experimental studies of the cavitation properties of technical liquids (sea and distilled water, saturated NaCl solution, and pure glycerol and as a 49/51% solution in water, mineral oil and jet fuel enabled

  17. Pump Cavitation Noise Estimation from Acceleration Signals

    Lee, Do Hwan; Ha, Che Woong [KHNP Central Research Institute, Daejeon (Korea, Republic of)


    The cavitation noise can be measured directly by using pressure sensing devices. However, penetration of pipes or pump casings is inevitable to install the devices. This increases the risk of leaks. In an effort to reduce that risk, a cavitation noise estimation model based on vibration signals has been proposed. In the present study, the applicability of cavitation noise estimation methods including the previously proposed model is investigated. In order to assess the severity of cavitation, the cavitation noise estimation is necessary. In the present study, the cavitation noise is estimated by using acceleration signals measured outside of pumps and the theory of the statistical energy analysis. The applicability and limit of the cavitation noise estimation from the acceleration signals are examined by comparing the cavitation noise obtained from the pressure signal. The results suggest that the acoustic cavitation inception can be detected by the cavitation noise estimation from acceleration signals. The accuracy of the cavitation noise estimates is highly dependent on the locations of the pump casing that accelerometers attached on and the cut-off frequency of high pass filtering.

  18. Nonlinear hydrodynamic effects induced by Rayleigh surface acoustic wave in sessile droplets.

    Alghane, M; Chen, B X; Fu, Y Q; Li, Y; Desmulliez, M P Y; Mohammed, M I; Walton, A J


    We report an experimental and numerical characterization of three-dimensional acoustic streaming behavior in small droplets of volumes (1-30 μl) induced by surface acoustic wave (SAW). We provide a quantitative evidence of the existence of strong nonlinear nature of the flow inertia in this SAW-driven flow over a range of the newly defined acoustic parameter F{NA}=Fλ/(σ/R_{d})≥0.01, which is a measure of the strength of the acoustic force to surface tension, where F is the acoustic body force, λ is the SAW wavelength, σ is the surface tension, and R{d} is the droplet radius. In contrast to the widely used Stokes model of acoustic streaming, which generally ignores such a nonlinearity, we identify that the full Navier-Stokes equation must be applied to avoid errors up to 93% between the computed streaming velocities and those from experiments as in the nonlinear case. We suggest that the Stokes model is valid only for very small acoustic power of ≤1 μW (F{NA}droplets.

  19. Formant method applied to analyze acoustic emission signals from ultrasonic cavitation%基于共振峰的超声空化声发射信号分析

    沈再阳; 何永勇


    为简单有效地提取超声空化时频信息而估计空化强度,提出应用基于全极点线性预测编码模型的共振峰分析方法,分析19 kHz超声作用下的空化场的声发射信号.将共振峰分析结果与常用的频谱分析和短时傅里叶分析结果进行了对比,发现共振峰分析方法更能从超声空化声发射信号中提取出简单但关键的时频信息.采用共振峰方法的分析结果表明,可以利用空化声发射的共振峰参数如基频频率和相对高频共振峰的幅值来分别反映超声空化的非线性振荡和瞬态空化,进而估计超声空化的强度.%To extract the time-frequency information of ultrasonic cavitation and estimate the intensity of the cavitation simply and effectively, the formant method based on all-poles linear predictive coding model was introduced and applied to analyze the acoustic emission signals of a cavitation field caused by 19 kHz ultrasound. The comparison study shows that it is more capable of extracting simple but important time-frequency information from the acoustic emission signals than the commonly used spectrum method and short time Fourier Transformation (STFT) method. The results of the signals' formant analysis shows that some formant parameters of the acoustic emission signals, such as the fundamental frequency and higher frequency formant's amplitude, can be used to describe the ultrasonic cavitation's nonlinear oscillation and transient cavitation, thus to estimate the intensity of ultrasonic cavitation.

  20. Numerical Prediction of Unsteady Behavior of Cavitating Flow on Hydrofoils using Bubble Dynamics Cavitation Model

    Nur-E- Mostafa


    Full Text Available This paper presents a numerical study with pressure-based finite volume method for prediction of non-cavitating and time dependent cavitating flow on hydrofoil. The phenomenon of cavitation is modeled through a mixture model. For the numerical simulation of cavitating flow, a bubble dynamics cavitation model is used to investigate the unsteady behavior of cavitating flow and describe the generation and evaporation of vapor phase. The non-cavitating study focuses on choosing mesh size and the influence of the turbulence model. Three turbulence models such as Spalart-Allmaras, Shear Stress Turbulence (SST k-ω model and Re-Normalization Group (RNG k-ε model with enhanced wall treatment are used to capture the turbulent boundary layer on the hydrofoil surface. The cavitating study presents an unsteady behavior of the partial cavity attached to the foil at different time steps for σ=0.8. Moreover, this study focuses on cavitation inception, the shape and general behavior of sheet cavitation, lift and drag forces for different cavitation numbers. Finally, the flow pattern and hydrodynamic characteristics are also studied at different angles of attack.

  1. Estimating hydrodynamic roughness in a wave-dominated environment with a high-resolution acoustic Doppler profiler

    Lacy, J.R.; Sherwood, C.R.; Wilson, D.J.; Chisholm, T.A.; Gelfenbaum, G.R.


    Hydrodynamic roughness is a critical parameter for characterizing bottom drag in boundary layers, and it varies both spatially and temporally due to variation in grain size, bedforms, and saltating sediment. In this paper we investigate temporal variability in hydrodynamic roughness using velocity profiles in the bottom boundary layer measured with a high-resolution acoustic Doppler profiler (PCADP). The data were collected on the ebb-tidal delta off Grays Harbor, Washington, in a mean water depth of 9 m. Significant wave height ranged from 0.5 to 3 m. Bottom roughness has rarely been determined from hydrodynamic measurements under conditions such as these, where energetic waves and medium-to-fine sand produce small bedforms. Friction velocity due to current u*c and apparent bottom roughness z0a were determined from the PCADP burst mean velocity profiles using the law of the wall. Bottom roughness kB was estimated by applying the Grant-Madsen model for wave-current interaction iteratively until the model u*c converged with values determined from the data. The resulting kB values ranged over 3 orders of magnitude (10-1 to 10-4 m) and varied inversely with wave orbital diameter. This range of kB influences predicted bottom shear stress considerably, suggesting that the use of time-varying bottom roughness could significantly improve the accuracy of sediment transport models. Bedform height was estimated from kB and is consistent with both ripple heights predicted by empirical models and bedforms in sonar images collected during the experiment. Copyright 2005 by the American Geophysical Union.

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

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


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

  3. Hydrodynamic Controls on Acoustical and Optical Water Properties in Tropical Reefs


    change, coral bleaching and the future of the world’s coral reefs . Mar. Freshw. Res., 50, 839-866. McKee and Cunningham, 2005. Evidence for wavelength...the dominant hydrodynamic controls across different reef environments? Tropical coral health can be significantly affected by sedimentation that can...collaborative field work by the PIs, carried out in collaboration with UCSD SIO (PI: Terrill) and the Coral Reef Research Foundation in Koror (PI

  4. 离心泵空化状态下声发射信号的小波能量特征%Wavelet energy features of acoustic emission signals under centrifugal pump cavitation conditions

    刘忠; 邹淑云; 李志鹏; 巨伟


    为了探究离心泵空化状态下声发射信号的频率分布特征及其变化规律,该文采用小波分析方法对离心泵空化试验过程中不同空化状态下的声发射信号进行了能量特征提取,研究了不同频段内声发射信号的能量特征随离心泵汽蚀余量变化的关系。试验分析结果表明,在离心泵的空化现象尚未出现以及不同的发展阶段,离心泵进、出口处声发射信号的全频段和各分频段绝对能量和相对能量的变化具有各不相同的特点。>31.25~62.5、>62.5~125和>125~250 kHz这3个分频段的绝对能量随空化状态改变而变化明显,且变化趋势与全频段的变化趋势类似。>31.25~62.5 kHz分频段的相对能量在空化状态变化过程中基本保持不变,而>62.5~125和>125~250 kHz 分频段的相对能量变化更为明显。研究结果可为离心泵空化状态的判别提供技术参考。%With the development of Acoustic Emission (AE) techniques, researches on the AE signals emitted during the cavitation process to judge whether the cavitation has occurred or not and its development degrees are getting more and more attentions. However, the frequency distribution features and their variation laws with the cavitation states of centrifugal pumps remain to be further studied. In this paper, the wavelet energy features of the AE signals under the cavitation conditions of a centrifugal pump were extracted with the wavelet analysis method, and the variation laws of these features were also revealed. Firstly, the cavitation processes of the centrifugal pump with constant flows and constant speeds at the 60%, 100%and 120%rated flow respectively were simulated on an open centrifugal pump test bench. Each cavitation process included such different stages as no cavitation, cavitation just appearing and cavitation developed with different degrees. Simultaneously, the corresponding operational parameters of the centrifugal pump

  5. Real-time two-dimensional imaging of microbubble cavitation

    Vignon, Francois; Shi, W. T.; Powers, J. E.; Liu, J.; Drvol, L.; Lof, J.; Everbach, C.; Gao, S.; Xie, F.; Porter, T.


    Ultrasound cavitation of microbubble contrast agents has a potential for therapeutic applications, including sonothrombolysis in acute ischemic stroke. For safety, efficacy, and reproducibility of treatment, it is critical to evaluate the cavitation state (e.g. stable versus inertial forms of cavitation) and intensity in and around a treatment area. Acoustic Passive Cavitation Detectors (PCDs) have been used but do not provide spatial information. This paper presents a prototype of a 2D cavitation imager capable of producing images of the dominant cavitation state and intensity in a region of interest at a frame rate of 0.6Hz. The system is based on a modified ultrasound scanner (iE33, Philips) with a sector imaging probe (S5-1). Cavitation imaging is based on the spectral analysis of the acoustic signal radiated by the cavitating microbubbles: ultraharmonics of the excitation frequency indicate stable cavitation, while noise bands indicate inertial cavitation. The system demonstrates the capability to robustly identify stable and inertial cavitation thresholds of Definity microbubbles (Lantheus) in a vessel phantom through 3 ex-vivo human temporal bones, as well as to spatially map cavitation activities.

  6. Detección de cavitación en una bomba centrífuga usando emisiones acústicas Cavitation detection in a centrifugal pump using acoustic emissions

    Jabid Quiroga M.


    Full Text Available En el presente artículo se propone el uso de las emisiones acústicas para el monitoreo de la cavitación en una bomba centrífuga. Este monitoreo se ejecuta a través del seguimiento a unos indicadores de falla obtenidos a partir del valor RMS de la señal de emisiones acústicas en dominio tiempo y el valor RMS de los coeficientes de la Transformada Discreta Wavelet (TDW usando la onda madre db6 de la misma señal acústica. La experimentación se realiza en un banco dedicado que permite cavitar a una bomba de ½ hp en distintos niveles de severidad y bajo diferentes condiciones de bombeo. Resultados experimentales mostraron que los indicadores propuestos permiten detectar y evaluar cualitativamente los niveles de severidad de la cavitación en una bomba centrífuga.In this paper an acoustic emission based cavitation fault detection system is proposed for a centrifugal pump. The monitoring is performed tracking a fault indicator obtained using the RMS value of the acoustic emission signal in time domain and the RMS value of the coefficients obtained by applying discrete wavelet transform on the acoustic signal using db6 mother wavelet. Experiments in different cavitation levels and under different operation conditions are carried out in a ½ hp centrifugal pump dedicated test bed. Results showed that the proposed fault indicators are suitable for detecting and evaluating cavitation severities in a centrifugal pump.

  7. Counterbalancing the use of ultrasound contrast agents by a cavitation-regulated system.

    Desjouy, C; Fouqueray, M; Lo, C W; Muleki Seya, P; Lee, J L; Bera, J C; Chen, W S; Inserra, C


    The stochastic behavior of cavitation can lead to major problems of initiation and maintenance of cavitation during sonication, responsible of poor reproducibility of US-induced bioeffects in the context of sonoporation for instance. To overcome these disadvantages, the injection of ultrasound contrast agents as cavitation nuclei ensures fast initiation and lower acoustic intensities required for cavitation activity. More recently, regulated-cavitation devices based on the real-time modulation of the applied acoustic intensity have shown their potential to maintain a stable cavitation state during an ultrasonic shot, in continuous or pulsed wave conditions. In this paper is investigated the interest, in terms of cavitation activity, of using such regulated-cavitation device or injecting ultrasound contrast agents in the sonicated medium. When using fixed applied acoustic intensity, results showed that introducing ultrasound contrast agents increases reproducibility of cavitation activity (coefficient of variation 62% and 22% without and with UCA, respectively). Moreover, the use of the regulated-cavitation device ensures a given cavitation activity (coefficient of variation less 0.4% in presence of UCAs or not). This highlights the interest of controlling cavitation over time to free cavitation-based application from the use of UCAs. Interestingly, during a one minute sonication, while ultrasound contrast agents progressively disappear, the regulated-cavitation device counterbalance their destruction to sustain a stable inertial cavitation activity.

  8. Simulations of Steady Cavitating Flow in a Small Francis Turbine

    Ahmed Laouari


    Full Text Available The turbulent flow through a small horizontal Francis turbine is solved by means of Ansys-CFX at different operating points, with the determination of the hydrodynamic performance and the best efficiency point. The flow structures at different regimes reveal a large flow eddy in the runner and a swirl in the draft tube. The use of the mixture model for the cavity/liquid two-phase flow allowed studying the influence of cavitation on the hydrodynamic performance and revealed cavitation pockets near the trailing edge of the runner and a cavitation vortex rope in the draft tube. By maintaining a constant dimensionless head and a distributor vane opening while gradually increasing the cavitation number, the output power and efficiency reached a critical point and then had begun to stabilize. The cavitation number corresponding to the safety margin of cavitation is also predicted for this hydraulic turbine.

  9. Cavitation occurrence around ultrasonic dental scalers.

    Felver, Bernhard; King, David C; Lea, Simon C; Price, Gareth J; Damien Walmsley, A


    Ultrasonic scalers are used in dentistry to remove calculus and other contaminants from teeth. One mechanism which may assist in the cleaning is cavitation generated in cooling water around the scaler. The vibratory motion of three designs of scaler tip in a water bath has been characterised by laser vibrometry, and compared with the spatial distribution of cavitation around the scaler tips observed using sonochemiluminescence from a luminol solution. The type of cavitation was confirmed by acoustic emission analysed by a 'Cavimeter' supplied by NPL. A node/antinode vibration pattern was observed, with the maximum displacement of each type of tip occurring at the free end. High levels of cavitation activity occurred in areas surrounding the vibration antinodes, although minimal levels were observed at the free end of the tip. There was also good correlation between vibration amplitude and sonochemiluminescence at other points along the scaler tip. 'Cavimeter' analysis correlated well with luminol observations, suggesting the presence of primarily transient cavitation.

  10. Single bubble sonoluminescence and stable cavitation

    CHEN Qian; QIAN Menglu


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

  11. The influence of acoustic field and frequency on Hydrodynamics of Group B particles

    R L Sonolikar


    Full Text Available Sound Assisted Fluidized Bed (SAFB of group B particles (180μm glass bead has been studied in a 46mm I.D. column with aspect ratios of 1.4 and 2.9. A loudspeaker mounted on the top of the bed was supplied by a function generator with square wave to generate the sound as the source of vibration of the fluidized bed. The sound pressure level (referred to 20μpa was varied from 102 to 140dB and frequencies from 70Hz to 170Hz were applied. The effects of sound pressure level, sound frequency and particle loading on the properties of SAFB were investigated. The experimental result showed that the minimum fluidization velocity decreased with the increase in sound pressure level, also minimum fluidization velocity was varied with variation of frequencies. At resonance frequency minimum fluidization velocity was found to be minimum. The bed height did not show an appreciable increase in presence of high acoustic field and at resonant frequency. Minimum fluidization velocity verses frequency curve in presence of sound intensity varied with variation of bed weight.

  12. Cavitating behaviour analysis of Darrieus-type cross flow water turbines

    Aumelas, V; Pellone, C; MaItre, T, E-mail: vivien.aumelas@hmg.inpg.f [Equipe Energetique, Grenoble-INP - LEGI (Laboratory of Geophysical and Industrial Flows) Domaine Universitaire - BP 53, Grenoble cedex 9, 38041 (France)


    The aim of this paper is to study the cavitating behaviour of bare Darrieus-type turbines. For that, the RANS code CAVKA, has been used. Under non-cavitating conditions, the power coefficient and the thrusts calculated with CAVKA are compared to experimental values obtained in the LEGI hydrodynamic tunnel. Under cavitating conditions, for several cavitation numbers, the numerical power coefficients and vapour structures are compared to experimental ones. Different blade profiles and camber lines are also studied for non-cavitating and cavitating conditions.

  13. Cavitating behaviour analysis of Darrieus-type cross flow water turbines

    Aumelas, V.; Pellone, C.; Maître, T.


    The aim of this paper is to study the cavitating behaviour of bare Darrieus-type turbines. For that, the RANS code CAVKA, has been used. Under non-cavitating conditions, the power coefficient and the thrusts calculated with CAVKA are compared to experimental values obtained in the LEGI hydrodynamic tunnel. Under cavitating conditions, for several cavitation numbers, the numerical power coefficients and vapour structures are compared to experimental ones. Different blade profiles and camber lines are also studied for non-cavitating and cavitating conditions.

  14. Rotating Cavitation Supression Project

    National Aeronautics and Space Administration — FTT proposes development of a rotating cavitation (RC) suppressor for liquid rocket engine turbopump inducers. Cavitation instabilities, such as rotating...

  15. Time-evolving statistics of cavitation damage on metallic surfaces.

    Diodati, P; Marchesoni, F


    The statistics of surface damage on polycrystalline aluminium plates caused by acoustic cavitation is studied experimentally as a function of time. Cavitation is shown to produce a uniform distribution of crater-like holes with different depth, area and eccentricity. Most notably, the size distribution of such craters evolves with time from a gamma function into a power law. By contrast, on the surface of a martensitic Cu-Ni-Al crystal cavitation damage generates ramified patterns, reminiscent of a fractal object.

  16. Cavitation for improved sludge conversion into biogas

    Stoop, A. H.; Bakker, T. W.; Kramer, H. J. M.


    In several studies the beneficial influence of pre-treatment of waste activated sludge with cavitation on the biogas production was demonstrated. It is however, still not fully certain whether this effect should be mainly contributed to an increase in conversion rate of organics into biogas by anaerobic bacteria, and how much cavitation increases the total biogas yield. An increase in yield is only the case if cavitation can further disrupt otherwise inaccessible cell membrane structures and long chain organic molecules. In this study the influence of hydrodynamic cavitation on sludge that was already digested for 30 days was investigated. The total biogas yield could indeed be increased. The effect of the backpressure behind the venturi tube on the yield could not yet be established.

  17. 航行器垂直入水空泡特性与流体动力研究%Research on Cavitation and Hydrodynamic of Vertical Water- Entry for Supercavitating Vehicles

    胡平超; 张宇文; 袁绪龙


    Study on caviting shape and hydrodynamic on vertical water - entry of supercavitating vehicles.Based on standard k - ε model, the unsteady cavity character in a longitudinal gravity force field was numerically simulated by using 3D dynamic mesh technique during the supercavitating vehicle vertical enter water.Result shows that the angle of attack is larger, the asymmetry of the cavity is more obvious, the cavity of the confronted stream surface is shorter and thinner, the cavity of the opposing stream surface is longer and thicker, and the time difference of the closed cavity of the confronted and the opposing stream surface is longer.The angle of attack is larger, the hydrodynamic coefficient is larger; at the same water - entry depth, the slop of the drag coefficient curve is approximate equivalent at different angle of attack, and the slop of the lift coefficient curve and the pitching moment coefficient curve is larger with a larger angle of attack.The result can be used for research on water - entry trajectory.%研究超空泡航行器垂直入水空泡形态与流体动力特性,针对空泡出现流体动力特性改变,为了确定入水参数,根据标准k-E模型,采用三维动网格技术,对超空泡航行器入水过程重力场下非定常空泡特性以及流体动力参数进行了数值仿真.得出结果,攻角越大,空泡形态不对称性越明显,迎流面空泡越短越薄,背流面空泡越长越厚,迎流面与背流面的空泡闭合时差越大,且流体动力系数越大.证明对同-入水深度时,从曲线上分析,阻力系数的斜率基本一致,升力系数与俯仰力矩系数的斜率随攻角的增大而增大.研究结果可为入水弹道的研究提供了流体动力参数.


    Beazit ALI


    Full Text Available The main problem of the hydrodynamics of cavitation implosion of a single bubble, consists inpressure and velocity fields determination, including the collapse velocity of the bubble wall. By analysis thetheoretic and experimental phenomenon it establish the implicit function which describes this phenomenon. Byapplication the  theorem for this implicit function it finds the criterion equation of phenomenon.Depending on operating condition various cavitation patterns can be observed on a body surface astravelling bubbles, attached sheet cavitation, shear cavitation or vortex cavitation. Leading edge attachedpartialcavitation is commonly encountered on rotor blades or on hydrofoil. It corresponds to the case for whichavapor cavity is attached in the vecinity of the leading edge and extends over a fraction of the foil surface. Itgenerally takes places at incidence angles for which a leading edge pressure peak occurs and reduced belowtheliquid vapor pressure. At the early phases of development, leading edge partial cavitation is steady.

  19. Acoustic dose and acoustic dose-rate.

    Duck, Francis


    Acoustic dose is defined as the energy deposited by absorption of an acoustic wave per unit mass of the medium supporting the wave. Expressions for acoustic dose and acoustic dose-rate are given for plane-wave conditions, including temporal and frequency dependencies of energy deposition. The relationship between the acoustic dose-rate and the resulting temperature increase is explored, as is the relationship between acoustic dose-rate and radiation force. Energy transfer from the wave to the medium by means of acoustic cavitation is considered, and an approach is proposed in principle that could allow cavitation to be included within the proposed definitions of acoustic dose and acoustic dose-rate.

  20. Synchronized passive imaging of single cavitation events

    Gateau, Jérôme; Aubry, Jean-François; Pernot, Mathieu; Chauvet, Daurian; Boch, Anne-Laure; Fink, Mathias; Tanter, Mickaël


    Passive cavitation detection techniques are usually of relatively low sensitivity to single cavitation events. Moreover, a single-element transducer is generally used, so that the spatial localization of these cavitation events is not possible, or is limited to the probing volume. To both detect and localize single cavitation events over an extended volume, the following experimental set-up has been used and validated: cavitation is induced with a focused single-element transducer (mean frequency 660 kHz, f♯ = 1) driven by a high power (up to 5 kW) electric burst of a few cycles, and the acoustic emission of the bubbles is recorded on a standard linear array (4-7 MHz), mounted on the side of the single element to probe its focal spot. Both the frequencies and the geometry used are appropriate to in vivo implementation. The recording of ultrasonic radio-frequency (RF) data was performed simultaneously on 64 channels of the array and was synchronized with the pulsed excitation. A single cavitation event results in a high frequency and coherent wave front on the RF data. Thanks to synchronization, these RF data are beam-formed to localize the event with a axial resolution of 0.3 mm. A small number of discrete events could also be separated with this method. Besides, B-mode images obtained with the linear array prior to passive detection allowed the positioning of the events within the tissue structure. This technique has been used first ex vivo on freshly harve pig and sheep thigh muscle: with a two cycle excitation, a 9 MPa cavitation threshold was found. Cavitation detection was also achieved in vivo with a five cycle burst excitation in sheep thigh muscle for a peak acoustic pressure of 11MPa. This technique could provide useful information in order to better understand, control and monitor the initiation phase of the histotripsy process.

  1. Fundamental studies on cavitation melt processing

    Tzanakis, I.; Hodnett, M.; Lebon, G. S. B.; Eskin, D. G.; Pericleous, K.


    The application of ultrasound to industrial casting processes has attracted research interest during the last 50 years. However, the transfer and scale-up of this advanced and promising technology to industry has been hindered by difficulties in treating large volumes of liquid metal due to the lack of understanding of certain fundamentals. In the current study experimental results on ultrasonic processing in deionised water and in liquid aluminium (Al) are reported. Cavitation activity was determined in both liquid environments and acoustic pressures were successfully measured using an advanced high-temperature cavitometer sensor. Results showed that highest cavitation intensity in the liquid bulk is achieved at lower amplitudes of the sonotrode tip than the maximum available, suggesting nonlinearity in energy transfer to the liquid, while the location of the sonotrode is seen to substantially affect cavitation activity within the liquid. Estimation of real-time acoustic pressures distributed inside a crucible with liquid Al was performed for the first time.

  2. Cavitation: Cavitation flow. Citations from the NTIS data base

    Habercom, G. E., Jr.


    Reports on general aspects of cavitating flow are included. A wide range of theoretical, analytical, and experimental information is presented involving mathematical analysis, computer programs, and testing. Topics include marine engineering, hydrodynamic and aerodynamic configurations, symmetric and nonaxisymmetric shapes, and measuring technology. Data is given on surface piercing struts, helical inducers, pumps, liquid metal systems, and venturi tubes. Applications include dam outlets and spillways, vertical conduits, deep rock drilling, heat pipe stability, water entry, and liquid cryogenic systems. Discussions are made of flow characteristics, noise, nucleate boiling, perturbation problems, and allied subjects. This updated bibliography contains 253 abstracts.


    Mohammad Reza Bagheri


    Full Text Available In this study, the hydrodynamics and noise prediction of a five blade marine propeller were analyzed through numerical and experimental methods under variety operational conditions. The hydrodynamics of the propeller was studied and the characteristic curves were presented in both numerical and experimental methods. Inception and development of sheet cavitation conditions are obtained in both numerical and experimental methods. The cavitation was started and developed by either increasing the propeller rotational speed in constant pressure or decreasing pressure, while the velocity was kept constant. Good agreements are observed between numerical and experimental results, qualitatively and quantitatively. The noise of the propeller was analyzed through Computational fluid dynamics (CFD method, based on the formulation of Ffowcs Williams and Hawkings (FW-H. Similarly, the experimental results collected from hydrophones were compared with numerical simulations. Finally, the effects of reflection in cavitation tunnel were obtained by considering overall sound pressure levels in numerical and experimental results.


    CHEN Xin; LU Chuan-jing; LI Jie; PAN Zhan-cheng


    For ventilated cavitating flows in a closed water tunnel, the wall effect may exert an important influence on cavity shape and hydrodynamics. An isotropic mixture multiphase model was established to study the wall effect based on the RANS equations,coupled with a natural cavitation model and the RaNG k-ε turbulent model. The governing equations were discrctized using the finite volume method and solved by the Gauss-Seidel linear equation solver on the basis of a segregation algorithm. The algebraic multigrid approach was carried through to accelerate the convergence of solution. The steady ventilated cavitating flows in water tunnels of different diameter were simulated for a conceptual underwater vehicle model which had a disk cavitator. It is found that the choked cavitation number derived is close to the approximate solution of natural cavitating flow for a 3-D disk. The critical ventilation rate falls with decreasing diameter of the water tunnel. However, the cavity size and drag coefficient are rising with the decrease in tunnel diameter for the same ventilation rate, and the cavity size will be much different in water tunnels of different diameter even for the same ventilated cavitation number.

  5. Promoting inertial cavitation by nonlinear frequency mixing in a bifrequency focused ultrasound beam.

    Saletes, Izella; Gilles, Bruno; Bera, Jean-Christophe


    Enhancing cavitation activity with minimal acoustic intensities could be interesting in a variety of therapeutic applications where mechanical effects of cavitation are needed with minimal heating of surrounding tissues. The present work focuses on the relative efficiency of a signal combining two neighbouring frequencies and a one-frequency signal for initiating ultrasound inertial cavitation. Experiments were carried out in a water tank, using a 550kHz piezoelectric composite spherical transducer focused on targets with 46μm roughness. The acoustic signal scattered, either by the target or by the cavitation bubbles, is filtered using a spectral and cepstral-like method to obtain an inertial cavitation activity measurement. The ultrasound excitations consist of 1.8ms single bursts of single frequency f(0)=550kHz excitation, in the monofrequency case, and of dual frequency f(1)=535kHz and f(2)=565kHz excitation, in the bifrequency case. It is shown that depending on the value of the monofrequency cavitation threshold intensity the bifrequency excitation can increase or reduce the cavitation threshold. The analysis of the thresholds indicates that the mechanisms involved are nonlinear. The progress of the cavitation activity beyond the cavitation threshold is also studied. The slope of the cavitation activity considered as a function of the acoustic intensity is always steeper in the case of the bifrequency excitation. This means that the delimitation of the region where cavitation occurs should be cleaner than with a classical monofrequency excitation.

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

    Chen, Hong; Li, Xiaojing; Wan, Mingxi


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

  7. Model of Light Scattering in Cavitation Area

    S. P. Skvortsov


    Full Text Available The offered work presents analysis of extinction mechanisms and justification of light scattering model in ultrasonic cavitation area to justify a control method of ultrasonic cavitation through its optical sounding by low-intensity laser radiation and through photo-detector record of last radiation.The analysis of the extinction mechanisms has shown that the most essential mechanism causing a change of the transmission coefficient with time is dispersion on pulsating cavitation bubbles. Other extinction mechanisms lead to the time-constant reduction of last radiation intensity and can be taken into consideration by normalizing a recorded transmission coefficient for a previously measured liquid transmission coefficient when there is no cavitation.The feature of light scattering on the cavitation bubbles is primary dispersion in a forward direction that is connected with great values of bubbles radius from units to hundreds of micrometers. In case of single bubbles, dispersion can be described by Mi's theory, and, as to the cavitation area, it is reasonable to use the theory of V. Tversky for multiple light scattering. Thus, dispersion section, according to the paradox of extinction, can be considered to be equal to doubled geometrical section of a bubble. With increasing bubble radius the transmission coefficient monotonically decreases. So, the law of bubble pulsations and the model of light scattering define the law of changing transmission coefficient.Therefore, the cavitation area with its optical sounding acts as a peculiar opto-acoustic modulator. Thus, the demodulated signal of a photo-detector comprises information on pulsations of bubbles.The paper examines the influence of cavitation area thickness and bubbles concentration on the transmission coefficient. It shows a type of transmission coefficient dependence on the radius of cavitation bubbles.The optical sounding method is attractive because it allows us to obtain data on the

  8. Hybrid reactor based on combined cavitation and ozonation: from concept to practical reality.

    Gogate, P R; Mededovic-Thagard, S; McGuire, D; Chapas, G; Blackmon, J; Cathey, R


    The present work gives an in depth discussion related to the development of a hybrid advanced oxidation reactor, which can be effectively used for the treatment of various types of water. The reactor is based on the principle of intensifying degradation/disinfection using a combination of hydrodynamic cavitation, acoustic cavitation, ozone injection and electrochemical oxidation/precipitation. Theoretical studies have been presented to highlight the uniform distribution of the cavitational activity and enhanced generation of hydroxyl radicals in the cavitation zone, as well as higher turbulence in the main reactor zone. The combination of these different oxidation technologies have been shown to result in enhanced water treatment ability, which can be attributed to the enhanced generation of hydroxyl radicals, enhanced contact of ozone and contaminants, and the elimination of mass transfer resistances during electrochemical oxidation/precipitation. Compared to the use of individual approaches, the hybrid reactor is expected to intensify the treatment process by 5-20 times, depending on the application in question, which can be confirmed based on the literature illustrations. Also, the use of Ozonix® has been successfully proven while processing recycled fluids at commercial sites on over 750 oil and natural gas wells during hydraulic operations around the United States. The superiority of the hybrid process over conventional chemical treatments in terms of bacteria and scale reduction as well as increased water flowability and better chemical compatibility, which is a key requirement for oil and gas applications, has been established. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Study on cavitation effect of mechanical seals with laser-textured porous surface

    Liu, T.; Chen, H. l.; Liu, Y. H.; Wang, Q.; Liu, Z. B.; Hou, D. H.


    Study on the mechanisms underlying generation of hydrodynamic pressure effect associated with laser-textured porous surface on mechanical seal, is the key to seal and lubricant properties. The theory model of mechanical seals with laser-textured porous surface (LES-MS) based on cavitation model was established. The LST-MS was calculated and analyzed by using Fluent software with full cavitation model and non-cavitation model and film thickness was predicted by the dynamic mesh technique. The results indicate that the effect of hydrodynamic pressure and cavitation are the important reasons to generate liquid film opening force on LST-MS; Cavitation effect can enhance hydrodynamic pressure effect of LST-MS; The thickness of liquid film could be well predicted with the method of dynamic mesh technique on Fluent and it becomes larger as the increasing of shaft speed and the decreasing of pressure.

  10. Ultrahigh-Speed Dynamics of Micrometer-Scale Inertial Cavitation from Nanoparticles

    Kwan, J. J.; Lajoinie, G.; de Jong, N.; Stride, E.; Versluis, M.; Coussios, C. C.


    Direct imaging of cavitation from solid nanoparticles has been a challenge due to the combined nanosized length and time scales involved. We report on high-speed microscopic imaging of inertial cavitation from gas trapped on nanoparticles with a tunable hemispherical depression (nanocups) at nanosecond time scales. The high-speed recordings establish that nanocups facilitate bubble growth followed by inertial collapse. Nanoparticle size, acoustic pressure amplitude, and frequency influence bubble dynamics and are compared to model predictions. Understanding these cavitation dynamics is critical for applications enhanced by acoustic cavitation.

  11. Cavitation in Hydraulic Machinery

    Kjeldsen, M.


    The main purpose of this doctoral thesis on cavitation in hydraulic machinery is to change focus towards the coupling of non-stationary flow phenomena and cavitation. It is argued that, in addition to turbulence, superimposed sound pressure fluctuations can have a major impact on cavitation and lead to particularly severe erosion. For the design of hydraulic devices this finding may indicate how to further limit the cavitation problems. Chapter 1 reviews cavitation in general in the context of hydraulic machinery, emphasizing the initial cavitation event and the role of the water quality. Chapter 2 discusses the existence of pressure fluctuations for situations common in such machinery. Chapter 3 on cavitation dynamics presents an algorithm for calculating the nucleation of a cavity cluster. Chapter 4 describes the equipment used in this work. 53 refs., 55 figs.,10 tabs.

  12. Relationship between cavitation and loss of echogenicity from ultrasound contrast agents.

    Radhakrishnan, Kirthi; Bader, Kenneth B; Haworth, Kevin J; Kopechek, Jonathan A; Raymond, Jason L; Huang, Shao-Ling; McPherson, David D; Holland, Christy K


    Ultrasound contrast agents (UCAs) have the potential to nucleate cavitation and promote both beneficial and deleterious bioeffects in vivo. Previous studies have elucidated the pulse-duration-dependent pressure amplitude threshold for rapid loss of echogenicity due to UCA fragmentation. Previous studies have demonstrated that UCA fragmentation was concomitant with inertial cavitation. The purpose of this study was to evaluate the relationship between stable and inertial cavitation thresholds and loss of echogenicity of UCAs as a function of pulse duration. Determining the relationship between cavitation thresholds and loss of echogenicity of UCAs would enable monitoring of cavitation based upon the onscreen echogenicity in clinical applications. Two lipid-shelled UCAs, echogenic liposomes (ELIP) and Definity®, were insonified by a clinical ultrasound scanner in duplex spectral Doppler mode at four pulse durations ('sample volumes') in both a static system and a flow system. Cavitation emissions from the UCAs insonified by Doppler pulses were recorded using a passive cavitation detection system and stable and inertial cavitation thresholds ascertained. Loss of echogenicity from ELIP and Definity® was assessed within regions of interest on B-mode images. A numerical model based on UCA rupture predicted the functional form of the loss of echogenicity from ELIP and Definity®. Stable and inertial cavitation thresholds were found to have a weak dependence on pulse duration. Stable cavitation thresholds were lower than inertial cavitation thresholds. The power of cavitation emissions was an exponential function of the loss of echogenicity over the investigated range of acoustic pressures. Both ELIP and Definity® lost more than 80% echogenicity before the onset of stable or inertial cavitation. Once this level of echogenicity loss occurred, both stable and inertial cavitation were detected in the physiologic flow phantom. These results imply that stable and inertial

  13. Unsteady hydrodynamics of blade forces and acoustic responses of a model scaled submarine excited by propeller's thrust and side-forces

    Wei, Yingsan; Wang, Yongsheng


    This study presents the unsteady hydrodynamics of the excitations from a 5-bladed propeller at two rotating speeds running in the wake of a small-scaled submarine and the behavior of the submarine's structure and acoustic responses under the propeller excitations. Firstly, the propeller flow and submarine flows are independently validated. The propulsion of the hull-propeller is simulated using computational fluid dynamics (CFD), so as to obtain the transient responses of the propeller excitations. Finally, the structure and acoustic responses of the submarine under propeller excitations are predicted using a finite element/boundary element model in the frequency domain. Results show that (1) the propeller excitations are tonal at the propeller harmonics, and the propeller transversal force is bigger than vertical force. (2) The structure and acoustic responses of the submarine hull is tonal mainly at the propeller harmonics and the resonant mode frequencies of the hull, and the breathing mode in axial direction as well as the bending modes in vertical and transversal directions of the hull can generate strong structure vibration and underwater noise. (3) The maximum sound pressure of the field points increases with the increasing propeller rotating speed at structure resonances and propeller harmonics, and the rudders resonant mode also contributes a lot to the sound radiation. Lastly, the critical rotating speeds of the submarine propeller are determined, which should be carefully taken into consideration when match the propeller with prime mover in the propulsion system. This work shows the importance of the propeller's tonal excitation and the breathing mode plus the bending modes in evaluating submarine's noise radiation.

  14. The use of hydrodynamic disintegration as a means to improve ...


    Sep 15, 2008 ... Disintegration by hydrodynamic cavitation has a positive effect on the degree and rate of sludge anaerobic digestion. ... (ball mill, ultrasonic), oxidation (ozone and hydrogen per- .... American Public Health Association, Wash-.

  15. Parallel Computing of the Underwater Explosion Cavitation Effects on Full-scale Ship Structures

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


    Abstract: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.

  16. Hydrodynamics of Ship Propellers

    Breslin, John P.; Andersen, Poul

    This book deals with flows over propellers operating behind ships, and the hydrodynamic forces and moments which the propeller generates on the shaft and on the ship hull.The first part of the text is devoted to fundamentals of the flow about hydrofoil sections (with and without cavitation......) and about wings. It then treats propellers in uniform flow, first via advanced actuator disc modelling, and then using lifting-line theory. Pragmatic guidance is given for design and evaluation of performance, including the use of computer modelling.The second part covers the development of unsteady forces...... arising from operation in non-uniform hull wakes. First, by a number of simplifications, various aspects of the problem are dealt with separately until the full problem of a non-cavitating, wide-bladed propeller in a wake is treated by a new and completely developed theory. Next, the complicated problem...

  17. Numerical investigation of cavitation flow in journal bearing geometry

    Riedel, M.; Schmidt, M.; Stücke, P.


    The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD) are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.

  18. Cavitation assisted delignification of wheat straw: a review.

    Iskalieva, Asylzat; Yimmou, Bob Mbouyem; Gogate, Parag R; Horvath, Miklos; Horvath, Peter G; Csoka, Levente


    Wheat is grown in most of the Indian and Chinese regions and after harvesting, the remaining straw offers considerable promise as a renewable source most suitable for papermaking and as a pulping resource. Delignification of wheat straw offers ample scope for energy conservation by way of the application of the process intensification principles. The present work reviews the pretreatment techniques available for improving the effectiveness of the conventional approach for polysaccharide component separation, softening and delignification. A detailed overview of the cavitation assisted delignification process has been presented based on the earlier literature illustrations and important operational guidelines have been presented for overall low-cost and amenable energy utilization in the processes. The effectiveness of the methods has been evaluated according to yield and properties of the isolated fibers in comparison to the conventional treatment. Also the experimental results of one such non-conventional treatment scheme based on the use of hydrodynamic cavitation have been presented for the pulping of wheat straw. The effect of hydrodynamically induced cavitation on cell wall matrix and its components have been characterized using FT-IR analysis with an objective of understanding the cavitation assisted digestion mechanism on straws. It has been observed that the use of hydrodynamic cavitation does not degrade the fibrillar structure of cellulose but causes relocalisation and partial removal of lignin. Overall it appears that considerable improvement can be obtained due to the use of pretreatment or alternate techniques for delignification, which is an energy intensive step in the paper making industries.

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

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


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

  20. Dynamics of Vortex Cavitation

    Pennings, P.C.


    This thesis describes the mechanisms with which tip vortex cavitation is responsible for broadband pressure fluctuations on ship propellers. Hypotheses for these are described in detail by Bosschers (2009). Validation is provided by three main cavitation-tunnel experiments, one on a model propeller

  1. Numerical Study on Characteristics of 3D Cavitating Hydrofoil

    Cao Wei


    Full Text Available The commercial software ANSYS CFX, APDL and Workbench are applied for modeling the hydrodynamic and structural interactions and characteristics of an elastic hydrofoil by means of a two-way FSI method. The SST (Shear Stress Transport turbulence model and the simplified Rayleigh-Plesset equations are employed for the cavitating flow simulation. Both CFX and APDL solvers are set to be transient. The fluid and solid computational domains are sequentially solved to simulate the interactions between the hydrofoil and the cavitating flow. The results show that the difference in stiffness of common metal materials has trifling effects on hydrofoil performance. But variations in cavitation number and angle of attack will dramatically affect the hydrodynamic and structural interactions and characteristics.

  2. Megasonic cleaning, cavitation, and substrate damage: an atomistic approach

    Kapila, Vivek; Deymier, Pierre A.; Shende, Hrishikesh; Pandit, Viraj; Raghavan, Srini; Eschbach, Florence O.


    Megasonic cleaning has been a traditional approach for the cleaning of photomasks. Its feasibility as a damage free approach to sub 50 nm particulate removal is under investigation for the cleaning of optical and EUV photomasks. Two major mechanisms are active in a megasonic system, namely, acoustic streaming and acoustic cavitation. Acoustic streaming is instrumental in contaminant removal via application of drag force and rolling of particles, while cavitation may dislodge particles by the release of large energy during cavity implosion or by acting as a secondary source of microstreaming. Often times, the structures (substrates with or without patterns) subjected to megasonic cleaning show evidence of damage. This is one of the impediments in the implementation of megasonic technology for 45 nm and future technology nodes. Prior work suggests that acoustic streaming does not lead to sufficiently strong forces to cause damage to the substrates or patterns. However, current knowledge of the effects of cavitation on cleaning and damage can be described, at best, as speculative. Recent experiments suggest existence of a cavity size and energy distributions in megasonic systems that may be responsible for cleaning and damage. In the current work, we develop a two-dimensional atomistic model to study such multibubble cavitation phenomena. The model consists of a Lennard-Jones liquid which is subjected to sinusoidal pressure changes leading to the formation of cavitation bubbles. The current work reports on the effects of pressure amplitude (megasonic power) and frequency on cavity size distributions in vaporous and gaseous cavitation. The findings of the work highlight the role of multibubble cavitation as cleaning and damage mechanism in megasonic cleaning.

  3. Cavitating Flow over a Mini Hydrofoil

    LUO Xian-Wu; JI Bin; ZHANG Yao; XU Hong-Yuan


    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.%We consider a cavitating flow over a mini hydrofoil (foil profile:Clark-Y-11.7) having a 14mm 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.


    Vasyl Buivol


    Full Text Available A mathematical model of a cavity under the influence of perturbations of various origins is evaluated. The model is based on hydrodynamics of flows with free boundaries and the theory of small perturbations. Specific analysis is provided for cavitational flows behind cones

  5. Submarine hydrodynamics

    Renilson, Martin


    This book adopts a practical approach and presents recent research together with applications in real submarine design and operation. Topics covered include hydrostatics, manoeuvring, resistance and propulsion of submarines. The author briefly reviews basic concepts in ship hydrodynamics and goes on to show how they are applied to submarines, including a look at the use of physical model experiments. The issues associated with manoeuvring in both the horizontal and vertical planes are explained, and readers will discover suggested criteria for stability, along with rudder and hydroplane effectiveness. The book includes a section on appendage design which includes information on sail design, different arrangements of bow planes and alternative stern configurations. Other themes explored in this book include hydro-acoustic performance, the components of resistance and the effect of hull shape. Readers will value the author’s applied experience as well as the empirical expressions that are presented for use a...

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

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


    .... In this article, we resolved the rapid development of all cavitation bubbles and demonstrated that each ultrasound emission was linked to the nucleation of one single bubble, whose acoustic energy...

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

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


    In this study, the negative pressure values at which inertial cavitation consistently occurs in response to a single, two-cycle, focused ultrasound pulse were measured in several media relevant to cavitation-based ultrasound therapy. The pulse was focused into a chamber containing one of the media, which included liquids, tissue-mimicking materials, and ex vivo canine tissue. Focal waveforms were measured by two separate techniques using a fiber-optic hydrophone. Inertial cavitation was identified by high-speed photography in optically transparent media and an acoustic passive cavitation detector. The probability of cavitation (P(cav)) for a single pulse as a function of peak negative pressure (p(-)) followed a sigmoid curve, with the probability approaching one when the pressure amplitude was sufficient. The statistical threshold (defined as P(cav) = 0.5) was between p(-) = 26 and 30 MPa in all samples with high water content but varied between p(-) = 13.7 and >36 MPa in other media. A model for radial cavitation bubble dynamics was employed to evaluate the behavior of cavitation nuclei at these pressure levels. A single bubble nucleus with an inertial cavitation threshold of p(-) = 28.2 megapascals was estimated to have a 2.5 nm radius in distilled water. These data may be valuable for cavitation-based ultrasound therapy to predict the likelihood of cavitation at various pressure levels and dimensions of cavitation-induced lesions in tissue.

  8. Precise spatial control of cavitation erosion in a vessel phantom by using an ultrasonic standing wave.

    Shi, Aiwei; Huang, Peixuan; Guo, Shifang; Zhao, Lu; Jia, Yingjie; Zong, Yujin; Wan, Mingxi


    In atherosclerotic inducement in animal models, the conventionally used balloon injury is invasive, produces excessive vessel injuries at unpredictable locations and is inconvenient in arterioles. Fortunately, cavitation erosion, which plays an important role in therapeutic ultrasound in blood vessels, has the potential to induce atherosclerosis noninvasively at predictable sites. In this study, precise spatial control of cavitation erosion for superficial lesions in a vessel phantom was realised by using an ultrasonic standing wave (USW) with the participation of cavitation nuclei and medium-intensity ultrasound pulses. The superficial vessel erosions were restricted between adjacent pressure nodes, which were 0.87 mm apart in the USW field of 1 MHz. The erosion positions could be shifted along the vessel by nodal modulation under a submillimetre-scale accuracy without moving the ultrasound transducers. Moreover, the cavitation erosion of the proximal or distal wall could be determined by the types of cavitation nuclei and their corresponding cavitation pulses, i.e., phase-change microbubbles with cavitation pulses of 5 MHz and SonoVue microbubbles with cavitation pulses of 1 MHz. Effects of acoustic parameters of the cavitation pulses on the cavitation erosions were investigated. The flow conditions in the experiments were considered and discussed. Compared to only using travelling waves, the proposed method in this paper improves the controllability of the cavitation erosion and reduces the erosion depth, providing a more suitable approach for vessel endothelial injury while avoiding haemorrhage.

  9. Theoretical study of stimulated and spontaneous Hawking effects from an acoustic black hole in a hydrodynamically flowing fluid of light

    Grišins, Pjotrs; Nguyen, Hai Son; Bloch, Jacqueline; Amo, Alberto; Carusotto, Iacopo


    We propose an experiment to detect and characterize the analog Hawking radiation in an analog model of gravity consisting of a flowing exciton-polariton condensate. Under a suitably designed coherent pump configuration, the condensate features an acoustic event horizon for sound waves that at the semiclassical level is equivalent to an astrophysical black-hole horizon. We show that a continuous-wave pump-and-probe spectroscopy experiment allows to measure the analog Hawking temperature from the dependence of the stimulated Hawking effect on the pump-probe detuning. We anticipate the appearance of an emergent resonant cavity for sound waves between the pump beam and the horizon, which results in marked oscillations on top of an overall exponential frequency dependence. We finally analyze the spatial correlation function of density fluctuations and identify the hallmark features of the correlated pairs of Bogoliubov excitations created by the spontaneous Hawking process, as well as novel signatures characterizing the emergent cavity.

  10. Surface tension and quasi-emulsion of cavitation bubble cloud.

    Bai, Lixin; Chen, Xiaoguang; Zhu, Gang; Xu, Weilin; Lin, Weijun; Wu, Pengfei; Li, Chao; Xu, Delong; Yan, Jiuchun


    A quasi-emulsion phenomenon of cavitation structure in a thin liquid layer (the thin liquid layer is trapped between a radiating surface and a hard reflector) is investigated experimentally with high-speed photography. The transformation from cloud-in-water (c/w) emulsion to water-in-cloud (w/c) emulsion is related to the increase of cavitation bubble cloud. The acoustic field in the thin liquid layer is analyzed. It is found that the liquid region has higher acoustic pressure than the cloud region. The bubbles are pushed from liquid region to cloud region by the primary Bjerknes forces. The rate of change of CSF increased with the increase of CSF. The cavitation bubbles on the surface of cavitation cloud are attracted by the cavitation bubbles inside the cloud due to secondary Bjerknes forces. The existence of surface tension on the interface of liquid region and cloud region is proved. The formation mechanism of disc-shaped liquid region and cloud region are analysed by surface tension and incompressibility of cavitation bubble cloud. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Verification of Nuclear Effect of Acoustic Cavitation Using Fast Neutron Activation Method%快中子活化法对声空化核效应的验证

    李欣年; 冯涛; 方晓明; 钱梦騄; 程茜


    采用纯铜作为阈探测器检测声致核聚变产生的14 MeV中子。根据14 MeV中子与Cu的核反应,选择合适的放射性核素及其特征γ峰作为测量依据。中子辐照时间为50 min ,经30 min和198 min冷却,NaI探测器分别测量了超声和非超声下活化铜片的511 keV特征γ峰计数,测量结果显示,采用短冷却时间可测得62 Cu的511 keV γ特征峰,γ峰净面积计数增量ΔC均为正值,具有统计意义,在声空化条件下核反应液体中D-T反应产生的14 M eV中子发生率大于在非声空化条件下的;采用长冷却时间可测得64 Cu的511 keV γ特征峰,ΔC均为正值,具有统计意义,在声空化条件下核反应液体中D-D反应产生的2.45 MeV中子发生率大于在非声空化条件下的。由此验证了声空化核效应(NEAC),并初步分析了中子成核声空化核效应的机制。%14 MeV neutrons originated in acoustic cavitation fusion were determined using copper threshold detector .According to the nuclear reaction of 14 MeV neutrons with copper ,the characteristic γ peaks of some radioactive nuclides were measured and the activation parameters of Cu were optimized . With neutron irradiation time of 50 min ,511 keV characteristic γpeak counts of activated copper pieces with or without ultrasonic field after 30 min and 198 min were respectively determined by NaI detector . Measurement results show that the characteristic γ peak counts of 62 Cu and 64 Cu can be respectively determined after 30 min and 198 min .511 keV characteristic γ peak net count increments are positive values and statistical significance , w hich indicates that 14 MeV and 2.45 MeV neutron generation rates originated in fusion with ultrasound are greater than that without ultrasound in nuclear reaction liquid .These results verify the nuclear effect of acoustic cavitation (NEAC) .The mechanism of NEAC nucleated by neutrons was proposed initially .

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

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


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

  13. On acoustics of cavitating flows and wave mechanics of two-phase fluids; Zur Akustik kavitierender Stroemungen und Wellenmechanik zweiphasiger Fluide

    Ricoeur, A.


    The subject under consideration is the development and propagation of sound in two-phase flows. The investigations are focused on fluids, which are composed of liquid and gas. The gaseous phase may consist of both noncondensable gas and of vapour, originating from phase transitions of the liquid. Fields of application are, among others, flow noise, sonochemistry, the acoustical surveillance of industrial flow processes or ocean acoustics. A stochastic model, which describes spectral properties of noise sources, conditioned by imploding vapour bubbles, is connected to transfer functions. The latter are based on constitutive equations, accounting for the wave mechanics of the two-phase fluids. In combination with a numerical algorithm they permit for the calculation of noise spectra at any distance from the noise sources. The field problem is solved by implementing the constitutive equations into a hybrid boundary element method, which combines low discretization effort with fast evaluation of domain variables. The constitutive equations are based on models for the dynamics of gas- and vapour bubbles. Therefore, the nonlinear and linear bubble dynamics are extensively investigated. Furthermore, fundamental knowledge concerning wave dispersion in two-phase fluids is presented. The constitutive equation for pseudocavitation is experimentally verified by means of an acoustical wave guide. Additionally the experimental set-up serves for investigating fluid-structure-interaction. (orig.) [German] Die Arbeit befasst sich mit der Entstehung und Ausbreitung von Schall in Zweiphasenstroemungen. Betrachtet werden Fluide aus Fluessigkeit und Gas, deren Gasphase sowohl als nichtkondensierendes Gas, als auch in Gestalt des Dampfes der Fluessigkeit vorliegt. Anwendungen liegen beispielsweise in der Stroemungsakustik, der Sonochemie, der akustischen Ueberwachung verfahrenstechnischer Prozesse oder der Meeresakustik. Ein stochastisches Modell zur spektralen Beschreibung von

  14. The Effect of Polymer Additives on the Cavitation Threshold of Water


    dependance of the acoustic cavitation threshold on the liquid surface tension. To examine this dependance , it was first necessary to measure the...weight. The measurements were made at a constant temperature of 170 C. Fig. 6 shows the dependance of the surface tension on concentration for aqueous...saturation appears to occur. Next, the dependance of the acoustic cavitation threshold on the concentration of the polymer was examined. In Figs. 7 and 8, the

  15. Sonoluminescence and sonochemiluminescence study of cavitation field in a 1.2MHz focused ultrasound

    Yin, Hui; Qiao, Yangzi; Cao, Hua; Wan, Mingxi


    An intensified CCD (ICCD) and an electron-multiplying CCD (EMCCD) were employed to observe the spatial distribution of sonoluminescence (SL) and sonochemiluminescence (SCL) generated by cavitation bubbles in a 1.2MHz HIFU field. Various sonication conditions, which are free field and focal region near a water-parenchyma interface, were studied. In addition, the differences of two shells coated UCAs were also investigated. In this study, an acoustic radiation force (ARF) counterbalance appliance was added to reduce bubble displacement. Cavitation mapping in this situation was also operated through SCL recording. SCL was also employed to measure cavitation does and map the spatial distribution of cavitation near a boundary of parenchyma.

  16. Experimental and numerical analysis of cavitating flow around a hydrofoil

    Müller Miloš


    Full Text Available 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.

  17. The effect of static pressure on the inertial cavitation threshold.

    Bader, Kenneth B; Raymond, Jason L; Mobley, Joel; Church, Charles C; Felipe Gaitan, D


    The amplitude of the acoustic pressure required to nucleate a gas or vapor bubble in a fluid, and to have that bubble undergo an inertial collapse, is termed the inertial cavitation threshold. The magnitude of the inertial cavitation threshold is typically limited by mechanisms other than homogeneous nucleation such that the theoretical maximum is never achieved. However, the onset of inertial cavitation can be suppressed by increasing the static pressure of the fluid. The inertial cavitation threshold was measured in ultrapure water at static pressures up to 30 MPa (300 bars) by exciting a radially symmetric standing wave field in a spherical resonator driven at a resonant frequency of 25.5 kHz. The threshold was found to increase linearly with the static pressure; an exponentially decaying temperature dependence was also found. The nature and properties of the nucleating mechanisms were investigated by comparing the measured thresholds to an independent analysis of the particulate content and available models for nucleation.

  18. Fundamentals of Cavitation

    Franc, Jean-Pierre


    The present book is aimed at providing a comprehensive presentation of cavitation phenomena in liquid flows. It is further backed up by the experience, both experimental and theoretical, of the authors whose expertise has been internationally recognized. A special effort is made to place the various methods of investigation in strong relation with the fundamental physics of cavitation, enabling the reader to treat specific problems independently. Furthermore, it is hoped that a better knowledge of the cavitation phenomenon will allow engineers to create systems using it positively. Examples in the literature show the feasibility of this approach.

  19. Application of cavitation promoting surfaces in management of acute ischemic stroke.

    Soltani, Azita


    High frequency, low intensity ultrasound has the potential to accelerate the clearance of thrombotic occlusion in the absence of cavitation. At high frequency ultrasound, high acoustic pressures, >5.2MPa, are required to generate cavitation in thrombus. The focus of this study was to reduce the cavitation threshold by applying materials with appropriate nucleation sites at the transducer-thrombus boundary to further augment sonothrombolysis. Heterogeneous and homogenous nucleation sites were generated on the outer surface of a polyimide tube (PI) using microfringed (MPI) and laser induced (LPI) microcavities. The cavitation threshold of these materials was determined using a passive cavitation detection system. Furthermore, the biological impact of both materials was investigated in vitro. The results revealed that both MPI and LPI have the potential to induce cavitation at acoustic pressure levels as low as 2.3MPa. In the presence of cavitation, thrombolysis rate could be enhanced by up to two times without any evidence of hemolysis that is generally associated with cavitation activities in blood. A prototype ultrasonic catheter operating at 1.7MHz frequency and acoustic pressure of 2.3MPa with either of MPI or LPI could be considered as a viable option for treatment of acute ischemic stroke.

  20. Instability and breakup of cavitation bubbles within diesel drops

    Ming Lü; Zhi Ning; Kai Yan; Juan Fu; Chunhua Sun


    A modified mathematical model is used to study the effects of various forces on the stability of cavitation bubbles within a diesel droplet. The principal finding of the work is that viscous forces of fluids stabilize the cavitation bubble, while inertial force destabilizes the cavitation bubble. The droplet viscosity plays a dominant role on the stability of cavitation bubbles compared with that of air and bubble. Bubble–droplet radius ratio is a key factor to control the bubble stability, especially in the high radius ratio range. Internal hydrodynamic and surface tension forces are found to stabilize the cavitation bubble, while bubble stability has little relationship with the external hydrodynamic force. Inertia makes bubble breakup easily, however, the breakup time is only slightly changed when bubble growth speed reaches a certain value (50 m·s−1). In contrast, viscous force makes bubble hard to break. With the increasing initial bubble–droplet radius ratio, the bubble growth rate increases, the bubble breakup radius decreases, and the bubble breakup time becomes shorter.

  1. Sonoporation of adherent cells under regulated ultrasound cavitation conditions.

    Muleki Seya, Pauline; Fouqueray, Manuela; Ngo, Jacqueline; Poizat, Adrien; Inserra, Claude; Béra, Jean-Christophe


    A sonoporation device dedicated to the adherent cell monolayer has been implemented with a regulation process allowing the real-time monitoring and control of inertial cavitation activity. Use of the cavitation-regulated device revealed first that adherent cell sonoporation efficiency is related to inertial cavitation activity, without inducing additional cell mortality. Reproducibility is enhanced for the highest sonoporation rates (up to 17%); sonoporation efficiency can reach 26% when advantage is taken of the standing wave acoustic configuration by applying a frequency sweep with ultrasound frequency tuned to the modal acoustic modes of the cavity. This device allows sonoporation of adherent and suspended cells, and the use of regulation allows some environmental parameters such as the temperature of the medium to be overcome, resulting in the possibility of cell sonoporation even at ambient temperature.

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

    Ida, Masato


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

  3. Relationship between cavitation and water uptake in rose stems

    Doorn, van W.G.; Suiro, V.


    Cavitation in rose stems (Rosa hybrida L.) was assessed in both intact plants and excised flowers, by measurement of ultrasonic acoustic emissions at the stem surface and determination of the air-conductivity of 2.5-cm segments that were attached at one end to air at low pressure (0.01 MPa). On

  4. Relationship between cavitation and water uptake in rose stems

    Doorn, van W.G.; Suiro, V.


    Cavitation in rose stems (Rosa hybrida L.) was assessed in both intact plants and excised flowers, by measurement of ultrasonic acoustic emissions at the stem surface and determination of the air-conductivity of 2.5-cm segments that were attached at one end to air at low pressure (0.01 MPa). On sunn

  5. Hydrodynamic and acoustic analysis in 3-D of a section of main steam line to EPU conditions; Analisis hidrodinamico y acustico en 3D de una seccion de linea de vapor principal a condiciones de EPU

    Centeno P, J.; Castillo J, V.; Espinosa P, G. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Area de Ingenieria en Recursos Energeticos, Av. San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Nunez C, A.; Polo L, M. A., E-mail: [Comision Nacional de Seguridad Nuclear y Salvaguardias, Dr. Jose Ma. Barragan No. 779, Col. Narvarte, 03020 Mexico D. F. (Mexico)


    The objective of this word is to study the hydrodynamic and acoustic phenomenon in the main steam lines (MSLs). For this study was considered the specific case of a pipe section of the MSL, where is located the standpipe of the pressure and/or safety relief valve (SRV). In the SRV cavities originates a phenomenon known as whistling that generates a hydrodynamic disturbance of acoustic pressure waves with different tones depending of the reactor operation conditions. In the SRV cavities the propagation velocity of the wave can originate mechanical damage in the structure of the steam dryer and on free parts. The importance of studying this phenomenon resides in the safety of the integrity of the reactor pressure vessel. To dissipate the energy of the pressure wave, acoustic side branches (ASBs) are used on the standpipe of the SRVs. The ASBs are arrangements of compacted lattices similar to a porous medium, where the energy of the whistling phenomenon is dissipate and therefore the acoustic pressure load that impacts in particular to the steam dryers, and in general to the interns of the vessel, diminishes. For the analysis of the whistling phenomenon two three-dimensional (3-D) models were built, one hydrodynamic in stationary state and other acoustic for the harmonic times in transitory regimen, in which were applied techniques of Computational Fluid Dynamics. The study includes the reactor operation analysis under conditions of extended power up rate (EPU) with ASB and without ASB. The obtained results of the gauges simulated in the MSL without ASB and with ASB, show that tones with values of acoustic pressure are presented in frequency ranges between 160 and 200 Hz around 12 MPa and of 7 MPa, respectively. This attenuation of tones implies the decrease of the acoustic loads in the steam dryer and in the interns of the vessel that are designed to support pressures not more to 7.5 MPa approximately. With the above-mentioned is possible to protect the steam dryer

  6. Cavitation guide for control valves

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


    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.

  7. Gauging the likelihood of stable cavitation from ultrasound contrast agents.

    Bader, Kenneth B; Holland, Christy K


    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 I(CAV) = P(r)/f (where P(r) 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.

  8. Cavitation damage prediction for the JSNS mercury target vessel

    Naoe, Takashi; Kogawa, Hiroyuki; Wakui, Takashi; Haga, Katsuhiro; Teshigawara, Makoto; Kinoshita, Hidetaka; Takada, Hiroshi; Futakawa, Masatoshi


    The liquid mercury target system for the Japan Spallation Neutron Source (JSNS) at the Materials and Life science experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC) is designed to produce pulsed neutrons. The mercury target vessel in this system, which is made of type 316L stainless steel, is damaged by pressure wave-induced cavitation due to proton beam bombardment. Currently, cavitation damage is considered to be the dominant factor influencing the service life of the target vessel rather than radiation damage. In this study, cavitation damage to the interior surface of the target vessel was predicted on the basis of accumulated damage data from off-beam and on-beam experiments. The predicted damage was compared with the damage observed in a used target vessel. Furthermore, the effect of injecting gas microbubbles on cavitation damage was predicted through the measurement of the acoustic vibration of the target vessel. It was shown that the predicted depth of cavitation damage is reasonably coincident with the observed results. Moreover, it was confirmed that the injection of gas microbubbles had an effect on cavitation damage.

  9. Stabilizing in vitro ultrasound-mediated gene transfection by regulating cavitation.

    Lo, Chia-Wen; Desjouy, Cyril; Chen, Shing-Ru; Lee, Jyun-Lin; Inserra, Claude; Béra, Jean-Christophe; Chen, Wen-Shiang


    It is well known that acoustic cavitation can facilitate the inward transport of genetic materials across cell membranes (sonoporation). However, partially due to the unstationary behavior of the initiation and leveling of cavitation, the sonoporation effect is usually unstable, especially in low intensity conditions. A system which is able to regulate the cavitation level during sonication by modulating the applied acoustic intensity with a feedback loop is implemented and its effect on in vitro gene transfection is tested. The regulated system provided better time stability and reproducibility of the cavitation levels than the unregulated conditions. Cultured hepatoma cells (BNL) mixed with 10 μg luciferase plasmids are exposed to 1-MHz pulsed ultrasound with or without cavitation regulation, and the gene transfection efficiency and cell viability are subsequently assessed. Experimental results show that for all exposure intensities (low, medium, and high), stable and intensity dependent, although not higher, gene expression could be achieved in the regulated cavitation system than the unregulated conditions. The cavitation regulation system provides a better control of cavitation and its bioeffect which are crucial important for clinical applications of ultrasound-mediated gene transfection.

  10. Hydrodynamics and Roughness of Irregular Boundaries


    principle component analysis (PCA) similar to that used by Preston (2009) for ship- mounted multibeam data. Several variables derived from the...complex boundaries as well as characterization of acoustic and optical processes. Turbulent processes at the seabed are at the foundation of littoral...nearshore hydrodynamics, turbulence over rough beds influences optical and acoustic properties. Bed roughness also directly affects acoustic propagation in

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

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


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

  12. Prediction of Non-Cavitation Propeller Noise in Time Domain

    YE Jin-ming; XIONG Ying; XIAO Chang-run; BI Yi


    The blade frequency noise of non-cavitation propeller in a uniform flow is analyzed in time domain.The unsteady loading (dipole source) on the blade surface is calculated by a potential-based surface panel method.Then the timedependent pressure data is used as the input for Ffowcs Williams-Hawkings formulation to predict the acoustics pressure.The integration of noise source is performed over the true blade surface rather than the nothickness blade surface,and the effect of hub can be considered.The noise characteristics of the non-cavitation propeller and the numerical discretization forms are discussed.

  13. Cavitation in liquid helium

    Finch, R. D.; Kagiwada, R.; Barmatz, M.; Rudnick, I.


    Ultrasonic cavitation was induced in liquid helium over the temperature range 1.2 to 2.3 deg K, using a pair of identical transducers. The transducers were calibrated using a reciprocity technique and the cavitation threshold was determined at 90 kc/s. It was found that this threshold has a sharp peak at the lambda point, but is, at all temperatures quite low, with an approximate range of 0.001 to 0.01 atm. The significance of the results is discussed. (auth)

  14. Numerical investigation of the hydroelastic response in cavitating flow around a flexible hydrofoil

    Wu, Q.; Huang, B.; Wang, G. Y.; Wang, J. D.


    The objective of this paper is to investigate the hydroelastic response of cavitating flows around a flexible hydrofoil. The numerical simulations are performed by solving the incompressible and unsteady Reynolds Average Navier-Stokes (URANS) equations via the commercial CFD software ANSYS CFX. The k-ω SST turbulence model with the turbulence viscosity correction and the Kubota cavitation model are introduced to the present simulations. The results showed that the cavitation has significantly affected the foil deformation and the evolution of the transient cavity shape and the corresponding hydrodynamic response with time can be divided into three stages: during the development of the attached cavity, the cavity formed on the suction side of the flexible hydrofoil is much larger with a steeper slope of the cavity area, which is caused by the increase of the effective angle of attack due to the twist deformation. During the vortex-cavitation interaction process, the hydrodynamic loads for the rigid hydrofoil remain relatively flat, while that for the flexible hydrofoil fluctuates with high frequency because of the foil deformation, leading to a more complex cavitation pattern due to the interaction with the foil vibration. During the cavity shedding process, both the primary and the residual cavities shed downstream totally, together with the counter-rotational vortex structures, corresponding to a sharp drop in the hydrodynamic loads. The larger effective angle of attack leads to the advanced cavity inception of the next cavitation period.

  15. Ultrasound-enhanced thrombolysis using Definity as a cavitation nucleation agent.

    Datta, Saurabh; Coussios, Constantin-C; Ammi, Azzdine Y; Mast, T Douglas; de Courten-Myers, Gabrielle M; Holland, Christy K


    Ultrasound has been shown previously to act synergistically with a thrombolytic agent, such as recombinant tissue plasminogen activator (rt-PA) to accelerate thrombolysis. In this in vitro study, a commercial contrast agent, Definity, was used to promote and sustain the nucleation of cavitation during pulsed ultrasound exposure at 120 kHz. Ultraharmonic signals, broadband emissions and harmonics of the fundamental were measured acoustically by using a focused hydrophone as a passive cavitation detector and used to quantify the level of cavitation activity. Human whole blood clots suspended in human plasma were exposed to a combination of rt-PA, Definity and ultrasound at a range of ultrasound peak-to-peak pressure amplitudes, which were selected to expose clots to various degrees of cavitation activity. Thrombolytic efficacy was determined by measuring clot mass loss before and after the treatment and correlated with the degree of cavitation activity. The penetration depth of rt-PA and plasminogen was also evaluated in the presence of cavitating microbubbles using a dual-antibody fluorescence imaging technique. The largest mass loss (26.2%) was observed for clots treated with 120-kHz ultrasound (0.32-MPa peak-to-peak pressure amplitude), rt-PA and stable cavitation nucleated by Definity. A significant correlation was observed between mass loss and ultraharmonic signals (r = 0.85, p cavitation activity. Stable cavitation activity plays an important role in enhancement of thrombolysis and can be monitored to evaluate the efficacy of thrombolytic treatment.


    BAI Li-xin; XU Wei-lin; TIAN Zhong; LI Nai-wen


    This article investigated an existing steady pattern of collapse and rebound (disintegration and aggregation) of cavitation bubbles near rigid boundary in acoustic field. A deformation process of cavitation bubble was accomplished in two acoustic cycles, namely, a spherical bubble collapsed towards the boundary to its minimum volume and then rebounded and grew into a toroidal bubble (or two individual bubbles) in one acoustic cycle, and the toroidal bubble (or two individual bubbles) collapsed towards the center offing to its minimum volume, and then rebounded into a spherical bubble in the next acoustic cycle. Inertia force plays a key role in the transition between these two states. The microjet produced during the collapse of spherical bubble and the shock wave produced during the collapse of toroidal bubble (or two individual bubbles) impacts the boundary alternately. A cavitation bubble operating in this pattern can thus be an effective corrosion mechanism of rigid boundary.

  17. Cavitation Instabilities in Inducers


    gas handling turbomachines . The fluctuation of the cavity length is plotted in Fig.8 under the surge mode oscillation vi . The major differences...Cavitation Instabilities of Turbomachines .” AIAA Journal of Propulsion and Power, Vol.17, No.3, 636-643. [5] Tsujimoto, Y., (2006), “Flow Instabilities in

  18. Cavitation during wire brushing

    Li, Bo; Zou, Jun; Ji, Chen


    In our daily life, brush is often used to scrub the surface of objects, for example, teeth, pots, shoes, pool, etc. And cleaning rust and stripping paint are accomplished using wire brush. Wire brushes also can be used to clean the teeth for large animals, such as horses, crocodiles. By observing brushing process in water, we capture the cavitation phenomenon on the track of moving brush wire. It shows that the cavitation also can affect the surface. In order to take clear and entire pictures of cavity, a simplified model of one stainless steel wire brushing a boss is adopted in our experiment. A transparent organic tank filled with deionized water is used as a view box. And a high speed video camera is used to record the sequences. In experiment, ambient pressure is atmospheric pressure and deionized water temperature is kept at home temperature. An obvious beautiful flabellate cavity zone appears behind the moving steel wire. The fluctuation of pressure near cavity is recorded by a hydrophone. More movies and pictures are used to show the behaviors of cavitation bubble following a restoring wire. Beautiful tracking cavitation bubble cluster is captured and recorded to show.

  19. Ozone and Cavitation Combination

    Carreon, Ernestina; Traversoni, Leonardo


    From laboratory measurements it is well known that the addition of ozone and cavitation enhances the properties of both, understanding for that the ones related to disinfection and carbon removal from waste water. This paper shows modeling of such phenomena that gives some light to the understanding of it and also provides the opportunity to improve the effectiveness of the current procedures.

  20. Numerical Modeling of Unsteady Cavitating Flows around a Stationary Hydrofoil

    Antoine Ducoin


    Full Text Available The objective of this paper is to evaluate the predictive capability of three popular transport equation-based cavitation models for the simulations of partial sheet cavitation and unsteady sheet/cloud cavitating flows around a stationary NACA66 hydrofoil. The 2D calculations are performed by solving the Reynolds-averaged Navier-Stokes equation using the CFD solver CFX with the k-ω SST turbulence model. The local compressibility effect is considered using a local density correction for the turbulent eddy viscosity. The calculations are validated with experiments conducted in a cavitation tunnel at the French Naval Academy. The hydrofoil has a fixed angle of attack of α=6° with a Reynolds number of Re = 750,000 at different cavitation numbers σ. Without the density modification, over-prediction of the turbulent viscosity near the cavity closure reduces the cavity length and modifies the cavity shedding characteristics. The results show that it is important to capture both the mean and fluctuating values of the hydrodynamic coefficients because (1 the high amplitude of the fluctuations is critical to capturing the extremes of the loads to ensure structural safety and (2 the need to capture the frequency of the fluctuations, to avoid unwanted noise, vibrations, and accelerated fatigue issues.

  1. A Theoretical Investigation of Acoustic Cavitation.


    Grebogi , Ott, and Yorke [22] are employed. This analysis will show that the type of damping used in the equations dramatically alters the results of...P. Crutchfield, "Chaotic States of Anharmonic Systems in Periodic Fields", Phys. Rev. Letters 43, 1743-1747 (1979). 22. C. Grebogi , E. Ott, and J. A

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

    Annamalai, Subramanian; Balachandar, S.


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

  3. Implicit large eddy simulation of unsteady cloud cavitation around a plane- convex hydrofoil

    罗先武; 季斌


    The present paper focuses on the erosive cavitation behavior around a plane convex hydrofoil. The Zwart-Gerber-Belamri cavitation model is implemented in a library form to be used with the OpenFOAM. The implicit large eddy simulation (ILES) is app- lied to analyze the three dimensional unsteady cavitating flow around a plane convex hydrofoil. The numerical results in the cases under the hydrodynamic-conditions, which were experimentally tested at the high speed cavitation tunnel of the École Polytechnique Fédérale de Lausanne (EPFL), clearly show the sheet cavitation development, the shedding and the collapse of vapor clouds. It is noted that the cavitation evolutions including the maximum vapor length, the detachment and the oscillation frequency, are captured fairly well. Furthermore, the pressure pulses due to the cavitation development as well as the complex vortex structures are reasona- bly well predicted. Consequently, it may be concluded that the present numerical method can be used to investigate the unsteady cavitation around hydrofoils with a satisfactory accuracy.

  4. Research on Cavitation Regions of Upstream Pumping Mechanical Seal Based on Dynamic Mesh Technique

    Huilong Chen


    Full Text Available In order to study the cavitation area of the Upstream Pumping Mechanical Seal, three-dimensional microgap inner flow field of the Upstream Pumping Mechanical Seal was simulated with multiphase flow cavitation model and dynamic mesh technique based on hydrodynamic lubrication theory. Furthermore, the simulated result was compared with the experimental data. The results show that the simulated result with the Zwart-Gerber-Belamri cavitation model was much closer to the experimental data. The area of cavitation inception mainly occurred at the concave side of the spiral groove and surrounding region without spiral grooves, which was nearly covered by the inner diameter to roots of grooves; in addition, the region near the surface of the stationary ring was primary cavitation location. The area of cavitation has little relationship with the medium pressure; however, it became larger following increasing rotating speed in the range of researched operating conditions. Moreover the boundary of cavitated area was transformed from smooth to rough, which occurred in similar film thickness. When cavitation number was decreasing, which was conducive to improving the lubrication performance of sealed auxiliary, it made the sealing stability decline.

  5. Inertial cavitation in theranostic nanoemulsions with simultaneous pulsed laser and low frequency ultrasound excitation

    Arnal, Bastien; Wei, Chen-Wei; Xia, Jinjun; Pelivanov, Ivan M.; Lombardo, Michael; Perez, Camilo; Matula, Thomas J.; Pozzo, Danilo; O'Donnell, Matthew


    Ultrasound-induced inertial cavitation is a mechanical process used for site-localized therapies such as non-invasive surgery. Initiating cavitation in tissue requires very high intensity focused ultrasound (HIFU) and low-frequencies. Hence, some applications like thrombolysis require targeted contrast agents to reduce peak intensities and the potential for secondary effects. A new type of theranostic nanoemulsion has been developed as a combined ultrasound (US)/photoacoustic(PA) agent for molecular imaging and therapy. It includes a nanoscale emulsion core encapsulated with a layer of gold nanospheres at the water/ oil interface. Its optical absorption exhibits a spectrum broadened up to 1100 nm, opening the possibility that 1064 nm light can excite cavitation nuclei. If optically-excited nuclei are produced at the same time that a low-frequency US wave is at peak negative pressure, then highly localized therapies based on acoustic cavitation may be enabled at very low US pressures. We have demonstrated this concept using a low-cost, low energy, portable 1064 nm fiber laser in conjunction with a 1.24 MHz US transducer for simultaneous laser/US excitation of nanoemulsions. Active cavitation detection from backscattered signals indicated that cavitation can be initiated at very low acoustic pressures (less than 1 MPa) when laser excitation coincides with the rarefaction phase of the acoustic wave, and that no cavitation is produced when light is delivered during the compressive phase. US can sustain cavitation activity during long acoustic bursts and stimulate diffusion of the emulsion, thus increasing treatment speed. An in vitro clot model has been used to demonstrate combined US and laser excitation of the nanoemulsion for efficient thrombolysis.

  6. Characteristics of Vibration Induced by Cavitation

    WANG Guo-yu; TAO Lei; LIU Shu-yan; QIAN Jian-jun


    Cavitation-induced vibration characteristics and the relations between the vibration and cavitation are studied. Cavitation vibrations are measured around a model hollow-jet valve by an accelerometer under cavitating and non-cavitating conditions. The measurement data is analyzed by FFT method. The corresponding cavitating flow patterns are photographed by a high-speed camera with an xenon flash lamp. The frequency band of the vibration induced by cavitation is determined. To compare the vibration intensities under different cavitation conditions, a definition of vibration acceleration level is introduced based on power spectral density of the vibration. By the analysis of vibration, the definitions of characteristic cavitation number are suggested. According to these cavitation numbers, the cavitation process is divided into three stages, that is, incipient cavitation, subcavitation and supercavitation.

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

    Hodnett, M.; Zeqiri, B.


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

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

    Hodnett, M; Zeqiri, B [National Physical Laboratory, Queens Road, Teddington, Middlesex, TW11 0LW (United Kingdom)


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

  9. Shock Waves in Cloud Cavitation

    Brennen, C. E.; Reisman, G. E.; Wang, Y.-C.


    Thie paper described experimental and computational investigations of the dynamics of clouds of cavitation bubbles. Recent studies have confirmed that the interactions between bubbles as they are manifest in the dynamics of bubble clouds lead to generation of very large impulsive pressures which, in turn, cause substantial enhancement of the radiated noise and the material damage which results from this form of cavitation. The experimental program focuses on cloud cavitation formed on th...

  10. Dynamics and measurement of cavitation bubble

    CHEN Weizhong; LIU Ya'nan; HUANG Wei; GAO Xianxian


    Based on the introduction of international progress, our investigations on acoustic cavitation have been reported. Firstly we considered the cavity's dynamics under the drive of the asymmetrical acoustic pressure. An aspheric dynamical model was proposed and a new stable and aspheric solution was found in numerical simulation of the theoretical framework of the aspheric model. Then, a dual Mie-scattering technique was developed to measure the cavity's aspheric pulsation. A significant asynchronous pulsation signal between two Mie-scattering channels was caught in the case of large cavity driven by low acoustic pressure. As a direct deduction, we observed an evidence of cavity's aspheric pulsation. Furthermore, we studied the dependency of the asynchronous pulsation signal on the various parameters, such as the amplitude and frequency of the driving acoustic pressure, and the surface tension, viscosity and gas concentration of the liquid. Finally, we introduced a new numeric imaging technique to measure the shapes of the periodic pulsation cavities. The time-resolution was in the order of 20 ns, one order of magnitude lower than that in the previous work, say, 200 ns.

  11. Phase-shift nano-emulsions induced cavitation and ablation during high intensity focused ultrasound exposure

    Qiao, Yangzi; Yin, Hui; Chang, Nan; Wan, Mingxi


    Phase-shift Nano-emulsions (PSNEs) with a small initial diameter in nanoscale have the potential to leak out of the blood vessels and to accumulate at target point of tissue. At desired location, PSNEs can undergo acoustic droplet vaporization (ADV) process, change into gas bubbles and enhance focused ultrasound efficiency. The aim of this work was to provide spatial and temporal information on PSNE induced cavitation and ablation effects during pulsed high intensity focused ultrasound (HIFU) exposure. The PSNEs were composed of perfluorohaxane (PFH) and bovine serum albumin (BSA), and then uniformly distributed in a transparent polyacrylamide phantom. The Sonoluminescence (SL) method was employed to visualize the cavitation distribution and formation process of PSNEs induced cavitation. For the phantom which was used for ablation observation, heat sensitive BSA was added. When the temperature generated by ultrasound exposure was high enough to denature BSA, the transparent phantom would turn out white lesions. The shape of the lesion and the formation process were compared with those of cavitation. Each of the pulse contained 12 cycles for a duration of 10 µs. And the duty cycle changed from 1:10 to 1:40. The total "on" time of HIFU was 2s. PSNE can evidently accelerate cavitation emitting bright SL in pre-focal region. The cavitation was generated layer by layer towards the transducer. The formed bubble wall can block acoustic waves transmitting to the distal end. And the lesion appeared to be separated into two parts. One in pre-focal region stemmed from one point and grew quickly toward the transducer. The other in focal region was formed by merging some small white dots, and grew much slower. The influence of duty cycle has also been examined. The lower duty cycle with longer pulse-off time would generate more intense cavitation, however, smaller lesion. Bubble cloud gradually developed within phantom would greatly influence the cavitation and ablation

  12. The numerical study of the cavitation-structure interaction around 3D flexible hydrofoil

    Shi-liang, Hu; Ying, Chen; Chuan-jing, Lu


    The closely coupled approach combined the Finite Volume Method (FVM) solver and the Finite Element Method (FEM) solver is applied to simulation the cavitation-structure interaction of a 3D cantilevered flexible hydrofoil in water tunnel. In the cavitating flow, the elastic hydrofoil would deform or vibrate in bending and twisting mode. And the motion of the foil would affect the characteristics of the cavity and the hydrodynamic load on the foil in turn. With smaller cavitation numbers (σv=2.15), the frequency spectrum of the lift on the foil would contain two frequencies which are associated to the cavity shedding and the first bend frequency of the hydrofoil. With larger cavitation number (σv=2.55), the frequency of the lift is completely dominated by the natural frequency of the foil.

  13. Controlled Cavitation in Microfluidic Systems

    Zwaan, Ed; le Gac, Severine; Tsuji, Kinko; Ohl, C.D.


    We report on cavitation in confined microscopic environments which are commonly called microfluidic or lab-on-a-chip systems. The cavitation bubble is created by focusing a pulsed laser into these structures filled with a lght-absorbing liquid. At hte center of a 20 mu m thick and 1 mm wide channel,


    Wu Lei


    A new model, which involves viscous and multi-phase effects, was given to study cavitating flows. A local compressible model was established by introducing a density-pressure function to account for the two-phase flow of water/vapor and the transition from one phase to the other. An algorithm for calculating variable-density N-S equations of cavitating flow problem was put forward. The present method yields reasonable results for both steady and unsteady cavitating flows in 2D and 3D cases. The numerical results of unsteady character of cavitating flows around hydrofoils coincide well with experimental data. It indicates the feasibility to apply this method to a variety of cavitating flows of practical problems.

  15. Monitoring of transient cavitation induced by ultrasound and intense pulsed light in presence of gold nanoparticles.

    Sazgarnia, Ameneh; Shanei, Ahmad; Shanei, Mohammad Mahdi


    One of the most important challenges in medical treatment is invention of a minimally invasive approach in order to induce lethal damages to cancer cells. Application of high intensity focused ultrasound can be beneficial to achieve this goal via the cavitation process. Existence of the particles and vapor in a liquid decreases the ultrasonic intensity threshold required for cavitation onset. In this study, synergism of intense pulsed light (IPL) and gold nanoparticles (GNPs) has been investigated as a means of providing nucleation sites for acoustic cavitation. Several approaches have been reported with the aim of cavitation monitoring. We conducted the experiments on the basis of sonochemiluminescence (SCL) and chemical dosimetric methods. The acoustic cavitation activity was investigated by determining the integrated SCL signal acquired over polyacrylamide gel phantoms containing luminol in the presence and absence of GNPs in the wavelength range of 400-500 nm using a spectrometer equipped with cooled charged coupled devices (CCD) during irradiation by different intensities of 1 MHz ultrasound and IPL pulses. In order to confirm these results, the terephthalic acid chemical dosimeter was utilized as well. The SCL signal recorded in the gel phantoms containing GNPs at different intensities of ultrasound in the presence of intense pulsed light was higher than the gel phantoms without GNPs. These results have been confirmed by the obtained data from the chemical dosimetry method. Acoustic cavitation in the presence of GNPs and intense pulsed light has been suggested as a new approach designed for decreasing threshold intensity of acoustic cavitation and improving targeted therapeutic effects. Copyright © 2013 Elsevier B.V. All rights reserved.

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

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


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

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

    Zeqiri, Bajram; Hodnett, Mark; Carroll, Anthony J


    This paper describes investigations of the spatial distribution of cavitation activity generated within an ultrasonic cleaning vessel, undertaken using a novel cavitation sensor concept. The new sensor monitors high frequency acoustic emissions (>1 MHz) generated by micron-sized bubbles driven into acoustic cavitation by the applied acoustic field. Novel design features of the sensor, including its hollow, cylindrical shape, provide the sensor with spatial resolution, enabling it to associate the megahertz acoustic emissions produced by the cavitating bubbles with specific regions of space within the vessel. The performance of the new sensor has been tested using a 40 kHz ultrasonic cleaner employing four transducers and operating at a nominal electrical power of 140 W under controlled conditions. The results demonstrate the ability of the sensors to identify 'hot-spots' and 'cold-spots' in cavitation activity within the vessel, and show good qualitative agreement with an assessment of the spatial distribution of cavitation determined through erosion monitoring of thin sheets of aluminium foil. The implications of the studies for the development of reliable methods of quantifying the performance of cleaning vessels are discussed in detail.

  18. Study of Cavitation Shedding Dynamics on a NACA0015 Hydrofoil Using X-Ray Densitometry

    Ganesh, Harish; Wu, Juliana; Ceccio, Steven


    Cavitation dynamics on the NACA0015 hydrofoil at several attack angles are found to be spectrally rich, being multi-modal with abrupt changes in Strouhal number with change in cavitation number. Present study focusses on identifying the physical mechanisms responsible for the change in cavitation dynamics on a NACA0015 hydrofoil in a re-circulating water tunnel using time resolved X-ray densitometry. Time-resolved void fraction flow fields obtained using X-ray densitometry, synchronized with acoustic noise measurements using a hydrophone, are used to identify different flow features and mechanisms that are responsible for the change in the observed spectral behavior. It is shown that under higher cavitation numbers, the shedding mechanism is predominantly re-entrant liquid flow based, but as the cavitation number drops many different processes are at play. At lower cavitation numbers, the shed cavity cloud collapse arrests cavity growth and this results in altered cycle dynamics and hence the Strouhal number. In addition, propagation bubbly shock waves are also found to be a dominant mechanism of shedding for certain conditions. The multi-modal nature of the acoustic pressure signature is explained by presence of different flow features, which could be concurrent or alternating. Office of Naval Research.

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

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


    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.

  20. A tissue phantom for visualization and measurement of ultrasound-induced cavitation damage.

    Maxwell, Adam D; Wang, Tzu-Yin; Yuan, Lingqian; Duryea, Alexander P; Xu, Zhen; Cain, Charles A


    Many ultrasound studies involve the use of tissue-mimicking materials to research phenomena in vitro and predict in vivo bioeffects. We have developed a tissue phantom to study cavitation-induced damage to tissue. The phantom consists of red blood cells suspended in an agarose hydrogel. The acoustic and mechanical properties of the gel phantom were found to be similar to soft tissue properties. The phantom's response to cavitation was evaluated using histotripsy. Histotripsy causes breakdown of tissue structures by the generation of controlled cavitation using short, focused, high-intensity ultrasound pulses. Histotripsy lesions were generated in the phantom and kidney tissue using a spherically focused 1-MHz transducer generating 15 cycle pulses, at a pulse repetition frequency of 100 Hz with a peak negative pressure of 14 MPa. Damage appeared clearly as increased optical transparency of the phantom due to rupture of individual red blood cells. The morphology of lesions generated in the phantom was very similar to that generated in kidney tissue at both macroscopic and cellular levels. Additionally, lesions in the phantom could be visualized as hypoechoic regions on a B-mode ultrasound image, similar to histotripsy lesions in tissue. High-speed imaging of the optically transparent phantom was used to show that damage coincides with the presence of cavitation. These results indicate that the phantom can accurately mimic the response of soft tissue to cavitation and provide a useful tool for studying damage induced by acoustic cavitation.

  1. Mapping of cavitational activity in a pilot plant dyeing equipment.

    Actis Grande, G; Giansetti, M; Pezzin, A; Rovero, G; Sicardi, S


    C). Different liquid flow rates were tested to investigate the effect of the hydrodynamics characterising the equipment. The mapping of the cavitation intensity in the pilot-plant machinery was performed to achieve with the following goals: (a) to evaluate the influence of turbulence on the cavitation intensity, and (b) to determine the optimal distance from the ultrasound device at which a fabric should be positioned, this parameter being a compromise between the cavitation intensity (higher next to the transducer) and the US field uniformity (achieved at some distance from this device). By carrying out dyeing tests of wool fabrics in the prototype unit, consistent results were confirmed by comparison with the mapping of cavitation intensity.

  2. Passive cavitation imaging with ultrasound arrays.

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


    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.

  3. Spatiotemporal evolution of cavitation dynamics exhibited by flowing microbubbles during ultrasound exposure.

    Choi, James J; Coussios, Constantin-C


    Ultrasound and microbubble-based therapies utilize cavitation to generate bioeffects, yet cavitation dynamics during individual pulses and across consecutive pulses remain poorly understood under physiologically relevant flow conditions. SonoVue(®) microbubbles were made to flow (fluid velocity: 10-40 mm/s) through a vessel in a tissue-mimicking material and were exposed to ultrasound [frequency: 0.5 MHz, peak-rarefactional pressure (PRP): 150-1200 kPa, pulse length: 1-100,000 cycles, pulse repetition frequency (PRF): 1-50 Hz, number of pulses: 10-250]. Radiated emissions were captured on a linear array, and passive acoustic mapping was used to spatiotemporally resolve cavitation events. At low PRPs, stable cavitation was maintained throughout several pulses, thus generating a steady rise in energy with low upstream spatial bias within the focal volume. At high PRPs, inertial cavitation was concentrated in the first 6.3 ± 1.3 ms of a pulse, followed by an energy reduction and high upstream bias. Multiple pulses at PRFs below a flow-dependent critical rate (PRF(crit)) produced predictable and consistent cavitation dynamics. Above the PRF(crit), energy generated was unpredictable and spatially biased. In conclusion, key parameters in microbubble-seeded flow conditions were matched with specific types, magnitudes, distributions, and durations of cavitation; this may help in understanding empirically observed in vivo phenomena and guide future pulse sequence designs.

  4. Ultrasonic cavitation for disruption of microalgae.

    Greenly, Justin M; Tester, Jefferson W


    Challenges with mid-stream fractionation steps in proposed microalgae biofuel pathways arise from the typically dilute cell density in growth media, micron scale cell sizes, and often durable cell walls. For microalgae to be a sustainable source of biofuels and co-products, efficient fractionation by some method will be necessary. This study evaluates ultrasonic cell disruption as a processing step that fractionates microalgae. A range of species types with different sizes and cell wall compositions were treated. The initial seconds of sonication offered the most significant disruption, even for the more durable Nannochloropsis cells. Following this initial period, diminishing effectiveness was attributed, by acoustic measurements, to attenuation of the ultrasound in the ensuing cloud of cavitating bubbles. At longer exposure times, differences between species were more pronounced. Processing higher concentrations of Isochrysis slowed cell disintegration only marginally, making the expenditure of energy more worthwhile.

  5. Research and development of improved cavitating jets for deep-hole drilling

    Johnson, V.E. Jr.; Lindenmuth, W.T.; Chahine, G.L.; Conn, A.F.; Frederick, G.S.


    Improved cavitating nozzles have been developed as part of an on-going program to increase the rate of penetration of deep-hole drill bits. Based on the four criteria of: incipient cavitation number, amplitude of pressure fluctuation (and hence enhanced structuring of the jet flow), rock cutting, and cleaning chips from the hole bottom - these new, STRATOJET (STRuctured Acoustically Tuned Oscillating JET) cavitating nozzle systems have out-performed both conventional drill bit nozzles and the basic CAVIJET cavitating jets. Although nozzle designs which provide large amplitude pressure modulations are now available for the operation in water, additional research is needed to optimize self-resonating jets for use: (a) in mud, (b) in specific drill bit designs, and (c) at higher system pressures than now currently used for deep-hole drilling.

  6. Dynamic response of cavitating turbomachines

    Ng, S. L.


    Stimulated by the pogo instability encountered in many liquid propellant rockets, the dynamic behavior of cavitating inducers is discussed. An experimental facility where the upstream and downstream flows of a cavitating inducer could be perturbed was constructed and tested. The upstream and downstream pressure and mass flow fluctuations were measured. Matrices representing the transfer functions across the inducer pump were calculated from these measurements and from the hydraulic system characteristics for two impellers in various states of cavitation. The transfer matrices when plotted against the perturbing frequency showed significant departure from steady state or quasi-steady predictions especially at higher frequencies.

  7. Radial Shock Wave Devices Generate Cavitation.

    Nikolaus B M Császár

    Full Text Available Conflicting reports in the literature have raised the question whether radial extracorporeal shock wave therapy (rESWT devices and vibrating massage devices have similar energy signatures and, hence, cause similar bioeffects in treated tissues.We used laser fiber optic probe hydrophone (FOPH measurements, high-speed imaging and x-ray film analysis to compare fundamental elements of the energy signatures of two rESWT devices (Swiss DolorClast; Electro Medical Systems, Nyon, Switzerland; D-Actor 200; Storz Medical, Tägerwillen, Switzerland and a vibrating massage device (Vibracare; G5/General Physiotherapy, Inc., Earth City, MO, USA. To assert potential bioeffects of these treatment modalities we investigated the influence of rESWT and vibrating massage devices on locomotion ability of Caenorhabditis elegans (C. elegans worms.FOPH measurements demonstrated that both rESWT devices generated acoustic waves with comparable pressure and energy flux density. Furthermore, both rESWT devices generated cavitation as evidenced by high-speed imaging and caused mechanical damage on the surface of x-ray film. The vibrating massage device did not show any of these characteristics. Moreover, locomotion ability of C. elegans was statistically significantly impaired after exposure to radial extracorporeal shock waves but was unaffected after exposure of worms to the vibrating massage device.The results of the present study indicate that both energy signature and bioeffects of rESWT devices are fundamentally different from those of vibrating massage devices.Prior ESWT studies have shown that tissues treated with sufficient quantities of acoustic sound waves undergo cavitation build-up, mechanotransduction, and ultimately, a biological alteration that "kick-starts" the healing response. Due to their different treatment indications and contra-indications rESWT devices cannot be equated to vibrating massage devices and should be used with due caution in clinical

  8. Flow Instabilities in Cavitating and Non-Cavitating Pumps


    stall and surge may occur in non-cavitating turbomachines at flow rates smaller than design. Rotating stall is a local instability at the...turbomachinery which is basically not dependent on the hydraulic system in which the turbomachine is installed. The stalled region rotates faster than impeller...rate and without significant head decrease. So, it is required to confirm the absence of cavitation instabilities, whenever the turbomachine is

  9. Microleakage of Cavit, CavitW, CavitG and IRM by impedance spectroscopy.

    Jacquot, B M; Panighi, M M; Steinmetz, P; G'Sell, C


    The aim of this study was to quantify the sealing ability of four temporary filling materials over 9 days using a new electrochemical technique. Fifty-two extracted human maxillary bicuspids were selected and prepared for the measurements. They were divided into four groups of 12 teeth each, in addition to two positive and two negative controls. After preparation of the endodontic access cavity the sealing ability was registered. After a randomization procedure one group was obturated with IRM, another group with Cavit, a third group with CavitW and the last group with CavitG. The sealability was measured just after obturation (time 0) and after days 1, 2, 3, 4, 7 and 9. The results showed that the IRM group was significantly more watertight than the different Cavit formulations. Throughout the experiment no significant difference was noticed between the Cavit and CavitW groups (P > 0.05). The CavitG group was significantly less watertight throughout the measurements (P < 0.05).

  10. Fracture of elastomers by cavitation

    Hamdi, Adel


    Cavitation phenomenon is studied in rubber-like materials by combining experimental, theoretical and numerical approaches. Specific tests are carried out on a Styrene Butadiene Rubber to point out main characteristics of cavitation phenomenon. Hydrostatic depression is numerically modelled using finite element method. Numerical results are compared to Ball\\'s and Hou & Abeyaratne\\'s models with regard to cavity nucleation in the material. Both models well fit experimental observations suggesting that the cavitation nucleation in elastomers depends on the confinement degree of the specimen. Finally, critical hydrostatic pressure and critical global deformation are proved to govern cavitation nucleation in the studied material. Critical loadings are identified by comparing experimental and numerical load-displacement curves. © 2013 Elsevier Ltd.

  11. Cavitation inception from bubble nuclei

    Mørch, Knud Aage


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

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

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


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

  13. Dynamic Behavior of Microbubbles during Long Ultrasound Tone-Burst Excitation: Mechanistic Insights into Ultrasound-Microbubble Mediated Therapeutics Using High-Speed Imaging and Cavitation Detection.

    Chen, Xucai; Wang, Jianjun; Pacella, John J; Villanueva, Flordeliza S


    Ultrasound (US)-microbubble (MB)-mediated therapies have been found to restore perfusion and enhance drug/gene delivery. On the presumption that MBs do not persist during long US exposure under high acoustic pressures, most schemes use short US pulses when a high US pressure is employed. However, we recently observed an enhanced thrombolytic effect using long US pulses at high acoustic pressures. Therefore, we explored the fate of MBs during long tone-burst exposures (5 ms) at various acoustic pressures and MB concentrations via direct high-speed optical observation and passive cavitation detection. MBs first underwent stable or inertial cavitation depending on the acoustic pressure and then formed gas-filled clusters that continued to oscillate, break up and form new clusters. Cavitation detection confirmed continued, albeit diminishing, acoustic activity throughout the 5-ms US excitation. These data suggest that persisting cavitation activity during long tone bursts may confer additional therapeutic effects.


    DONG Zhi-yong; LU Yang-quan; JU Wen-jie; CAI Xin-ming; DING Chun-sheng


    This experimental investigation was systematically conducted with the aid of a non-circulating water tunnel in the Hydraulics Laboratory at Zhejiang University of Technology in China.The test velocity is between 20m/s and 40m/s.The least air concentration to prevent cavitation erosion lies between 1.7% and 4.5%.Pressure waveforms with and without aeration in cavitation and cavitation erosion regions were measured.Time-averaged pressure profiles with and without aeration were compared.Pressure characteristics corresponding to least air concentration to prevent cavitation erosion in cavitation and cavitation erosion regions were analyzed.

  15. Compare ultrasound-mediated heating and cavitation between flowing polymer- and lipid-shelled microbubbles during focused ultrasound exposures.

    Zhang, Siyuan; Zong, Yujin; Wan, Mingxi; Yu, Xiaojun; Fu, Quanyou; Ding, Ting; Zhou, Fanyu; Wang, Supin


    This paper compares the efficiency of flowing polymer- and lipid-shelled microbubbles (MBs) in the heating and cavitation during focused ultrasound exposures. Temperature and cavitation activity were simultaneously measured as the two types of shelled MBs and saline flowing through a 3 mm diameter vessel in the phantom with varying flow velocities (0-20 cm/s) at different acoustic power levels (0.6-20 W) with each exposure for 5 s. Temperature and cavitation for the lipid-shelled MBs were higher than those for the polymer-shelled MBs. Temperature rise decreased with increasing flow velocities for the two types of shelled MBs and saline at acoustic power 1.5 W. At acoustic power 11.1 W, temperature rise increased with increasing flow velocities for the lipid-shelled MBs. For the polymer-shelled MBs, the temperature rise increased with increasing flow velocities from 3-15 cm/s and decreased at 20 cm/s. Cavitation increased with increasing flow velocity for the two shelled MBs and there were no significant changes of cavitation with increasing flow velocities for saline. These results suggested that lipid-shelled MBs may have a greater efficiency than polymer-shelled MBs in heating and cavitation during focused ultrasound exposures.

  16. Relativistic hydrodynamics

    Luciano, Rezzolla


    Relativistic hydrodynamics is a very successful theoretical framework to describe the dynamics of matter from scales as small as those of colliding elementary particles, up to the largest scales in the universe. This book provides an up-to-date, lively, and approachable introduction to the mathematical formalism, numerical techniques, and applications of relativistic hydrodynamics. The topic is typically covered either by very formal or by very phenomenological books, but is instead presented here in a form that will be appreciated both by students and researchers in the field. The topics covered in the book are the results of work carried out over the last 40 years, which can be found in rather technical research articles with dissimilar notations and styles. The book is not just a collection of scattered information, but a well-organized description of relativistic hydrodynamics, from the basic principles of statistical kinetic theory, down to the technical aspects of numerical methods devised for the solut...

  17. Robust acoustic wave manipulation of bubbly liquids

    Gumerov, N. A., E-mail: [Institute for Advanced Computer Studies, University of Maryland, College Park, Maryland 20742 (United States); Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Akhatov, I. S. [Center for Design, Manufacturing and Materials, Skolkovo Institute of Science and Technology, Moscow 143026 (Russian Federation); Ohl, C.-D. [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore); Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Sametov, S. P. [Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Khazimullin, M. V. [Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Institute of Molecule and Crystal Physics, Ufa Research Center of Russian Academy of Sciences, Ufa 450054 (Russian Federation); Gonzalez-Avila, S. R. [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore)


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

  18. Modeling liquid hydrogen cavitating flow with the full cavitation model

    Zhang, X.B.; Qiu, L.M.; Qi, H.; Zhang, X.J.; Gan, Z.H. [Institute of Refrigeration and Cryogenic Engineering, Zhejiang University, Hangzhou 310027 (China)


    Cavitation is the formation of vapor bubbles within a liquid where flow dynamics cause the local static pressure to drop below the vapor pressure. This paper strives towards developing an effective computational strategy to simulate liquid hydrogen cavitation relevant to liquid rocket propulsion applications. The aims are realized by performing a steady state computational fluid dynamic (CFD) study of liquid hydrogen flow over a 2D hydrofoil and an axisymmetric ogive in Hord's reports with a so-called full cavitation model. The thermodynamic effect was demonstrated with the assumption of thermal equilibrium between the gas phase and liquid phase. Temperature-dependent fluid thermodynamic properties were specified along the saturation line from the ''Gaspak 3.2'' databank. Justifiable agreement between the computed surface pressure, temperature and experimental data of Hord was obtained. Specifically, a global sensitivity analysis is performed to examine the sensitivity of the turbulent computations to the wall grid resolution, wall treatments and changes in model parameters. A proper near-wall model and grid resolution were suggested. The full cavitation model with default model parameters provided solutions with comparable accuracy to sheet cavitation in liquid hydrogen for the two geometries. (author)

  19. Theoretical hydrodynamics

    Milne-Thomson, L M


    This classic exposition of the mathematical theory of fluid motion is applicable to both hydrodynamics and aerodynamics. Based on vector methods and notation with their natural consequence in two dimensions - the complex variable - it offers more than 600 exercises and nearly 400 diagrams. Prerequisites include a knowledge of elementary calculus. 1968 edition.

  20. Hydrodynamic bearings

    Bonneau, Dominique; Souchet, Dominique


    This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.

  1. Ship Hydrodynamics

    Lafrance, Pierre


    Explores in a non-mathematical treatment some of the hydrodynamical phenomena and forces that affect the operation of ships, especially at high speeds. Discusses the major components of ship resistance such as the different types of drags and ways to reduce them and how to apply those principles for the hovercraft. (GA)

  2. On the hydrodynamics of rocket propellant engine inducers and turbopumps

    d'Agostino, L.


    The lecture presents an overview of some recent results of the work carried out at Alta on the hydrodynamic design and rotordynamic fluid forces of cavitating turbopumps for liquid propellant feed systems of modern rocket engines. The reduced order models recently developed for preliminary geometric definition and noncavitating performance prediction of tapered-hub axial inducers and centrifugal turbopumps are illustrated. The experimental characterization of the rotordynamic forces acting on a whirling four-bladed, tapered-hub, variable-pitch high-head inducer, under different load and cavitation conditions is presented. Future perspectives of the work to be carried out at Alta in this area of research are briefly illustrated.

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

    Hattori, Shuji; Motoi, Yoshihiro [Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fuku-shi, Fukui 910-8507 (Japan); Kikuta, Kengo; Tomaru, Hiroshi [IHI Corperation, TOYOSU IHI BUILDING, 1-1, Toyosu 3-chome, Koto-ku, Tokyo 1358710 (Japan)


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

  4. Visualization of cavitation bubbles; Visualisation de bulles de cavitation

    Chouvellon, M.; Fournel, Th.; Ducottet, Ch. [Universite Jean Monnet, 31 Saint-Etienne (France). Laboratoire Traitement du Signal et Instrumentation-UMR CNRS 5516


    A high frequency ultrasonic reactor allows the degradation of some organic compounds which are not or poorly biodegradable by usual methods in industrial flows. The propagation of an ultrasonic wave in a liquid induces cavitation phenomena. The implosion of cavitation bubble locally causes a temperature of about several thousand Kelvins and a pressure of about several hundred bars. Such conditions allow the creation of the hydroxyl radicals and then the oxidation of organic compounds. The aim of this paper is to describe the method used to visualize cavitation bubbles in an ultrasonic reactor at a frequency of 500 kHz. The experimental set-up and the measurement of both the bubble radius and the fringe separation are presented. (authors)

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

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


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

  6. Application of signal processing techniques to the detection of tip vortex cavitation noise in marine propeller

    LEE Jeung-Hoon; HAN Jae-Moon; PARK Hyung-Gil; SEO Jong-Soo


    The tip vortex cavitation and its relevant noise has been the subject of extensive researches up to now.In most cases of experimental approaches,the accurate and objective decision of cavitation inception is primary,which is the main topic of this paper.Although the conventional power spectrum is normally adopted as a signal processing tool for the analysis of cavitation noise,a faithful exploration cannot be made especially for the cavitation inception.Alternatively,the periodic occurrence of bursting noise induced from tip vortex cavitation gives a diagnostic proof that the repeating frequency of the bursting contents can be exploited as an indication of the inception.This study,hence,employed the Short-Time Fourier Transform (STFT) analysis and the Detection of Envelope Modulation On Noise (DEMON) spectrum analysis,both which are appropriate for finding such a repeating frequency.Through the acoustical measurement in a water tunnel,the two signal processing techniques show a satisfactory result in detecting the inception of tip vortex cavitation.

  7. Numerical investigation on cavitation flow of hydrofoil and its flow noise with emphasis on turbulence models

    Sanghyeon Kim


    Full Text Available In this study, cavitation flow of hydrofoils is numerically investigated to characterize the effects of turbulence models on cavitation-flow patterns and the corresponding radiated sound waves. The two distinct flow conditions are considered by varying the mean flow velocity and angle of attack, which are categorized under the experimentally observed unstable or stable cavitation flows. To consider the phase interchanges between the vapor and the liquid, the flow fields around the hydrofoil are analyzed by solving the unsteady compressible Reynolds-averaged Navier–Stokes equations coupled with a mass-transfer model, also referred to as the cavitation model. In the numerical solver, a preconditioning algorithm with dual-time stepping techniques is employed in generalized curvilinear coordinates. The following three types of turbulence models are employed: the laminar-flow model, standard k − ε turbulent model, and filter-based model. Hydro-acoustic field formed by the cavitation flow of the hydrofoil is predicted by applying the Ffowcs Williams and Hawkings equation to the predicted flow field. From the predicted results, the effects of the turbulences on the cavitation flow pattern and radiated flow noise are quantitatively assessed in terms of the void fraction, sound-pressure-propagation directivities, and spectrum.

  8. Numerical investigation on cavitation flow of hydrofoil and its flow noise with emphasis on turbulence models

    Kim, Sanghyeon; Cheong, Cheolung; Park, Warn-Gyu


    In this study, cavitation flow of hydrofoils is numerically investigated to characterize the effects of turbulence models on cavitation-flow patterns and the corresponding radiated sound waves. The two distinct flow conditions are considered by varying the mean flow velocity and angle of attack, which are categorized under the experimentally observed unstable or stable cavitation flows. To consider the phase interchanges between the vapor and the liquid, the flow fields around the hydrofoil are analyzed by solving the unsteady compressible Reynolds-averaged Navier-Stokes equations coupled with a mass-transfer model, also referred to as the cavitation model. In the numerical solver, a preconditioning algorithm with dual-time stepping techniques is employed in generalized curvilinear coordinates. The following three types of turbulence models are employed: the laminar-flow model, standard k - ɛ turbulent model, and filter-based model. Hydro-acoustic field formed by the cavitation flow of the hydrofoil is predicted by applying the Ffowcs Williams and Hawkings equation to the predicted flow field. From the predicted results, the effects of the turbulences on the cavitation flow pattern and radiated flow noise are quantitatively assessed in terms of the void fraction, sound-pressure-propagation directivities, and spectrum.

  9. Prediction of Shock-Induced Cavitation in Water

    Brundage, Aaron


    Fluid-structure interaction problems that require estimating the response of thin structures within fluids to shock loading has wide applicability. For example, these problems may include underwater explosions and the dynamic response of ships and submarines; and biological applications such as Traumatic Brain Injury (TBI) and wound ballistics. In all of these applications the process of cavitation, where small cavities with dissolved gases or vapor are formed as the local pressure drops below the vapor pressure due to shock hydrodynamics, can cause significant damage to the surrounding thin structures or membranes if these bubbles collapse, generating additional shock loading. Hence, a two-phase equation of state (EOS) with three distinct regions of compression, expansion, and tension was developed to model shock-induced cavitation. This EOS was evaluated by comparing data from pressure and temperature shock Hugoniot measurements for water up to 400 kbar, and data from ultrasonic pressure measurements in tension to -0.3 kbar, to simulated responses from CTH, an Eulerian, finite volume shock code. The new EOS model showed significant improvement over pre-existing CTH models such as the SESAME EOS for capturing cavitation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy/NNSA under contract DE-AC04-94AL85000.

  10. Radiation Hydrodynamics

    Castor, J I


    The discipline of radiation hydrodynamics is the branch of hydrodynamics in which the moving fluid absorbs and emits electromagnetic radiation, and in so doing modifies its dynamical behavior. That is, the net gain or loss of energy by parcels of the fluid material through absorption or emission of radiation are sufficient to change the pressure of the material, and therefore change its motion; alternatively, the net momentum exchange between radiation and matter may alter the motion of the matter directly. Ignoring the radiation contributions to energy and momentum will give a wrong prediction of the hydrodynamic motion when the correct description is radiation hydrodynamics. Of course, there are circumstances when a large quantity of radiation is present, yet can be ignored without causing the model to be in error. This happens when radiation from an exterior source streams through the problem, but the latter is so transparent that the energy and momentum coupling is negligible. Everything we say about radiation hydrodynamics applies equally well to neutrinos and photons (apart from the Einstein relations, specific to bosons), but in almost every area of astrophysics neutrino hydrodynamics is ignored, simply because the systems are exceedingly transparent to neutrinos, even though the energy flux in neutrinos may be substantial. Another place where we can do ''radiation hydrodynamics'' without using any sophisticated theory is deep within stars or other bodies, where the material is so opaque to the radiation that the mean free path of photons is entirely negligible compared with the size of the system, the distance over which any fluid quantity varies, and so on. In this case we can suppose that the radiation is in equilibrium with the matter locally, and its energy, pressure and momentum can be lumped in with those of the rest of the fluid. That is, it is no more necessary to distinguish photons from atoms, nuclei and electrons, than it is

  11. Influence of the working electrode area on the cavitation-corrosion behaviour of a duplex stainless steel in aqueous LiBr solution

    Garcia-Garcia, D.M.; Blasco-Tamarit, E.; Igual-Munoz, A.; Garcia-Anton, J. [Valencia Univ. Politecnica, Dept. de Ingenieria Quimica y Nuclear. ETSI Industriales, Valencia (Spain)


    Cavitation erosion can occur in almost all hydrodynamic systems and turbo machines, e.g. pumps, valves, marine propeller and hydraulic turbines. It causes serious material damage. Corrosion problems associated with cavitation can appear on different points in LiBr absorption machines. Many efforts have been made to solve this problem, such as optimizing the design of the flow-handling component and selecting better materials and coatings to resist the cavitation erosion-corrosion. A better understanding of cavitation erosion-corrosion mechanisms is very important for the selection materials and coatings. The objective of the present work was to study the influence of the exposed area of the working electrode on the corrosion behaviour of a duplex stainless steel (EN 1.4462) in a 992 g/l LiBr solution under static conditions (without cavitation) and dynamic conditions (with cavitation) at 25 C. Potentiodynamic cyclic curves were obtained under static and dynamic conditions exposing different areas of the working electrode: 1.6 mm diameter (0.02 cm{sup 2} area ), 4 mm diameter (0.12 cm{sup 2} area), 6 mm diameter (0.28 cm{sup 2} area) and 8 mm diameter (0.5 cm{sup 2} area). The dynamic conditions were generated using an ultrasonic cavitation facility in a three-electrode electrochemical cell. The Potentiodynamic Cyclic curves obtained with and without cavitation have been compared and different tendencies were observed. Cavitation increased the cathodic current density when the exposed area to the solution is large (6 mm and 8 mm diameters). This behaviour was not observed during the tests with smaller electrode areas (1.6 mm and 4 mm diameters). In all cases, cavitation increased the anodic current densities independently of the exposed area to the solution. Besides, cavitation favoured the pitting corrosion, since lower pitting potentials were obtained under cavitation conditions than under static conditions. (authors)

  12. Numerical investigation of cavitation flow inside spool valve with large pressure drop

    Deng, Jian; Pan, Dingyi; Xie, Fangfang; Shao, Xueming


    Spool valves play an important role in fluid power system. Cavitation phenomena happen frequently inside the spool valves, which cause structure damages, noise and lower down hydrodynamic performance. A numerical tools incorporating the cavitation model, are developed to predict the flow structure and cavitation pattern in the spool valve. Two major flow states in the spool valve chamber, i.e. flow-in and flow-out, are studies. The pressure distributions along the spool wall are first investigated, and the results agree well with the experimental data. For the flow-in cases, the local pressure at the throttling area drops much deeper than the pressure in flow-out cases. Meanwhile, the bubbles are more stable in flow-in cases than those in flow-out cases, which are ruptured and shed into the downstream.

  13. Bacterial hydrodynamics

    Lauga, Eric


    Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells yet they represent the bulk of the world's biomass, and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds-number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micron scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically-complex environments. Using hydrodynamics as an organizing framework, we review the biomechanics of bacterial motility and look ahead to future challenges.

  14. Nanoflow hydrodynamics

    Hansen, Jesper Schmidt; Dyre, Jeppe C.; Daivis, Peter J.;


    We show by nonequilibrium molecular dynamics simulations that the Navier-Stokes equation does not correctly describe water flow in a nanoscale geometry. It is argued that this failure reflects the fact that the coupling between the intrinsic rotational and translational degrees of freedom becomes...... important for nanoflows. The coupling is correctly accounted for by the extended Navier-Stokes equations that include the intrinsic angular momentum as an independent hydrodynamic degree of freedom. © 2011 American Physical Society....

  15. Modeling Cavitation in ICE Pistons Made with Isothermal Forging

    V.V. Astanin


    Full Text Available Possible causes for cavitations in parts made with an Al-Si eutectic alloy AK12D (AlSi12 were explored with mathematical and physical modeling with involved acoustic emission. Pores were formed from micro-cracks, which appear during the early stages of a deformation process, with the help of micro-stresses appearing at phase boundaries (Al/Si interface due to thermal expansion. At the design stage of isothermal forgings of such products it is recommended to provide a scheme of the deformed shape, which is under uniform compression, to compensate for the inter-phase stresses.

  16. Inverse effects of flowing phase-shift nanodroplets and lipid-shelled microbubbles on subsequent cavitation during focused ultrasound exposures.

    Zhang, Siyuan; Cui, Zhiwei; Xu, Tianqi; Liu, Pan; Li, Dapeng; Shang, Shaoqiang; Xu, Ranxiang; Zong, Yujin; Niu, Gang; Wang, Supin; He, Xijing; Wan, Mingxi


    This paper compared the effects of flowing phase-shift nanodroplets (NDs) and lipid-shelled microbubbles (MBs) on subsequent cavitation during focused ultrasound (FUS) exposures. The cavitation activity was monitored using a passive cavitation detection method as solutions of either phase-shift NDs or lipid-shelled MBs flowed at varying velocities through a 5-mm diameter wall-less vessel in a transparent tissue-mimicking phantom when exposed to FUS. The intensity of cavitation for the phase-shift NDs showed an upward trend with time and cavitation for the lipid-shelled MBs grew to a maximum at the outset of the FUS exposure followed by a trend of decreases when they were static in the vessel. Meanwhile, the increase of cavitation for the phase-shift NDs and decrease of cavitation for the lipid-shelled MBs had slowed down when they flowed through the vessel. During two discrete identical FUS exposures, while the normalized inertial cavitation dose (ICD) value for the lipid-shelled MB solution was higher than that for the saline in the first exposure (p-value 0.95). Meanwhile, the normalized ICD value for the phase-shift NDs was 0.182 at a flow velocity of 5cm/s and increased to 0.188 at a flow velocity of 15cm/s. As the flow velocity increased to 20cm/s, the normalized ICD was 0.185 and decreased to 0.178 at a flow velocity of 30cm/s. At high acoustic power, the normalized ICD values for both the lipid-shelled MBs and the phase-shift NDs increased with increasing flow velocities from 5 to 30cm/s (r>0.95). The effects of the flowing phase-shift NDs vaporized into gas bubbles as cavitation nuclei on the subsequent cavitation were inverse to those of the flowing lipid-shelled MBs destroyed after focused ultrasound exposures.

  17. Numerical Study of Unsteady Cavitating Flows around a Hydrofoil

    Ahmed Bel Hadj Taher


    Full Text Available In this paper, we report the results of a numerical investigation on unsteady cavitating flows around a circular leading edge (CLE hydrofoil. The objective of this study is to properly predict the appearance of cavitation pocket, its development and its detachment causing adverse effects on industrial systems such as microscopic plastic deformations at the solid walls. For this reason it is very important to study the influence of turbulence models on simulation results. We present a closing of the hydrodynamic equation system by a transport equation of an active scalar (volume fraction of the vapor phase with a source terms. The Computational Fluid Dynamics (CFD code used is ANSYS CFX. Before comparing the capability of the different turbulent models to predict unsteady behavior of cavitating flow along the hydrofoil, the study of the influence of the mesh resolution was performed in cavitating condition. This investigation was performed, on CLE hydrofoil, by monitoring the influence of for progressively finer meshes on the values of the drag CD and lift CL coefficients. Moreover, a study of the influence of the normal dimensionless distance to the wall (y+ was carried out on the hydrofoil surface. For the unsteady flow, a comparison of different turbulence models with the experiment leads to study the interaction of these models with the vapor pocket (detachment and collapse of vapor pocket. Two turbulence models were tested in this study: modified k-ε model and large eddy simulation (LES. In the present work, the predictions of velocity and pressure evolutions in the vicinity of the hydrofoil are compared to experimental data.


    CHEN Xin; LU Chuan-jing; LI Jie; CHEN Ying


    When a body navigates with cavity in shallow water,both flexible free surface and rigid bottom wall will produce great influences on the cavity shape and hydrodynamic performances,and further affect the motion attitude and stability of the body.In the present work,characteristics of the natural cavitating flow around a 2-D symmetrical wedge in shallow water were investigated and the influences of two type boundaries on the flow pattern were analyzed.The Volume Of Fluid (VOF) multiphaseflow method which is suitable for free surface problems was utilized,coupled with a natural cavitation model to deal with the mass-transfer process between liquid and vapor phases.Within the range of the cavitation number for computation (0.07-1.81),the cavity configurations would be divided into three types,viz.,stable type,transition type and wake-vortex type.In this article,the shapes of the free surface and the cavity surface,and the hydrodynamic performance of the wedge were discussed under the conditions of relatively small cavitation number ( < 0.256 ).The present numerical cavity lengths generally accord with experimental data.When the cavitation number was decreased,the cavity was found to become longer and thicker,and the scope of the deformation of the free surface also gradually extends.The free surface and the upper cavity surface correspond fairly to their shapes.However,the lower side of the cavity surface was rather leveled due to the influence of wall boundary.The lift and drag coefficients of this 2-D wedge basically keep linear relations with the natural cavitation number smaller than 0.157,whereas direct proportion for drag and inverse proportion for lift.

  19. Cavitation Effects in Centrifugal Pumps- A Review

    Maxime Binama


    Full Text Available Cavitation is one of the most challenging fluid flow abnormalities leading to detrimental effects on both the centrifugal pump flow behaviors and physical characteristics. Centrifugal pumps’ most low pressure zones are the first cavitation victims, where cavitation manifests itself in form of pitting on the pump internal solid walls, accompanied by noise and vibration, all leading to the pump hydraulic performance degradation. In the present article, a general description of centrifugal pump performance and related parameters is presented. Based on the literature survey, some light were shed on fundamental cavitation features; where different aspects relating to cavitation in centrifugal pumps were briefly discussed

  20. 超声场中声压与空化对冰晶分裂的影响%The Effect of Acoustic Pressure and Cavitation on the Secondary Nucleation of Ice

    余德洋; 刘宝林; 王伯春


    In order to clarify the mechanism of secondary nucleation of iceinduced by ultrasound, experiments on ice crystals in degassed sucrose solutions and untreated solutions have been carried out using a novel ultrasonic cold stage device. For each experiment, the ultrasonic waves operated at a power output of 120W. The results show that the ice dendrite crystals growing in a sucrose solution can be broken up into smaller fragments when ultrasound was applied for 2 s, but the pre-existing ice dendrite crystals in a degassed sucrose solution are still unbroken when ultrasound was applied for 6 s. These findings confirm that cavitation induced by ultrasound is a major factor for the fragmentation of ice crystals.%为了探讨超声波强化冰晶二次成核的机理,利用自行研制的超声波冷却实验台,研究了超声波对未脱气蔗糖稀溶液和脱气蔗糖稀溶液中树枝状冰晶体的影响.实验结果表明:未脱气蔗糖稀溶液中的树枝状冰晶体受超声波辐射2s后已发生分裂,而脱气溶液中的树枝状冰晶体受功率相同的超声波辐射6s后却仍未分裂.说明超声场中冰晶发生分裂的主要原因是空化效应,而不是超声波在溶液中传播所引起的声压.

  1. Cavitation pulse extraction and centrifugal pump analysis

    Luo, Hong Lind Shaoran [University of Electronic Science and Technology of China, Chengdu (China); Yu, Bo; Qing, Biao [Xihua University, Chengdu (China)


    This study extracted cavitation pulses from hydrophone signals sampled in a centrifugal pump and analyzed their characteristics. The modified and simplified Empirical mode decomposition (EMD) algorithm was proposed for extracting cavitation pulses from strong background noise. Experimental results showed that EMD can effectively suppress noise and obtain clear cavitation pulses, facilitating the identification of the number of pulses associated with the degree of cavitation. The cavitation characteristics were modeled to predict the value of incipient cavitation. Then, we proposed a method for detecting the wear of the impeller surface. That is, the information on the impeller surface of the centrifugal pump, including the roughness of the impeller surface and its wear trends, were quantified based on the net positive suction head available of incipient cavitation. The findings indicate that the proposed technique is suitable for condition monitoring of the pump.

  2. On thermonuclear processes in cavitation bubbles

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


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

  3. Numerical Analysis of Cavitation Processes in a Nozzle with Variable Cross-Section

    N.L. Zagordan


    Full Text Available Numerical simulation approach addressing problems of cavitation processes and vapor-liquid two-phase flow dynamics research is discussed. The Navier-Stokes equations, supplemented by transport equation containing source terms, responsible for the interphase exchange, are solved to obtain hydrodynamic characteristics of the system. Mathematical model of unsteady conjugate heat-mass transfer between the bubble and the surrounding liquid is proposed to describe the evolution of a two-component (gas-vapor bubble. The model takes into account a spatial nonuniformity of the gas and liquid temperature fields as well as nonuniformity of the component concentration inside the bubble. A comparative analysis of the experimental data and computational results is carried out for different regimes of cavitating flows inside a two-dimensional nozzle with variable cross-section. The oscillation characteristics of hydrodynamic parameters and the gas-vapor bubbles behavior are investigated.

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

    Patek, S N; Caldwell, R L


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

  5. Experimental Observations of Cavitating Flows Around a Hydrofoil

    ZHANG Min-di; WANG Guo-yu; DONG Zi-qiao; LI Xiang-bin; GAO De-ming


    The cavitation around a hydrofoil is studied experimentally tO shed light on the multiphase fluid dynamies.Different cavitation regimes are studied by using high speed visualization and particle image velocimetry(PIV).As decreasing the cavitation number,four cavitating flow regimes are observed:incipient cavitation,sheet cavitation,cloud cavitation,and supercavitation.From the incipient cavitation to the cloud cavitation,bubbles become more and more.Phenomena with large-scale vortex structure and rear re-entrant jet associated with the cloud cavitation,and subsequent development in the supercavitation are described.The velocity in the cavitation regions in the different cavitation conditions is low compared to that of the free stream.The large velocity gradient is also observed in the cavitating flow region near the suHace of the hydrofoil.

  6. Stochastic-field cavitation model

    Dumond, J., E-mail: [AREVA Nuclear Professional School, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); AREVA GmbH, Erlangen, Paul-Gossen-Strasse 100, D-91052 Erlangen (Germany); Magagnato, F. [Institute of Fluid Mechanics, Karlsruhe Institute of Technology, Kaiserstrasse 12, D-76131 Karlsruhe (Germany); Class, A. [AREVA Nuclear Professional School, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Institute for Nuclear and Energy Technologies, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)


    Nonlinear phenomena can often be well described using probability density functions (pdf) and pdf transport models. Traditionally, the simulation of pdf transport requires Monte-Carlo codes based on Lagrangian “particles” or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic-field method solving pdf transport based on Eulerian fields has been proposed which eliminates the necessity to mix Eulerian and Lagrangian techniques or prescribed pdf assumptions. In the present work, for the first time the stochastic-field method is applied to multi-phase flow and, in particular, to cavitating flow. To validate the proposed stochastic-field cavitation model, two applications are considered. First, sheet cavitation is simulated in a Venturi-type nozzle. The second application is an innovative fluidic diode which exhibits coolant flashing. Agreement with experimental results is obtained for both applications with a fixed set of model constants. The stochastic-field cavitation model captures the wide range of pdf shapes present at different locations.

  7. Stochastic-field cavitation model

    Dumond, J.; Magagnato, F.; Class, A.


    Nonlinear phenomena can often be well described using probability density functions (pdf) and pdf transport models. Traditionally, the simulation of pdf transport requires Monte-Carlo codes based on Lagrangian "particles" or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic-field method solving pdf transport based on Eulerian fields has been proposed which eliminates the necessity to mix Eulerian and Lagrangian techniques or prescribed pdf assumptions. In the present work, for the first time the stochastic-field method is applied to multi-phase flow and, in particular, to cavitating flow. To validate the proposed stochastic-field cavitation model, two applications are considered. First, sheet cavitation is simulated in a Venturi-type nozzle. The second application is an innovative fluidic diode which exhibits coolant flashing. Agreement with experimental results is obtained for both applications with a fixed set of model constants. The stochastic-field cavitation model captures the wide range of pdf shapes present at different locations.

  8. Size effects on cavitation instabilities

    Niordson, Christian Frithiof; Tvergaard, Viggo


    In metal-ceramic systems the constraint on plastic flow leads to so high stress triaxialities that cavitation instabilities may occur. If the void radius is on the order of magnitude of a characteristic length for the metal, the rate of void growth is reduced, and the possibility of unstable cavi...... as the void grows to a size well above the characteristic material length....

  9. In Vivo Microbubble Cavitation Imaging

    Vignon, F.; Shi, W.; Liu, J.; Xie, F.; Gao, S.; Drvol, L.; Lof, J.; Everbach, C.; Porter, T.; Powers, J.


    Stroke is the second cause of death and leading cause of disabilityworldwide. Less than 5% of ischemic stroke patients receive the state-of-the art treatment of a thrombolytic drug tPA, and only about 10% of these gain additional benefit from it. Ultrasound (US)-inducedmicrobubble (MB) cavitation ha



    The unsteady sheet cavitation of podded propeller was predicted by using a surface panel method. The interaction between propeller and pod was treated with the iterative calculation of induced velocity potential, and the method of induced velocity potential can save a great deal of storage and computation time compared to the method of induced velocity. The induced velocity potential of unit singularity on every pod panel to every key blade panel and of unit singularity on every key blade panel and its wake panel to every pod panel were calculated when the key blade is at every angle position. Based on the wake model of the conventional single propeller, a new wake model of podded propeller was constructed. The propeller is analyzed only on the key blade in order to save computation time and memory space. The method can be used to calculate the hydrodynamics performance and cavitation of propeller in uniform and non-uniform inflows. It can give the unsteady force and cavitation shape of propeller. The propeller cavitation range determined by the present method agrees with the observation results of cavity image given in cavitation tunnel well, and this proves the practicability of the method.

  11. Nucleus factory on cavitation bubble for amyloid β fibril

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


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

  12. Role of cavitation in the phacoemulsification process.

    Zacharias, Jaime


    To determine the role of cavitational energy as a mechanism responsible for the emulsification of the lens during phacoemulsification. Clinica Ophthalmologica Pasteur, Santiago, Chile. Cavitation and its relationship to phacoemulsification power were documented using a combination of light sources, high-speed video recording techniques, and computerized control and by monitoring environmental pressure. The suppression of cavitation from the phaco process was achieved by building an environmental hyperbaric system capable of retaining the phacoemulsification system's ability to provide irrigation, aspiration, and vacuum necessary at standard and elevated pressures. The pressure level was controlled and monitored through a computer interface alongside the simultaneous video monitoring of cavitation bubble creation changes during pressure rise or fall. Last, evaluation and measurement of phacoemulsification was performed on real cataract fragments in the presence and absence of cavitation. Cavitation around the phaco tip mainly occurred at longitudinal ultrasonic power levels of 30% or more. Cavitation bubble formation was observed during the backstroke or as the tip moved away from the lens material and collapsed during the forward displacement of the phaco tip. Cavitation at any power level was successfully suppressed when the pressure in the hyperbaric chamber increased beyond 2.0 bar (29.1 psi) above atmospheric pressure. Phacoemulsification performance in the presence or absence of cavitation was comparable. This study found strong evidence that cavitation plays no role in phacoemulsification, leaving the jackhammer effect as the only important mechanism responsible for the lens-disrupting power of phacoemulsification.

  13. Introduction to Hydrodynamics

    Jeon, Sangyong


    We give a pedagogical review of relativistic hydrodynamics relevant to relativistic heavy ion collisions. Topics discussed include linear response theory derivation of 2nd order viscous hydrodynamics including the Kubo formulas, kinetic theory derivation of 2nd order viscous hydrodynamics, anisotropic hydrodynamics and a brief review of numerical algorithms. Emphasis is given to the theory of hydrodynamics rather than phenomenology.

  14. Numerical Investigation Cavitation Buckets for Hydrofoil Parametrically

    Mehmet Salih KARAALİOĞLU


    Full Text Available Cavitation is a general fluid mechanics phenomenon that is appeared in system such as pumps, turbines, marine propellers and hydrofoils which induces pressure and velocity fluctuation in the fluid (Brennen, 2013. Cavitation can be defined as the formation of vapour regions due to a decrease in local pressure. Undesirable consequences which can cause a fall in the performance of a system, structural failure, production of noise and vibration, material damage, are encountered due to cavitation (Uşar, 2015. In this study, cavitation was analysed using a bucket diagram. Bucket diagram represents the cavitation behaviour of a wing, fin or propeller blade in a two dimensional sense. This diagram is plotted as a function of section (hydrofoil angle of attack (α versus section cavitation number (σ. Pressure distribution can be calculated on two dimensional geometry of hydrofoil by using BEM (Boundary Element Method and cavitation bucket diagram can be computed. The cavitation inception case and partial cavitation cases have been investigated and the results of the present BEM were successfully compared with those of given in literature in the past and each other. While a constant source-dipole panel method has been used to calculate the pressure distribution at cavitation inception case, PCPAN programme that solves the sheet type of cavity on the hydrofoil by potential based panel method, has been used to calculate pressure distribution for the cases of partial cavitation. Effects of maximum hydrofoil thickness, maximum camber and location of maximum camber on cavitation have been analyzed by means of cavitation bucklet diagrams. All results are discussed in a detailed manner.

  15. Prediction of cryogenic cavitation around hydrofoil by an extensional Schnerr-Sauer cavitation model

    Sun, T. Z.; Wei, Y. J.; Wang, C.


    Developing a robust computational strategy to address the rich physics characteristic involved in the thermodynamic effects on the cryogenic cavitation remains a challenging problem. The objective of this present study is to model the numerical methodology to simulate the cryogenic cavitation by implanting the thermodynamic effects to the Schnerr-Sauer cavitation model, and coupling the energy equation considered the latent heat. For this purpose, cavitating flows are investigated over a three dimensional hydrofoil in liquid hydrogen and nitrogen. Experimental measurements of pressure and temperature are utilized to validate the extensional Schnerr-Sauer cavitation model. Specifically, the further analysis of the cavitation solution with respect to the thermodynamic term is conducted. The results show that the extensional Schnerr-Sauer cavitation model predicts better accuracy to the quasi-steady cavitation over hydrofoil in the two cryogenic fluids.

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

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


    When focused ultrasound waves of moderate intensity in liquid encounter an air interface, a chain of drops emerges from the liquid surface to form what is known as a drop-chain fountain. Atomization, or the emission of micro-droplets, occurs when the acoustic intensity exceeds a liquid-dependent threshold. While the cavitation-wave hypothesis, which states that atomization arises from a combination of capillary-wave instabilities and cavitation bubble oscillations, is currently the most accep...

  17. Predicting the Onset of Cavitation in Automotive Torque Converters—Part I: Designs with Geometric Similitude

    D. L. Robinette


    Full Text Available Dimensional analysis has been applied to automotive torque converters to understand the response of performance to changes in torque, size, working fluid, or operating temperature. The objective of this investigation was to develop a suitable dimensional analysis for estimating the effect of exact geometric scaling of a particular torque converter design on the onset of cavitation. Torque converter operating thresholds for cavitation were determined experimentally with a dynamometer test cell at the stall operating condition using nearfield acoustical measurements. Dimensionless quantities based upon either speed or torque at the onset of cavitation and flow properties (e.g., pressures and temperature dependent fluid properties were developed and compared. The proposed dimensionless stator torque quantity was found to be the most appropriate scaling law for extrapolating cavitation thresholds to multiple diameters. A power product model was fit on dimensionless stator torque data to create a model capable of predicting cavitation thresholds. Comparison of the model to test data taken over a range of operating points showed an error of 3.7%. This is the first paper of a two-part paper. In Part II, application of dimensional analysis will be expanded from torque converters with exact geometric similitude to those of more general design.

  18. A suppressor to prevent direct wave-induced cavitation in shock wave therapy devices

    Matula, Thomas J.; Hilmo, Paul R.; Bailey, Michael R.


    Cavitation plays a varied but important role in lithotripsy. Cavitation facilitates stone comminution, but can also form an acoustic barrier that may shield stones from subsequent shock waves. In addition, cavitation damages tissue. Spark-gap lithotripters generate cavitation with both a direct and a focused wave. The direct wave propagates as a spherically diverging wave, arriving at the focus ahead of the focused shock wave. It can be modeled with the same waveform (but lower amplitude) as the focused wave. We show with both simulations and experiments that bubbles are forced to grow in response to the direct wave, and that these bubbles can still be large when the focused shock wave arrives. A baffle or ``suppressor'' that blocks the propagation of the direct wave is shown to significantly reduce the direct wave pressure amplitude, as well as direct wave-induced bubble growth. These results are applicable to spark-gap lithotripters and extracorporeal shock wave therapy devices, where cavitation from the direct wave may interfere with treatment. A simple direct-wave suppressor might therefore be used to improve the therapeutic efficacy of these devices.

  19. Visualization and optimization of cavitation activity at a solid surface in high frequency ultrasound fields.

    Kauer, Markus; Belova-Magri, Valentina; Cairós, Carlos; Schreier, Hans-Jürgen; Mettin, Robert


    Despite the increasing use of high frequency ultrasound in heterogeneous reactions, knowledge about the spatial distribution of cavitation bubbles at the irradiated solid surface is still lacking. This gap hinders controllable surface sonoreactions. Here we present an optimization study of the cavitation bubble distribution at a solid sample using sonoluminescence and sonochemiluminescence imaging. The experiments were performed at three ultrasound frequencies, namely 580, 860 and 1142kHz. We found that position and orientation of the sample to the transducer, as well as its material properties influence the distribution of active cavitation bubbles at the sample surface in the reactor. The reason is a significant modification of the acoustic field due to reflections and absorption of the ultrasonic wave by the solid. This is retraced by numerical simulations employing the Finite Element Method, yielding reasonable agreement of luminescent zones and high acoustic pressure amplitudes in 2D simulations. A homogeneous coverage of the test sample surface with cavitation is finally reached at nearly vertical inclination with respect to the incident wave.

  20. Investigation of Boundary Effects on the Natural Cavitating Flow around a 2D Wedge in Shallow Water

    Xin Chen


    Full Text Available When a cavitated body moves in shallow water, both flexible free surface and rigid bottom wall will produce great influence on the cavity pattern and hydrodynamics to change the motion attitude and stability of the body. In this paper, a single-fluid multiphase flow method coupled with a natural cavitation model was employed to study the effects of two kinds of boundaries on the natural cavitating flow around a two-dimensional symmetry wedge in shallow water. Within the range of the cavitation number for computation (0.05 ~ 2.04, the cavity pattern would be divided into three types, namely, stable type, transition type and wake-vortex type. The shape of the free surface is fairly similar to that of the cavity's upper surface with well right-and-left symmetry. However, when the immersion depth and the cavitation number are decreasing, the symmetry of the cavity shape is destroyed due to the influence of bottom wall effects. When the cavitation number is less than about 0.1, with the immersion depth going down, free surface effects exerts a stronger influence on the drag coefficient of this 2D wedge, whereas wall effects bring a stronger influence on the lift coefficient.

  1. Cavitation study of a pump-turbine at turbine mode with critical cavitation coefficient condition

    Wang, J.; Yang, D.; Xu, J. W.; Liu, J. T.; Jiao, L.


    To study the cavitation phenomenon of a pump-turbine at turbine mode when it ran at the critical cavitation coefficient condition, a high-head model pump-turbine was disperse using hexahedron grid. Three dimensional, steady cavitating flow was numerically studied using SST k-ω model. It is confirmed that ZGB cavitation model and SST k-ω model are useful ways to study the two-phase cavitation flow in pump-turbine. Mass flow inlet and pressure outlet were specified at the casing inlet and draft tube outlet, respectively. The static pressure was set according to the cavitation coefficient. The steady cavitating flows at critical cavitation coefficient condition were analysed. The cavitation area in the runner was investigated. It was found that the pressure of the suction on the blade surface was decreasing gradually with the decrease of the cavitation coefficient. In addition, the vortex flow in the draft tube was observed at the critical cavitation coefficient. It was found that the vortex flow appeared at the center of the draft tube inlet with the decreasing of the cavitation coefficient. Compared with the experimental data, the simulation results show reasonable agreement with the experimental data.

  2. Measuring Dynamic Transfer Functions of Cavitating Pumps

    Baun, Daniel


    A water-flow test facility has been built to enable measurement of dynamic transfer functions (DTFs) of cavitating pumps and of inducers in such pumps. Originally, the facility was intended for use in an investigation of the effects of cavitation in a rocket-engine low-pressure oxygen turbopump. The facility can also be used to measure DTFs of cavitating pumps in general

  3. The domain of validity of fluid dynamics and the onset of cavitation in ultrarelativistic heavy ion collisions

    Denicol, Gabriel S; Jeon, Sangyong


    If the bulk viscosity of QCD matter is large, the effective pressure of the hot and dense matter created in ultrarelativistic heavy ion collisions can become negative, leading to instabilities in the evolution of the plasma. In the context of heavy ion collisions, this effect is sometimes referred to as cavitation. In this contribution we discuss the onset of cavitation in event-by-event hydrodynamic simulations of ultrarelativistic heavy ion collisions at LHC energies. We estimate how large the bulk viscosity of the QGP has to be in the QCD (pseudo) phase transition region in order for the effective pressure of the system to actually become negative.

  4. Acoustofluidics 14: Applications of acoustic streaming in microfluidic devices.

    Wiklund, Martin; Green, Roy; Ohlin, Mathias


    In part 14 of the tutorial series "Acoustofluidics--exploiting ultrasonic standing wave forces and acoustic streaming in microfluidic systems for cell and particle manipulation", we provide a qualitative description of acoustic streaming and review its applications in lab-on-a-chip devices. The paper covers boundary layer driven streaming, including Schlichting and Rayleigh streaming, Eckart streaming in the bulk fluid, cavitation microstreaming and surface-acoustic-wave-driven streaming.

  5. Cavitation Nuclei: Experiments and Theory

    Mørch, Knud Aage


    The Swedish astrophysicist and Nobel Prize winner Hannes Alfven said: Theories come and go - the experiment is here forever. Often a theory, which we set up to describe an observed physical phenomenon, suffers from the lack of knowledge of decisive parameters, and therefore at best the theory...... becomes insufficient. Contrary, the experiment always reveals nature itself, though at prevailing experimental conditions. With essential parameters being out of control and even maybe unidentified, apparently similar experiments may deviate way beyond our expectations. However, these discrepancies offer...... us a chance to reflect on the character of the unknown parameters. In this way non-concordant experimental results may hold the key to the development of better theories - and to new experiments for the testing of their validity. Cavitation and cavitation nuclei are phenomena of that character....


    MфRCH K. A.


    The Swedish astrophysicist and Nobel Prize winner Hannes Alfvén said: Theories come and go ─ the experiment is here forever. Often a theory, which we set up to describe an observed physical phenomenon, suffers from the lack of knowledge of decisive parameters, and therefore at best the theory becomes insufficient. Contrary, the experiment always reveals nature itself, though at prevailing experimental conditions. With essential parameters being out of control and even maybe unidentified, apparently similar experiments may deviate way beyond our expectations. However, these discrepancies offer us a chance to reflect on the character of the unknown parameters. In this way non-concordant experimental results may hold the key to the development of better theories – and to new experiments for the testing of their validity. Cavitation and cavitation nuclei are phenomena of that character.

  7. Mesenteric lymph node cavitation syndrome

    Hugh; James; Freeman


    The mesenteric lymph node cavitation syndrome consists of central necrosis of mesenteric lymph nodes and may occur with either celiac disease or a sprue-like intestinal disease that fails to respond to a gluten-free diet. Splenic hypofunction may also be present. The cause is not known but its development during the clinical course of celiac disease is usually indicative of a poor prognosis for the intestinal disorder, a potential for signif icant compli-cations including sepsis and malignancy, particularly...

  8. Breaking beer bottles with cavitation

    Jung, Sunny; Fontana, Jake; Palffy-Muhoray, Peter; Shelley, Michael


    Hitting the top of a beer bottle, nearly full of water, with an open hand can cause the bottle to break, with the bottom separating from upper section. We have studied this phenomenon using a high-speed camera, and observed the formation, coalescence and collapse of bubbles. The breaking of glass is due to cavitation, typically occurring near the bottom edge. We make numerical estimates of the relevant physical parameters, and compare these with experimental observations.

  9. Cavitation on hydrofoils with sinusoidal leading edge

    Johari, H.


    Cavitation characteristics of hydrofoils with sinusoidal leading edge were examined experimentally at a Reynolds number of 7.2 × 105. The hydrofoils had an underlying NACA 634-021 profile and an aspect ratio of 4.3. The sinusoidal leading edge geometries included three amplitudes of 2.5%, 5%, and 12% and two wavelengths of 25% and 50% of the mean chord length. Results revealed that cavitation on the leading edge-modified hydrofoils existed in pockets behind the troughs whereas the baseline hydrofoil produced cavitation along its entire span. Moreover, cavitation on the modified hydrofoils appeared at consistently lower angles of attack than on the baseline hydrofoil.

  10. A benchmark experiment on gas cavitation

    Peters, Franz; Honza, Rene


    Cavitation research is often a matter of experiments conducted in complex machinery. There, it is extremely difficult to look into one of the most important issues of cavitation which is nucleation. This work investigates gas cavitation under well-defined flow conditions. Nuclei are placed in wall bound cavities and are exposed to a radial gap flow featuring independent pressure and shear stress. A reciprocating bubble generation is achieved. Bubble frequency and size are evaluated which turn out to depend on pressure and wall shear stress. The experiment lends itself to systematic research in cavitation.

  11. Temperature measurements in cavitation bubbles

    Coutier-Delgosha, Olivier


    Cavitation is usually a nearly isothermal process in the liquid phase, but in some specific flow conditions like hot water or cryogenic fluids, significant temperature variations are detected. In addition, a large temperature increase happens inside the cavitation bubbles at the very end of their collapse, due to the fast compression of the gas at the bubble core, which is almost adiabatic. This process is of primary interest in various biomedical and pharmaceutical applications, where the mechanisms of bubble collapse plays a major role. To investigate the amplitude and the spatial distribution of these temperature variations inside and outside the cavitation bubbles, a system based on cold wires has been developed. They have been tested in a configuration of a single bubble obtained by submitting a small air bubble to a large amplitude pressure wave. Some promising results have been obtained after the initial validation tests. This work is funded by the Office of Naval Research Global under Grant N62909-16-1-2116, Dr. Salahuddin Ahmed & Ki-Han Kim program managers.

  12. Cavitation Generated by Amplitude Modulated HIFU: Investigation on the Inertial Cavitation Threshold

    Gilles, Bruno; Saletes, Izella; Béra, Jean-Christophe


    An experimental investigation on cavitation threshold was carried out in order to compare monochromatic and dichromatic ultrasound excitations in their ability to generate inertial cavitation on a target. Using a cavitation activity spectral criterion, a precise inertial cavitation threshold could be extracted in every case considered. The results showed that these thresholds could be very different depending on the type of excitation used. More precisely, for the parameters investigated in the present study, the ratio between monochromatic and dichromatic thresholds decreased when cavitation thresholds are increased. The potential application of this study to purely ultrasonic thrombolysis is discussed.

  13. Report on research of calculus fragmentation by HIFU-induced cavitation in Tsinghua University: 1. Effects of tissue-mimicking phantom

    Zuo, Z. G.; Liu, S. H.


    Study of the acoustic attenuation through human tissues was carried out, in order to accurately evaluate the damaging power of the generated cavitation cloud. Tissue phantom was made, with acoustic properties (acoustic speed and acoustic attenuation factor) similar to human tissues. Preliminary results show that, with the increase of intensity and acting time of the HIFU acoustic waves, the depths of the craters increase rapidly, while the radii of the craters increase mildly. Mass loss of the artificial stones in phantom is less than in water (about 50%), indicating considerable energy dissipation in tissues.

  14. Cavitation Enhancing Nanodroplets Mediate Efficient DNA Fragmentation in a Bench Top Ultrasonic Water Bath.

    Sandeep K Kasoji

    Full Text Available A perfluorocarbon nanodroplet formulation is shown to be an effective cavitation enhancement agent, enabling rapid and consistent fragmentation of genomic DNA in a standard ultrasonic water bath. This nanodroplet-enhanced method produces genomic DNA libraries and next-generation sequencing results indistinguishable from DNA samples fragmented in dedicated commercial acoustic sonication equipment, and with higher throughput. This technique thus enables widespread access to fast bench-top genomic DNA fragmentation.

  15. Cavitation Enhancing Nanodroplets Mediate Efficient DNA Fragmentation in a Bench Top Ultrasonic Water Bath

    Malc, Ewa P.; Jayakody, Chatura N.; Tsuruta, James K.; Mieczkowski, Piotr A.; Janzen, William P.; Dayton, Paul A.


    A perfluorocarbon nanodroplet formulation is shown to be an effective cavitation enhancement agent, enabling rapid and consistent fragmentation of genomic DNA in a standard ultrasonic water bath. This nanodroplet-enhanced method produces genomic DNA libraries and next-generation sequencing results indistinguishable from DNA samples fragmented in dedicated commercial acoustic sonication equipment, and with higher throughput. This technique thus enables widespread access to fast bench-top genomic DNA fragmentation. PMID:26186461

  16. Cavitation instabilities of an inducer in a cryogenic pump

    Kim, Dae-Jin; Sung, Hyung Jin; Choi, Chang-Ho; Kim, Jin-Sun


    Inducers assist cryogenic pumps to operate safely under cavitation conditions by increasing the pressure of the impeller inlet, but create cavitation instabilities. The use of cryogenic fluids requires special attention because of safety and handling concerns. To examine the cavitation instabilities of a cryogenic pump, two kinds of working fluids, water and liquid oxygen, were employed. The cavitation instabilities were measured with an accelerometer installed on the pump casing. The flow coefficient and the head slightly decrease with decreases in the cavitation number before the cavitation breakdown. These trends are true of both fluids. Several cavitation instabilities were identified with the accelerometer. At lower flow coefficients, super-synchronous rotating cavitation was found in a similar cavitation number range for both fluids. At higher flow coefficients, the cavitation numbers of the cavitation instabilities in the liquid oxygen test are smaller than those of the water test.

  17. Cavitation thresholds of contrast agents in an in vitro human clot model exposed to 120-kHz ultrasound.

    Gruber, Matthew J; Bader, Kenneth B; Holland, Christy K


    Ultrasound contrast agents (UCAs) can be employed to nucleate cavitation to achieve desired bioeffects, such as thrombolysis, in therapeutic ultrasound applications. Effective methods of enhancing thrombolysis with ultrasound have been examined at low frequencies (cavitation thresholds for two UCAs exposed to 120-kHz ultrasound. A commercial ultrasound contrast agent (Definity(®)) and echogenic liposomes were investigated to determine the acoustic pressure threshold for ultraharmonic (UH) and broadband (BB) generation using an in vitro flow model perfused with human plasma. Cavitation emissions were detected using two passive receivers over a narrow frequency bandwidth (540-900 kHz) and a broad frequency bandwidth (0.54-1.74 MHz). UH and BB cavitation thresholds occurred at the same acoustic pressure (0.3 ± 0.1 MPa, peak to peak) and were found to depend on the sensitivity of the cavitation detector but not on the nucleating contrast agent or ultrasound duty cycle.

  18. Ultrasound-induced cavitation enhances the delivery and therapeutic efficacy of an oncolytic virus in an in vitro model.

    Bazan-Peregrino, Miriam; Arvanitis, Costas D; Rifai, Bassel; Seymour, Leonard W; Coussios, Constantin-C


    We investigated whether ultrasound-induced cavitation at 0.5 MHz could improve the extravasation and distribution of a potent breast cancer-selective oncolytic adenovirus, AdEHE2F-Luc, to tumour regions that are remote from blood vessels. We developed a novel tumour-mimicking model consisting of a gel matrix containing human breast cancer cells traversed by a fluid channel simulating a tumour blood vessel, through which the virus and microbubbles could be made to flow. Ultrasonic pressures were chosen to maximize either broadband emissions, associated with inertial cavitation, or ultraharmonic emissions, associated with stable cavitation, while varying duty cycle to keep the total acoustic energy delivered constant for comparison across exposures. None of the exposure conditions tested affected cell viability in the absence of the adenovirus. When AdEHE2F-Luc was delivered via the vessel, inertial cavitation increased transgene expression in tumour cells by up to 200 times. This increase was not observed in the absence of Coxsackie and Adenovirus Receptor cell expression, discounting sonoporation as the mechanism of action. In the presence of inertial cavitation, AdEHE2F-Luc distribution was greatly improved in the matrix surrounding the vessel, particularly in the direction of the ultrasound beam; this enabled AdEHE2F-Luc to kill up to 80% of cancer cells within the ultrasound focal volume in the gel 24 hours after delivery, compared to 0% in the absence of cavitation.

  19. Cavitation-enhanced nonthermal ablation in deep brain targets: feasibility in a large animal model.

    Arvanitis, Costas D; Vykhodtseva, Natalia; Jolesz, Ferenc; Livingstone, Margaret; McDannold, Nathan


    OBJECT Transcranial MRI-guided focused ultrasound (TcMRgFUS) is an emerging noninvasive alternative to surgery and radiosurgery that is undergoing testing for tumor ablation and functional neurosurgery. The method is currently limited to central brain targets due to skull heating and other factors. An alternative ablative approach combines very low intensity ultrasound bursts and an intravenously administered microbubble agent to locally destroy the vasculature. The objective of this work was to investigate whether it is feasible to use this approach at deep brain targets near the skull base in nonhuman primates. METHODS In 4 rhesus macaques, targets near the skull base were ablated using a clinical TcMRgFUS system operating at 220 kHz. Low-duty-cycle ultrasound exposures (sonications) were applied for 5 minutes in conjunction with the ultrasound contrast agent Definity, which was administered as a bolus injection or continuous infusion. The acoustic power level was set to be near the inertial cavitation threshold, which was measured using passive monitoring of the acoustic emissions. The resulting tissue effects were investigated with MRI and with histological analysis performed 3 hours to 1 week after sonication. RESULTS Thirteen targets were sonicated in regions next to the optic tract in the 4 animals. Inertial cavitation, indicated by broadband acoustic emissions, occurred at acoustic pressure amplitudes ranging from 340 to 540 kPa. MRI analysis suggested that the lesions had a central region containing red blood cell extravasations that was surrounded by edema. Blood-brain barrier disruption was observed on contrast-enhanced MRI in the lesions and in a surrounding region corresponding to the prefocal area of the FUS system. In histology, lesions consisting of tissue undergoing ischemic necrosis were found in all regions that were sonicated above the inertial cavitation threshold. Tissue damage in prefocal areas was found in several cases, suggesting that in

  20. Cavitation dispersion of carbon nanotubes and modification of cement systems

    GUSEV Boris Vladimirovich


    Full Text Available The most common research areas in construction material science deals with the development of new efficient methods to increase strength properties of materials. One of such methods is modification of composite matrices with carbon nanotubes. The characteristics of nanomodified concretes to a great extent depend on selected method of introduction of carbon nanotubes into material. The predispersion of CNT in mixing water with plasticizing additive through ultrasound impact on the environment with colloid and other types of particles including nanoparticles is the most frequently used scientific method which provides even distribution of nanoparticles in cement. In some works the separation of agglomerated CNT in suspension was conducted by means of ultrasound treatment. The further analysis showed that the main drawbacks of ultrasound dispersion are high energy output and low performance. That causes inconvenience for application of them in manufacturing process. The methods of cavitation dispersion which were developed in the late 90ies in the XXI century today are becoming commonly used in practice. The work presents the results of dispersion of multi-layer nanotubes performed on the hydrodynamic cavitation equipment. It was determined that the use of such equipment makes it possible to produce stable and even carbon dispersions and to introduce and distribute them uniformly in concrete in the same way as in the case when ultrasound treatment is performed. The advantages of this technology are considerable decrease of energy consumption and possibility to treat enormous amounts of liquids which are necessary for modification of concrete in real production process.

  1. Interaction of cavitation bubbles on a wall

    Bremond, Nicolas; Arora, Manish; Dammer, Stephan M.; Lohse, Detlef


    We report experimental and numerical investigations on the dynamics of the cavitation of bubbles on a solid surface and the interaction between them with the help of controlled cavitation nuclei: hemispherical bubbles are nucleated from hydrophobic microcavities that act as gas traps when the substr


    CHEN Zhaoyun


    By cavitation tests and scanning electron microscope (SEM) microanalysis, the micro- appearance of cavitation samples is studied. It is the first time that the micro-appearance of metals is pursued successfully. According to the changing course of the micro-appearance of metals, the damaging course of cavitation erosion is determined. The destructive way of collapsing bubbles on the metal surface is known. Firstly cavitation pinholes appear on the metal surface, then cracks generate and grow under the action of collapsing bubbles. When cracks connect each other, small pieces are removed from pinhole wall and pinholes develop into cavitation pits. When the previous surface is removed completely, new pinholes are produced again on the new surface. A pinhole is the result of the powerful striking of a micro-liquid jet ejected by a large collapsed bubble near the surface. At some stages, cracks grow in the way of fatigue. The corrosion phenomenon is observed during the cavitation erosion. The cavitation pattern can be used to explain the cavitation pregnancy and the changing regulation of sample surface.

  3. Numerical study of a confocal ultrasonic setup for creation of cavitation

    Lafond, Maxime, E-mail:; Chavrier, Françoise; Prieur, Fabrice [Inserm, U1032, LabTau, Lyon, F-69003 (France); Université de Lyon, Lyon, F-69003 (France); Université Lyon 1, Lyon, F-69003 (France); Mestas, Jean-Louis; Lafon, Cyril [Inserm, U1032, LabTau, Lyon, F-69003 (France); Université de Lyon, Lyon, F-69003 (France); Université Lyon 1, Lyon, F-69003 (France); Caviskills SAS, Vaulx-En-Velin, F-69120 (France)


    Acoustic cavitation is used for various therapeutic applications such as local enhancement of drug delivery, histotripsy or hyperthermia. One of the utmost important parameter for cavitation creation is the rarefaction pressure. The typical magnitude of the rarefaction pressure required to initiate cavitation from gas dissolved in tissue is beyond the range of the megapascal. Because nonlinear effects need to be taken into account, a numerical simulator based on the Westervelt equation was used to study the pressure waveform and the acoustic field generated by a setup for creation of cavitation consisting of two high intensity focused ultrasound transducers mounted confocally. At constant acoustic power, simulations with only one and both transducers from the confocal setup showed that the distortion of the pressure waveform due to the combined effects of nonlinearity and diffraction is less pronounced when both confocal transducers are used. Consequently, the confocal setup generates a greater peak negative pressure at focus which is more favorable for cavitation initiation. Comparison between the confocal setup and a single transducer with the same total emitting surface puts in evidence the role of the spatial separation of the two beams. Furthermore, it has been previously shown that the location of the peak negative pressure created by a single transducer shifts from focus towards the transducers in the presence of nonlinear effects. The simulator was used to study a configuration where the acoustical axes of transducers intersect on the peak negative pressure instead of the geometrical focus. For a representative confocal setup, namely moderate nonlinear effects, a 2% increase of the peak negative pressure and 8% decrease of the peak positive pressure resulted from this configuration. These differences tend to increase by increasing nonlinear effects. Although the optimal position of the transducers varies with the nonlinear regimen, the intersection point

  4. Comparison of Different Mathematical Models of Cavitation

    Dorota HOMA


    Full Text Available Cavitation occurs during the flow when local pressure drops to the saturation pressure according to the temperature of the flow. It includes both evaporation and condensation of the vapor bubbles, which occur alternately with high frequency. Cavitation can be very dangerous, especially for pumps, because it leads to break of flow continuity, noise, vibration, erosion of blades and change in pump’s characteristics. Therefore it is very important for pump designers and users to avoid working in cavitation conditions. Simulation of flow can be very useful in that and can indicate if there is risk of cavitating flow occurrence. As this is a multiphase flow and quite complicated phenomena, there are a few mathematical models describing it. The aim of this paper is to make a short review of them and describe their approach to model cavitation. It is desirable to know differences between them to model this phenomenon properly.

  5. Reflections on cavitation nuclei in water

    Mørch, Knud Aage


    The origin of cavitation bubbles, cavitation nuclei, has been a subject of debate since the early years of cavitation research. This paper presents an analysis of a representative selection of experimental investigations of cavitation inception and the tensile strength of water. At atmospheric...... to explaining why the tensile strength of water varies so dramatically between the experiments reported. A model for calculation of the critical pressure of skin-covered free gas bubbles as well as that of interfacial gaseous nuclei covered by a skin is presented. This model is able to bridge the apparently...... pressure, the possibility of stabilization of free gas bubbles by a skin has been documented, but only within a range of bubble sizes that makes them responsible for tensile strengths up to about 1.5 bar, and values reaching almost 300 bar have been measured. However, cavitation nuclei can also be harbored...

  6. Steady State Thermo-Hydrodynamic Analysis of Two-Axial groove and Multilobe Hydrodynamic Bearings

    C. Bhagat


    Full Text Available Steady state thermo-hydrodynamic analysis of two axial groove and multi lobe oil journal bearings is performed in this paper. To study the steady state thermo-hydrodynamic characteristics Reynolds equation is solved simultaneously along with the energy equation and heat conduction equation in bush and shaft. The effect of groove geometry, cavitation in the fluid film, the recirculation of lubricant, shaft speed has also been taken into account. Film temperature in case of three-lobe bearing is found to be high as compared to other studied bearing configurations. The data obtained from this analysis can be used conveniently in the design of such bearings, which are presented in dimensionless form.

  7. Lubrication and thermal characteristics of mechanical seal with porous surface based on cavitation

    Huilong, Chen; Muzi, Zuo; Tong, Liu; Yu, Wang; Cheng, Xu; Qiangbo, Wu


    The theory model of mechanical seals with laser-textured porous surface (LST-MS) was established. The liquid film of LST-MS was simulated by the Fluent software, using full cavitation model and non-cavitation model separately. Dynamic mesh technique and relationship between viscosity and temperature were applied to simulate the internal flow field and heat characteristics of LST-MS, based on the more accurate cavitation model. Influence of porous depth ratio porous diameter ɛ and porous density SP on lubrication performance and the variation of lubrication and thermal properties with shaft speed and sealing pressure were analyzed. The results indicate that the strongest hydrodynamic pressure effect and the biggest thickness of liquid film are obtained when ɛ and SP are respectively about 0.025 and 0.5 which were thought to be the optimum value. The frictional heat leads to the increase of liquid film temperature and the decrease of medium viscosity with the shaft speed increasing. The hydrodynamic pressure effect increases as shaft speed increasing, however it decreases as the impact of frictional heat.


    ARNDT Roger E.A.


    This paper reviews numerical and experimental investigations of sheet/cloud cavitation carried out at the St.Anthony Falls Laboratory and at two collaborating facilities (Versuchsanstalt Für Wasserbau,Obernach,Germany and Osaka University,Japan) for more than a decade.Although significant advances have been made in the analysis of this flow several issues are still unresolved.The purpose of this paper is to examine the overall features of the problem,review the progress made to date and suggest avenues for new investigation.

  9. Enterobacter Asburiae Pneumonia with Cavitation

    Cha, Seung Woo; Heo, Jeong Nam; Park, Choong Ki [Dept. of Radiology, Hanyang University College of Medicine, Guri Hospital, Guri (Korea, Republic of); Choi, Yo Won; Jeon, Seok Chol [Dept. of Radiology, Hanyang University College of Medicine, Seoul Hospital, Seoul (Korea, Republic of)


    Enterobacter species have increasingly been identified as pathogens over the past several decades. These bacterial species have become more important because most are resistant to cephalothin and cefoxitin, and can produce extended-spectrum {beta}-lactamase. Enterobacter asburiae (E. asburiae) is a gram-negative rod of the family Enterobacteriaceae, named in 1986. Since then, there has been only one clinical report of E. asburiae pneumonia. We report a case of E. asburiae pneumonia with cavitation and compare it with the previous case.

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

    Takahira, Hiroyuki, E-mail:; Ogasawara, Toshiyuki, E-mail:; Mori, Naoto, E-mail:; Tanaka, Moe [Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka 599-8531 (Japan)


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

  11. Ultrasound-microbubble mediated cavitation of plant cells: effects on morphology and viability.

    Qin, Peng; Xu, Lin; Zhong, Wenjing; Yu, Alfred C H


    The interaction between ultrasound pulses and microbubbles is known to generate acoustic cavitation that may puncture biological cells. This work presents new experimental findings on the bioeffects of ultrasound-microbubble mediated cavitation in plant cells with emphasis on direct observations of morphological impact and analysis of viability trends in tobacco BY-2 cells that are widely studied in higher plant physiology. The tobacco cell suspensions were exposed to 1 MHz ultrasound pulses in the presence of 1% v/v microbubbles (10% duty cycle; 1 kHz pulse repetition frequency; 70 mm between probe and cells; 1-min exposure time). Few bioeffects were observed at low peak negative pressures (cavitation presumably occurred. In contrast, at 0.9 MPa peak negative pressure (with more inertial cavitation activities according to our passive cavitation detection results), random pores were found on tobacco cell wall (observed via scanning electron microscopy) and enhanced exogenous uptake into the cytoplasm was evident (noted in our fluorescein isothiocyanate dextran uptake analysis). Also, instant lysis was observed in 23.4% of cells (found using trypan blue staining) and programmed cell death was seen in 23.3% of population after 12 h (determined by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling [TUNEL]). These bioeffects generally correspond in trend with those for mammalian cells. This raises the possibility of developing ultrasound-microbubble mediated cavitation into a targeted gene transfection paradigm for plant cells and, conversely, adopting plant cells as experimental test-beds for sonoporation-based gene therapy in mammalian cells.

  12. Study on cavitation characteristics of horizontal axis tidal turbine%水平轴潮流能水轮机空化特性研究

    张亮; 房良; 张学伟


    采用C FD (计算流体力学)数值模拟的方法,对水平轴潮流能水轮机的空化特性进行研究。重点讨论叶片空化的特性和对水轮机水动力性能的影响,得出不同空化数下叶片空化程度和位置及对水动力性能的损耗。在相同空化数下,分别研究来流速度及叶轮旋转角速度对叶片空化情况的影响,得出不同工况下叶片的空化区域,针对空化区域的不同研究水动力性能的降低程度。结果表明:叶片的空化程度及区域不仅和空化数有关,还受到叶尖速比的影响;空化的发生并不一定会严重影响水轮机的水动力性能,空化对水动力性能的影响关键在于空化发生的区域,只有当空化数低于一定数值,叶片中段发生空化时,才会大幅影响水动力性能。%T he cavitation characteristics of horizontal axis tidal turbine w as studied by using CFD (computational fluid dynamics)numerical simulation method .The cavitation characteristics of blade and the effect of hydrodynamic performance were focused on ,the extent and location of cavitation on the blade in different cavitation number ,and the loss of the hydrodynamic performance was obtained meanwhile .At the same cavitation number ,the impact of the flow velocity and the angular velocity of rotation were studied ,the region of cavitation on the blade in different situation was obtained ,and then the reduction of hydrodynamic performances of the turbine were studied at the different region of cavitation .The results show that the extent and region of cavitation is not only associated with the cavitation number ,but also affected by the tip speed ratio ;the occurrence of cavitation will not neces‐sarily affect the hydrodynamic performance of the turbine ,the key of the influence of the cavitation on the hydrodynamic performance is the area of cavitation ,which would greatly affect on the hydrody‐namic performance only when the

  13. Simulations of Cavitating Cryogenic Inducers

    Dorney, Dan (Technical Monitor); Hosangadi, Ashvin; Ahuja, Vineet; Ungewitter, Ronald J.


    Simulations of cavitating turbopump inducers at their design flow rate are presented. Results over a broad range of Nss, numbers extending from single-phase flow conditions through the critical head break down point are discussed. The flow characteristics and performance of a subscale geometry designed for water testing are compared with the fullscale configuration that employs LOX. In particular, thermal depression effects arising from cavitation in cryogenic fluids are identified and their impact on the suction performance of the inducer quantified. The simulations have been performed using the CRUNCH CFD[R] code that has a generalized multi-element unstructured framework suitable for turbomachinery applications. An advanced multi-phase formulation for cryogenic fluids that models temperature depression and real fluid property variations is employed. The formulation has been extensively validated for both liquid nitrogen and liquid hydrogen by simulating the experiments of Hord on hydrofoils; excellent estimates of the leading edge temperature and pressure depression were obtained while the comparisons in the cavity closure region were reasonable.

  14. Simulation and Experimental Study on Cavitating Water Jet Nozzle

    Zhou, Wei; He, Kai; Cai, Jiannan; Hu, Shaojie; Li, Jiuhua; Du, Ruxu


    Cavitating water jet technology is a new kind of water jet technology with many advantages, such as energy-saving, efficient, environmentally-friendly and so on. Based on the numerical simulation and experimental verification in this paper, the research on cavitating nozzle has been carried out, which includes comparison of the cleaning ability of the cavitating jet and the ordinary jet, and comparison of cavitation effects of different structures of cavitating nozzles.

  15. Numerical simulation of multiphase cavitating flows around an underwater projectile


    The present simulation investigates the multiphase cavitating flow around an underwater projectile.Based on the Homogeneous Equilibrium Flow assumption,a mixture model is applied to simulate the multiphase cavitating flow including ventilated cavitation caused by air injection as well as natural cavitation that forms in a region where the pressure of liquid falls below its vapor pressure. The transport equation cavitating model is applied.The calculations are executed based on a suite of CFD code.The hyd...

  16. 水力空化水处理设备的控制系统设计%The Design of Control System for Hydrodynmic Cavitation Water Treatment Equipment

    刘志猛; 陈平; 邓橙; 苑英海; 朱孟府


    为了完成对水力空化水处理设备的自动控制,结合水力空化水处理技术工艺,应用PLC控制器和触摸屏技术,开发并设计一套水力空化水处理设备的控制系统.采用触摸屏作为人机界面,可实现pH、ORP、电导率、DO等水质参数实时检测、设定和修改等功能,并能方便直观地对水力空化水处理设备的工作过程进行监控.经过实际运行和调试,基于PLC和触摸屏的水力空化水处理设备的控制系统稳定性好、可靠性高、易于维护,提高了水力空化水处理设备的效率和自动化水平.%In order to complete automatic control of the hydrodynamic cavitation water treatment equipment, by adopting PLC and touch screen technologies, a control system of the hydrodynamic cavitation water treatment equipment is designed and developed it is based on technological process of the hydrodynamic cavitation water treatment. The system equips with touch screen as the human machine interface implementes the functions of real-time detection, parameter setting and modification of the water quality parameters such as pH, ORP, TDS and DO. Thus the operating process of the hydrodynamic cavitation water treatment equipment can be easily and directly perceived and controlled. The control system of the hydrodynamic cavitation water treatment equipment has good stability and reliability, and is easy to maintenance for enhancing operation efficiency and automation level after practically working and debugging.

  17. Cavitation passive control on immersed bodies

    Javadi, Khodayar; Dorostkar, Mohammad Mortezazadeh; Katal, Ali


    This paper introduces a new idea of controlling cavitation around a hydrofoil through a passive cavitation controller called artificial cavitation bubble generator (ACG). Cyclic processes, namely, growth and implosion of bubbles around an immersed body, are the main reasons for the destruction and erosion of the said body. This paper aims to create a condition in which the cavitation bubbles reach a steady-state situation and prevent the occurrence of the cyclic processes. For this purpose, the ACG is placed on the surface of an immersed body, in particular, the suction surface of a 2D hydrofoil. A simulation was performed with an implicit finite volume scheme based on a SIMPLE algorithm associated with the multiphase and cavitation model. The modified k-ɛ RNG turbulence model equipped with a modification of the turbulent viscosity was applied to overcome the turbulence closure problem. Numerical simulation of water flow over the hydrofoil equipped with the ACG shows that a low-pressure recirculation area is produced behind the ACG and artificially generates stationary cavitation bubbles. The location, shape, and size of this ACG are the crucial parameters in creating a proper control. Results show that the cavitation bubble is controlled well with a well-designed ACG.

  18. Cavitation passive control on immersed bodies

    Javadi, Khodayar; Dorostkar, Mohammad Mortezazadeh; Katal, Ali


    This paper introduces a new idea of controlling cavitation around a hydrofoil through a passive cavitation controller called artificial cavitation bubble generator (ACG). Cyclic processes, namely, growth and implosion of bubbles around an immersed body, are the main reasons for the destruction and erosion of the said body. This paper aims to create a condition in which the cavitation bubbles reach a steady-state situation and prevent the occurrence of the cyclic processes. For this purpose, the ACG is placed on the surface of an immersed body, in particular, the suction surface of a 2D hydrofoil. A simulation was performed with an implicit finite volume scheme based on a SIMPLE algorithm associated with the multiphase and cavitation model. The modified k-ɛ RNG turbulence model equipped with a modification of the turbulent viscosity was applied to overcome the turbulence closure problem. Numerical simulation of water flow over the hydrofoil equipped with the ACG shows that a low-pressure recirculation area is produced behind the ACG and artificially generates stationary cavitation bubbles. The location, shape, and size of this ACG are the crucial parameters in creating a proper control. Results show that the cavitation bubble is controlled well with a well-designed ACG.

  19. Numerical simulation of 3-D incompressible, multi-phase flows over cavitating projectiles

    Owis, F.M.; Nayfeh, A.H. [Blacksburg State University, Dept. of Engineering Science and Mechanics, MC 0219, Virginia Polytechnic Institute, VA (United States)


    The hydrodynamic cavitation over axisymmetric projectiles is computed using the unsteady incompressible Navier-Stokes equations for multi-fluid elements. The governing equations are discretized on a structured grid using an upwind difference scheme with flux limits. A preconditioning dual-time stepping method is used for the unsteady computations. The Eigen-system is derived for the Jacobian matrices. This Eigen-system is suitable for high-density ratio multi-fluid flows and it provides high numerical stability and fast convergence. This method can be used to compute single- as well as multi-phase flows. Cavitating flows over projectiles with different geometries are computed and the results are in good agreement with available experimental data and other published computations. (authors)

  20. A cavitation aggressiveness index within the Reynolds averaged Navier Stokes methodology for cavitating flows



    The paper proposes a methodology within the Reynolds averaged Navier Stokes (RANS) solvers for cavitating flows capable of predicting the flow regions of bubble collapse and the potential aggressiveness to material damage. An aggressiveness index is introduced, called cavitation aggressiveness index (CAI) based on the total derivative of pressure which identifies surface areas exposed to bubble collapses, the index is tested in two known cases documented in the open literature and seems to identify regions of potential cavitation damage.

  1. The detection of cavitation in hydraulic machines by use of ultrasonic signal analysis

    Gruber, P.; Odermatt, P.; Etterlin, M.; Lerch, T.; Frei, M.; Farhat, M.


    This presentation describes an experimental approach for the detection of cavitation in hydraulic machines by use of ultrasonic signal analysis. Instead of using the high frequency pulses (typically 1MHz) only for transit time measurement different other signal characteristics are extracted from the individual signals and its correlation function with reference signals in order to gain knowledge of the water conditions. As the pulse repetition rate is high (typically 100Hz), statistical parameters can be extracted of the signals. The idea is to find patterns in the parameters by a classifier that can distinguish between the different water states. This classification scheme has been applied to different cavitation sections: a sphere in a water flow in circular tube at the HSLU in Lucerne, a NACA profile in a cavitation tunnel and a Francis model test turbine both at LMH in Lausanne. From the signal raw data several statistical parameters in the time and frequency domain as well as from the correlation function with reference signals have been determined. As classifiers two methods were used: neural feed forward networks and decision trees. For both classification methods realizations with lowest complexity as possible are of special interest. It is shown that three signal characteristics, two from the signal itself and one from the correlation function are in many cases sufficient for the detection capability. The final goal is to combine these results with operating point, vibration, acoustic emission and dynamic pressure information such that a distinction between dangerous and not dangerous cavitation is possible.

  2. The cavitational erosion resistance of the B2-type Fe-Al casting alloys

    R. Jasionowski


    Full Text Available The problem of the destruction of turbo-machinery components is very complex, because it consists of processes of erosion and corrosion. The most dangerous factor is the cavitation phenomenon, which is very difficult to eliminate through the use of design solutions. It causes deterioration of the operating characteristics of machinery and equipment, such as water turbines, steam turbines, centrifugal pumps, screw vessels, cylinder liners with water-cooled engines, acoustic probe. The most commonly used method of limiting the destruction of cavitation phenomenon is the optimum choice of parameters of geometric and hydraulic machines, the appropriate design of elements and streamlined flow and providing working conditions of flow devices. The above-mentioned methods by design, the size of flow devices are limited, so better action to prevent the flow of erosion may use the material for greater resistance to erosion and cavitation corrosion is the alloy of intermetallic FeAl phase, which production costs are low compared to cast steel and cast iron alloy based on chromium and nickel.The paper presents results of an investigation carried out for cavitational resistance of the B2-type Fe-Al casting alloys using a flux-impact measuring device. The intermetallic FeAl alloys proved to have good resistance to this type of erosion in comparison to other construction materials, investigated by flux-impact device.

  3. Cavitation studies on axi-symmetric underwater body with pumpjet propulsor in cavitation tunnel

    Ch. Suryanarayana


    Full Text Available A pumpjet propulsor (PJP was designed for an underwater body (UWB with axi-symmetric configuration. Its performance was predicted through CFD study and models were manufactured. The propulsor design was evaluated for its propulsion characteristics through model tests conducted in a Wind Tunnel (WT. In the concluding part of the study, evaluation of the cavitation performance of the pumpjet was undertaken in a cavitation tunnel (CT. In order to assess the cavitation free operation speeds and depths of the body, cavitation tests of the PJP were carried out in behind condition to determine the inception cavitation numbers for rotor, stator and cowl. The model test results obtained were corrected for full scale Reynolds number and subsequently analyzed for cavitation inception speeds at different operating depths. From model tests it was also found that the cavitation inception of the rotor takes place on the tip face side at higher advance ratios and cavitation shifts towards the suction side as the RPS increases whereas the stator and cowl are free from cavitation.

  4. Cleaning lateral morphological features of the root canal: the role of streaming and cavitation.

    Robinson, J P; Macedo, R G; Verhaagen, B; Versluis, M; Cooper, P R; van der Sluis, L W M; Walmsley, A D


    To investigate the effects of ultrasonic activation file type, lateral canal location and irrigant on the removal of a biofilm-mimicking hydrogel from a fabricated lateral canal. Additionally, the amount of cavitation and streaming was quantified for these parameters. An intracanal sonochemical dosimetry method was used to quantify the cavitation generated by an IrriSafe 25 mm length, size 25 file inside a root canal model filled with filtered degassed/saturated water or three different concentrations of NaOCl. Removal of a hydrogel, demonstrated previously to be an appropriate biofilm mimic, was recorded to measure the lateral canal cleaning rate from two different instruments (IrriSafe 25 mm length, size 25 and K 21 mm length, size 15) activated with a P5 Suprasson (Satelec) at power P8.5 in degassed/saturated water or NaOCl. Removal rates were compared for significant differences using nonparametric Kruskal-Wallis and/or Mann-Whitney U-tests. Streaming was measured using high-speed particle imaging velocimetry at 250 kfps, analysing both the oscillatory and steady flow inside the lateral canals. There was no significant difference in amount of cavitation between tap water and oversaturated water (P = 0.538), although more cavitation was observed than in degassed water. The highest cavitation signal was generated with NaOCl solutions (1.0%, 4.5%, 9.0%) (P streaming. The oscillatory velocities were higher inside the lateral canal 3 mm compared to 6 mm from WL and were higher for NaOCl than for saturated water, which in turn was higher than for degassed water. Measurements of cavitation and acoustic streaming have provided insight into their contribution to cleaning. Significant differences in cleaning, cavitation and streaming were found depending on the file type and size, lateral canal location and irrigant used. In general, the IrriSafe file outperformed the K-file, and NaOCl performed better than the other irrigants tested. The cavitation and

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

    苗博雅; 安宇


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

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

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


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

  7. Cell mechanics in biomedical cavitation

    Wang, Qianxi; Manmi, Kawa; Liu, Kuo-Kang


    Studies on the deformation behaviours of cellular entities, such as coated microbubbles and liposomes subject to a cavitation flow, become increasingly important for the advancement of ultrasonic imaging and drug delivery. Numerical simulations for bubble dynamics of ultrasound contrast agents based on the boundary integral method are presented in this work. The effects of the encapsulating shell are estimated by adapting Hoff's model used for thin-shell contrast agents. The viscosity effects are estimated by including the normal viscous stress in the boundary condition. In parallel, mechanical models of cell membranes and liposomes as well as state-of-the-art techniques for quantitative measurement of viscoelasticity for a single cell or coated microbubbles are reviewed. The future developments regarding modelling and measurement of the material properties of the cellular entities for cutting-edge biomedical applications are also discussed. PMID:26442142

  8. Reflections on cavitation nuclei in water

    Mørch, Knud Aage


    The origin of cavitation bubbles, cavitation nuclei, has been a subject of debate since the early years of cavitation research. This paper presents an analysis of a representative selection of experimental investigations of cavitation inception and the tensile strength of water. At atmospheric...... on the surface of particles and bounding walls. Such nuclei can be related to the full range of tensile strengths measured, when differences of experimental conditions are taken into consideration. The absence or presence of contamination on surfaces, as well as the structure of the surfaces, are central...... to explaining why the tensile strength of water varies so dramatically between the experiments reported. A model for calculation of the critical pressure of skin-covered free gas bubbles as well as that of interfacial gaseous nuclei covered by a skin is presented. This model is able to bridge the apparently...

  9. Two-Phase Cavitating Flow in Turbomachines

    Sandor I. Bernad


    Full Text Available Cavitating flows are notoriously complex because they are highly turbulent and unsteady flows involving two species (liquid/vapor with a large density difference. These features pose a unique challenge to numerical modeling works. The study briefly reviews the methodology curently employed for industrial cavitating flow simulations using the two-phase mixture model. The two-phase mixture model is evaluated and validated using benchmark problem where experimental data are available. A 3D cavitating flow computation is performed for the GAMM Francis runner. The model is able to qualitatively predict the location and extent of the 3D cavity on the blade, but further investigation are needed to quatitatively assess the accuracy for real turbomachinery cavitating flows.

  10. Numerical analysis of cavitation within slanted axial-flow pump

    张睿; 陈红勋


    In this paper, the cavitating flow within a slanted axial-flow pump is numerically researched. The hydraulic and cavitation performance of the slanted axial-flow pump under different operation conditions are estimated. Compared with the experimental hydraulic performance curves, the numerical results show that the filter-based model is better than the standard k-e model to predict the parameters of hydraulic performance. In cavitation simulation, compared with the experimental results, the proposed numerical method has good predicting ability. Under different cavitation conditions, the internal cavitating flow fields within slanted axial-flow pump are investigated. Compared with flow visualization results, the major internal flow features can be effectively grasped. In order to explore the origin of the cavitation performance breakdown, the Boundary Vorticity Flux (BVF) is introduced to diagnose the cavitating flow fields. The analysis results indicate that the cavitation performance drop is relevant to the instability of cavitating flow on the blade suction surface.

  11. Assessment of Cavitation Erosion with a Multiphase Reynolds-Averaged Navier-Stokes Method

    Li, Z.R.


    Cavitation erosion is one of the remarkable catastrophic consequences of cavitation. Predicting the cavitation aggressiveness quantitatively and predicting the most probable location of cavitation erosion are complex problems that currently still motivate an important amount of basic and applied res


    ZUO Zhi-gang; LI Sheng-cai; LIU Shu-hong; LI Shuang; CHEN Hui


    In order to further verify the proposed theory of cavitation resonance, as well as to proceed the investigations into microscopic level, a series of studies are being carried out on the Warwick venturi. The analysis of the oscillation characteristics of the cavitation resonance has conclusively verified the macro-mechanism proposed through previous studies on other cavitating flows by the authors. The initial observations using high-speed photographic approach have revealed a new attribution of cavitation resonance. That is, the volumetric oscillation of cavitation cloud is associated with the cavitation resonance, which is a collective behaviour of the bubbles in the cloud.

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

    Ye, Peng-Cheng; Pan, Guang


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

  14. Enhancement of High-Intensity Focused Ultrasound Heating by Short-Pulse Generated Cavitation

    Shin Yoshizawa


    Full Text Available A target tissue can be thermally coagulated in high-intensity focused ultrasound (HIFU treatment noninvasively. HIFU thermal treatments have been clinically applied to various solid tumors. One of the problems in HIFU treatments is a long treatment time. Acoustically driven microbubbles can accelerate the ultrasonic heating, resulting in the significant reduction of the treatment time. In this paper, a method named “trigger HIFU exposure” which employs cavitation microbubbles is introduced and its results are reviewed. A trigger HIFU sequence consists of high-intensity short pulses followed by moderate-intensity long bursts. Cavitation bubbles induced in a multiple focal regions by rapidly scanning the focus of high-intensity pulses enhanced the temperature increase significantly and produced a large coagulation region with high efficiency.

  15. Unsteady hydraulic simulation of the cavitating part load vortex rope in Francis turbines

    Brammer, J.; Segoufin, C.; Duparchy, F.; Lowys, P. Y.; Favrel, A.; Avellan, F.


    For Francis turbines at part load operation a helical vortex rope is formed due to the swirling nature of the flow exiting the runner. This vortex creates pressure fluctuations which can lead to power swings, and the unsteady loading can lead to fatigue damage of the runner. In the case that the vortex rope cavitates there is the additional risk that hydro-acoustic resonance can occur. It is therefore important to be able to accurately simulate this phenomenon to address these issues. In this paper an unsteady, multi-phase CFD model was used to simulate two part-load operating points, for two different cavitation conditions. The simulation results were validated with test-rig data, and showed very good agreement. These results also served as an input for FEA calculations and fatigue analysis, which are presented in a separate study.

  16. Numerical and Experimental Studies of Cavitation Behavior in Water-Jet Cavitation Peening Processing

    H. Zhang


    Full Text Available Water-jet cavitation peening (WCP is a new technology for the surface modification of metallic materials. The cavitation behavior in this process involves complex and changeable physics phenomena, such as high speed, high pressure, multiple phases, phase transition, turbulence, and unstable features. Thus, the cavitation behavior and impact-pressure distribution in WCP have always been key problems in this field. Numerous factors affect the occurrence of cavitation. These factors include flow-boundary conditions, absolute pressure, flow velocity, flow viscosity, surface tension, and so on. Among these factors, pressure and vapor fraction are the most significant. Numerical simulations are performed to determine the flow-field characteristics of both inside and outside the cavitating nozzle of a submerged water jet. The factors that influence the cavitation intensity of pressure are simulated. Fujifilm pressure-sensitive paper is used to measure the distribution of impact pressure along the jet direction during the WCP process. The results show that submerged cavitation jets can induce cavitation both inside and outside a conical nozzle and a convergent-divergent nozzle when the inlet pressure is 32 MPa. Moreover, the shock wave pressure induced by the collapse of the bubble group reaches up to 300 MPa.

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

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


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

  18. Numerical analysis of the interactions of sheet cavitation and cloud cavitation around a hydrofoil

    Pan, D. Z.; Zhang, D. S.; Wang, H. Y.; Shi, W. D.; Shi, L.


    Partial cavitation and cloud cavitation on NACA66(MOD) was studied based on PANS turbulence model combined with the Zwart cavitation model. The results agree well with the data from the experimental results. The existence of a kind of unsteady characteristics of cloud cavitation is analysed in details. The reasons for the inhibition mechanism of the sheet cavitation are discussed. Pressure shock wave occurs near the tailing edge of the hydrofoil when the collapse of cloud is so large leading to great influence on the cavity closed to the leading edge. The evolution of the pressure peak and its propagation toward the leading edge were investigated through the study of the time domain signal of the monitor points along the streamline of flow. Finally, the propagation of the pressure wave on the suction side was further investigated through analysing the spatial-time history of wall pressure.

  19. Numerical prediction of impact force in cavitating flows

    Zhu, B [Department of Thermal Engineering, State Key Laboratory of Hydroscience and Engineering, Tsinghua Univeersity, Beijing, 100084 (China); Wang, H, E-mail: [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084 (China)


    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.

  20. Ion holes in the hydrodynamic regime in ultracold neutral plasmas

    McQuillen, P.; Castro, J.; Strickler, T.; Bradshaw, S. J.; Killian, T. C. [Department of Physics and Astronomy, Rice University, Houston, Texas 77005 (United States)


    We describe the creation of localized density perturbations, or ion holes, in an ultracold neutral plasma in the hydrodynamic regime, and show that the holes propagate at the local ion acoustic wave speed. We also observe the process of hole splitting, which results from the formation of a density depletion initially at rest in the plasma. One-dimensional, two-fluid hydrodynamic simulations describe the results well. Measurements of the ion velocity distribution also show the effects of the ion hole and confirm the hydrodynamic conditions in the plasma.

  1. Evaluation of high frequency ghost cavitation emissions for two different seismic air-gun arrays using numerical modelling

    Khodabandeloo, Babak; Landrø, Martin


    Sound is deployed by marine mammals for variety of vital purposes such as finding food, communication, echolocation, etc. On the other hand human activities generate underwater noise. One major type of acoustic source is marine seismic acquisition which is carried out to image layers beneath the seabed exploiting reflected acoustic and elastic waves. Air-gun arrays are the most common and efficient marine seismic sources. Field measurements using broad band hydrophones have revealed that acoustic energies emitted by air-gun arrays contains frequencies from a few Hz up to tens of kHz. Frequencies below 200 Hz benefit seismic imaging and the rest is normally considered as wasted energy. On the other hand, the high frequency range (above 200 Hz) overlaps with hearing curves of many marine mammals and especially toothed whales and may have an impact on their behavior. A phenomenon called ghost cavitation is recently recognized to be responsible for a major part of these high frequencies (> 5 kHz). Acoustic pressure waves of individual air guns reflected from sea surface can cause the hydrostatic pressure to drop towards zero close to the source array. In these regions there is a high probability for water vapor cavity growth and subsequent collapse. We have simulated ghost cavitation cloud using numerical modelling and the results are validated by comparing with field measurements. The model is used to compare the amount of high frequency noise due to ghost cavitation for two different air gun arrays. Both of the arrays have three subarrays but the array distance for the one with 2730 in3 air volume is 6 meters and for the slightly bigger array (3250 in3 in air volume) the subarrays are separated by 8 meters. Simulation results indicate that the second array, despite larger subarray distance, generates stronger ghost cavitation signal.

  2. Cavitation Measurement during Sonic and Ultrasonic Activated Irrigation

    Macedo, Ricardo; Verhaagen, Bram; Rivas, David Fernandez; Versluis, Michel; Wesselink, Paul; van der Sluis, Luc

    Introduction: The aims of this study were to quantify and to visualize the possible occurrence of transient cavitation (bubble formation and implosion) during sonic and ultrasonic (UAI) activated irrigation. Methods: The amount of cavitation generated around several endodontic instruments was

  3. Advanced experimental and numerical techniques for cavitation erosion prediction

    Chahine, Georges; Franc, Jean-Pierre; Karimi, Ayat


    This book provides a comprehensive treatment of the cavitation erosion phenomenon and state-of-the-art research in the field. It is divided into two parts. Part 1 consists of seven chapters, offering a wide range of computational and experimental approaches to cavitation erosion. It includes a general introduction to cavitation and cavitation erosion, a detailed description of facilities and measurement techniques commonly used in cavitation erosion studies, an extensive presentation of various stages of cavitation damage (including incubation and mass loss), and insights into the contribution of computational methods to the analysis of both fluid and material behavior. The proposed approach is based on a detailed description of impact loads generated by collapsing cavitation bubbles and a physical analysis of the material response to these loads. Part 2 is devoted to a selection of nine papers presented at the International Workshop on Advanced Experimental and Numerical Techniques for Cavitation Erosion (Gr...


    NI Yongyan; YUAN Shouqi; PAN Zhongyong; YUAN Jianping


    For the purpose of detecting the cavitation of centrifugal pump onsite and real time, the vibration signals on varied operation conditions of both cavitation and non-cavitation obtained through acceleration sensors were analyzed. When cavitation occurs, the cavities near the leading edge of the blade will appear periodic oscillating, which will induce quasi-synchronous vibration. The frequency of the quasi-synchronous vibration symmetrically appears on the two sides of the blade passing frequency, by which the cavitation incipiency can be detected. During the developing process of the cavitation, as the severe complexity of the unsteady flow, it is very difficult to detect the development of cavitation by classical analysis methods. Fractal method of Higuchi is successfully used for detecting the incipiency, fully development of cavitation and the development between them.

  5. Enhanced cavitation and heating of flowing polymer- and lipid-shelled microbubbles and phase-shift nanodroplets during focused ultrasound exposures

    Zhang, Siyuan; Cui, Zhiwei; Li, Chong; Zhou, Fanyu; Zong, Yujin; Wang, Supin; Wan, Mingxi


    Cavitation and heating are the primary mechanisms of numerous therapeutic applications of ultrasound. Various encapsulated microbubbles (MBs) and phase-shift nanodroplets (NDs) have been used to enhance local cavitation and heating, creating interests in developing ultrasound therapy using these encapsulated MBs and NDs. This work compared the efficiency of flowing polymer- and lipid-shelled MBs and phase-shift NDs in cavitation and heating during focused ultrasound (FUS) exposures. Cavitation activity and temperature were investigated when the solution of polymer- and lipid-shelled MBs and NDs flowed through the vessel in a tissue-mimicking phantom with varying flow velocities when exposed to FUS at various acoustic power levels. The inertial cavitation dose (ICD) for the encapsulated MBs and NDs were higher than those for the saline. Temperature initially increased with increasing flow velocities of the encapsulated MBs, followed by a decrease of the temperature with increasing flow velocities when the velocity was much higher. Meanwhile, ICD showed a trend of increases with increasing flow velocity. For the phase-shift NDs, ICD after the first FUS exposure was lower than those after the second FUS exposure. For the encapsulated MBs, ICD after the first FUS exposure was higher than those after the second FUS exposure. Further studies are necessary to investigate the treatment efficiency of different encapsulated MBs and phase-shift NDs in cavitation and heating.

  6. Improving the cardio protective effect of aFGF in ischemic myocardium with ultrasound-mediated cavitation of heparin modified microbubbles: preliminary experiment.

    Zhao, Ying-Zheng; Lu, Cui-Tao; Li, Xiao-Kun; Tang, Qin-Qin; Tian, Xin-Qiao; Zhao, Ya-Ping; Zhang, Yan; Tian, Ji-Lai; Yang, Wei; Ge, Shuping; Nair, Chandra K; Shen, Xuedong


    Ultrasound (US)-mediated cavitation of microbubbles has evolved into a new tool for organ-specific gene and drug delivery. This paper was to investigate the feasibility of acidic fibroblast growth factor (aFGF) intravenous delivery to the ischemic myocardium of rats by ultrasonic microbubbles modified with heparin. Heparin modified microbubbles (HMB) were prepared by the freeze-dried method. Acute myocardial infarction (AMI) model was established and the cardio protective effect of the aFGF combing with HMB (aFGF-HMB) under US-mediated cavitation technique was investigated. aFGF-HMB combined with US-mediated cavitation technique was examined by ECG. Ejection fraction (EF), fractional shortening (FS) and left ventricular diastolic diameter (LVDd) were measured to monitor the improvement of global myocardial contractile function. Myocardial tissue was stained with hematoxylin and eosine (HE) to evaluate the elaborate general morphology of the ischemic myocardium. From morphologic observation and echocardiography in rat heart, aFGF-HMB had suitable size distribution, physical stability and good acoustic resonance function. From AMI rat experiments, aFGF-HMB under US-mediated cavitation technique exerted aFGF cardio protective effect in ischemic myocardium. From histological evaluation, US-mediated cavitation of aFGF-HMB showed improvement of myocardial ischemia. With the visual imaging and US-triggered drug release advantages, US-mediated cavitation of aFGF-HMB might be developed as a novel technique for targeting delivery of aFGF into ischemic myocardium.

  7. Architectural acoustics

    Long, Marshall


    .... Beginning with a brief history, it reviews the fundamentals of acoustics, human perception and reaction to sound, acoustic noise measurements, noise metrics, and environmental noise characterization...

  8. Elasto-hydrodynamic lubrication

    Dowson, D; Hopkins, D W


    Elasto-Hydrodynamic Lubrication deals with the mechanism of elasto-hydrodynamic lubrication, that is, the lubrication regime in operation over the small areas where machine components are in nominal point or line contact. The lubrication of rigid contacts is discussed, along with the effects of high pressure on the lubricant and bounding solids. The governing equations for the solution of elasto-hydrodynamic problems are presented.Comprised of 13 chapters, this volume begins with an overview of elasto-hydrodynamic lubrication and representation of contacts by cylinders, followed by a discussio

  9. Elementary classical hydrodynamics

    Chirgwin, B H; Langford, W J; Maxwell, E A; Plumpton, C


    Elementary Classical Hydrodynamics deals with the fundamental principles of elementary classical hydrodynamics, with emphasis on the mechanics of inviscid fluids. Topics covered by this book include direct use of the equations of hydrodynamics, potential flows, two-dimensional fluid motion, waves in liquids, and compressible flows. Some general theorems such as Bernoulli's equation are also considered. This book is comprised of six chapters and begins by introducing the reader to the fundamental principles of fluid hydrodynamics, with emphasis on ways of studying the motion of a fluid. Basic c

  10. Influence of microparticle size on cavitation noise during ultrasonic vibration

    H. Ge


    Full Text Available The cavitation noise in the ultrasonic vibration system was found to be influenced by the size of microparticles added in water. The SiO2 microparticles with the diameter smaller than 100 μm reduced the cavitation noise, and the reason was attributed to the constrained oscillation of the cavitation bubbles, which were stabilized by the microparticles.

  11. Static and Transient Cavitation Threshold Measurements for Mercury

    Moraga, F.; Taleyarkhan, R.P.


    Transient and static cavitation thresholds for mercury as a function of the cover gas (helium or air), and pressure are reported. Both static and transient cavitation onset pressure thresholds increase linearly with cover gas pressure. Additionally, the cavitation thresholds as a function of dissolved gases were also measured and are reported.

  12. Combining COMSOL modeling with acoustic pressure maps to design sono-reactors.

    Wei, Zongsu; Weavers, Linda K


    Scaled-up and economically viable sonochemical systems are critical for increased use of ultrasound in environmental and chemical processing applications. In this study, computational simulations and acoustic pressure maps were used to design a larger-scale sono-reactor containing a multi-stepped ultrasonic horn. Simulations in COMSOL Multiphysics showed ultrasonic waves emitted from the horn neck and tip, generating multiple regions of high acoustic pressure. The volume of these regions surrounding the horn neck were larger compared with those below the horn tip. The simulated acoustic field was verified by acoustic pressure contour maps generated from hydrophone measurements in a plexiglass box filled with water. These acoustic pressure contour maps revealed an asymmetric and discrete distribution of acoustic pressure due to acoustic cavitation, wave interaction, and water movement by ultrasonic irradiation. The acoustic pressure contour maps were consistent with simulation results in terms of the effective scale of cavitation zones (∼ 10 cm and acoustic field and identified cavitation location, a cylindrically-shaped sono-reactor with a conical bottom was designed to evaluate the treatment capacity (∼ 5 L) for the multi-stepped horn using COMSOL simulations. In this study, verification of simulation results with experiments demonstrates that coupling of COMSOL simulations with hydrophone measurements is a simple, effective and reliable scientific method to evaluate reactor designs of ultrasonic systems.

  13. Modelling vaporous cavitation on fluid transients

    Shu, Jian-Jun


    A comprehensive study of the problem of modelling vaporous cavitation in transmission lines is presented. The two-phase homogeneous equilibrium vaporous cavitation model which has been developed is compared with the conventional column separation model. The latter predicts unrealistically high pressure spikes because of a conflict arising from the prediction of negative cavity sizes if the pressure is not permitted to fall below the vapour pressure, or the prediction of negative absolute pressures if the cavity size remains positive. This is verified by a comparison of predictions with previously published experimental results on upstream, midstream and downstream cavitation. The new model has been extended to include frequency-dependent friction. The characteristics predicted by the frequency-dependent friction model show close correspondence with experimental data.

  14. Cavitation erosion of NiAl

    Akhtar, A. [Powertech Labs. Inc., Surrey, British Columbia (Canada)]|[Univ. of British Columbia (Canada). Metals and Materials Engineering Dept.; Salvi, R. [Univ. of British Columbia (Canada). Metals and Materials Engineering Dept.; Sikka, V.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.


    Vibratory cavitation erosion tests were carried out on as-cast NiAl intermetallic compounds containing 46.5 to 62.1 at. pct Ni. The erosion rate decreased with increasing nickel content by over two orders of magnitude, from a high of 16.4 to 0.11 mg{center_dot}h{sup {minus}1}. These low erosion rates exhibited by the nickel-rich alloys containing 58 and 62.1 at. pct Ni, the interruptions in their mass loss with time, and the unusual effects associated with surface finish and intensity of cavitation were found to be associated with the stress-induced martensitic transformation. Alloys containing 58 to 62 at. pct Ni have the potential for use as materials for the cavitation protection of hydraulic machinery.

  15. Analogy between fluid cavitation and fracture mechanics

    Hendricks, R. C.; Mullen, R. L.; Braun, M. J.


    When the stresses imposed on a fluid are sufficiently large, rupture or cavitation can occur. Such conditions can exist in many two-phase flow applications, such as the choked flows, which can occur in seals and bearings. Nonspherical bubbles with large aspect ratios have been observed in fluids under rapid acceleration and high shear fields. These bubbles are geometrically similar to fracture surface patterns (Griffith crack model) existing in solids. Analogies between crack growth in solid and fluid cavitation are proposed and supported by analysis and observation (photographs). Healing phenomena (void condensation), well accepted in fluid mechanics, have been observed in some polymers and hypothesized in solid mechanics. By drawing on the strengths of the theories of solid mechanics and cavitation, a more complete unified theory can be developed.

  16. On the mechanism of explosive eruption of mount erebus volcano: the dynamics of the rupture structure in a cavitating layer

    Bol'shakova, E. S.; Kedrinskiy, V. K.


    This paper presents the results of an experimental simulation of rupture development in heavily cavitating magma melt flow in volcanic conduits and its effect on the structure of explosive volcanic eruptions. The dynamics of the state of a layer of distilled water (similar in the density of cavitation nuclei to magma melt) under shock-wave loading was studied. The experiments were performed using electromagnetic hydrodynamic shock tubes (EM HST) with maximum capacitor bank energy of up to 100 J and 5 kJ. It was found that the topology of the rupture formed on the membrane surface did not change during its development. Empirical estimates were obtained for the proportion of the capacitor bank energy expended in the development of the rupture and the characteristic time of its existence. The study revealed a number of fundamentally new physical effects in the cavity dynamics in a cavitating medium: a cavitation “boundary layer” is formed on the surface of the quasi-empty rupture, which is transformed into a cluster of high energy density upon closure of the flow.

  17. Single-phase and modified turbulence models for simulation of unsteady cavitating flows

    Basuki, W.; Schnerr, G.H.; Yuan, W. [Univ. Karlsruhe (Germany)


    The aim of this research is to provide a physical complete and numerical efficient simulation method to predict developed cavitation in hydrodynamic turbomachinery as well as in micro fluid dynamic applications, e.g. in high pressure injection nozzles of combustion engines. Cavitating two-phase flows are always very unstable, highly unsteady, 3-D and turbulent. To understand cavitation dynamics and its interaction with viscous effects like boundary layers and separation, we introduce the single-phase turbulence k - {omega} model of Wilcox without modifications with respect to dispersed structures of bubbly liquids, which overestimates viscous effects in the transitional regime between the vapor and liquid phase and tends to suppress typical cavitation instabilities. Consequently our further approach consists of modifications of the single-phase Wilcox model to account for the strong nonlinear variation of the turbulent viscosity {mu}{sub t}, depending on the local void fraction {alpha}. The key issue of all numerical methods for simulation of cavitating flows is the treatment of the sudden density change of the fluid, in cold water up to 40.000:1, embedded in a global incompressible liquid flow. Here the two-phase fluid is modeled as dispersed mixture of an incompressible liquid and tiny vapor bubbles which grow or collapse, accordingly to the local static pressure and their convective transport. Therefore, the standard VOF method for capturing distinct interfaces without phase transition, e.g. free surface flow or single bubbles, is extended to include phase transition of dispersed mixtures. For simulation of bubble dynamics we apply the Rayleigh equation, which is completed by an energy balance to account for thermal effects, if hot water or if technical fluids others than water, e.g. refrigerants, with high vapor densities are considered. By using our CFD tool CAVKA we present examples of cavitating flow around hydrofoils and through single hole injection

  18. The Hydroelastic Response of a Flexible Surface-Piercing Strut in Wetted, Ventilated, and Cavitating Flows

    Harwood, Casey; Ward, Jacob; Young, Yin Lu; Felli, Mario; Falchi, Massimo; Ceccio, Steven


    High-speed and highly loaded lifting surfaces are prone to ventilation and cavitation. Increasing use of compliant materials (e.g. composites) in such systems necessitates a better understanding of the fluid-structure interactions of lifting surfaces in multiphase flow. Experiments on a flexible surface-piercing hydrofoil have been performed in a towing tank and a free-surface cavitation tunnel. The objectives are (i) to demonstrate the effects of material compliance upon hydrodynamic performance and stability of multiphase flow regimes, and (ii) to quantify the effects of multiphase flow upon the structural response and hydroelastic stability of flexible lifting bodies. A non-optical shape-sensing method is developed, which permits 3D bending and twisting deformations of the hydrofoil to be accurately inferred. The effects of the foil's compliance on hydrodynamic loads, structural motions and flow regimes are discussed. Partial immersion of the hydrofoil causes a mode-dependent change in added-mass that can encourage coalescence of higher modes. At the same time, increasing flow speed and ventilated flow decrease the damping associated with certain modes. Unsteady cavity shedding modulates the system parameters, causing a broadening of the frequency response. The authors would like to acknowledge the support of Dr. Ki-Han Kim under ONR Grant Number N00014-13-1-0383 and N00014-16-1-2433.

  19. Optimization of cavitation venturi tube design for pico and nano bubbles generation

    Xiong Yu; Peng Felicia⇑


    Hydrodynamic cavitaion venturi tube technique is used for pico and nano bubble generations in coal column flotation. In order to determine the optimal design of hydrodynamic cavitation venture tube for pico and nano bubble generation, a four-factor three-level Central Composite Design of Experimental was conducted for investigating four important design parameters of cavitation venturi tube governing the median size and the volume of pico and nano bubbles. The test results showed that maximum volume of pico and nano bubbles, 65–75%, and minimum mean pico and nano bubble size, 150–240 nm, were achieved at the medium ratio of the diameter of outlet of the venturi-tube and diam-eter of throat (3–4), medium outlet angle (11–13?), high inlet angle (26–27?) and high ratio of the length of the throat and the diameter of throat (2.3–3). Study the effects of the producing pico and nano bubbles on fine coal flotation was performed in a 5 cm diameter 260 cm height flotation column. The optimal percentage of pico and nano bubbles was about 70%, which produced maximum combustible material recovery of 86%with clean coal ash content of 11.7%.

  20. Dynamics of cavitating cascades. [transfer functions

    Brennen, C. E.; Acosta, A. J.


    The unsteady dynamics of cavitating cascades and inducer pumps were studied with a view to understanding (and possibly predicting) the dynamic characteristics of these devices. The chronology of the research is summarized as well as the final conculsions for each task. The construction of a dynamic pump test facility and its use in making experimental measurements of the transfer function is described as well as tests conducted using a scale model of the low pressure liquid oxygen turbopump inducer in the shuttle main engine. Auto-oscillation and unsteady inlet flow characteristics are discussed in addition to blade cavity influence and bubbly cavitation.

  1. Cavitation wear resistance of engine bearing materials

    Rac, Aleksandar


    The resistance to cavitation erosion of aluminum alloy, and cast and sinte-red lead-bronze, materials which are most frequently used for engine bearings, has been evaluated. The tests were carried out in motor oil at a temperature of 80 C, using a magnetostrictive vibratory tester (20 kHz). The results showed that the cavitation erosion resistance was the greatest in cast lead-bronze. On the contrary, sintered lead-bronze, though of the same chemical composition, had the greatest erosion rate. Additionally, the investigation of the overlay plated bearings showed the overlay was nonresistive to this type of wear.

  2. Effect of cavitation on comminution of mica powder

    ChuwenGuo; LinshengLiu; 等


    The cavitation abrasive water jet was used in the comminution of mica.By applying a cavitation nozzle in the abrasive water jet system to enhance the effect of cavitation and friction,better comminution results were obtained.The JME-200CX transmission electron microscope was used for observing the size distribution of particles.As using cavitation abrasive water jet,the relative comminution effect is raised by more than 25% compared with using abrasive water jet oly.It can be concluded that the effect of cavitation is much more significant than that of impacting in the comminution of mica.

  3. Effect of cavitation on comminution of mica powder


    The cavitation abrasive water jet was used in the comminution of mica. By applying a cavitation nozzle in the abrasive water jet system to enhance the effect of cavitation and friction, better comminution results were obtained. The JME-200CX transmission electron microscope was used for observing the size distribution of particles. As using cavitation abrasive water jet, the relative comminution effect is raised by more than 25% compared with using abrasive water jet only. Itcan be concluded that the effect of cavitation is much more significant than that of impacting in the comminution of mica.

  4. Virtual Acoustics

    Lokki, Tapio; Savioja, Lauri

    The term virtual acoustics is often applied when sound signal is processed to contain features of a simulated acoustical space and sound is spatially reproduced either with binaural or with multichannel techniques. Therefore, virtual acoustics consists of spatial sound reproduction and room acoustics modeling.

  5. Quasiparticle anisotropic hydrodynamics

    Alqahtani, Mubarak


    We study an azimuthally-symmetric boost-invariant quark-gluon plasma using quasiparticle anisotropic hydrodynamics including the effects of both shear and bulk viscosities. We compare results obtained using the quasiparticle method with the standard anisotropic hydrodynamics and viscous hydrodynamics. We consider the predictions of the three methods for the differential particle spectra and mean transverse momentum. We find that the three methods agree for small shear viscosity to entropy density ratio, $\\eta/s$, but show differences at large $\\eta/s$. Additionally, we find that the standard anisotropic hydrodynamics method shows suppressed production at low transverse-momentum compared to the other two methods, and the bulk-viscous correction can drive the primordial particle spectra negative at large $p_T$ in viscous hydrodynamics.

  6. Hydrodynamics of Pumps

    Brennen, Christopher Earls


    The subject of this monograph is the fluid dynamics of liquid turbomachines, particularly pumps. Rather than attempt a general treatise on turbomachines, we shall focus attention on those special problems and design issues associated with the flow of liquid through a rotating machine. There are two characteristics of a liquid that lead to these special problems, and cause a significantly different set of concerns than would occur in, say, a gas turbine. These are the potential for cavitation ...

  7. Magnetic resonance imaging of velocity fields, the void fraction and gas dynamics in a cavitating liquid

    Mastikhin, Igor V.; Arbabi, Aidin; Newling, Benedict; Hamza, Abdelhaq; Adair, Alexander [University of New Brunswick, UNB MRI Centre, Department of Physics, Fredericton, NB (Canada)


    In acoustic cavitation, the relationship between the bubble dynamics on the microscale and the flow properties on the macroscale is critical in determining sonochemical reaction kinetics. A new technique was developed to measure the void fraction and estimate water mobility in the vicinity of cavitating bubbles using phase-encoded magnetic resonance imaging with short characteristic measurement timescales (0.1-1 ms). The exponential behavior of the NMR signal decay indicated the fast diffusion regime, with the relationship between local mechanical dispersion D{sub mix} and the average bubble radius R, D{sub mix}>>(2R{sup 2})/(10{sup -4}s), resulting in dispersion of orders of magnitude greater than diffusion in quiescent water. For two different samples (water and a surfactant solution), the independent measurements of three-dimensional void fraction and velocity fields permitted the calculation of compressibility, divergence and vorticity of the cavitating medium. The measured dynamics of the dissolved gas, compared with that of the surrounding liquid, reflected the difference in the bubble coalescence and lifetimes and correlated with the macroscopic flow parameters. (orig.)

  8. Noise generated by cavitating single-hole and multi-hole orifices in a water pipe

    Testud, P.; Moussou, P.; Hirschberg, A.; Aurégan, Y.


    This paper presents an experimental study of the acoustical effects of cavitation caused by a water flow through an orifice. A circular-centered single-hole orifice and a multi-hole orifice are tested. Experiments are performed under industrial conditions: the pressure drop across the orifice varies from 3 to 30 bar, corresponding to cavitation numbers from 0.74 to 0.03. Two regimes of cavitation are discerned. In each regime, the broadband noise spectra obtained far downstream of the orifice are presented. A nondimensional representation is proposed: in the intermediate ‘developed cavitation’ regime, spectra collapse reasonably well; in the more intense ‘super cavitation’ regime, spectra depend strongly on the quantity of air remaining in the water downstream of the orifice, which is revealed by the measure of the speed of sound at the downstream transducers. In the ‘developed cavitation’ regime, whistling associated with periodic vortex shedding is observed. The corresponding Strouhal number agrees reasonably well with literature for single-phase flows. In the 'super cavitation’ regime, the whistling disappears.

  9. Cavitation-enhanced delivery of a replicating oncolytic adenovirus to tumors using focused ultrasound.

    Bazan-Peregrino, Miriam; Rifai, Bassel; Carlisle, Robert C; Choi, James; Arvanitis, Costas D; Seymour, Leonard W; Coussios, Constantin C


    Oncolytic viruses (OV) and ultrasound-enhanced drug delivery are powerful novel technologies. OV selectively self-amplify and kill cancer cells but their clinical use has been restricted by limited delivery from the bloodstream into the tumor. Ultrasound has been previously exploited for targeted release of OV in vivo, but its use to induce cavitation, microbubble oscillations, for enhanced OV tumor extravasation and delivery has not been previously reported. By identifying and optimizing the underlying physical mechanism, this work demonstrates that focused ultrasound significantly enhances the delivery and biodistribution of systemically administered OV co-injected with microbubbles. Up to a fiftyfold increase in tumor transgene expression was achieved, without any observable tissue damage. Ultrasound exposure parameters were optimized as a function of tumor reperfusion time to sustain inertial cavitation, a type of microbubble activity, throughout the exposure. Passive detection of acoustic emissions during treatment confirmed inertial cavitation as the mechanism responsible for enhanced delivery and enabled real-time monitoring of successful viral delivery.

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

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


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

  11. Validation of full cavitation model in cryogenic fluids

    CAO XiaoLi; ZHANG XiaoBin; QIU LiMin; GAN ZhiHua


    Numerical simulation of cavitation in cryogenic fluids is important in improving the stable operation of he propulsion system in liquid-fuel rocket. It also represents a broader class of problems where the fluid is operating close to its critical point and the thermal effects of cavitation are pronounced. The present article focuses on simulating cryogenic cavitation by implementing the "full cavitation model", coupled with energy equation, in conjunction with iteraUve update of the real fluid properties at local temperatures. Steady state computations are then conducted on hydrofoil and ogive in liquid nitrogen and hydrogen respectively, based on which we explore the mechanism of cavitation with thermal ef-fects. Comprehensive comparisons between the simulation results and experimental data as well as previous computations by other researchers validate the full cavitation model in cryogenic fluids. The sensitivity of cavity length to cavitation number is also examined.

  12. Effects of cavitation on performance of automotive torque converter

    Jaewon Ju


    Full Text Available Cavitation is a phenomenon whereby vapor bubbles of a flowing liquid are formed in a local region where the pressure of the liquid is below its vapor pressure. It is well known that cavitation in torque converters occurs frequently when a car with an automatic transmission makes an abrupt start. Cavitation is closely related to a performance drop and noise generation at a specific operating condition in a car and a torque converter itself. This study addressed the relation between cavitation and performance in an automotive torque converter in a quantitative and qualitative manner using numerical simulations. The cavitation was calculated at various operating conditions using a commercial flow solver with the homogeneous cavitation model, and the torque converter performance was compared with the experimental data. Numerical results well match to the data and indicate that the cavitation causes significant performance drop, as the pump speed increases or both speed ratio and reference pressure decrease.

  13. Mechanism of an acoustic wave impact on steel during solidification

    K. Nowacki


    Full Text Available Acoustic steel processing in an ingot mould may be the final stage in the process of quality improvement of a steel ingot. The impact of radiation and cavitation pressure as well as the phenomena related to the acoustic wave being emitted and delivered to liquid steel affect various aspects including the internal structure fragmentation, rigidity or density of steel. The article provides an analysis of the mechanism of impact of physical phenomena caused by an acoustic wave affecting the quality of a steel ingot.

  14. Cavitationally induced biodegradability enhancement of a distillery wastewater.

    Padoley, K V; Saharan, Virendra Kumar; Mudliar, S N; Pandey, R A; Pandit, Aniruddha B


    Hydrodynamic cavitation (HC) was evaluated as a pretreatment option for the complex/recalcitrant biomethanated distillery wastewater (B-DWW). The effect of various process parameters such as inlet pressure, dilution and reaction time on reduction of COD/TOC and enhancement of biodegradability index (BI:BOD(5):COD ratio) of the B-DWW was studied with an aim to maximize the biodegradability index and reducing the toxicity of the distillery wastewater. It was observed that higher operating pressure (13 bar) yielded the maximum BI whereas the lower pressure (5 bar) is suitable for the reduction in the toxicity of B-DWW. The toxicity of the distillery wastewater was analyzed by measuring the COD, TOC and color of the wastewater sample. The HC pretreatment under optimized conditions leads to a BI of 0.32, COD and TOC reduction of 32.24% and 31.43%, respectively along with a color reduction by 48%. These results indicate the potential of HC as a pretreatment option for enhancing the biodegradability index of the recalcitrant wastewater such as B-DWW along with reduced toxicity of wastewater as observed from COD, TOC and color reduction profile under optimized conditions.

  15. Cavitation inception following shock wave passage

    Ohl, C.D.


    Cavitation bubble nucleation following the passage of an extracorporeal shock wave lithotripter pulse is investigated experimentally and numerically. In the experiments two configurations are considered: Free passage of the shock wave, and reflection of the shock wave from a rigid reflector. The nuc

  16. Classification of lubricants according to cavitation criteria

    Meged, Y.; Venner, C.H.; Napel, ten W.E


    Cavitation in lubrication liquids has long been known to be detrimental to components in hydraulic systems. Damage has been detected in journal bearings, especially under severe dynamic loading, gears, squeeze film dampers and valves. These findings have led to intensive studies of metal resistance

  17. The making of a cavitation children's book

    Henry de Frahan, Marc; Patterson, Brandon; Lazar, Erika


    Engaging young children in science is particularly important to future scientific endeavors. From thunderstorms to the waterpark, children are constantly exposed to the wonders of fluid dynamics. Among fluid phenomena, bubbles have always fascinated children. Yet some of the most exciting aspects of bubbles, such as cavitation, are scarcely known to non-experts. To introduce cavitation to a five year old audience, we wrote "Brooke Bubble Breaks Things", a children's book about the adventures of a cavitation bubble learning about all the things she could break. In this talk, we discuss how a children's book is made by walking through the steps involved in creating the book from concept to publication. We focus on strategies for successfully communicating a technical message while balancing entertainment and fidelity to nature. To provide parents, teachers, and young inquiring minds with a detailed explanation of the physics and applications of cavitation, we also created a website with detailed explanations, animations, and links to further information. We aim to convince the fluids community that writing picture books is an intellectually stimulating and fun way of communicating fluids principles and applications to children. ArtsEngine Microgrant at the University of Michigan.

  18. On cavitation instabilities with interacting voids

    Tvergaard, Viggo


    voids so far apart that the radius of the plastic zone around each void is less than 1% of the current spacing between the voids, can still affect each others at the occurrence of a cavitation instability such that one void stops growing while the other grows in an unstable manner. On the other hand...

  19. Cavitation inception following shock wave passage

    Ohl, C.D.


    Cavitation bubble nucleation following the passage of an extracorporeal shock wave lithotripter pulse is investigated experimentally and numerically. In the experiments two configurations are considered: Free passage of the shock wave, and reflection of the shock wave from a rigid reflector. The nuc

  20. Cavitation of a Physically Associating Gel

    Mishra, Satish; Kundu, Santanu

    Self-assembly of block copolymers in selective solvents form ordered structures such as micelles, vesicles, and physically crosslinked gels due to difference in their interaction with solvents. These gels have wide range of applications in tissue engineering, food science and biomedical field due to their tunable properties and responsiveness with changing environmental conditions. Pressurization of a defect inside a physically associating gel can lead to elastic instability (cavitation) leading to failure of the gel. The failure behavior involves dissociation of physical networks. A thermoreversible, physically associating gel with different volume fractions of a triblock copolymer, poly (methyl methacrylate)-poly (n-butyl acrylate)-poly (methyl methacrylate) [PMMA-PnBA-PMMA] in 2-ethyl 1-hexanol, a midblock selective solvent, is considered here. Mechanical properties were investigated using shear rheology and cavitation experiments. The experimental data is fitted with a constitutive model that captures the stiffening behavior followed by softening behavior of a physical gel. Finite element analysis has been performed on cavitation rheology geometry to capture the failure behavior and to calculate energy release rate during cavitation experiments.

  1. Modeling of Cavitating Flow through Waterjet Propulsors


    break down due to massive suction side flow separation (stall). In Figure 3, photographs from tunnel testing and computed results are shown. The...128, pp. 1308-1323. Mishra C. & Peles, Y. (2005) "Cavitation in flow through a micro- orifice inside a silicon micro- channel,’ Phvs. Fluids 17

  2. Measuring cavitation and its cleaning effect

    Verhaagen, Bram; Fernandez Rivas, David


    The advantages and limitations of techniques for measuring the presence and amount of cavitation, and for quantifying the removal of contaminants, are provided. After reviewing chemical, physical, and biological studies, a universal cause for the cleaning effects of bubbles cannot yet be concluded.

  3. Ultrasound induced by CW laser cavitation bubbles

    Korneev, N; Montero, P Rodriguez; Ramos-Garcia, R; Ramirez-San-Juan, J C; Padilla-Martinez, J P, E-mail: [Instituto Nacional de Astrofisica, Optica y Electronica, Apt. Postal 51 y 216 CP72000, Puebla, Pue. (Mexico)


    The generation of ultrasound by a collapsing single cavitation bubble in a strongly absorbing liquid illuminated with a moderate power CW laser is described. The ultrasound shock wave is detected with hydrophone and interferometric device. To obtain a stronger pulse it is necessary to adjust a liquid absorption and a beam diameter. Their influence can be qualitatively understood with a simple model.

  4. Modelling cavitating flow around underwater missiles

    Fabien Petitpas


    Full Text Available The diffuse interface model of Saurel et al. (2008 is used for the computation of compressible cavitating flows around underwater missiles. Such systems use gas injection and natural cavitation to reduce drag effects. Consequently material interfaces appear separating liquid and gas. These interfaces may have a really complex dynamics such that only a few formulations are able to predict their evolution. Contrarily to front tracking or interface reconstruction method the interfaces are computed as diffused numerical zones, that are captured in a routinely manner, as is done usually with gas dynamics solvers for shocks and contact discontinuity. With the present approach, a single set of partial differential equations is solved everywhere, with a single numerical scheme. This leads to very efficient solvers. The algorithm derived in Saurel et al. (2009 is used to compute cavitation pockets around solid bodies. It is first validated against experiments done in cavitation tunnel at CNU. Then it is used to compute flows around high speed underwater systems (Shkval-like missile. Performance data are then computed showing method ability to predict forces acting on the system.

  5. Control of Propeller Cavitation in Operational Conditions

    Vrijdag, A.


    Off design conditions can have a severe impact on ship propulsion system behaviour. Resistance increase for instance leads to a higher engine loading, and can also easily lead to a decrease of cavitation inception speed with respect to calm water conditions. Wakefield variations due to ship motions,

  6. Cavitation for improved sludge conversion into biogas

    Stoop, A.H.; Bakker, T.W.; Kramer, H.J.M.


    In several studies the beneficial influence of pre-treatment of waste activated sludge with cavitation on the biogas production was demonstrated. It is however, still not fully certain whether this effect should be mainly contributed to an increase in conversion rate of organics into biogas by anaer

  7. Adaptable Design Improvements for Electromagnetic Shock Wave Lithotripters and Techniques for Controlling Cavitation

    Smith, Nathan Birchard

    In this dissertation work, the aim was to garner better mechanistic understanding of how shock wave lithotripsy (SWL) breaks stones in order to guide design improvements to modern electromagnetic (EM) shock wave lithotripters. To accomplish this goal, experimental studies were carefully designed to isolate mechanisms of fragmentation, and models for wave propagation, fragmentation, and stone motion were developed. In the initial study, a representative EM lithotripter was characterized and tested for in vitro stone comminution efficiency at a variety of field positions and doses using phantom kidney stones of variable physical properties, and in different fluid mediums to isolate the contribution of cavitation. Through parametric analysis of the acoustic field measurements alongside comminution results, a logarithmic correlation was determined between average peak pressure incident on the stone surface and comminution efficiency. It was also noted that for a given stone type, the correlations converged to an average peak pressure threshold for fragmentation, independent of fluid medium in use. The correlation of average peak pressure to efficacy supports the rationale for the acoustic lens modifications, which were pursued to simultaneously enhance beam width and optimize the pulse profile of the lithotripter shock wave (LSW) via in situ pulse superposition for improved stone fragmentation by stress waves and cavitation, respectively. In parallel, a numerical model for wave propagation was used to investigate the variations of critical parameters with changes in lens geometry. A consensus was reached on a new lens design based on high-speed imaging and stone comminution experiments against the original lens at a fixed acoustic energy setting. The results have demonstrated that the new lens has improved efficacy away from the focus, where stones may move due to respiration, fragmentation, acoustic radiation forces, or voluntary patient movements. Using the

  8. Communication Acoustics

    Blauert, Jens

    Communication Acoustics deals with the fundamentals of those areas of acoustics which are related to modern communication technologies. Due to the advent of digital signal processing and recording in acoustics, these areas have enjoyed an enormous upswing during the last 4 decades. The book...... the book a source of valuable information for those who want to improve or refresh their knowledge in the field of communication acoustics - and to work their way deeper into it. Due to its interdisciplinary character Communication Acoustics is bound to attract readers from many different areas, such as......: acoustics, cognitive science, speech science, and communication technology....

  9. Hydrodynamics and black holes

    Oz, Yaron


    This chapter describes how the AdS/CFT correspondence (the Holographic Principle) relates field theory hydrodynamics to perturbations of black hole (brane) gravitational backgrounds. The hydrodynamics framework is first presented from the field theory point of view, after which the dual gravitational description is outlined, first for relativistic fluids and then for the nonrelativistic case. Further details of the fluid/gravity correspondence are then discussed, including the bulk geometry and the dynamics of the black hole horizon.

  10. Investigation on the inertial cavitation threshold and shell properties of commercialized ultrasound contrast agent microbubbles.

    Guo, Xiasheng; Li, Qian; Zhang, Zhe; Zhang, Dong; Tu, Juan


    The inertial cavitation (IC) activity of ultrasound contrast agents (UCAs) plays an important role in the development and improvement of ultrasound diagnostic and therapeutic applications. However, various diagnostic and therapeutic applications have different requirements for IC characteristics. Here through IC dose quantifications based on passive cavitation detection, IC thresholds were measured for two commercialized UCAs, albumin-shelled KangRun(®) and lipid-shelled SonoVue(®) microbubbles, at varied UCA volume concentrations (viz., 0.125 and 0.25 vol. %) and acoustic pulse lengths (viz., 5, 10, 20, 50, and 100 cycles). Shell elastic and viscous coefficients of UCAs were estimated by fitting measured acoustic attenuation spectra with Sarkar's model. The influences of sonication condition (viz., acoustic pulse length) and UCA shell properties on IC threshold were discussed based on numerical simulations. Both experimental measurements and numerical simulations indicate that IC thresholds of UCAs decrease with increasing UCA volume concentration and acoustic pulse length. The shell interfacial tension and dilatational viscosity estimated for SonoVue (0.7 ± 0.11 N/m, 6.5 ± 1.01 × 10(-8) kg/s) are smaller than those of KangRun (1.05 ± 0.18 N/m, 1.66 ± 0.38 × 10(-7) kg/s); this might result in lower IC threshold for SonoVue. The current results will be helpful for selecting and utilizing commercialized UCAs for specific clinical applications, while minimizing undesired IC-induced bioeffects.

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

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


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

  12. Acoustic telemetry

    National Oceanic and Atmospheric Administration, Department of Commerce — To determine movements of green turtles in the nearshore foraging areas, we deployed acoustic tags and determined their movements through active and passive acoustic...

  13. Investigation of Two-Phase Flow in AxialCentrifugal Impeller by Hydrodynamic Modeling Methods

    V. O. Lomakin


    Full Text Available The article provides a methodology to study the flow in the wet part of the pump with fundamentally new axial-centrifugal impeller by methods of hydrodynamic modeling in the software package STAR CCM +. The objective of the study was to determine the normal and cavitation characteristics of the pump with a new type of wet part, as well as optimization of the geometrical parameters of the pump. Authors solved this problem using an example of the hot coolant pump, which should meet high requirements for cavitation quality and efficiency (hydraulic efficiency up to 87%, critical value of NPSH to 2.2 m.Also, the article focuses on the methods of numerical solution of two-phase flow simulation in a pump that are needed for a more accurate simulation of cavitation in the pump and research work in liquids with high gas content.Hydrodynamic modeling was performed on a computing cluster at the department E-10 of BMSTU for pump flow simulation in unsteady statement of problem using the computational grid size to 1.5 million cells. Simultaneously, the experimental model of the pump was made by 3D printing and tested at the stand in the BMSTU. Test results, which were compared with the calculated data are also given in the article. Inaccuracy of the calculation of pump head does not exceed 5%.The simulation results may be of interest to specialists in the field of hydrodynamic modeling, and for designers of such pumps. The authors also report production of a full-length prototype of the pump in order to conduct further testing for the verification of the data in the article, primarily in terms of cavitation characteristics.

  14. Primary acoustic signal structure during free falling drop collision with a water surface

    Chashechkin, Yu. D., E-mail:; Prokhorov, V. E., E-mail: [Russian Academy of Sciences, Ishlinskii Institute for Problems in Mechanics (Russian Federation)


    Consistent optical and acoustic techniques have been used to study the structure of hydrodynamic disturbances and acoustic signals generated as a free falling drop penetrates water. The relationship between the structures of hydrodynamic and acoustic perturbations arising as a result of a falling drop contacting with the water surface and subsequent immersion into water is traced. The primary acoustic signal is characterized, in addition to stably reproduced features (steep leading edge followed by long decay with local pressure maxima), by irregular high-frequency packets, which are studied for the first time. Reproducible experimental data are used to recognize constant and variable components of the primary acoustic signal.

  15. Computational Analyses of Cavitating Flows in Cryogenic Liquid Hydrogen

    Tiezhi Sun; Yingjie Wei; Cong Wang∗


    The objective of this study is to analyze the fundamental characteristics and the thermodynamic effects of cavitating flows in liquid hydrogen. For this purpose, numerical simulation of cavitating flows are conducted over a three dimensional hydrofoil in liquid hydrogen. Firstly, the efficiency of this computational methodology is validated through comparing the simulation results with the experimental measurements of pressure and temperature. Secondly, after analysing the cavitating flows in liquid hydrogen and water, the characteristics under cryogenic conditions are highlighted. The results show that the thermodynamic effects play a significant role in the cavity structure and the mass transfer, the dimensionless mass transfer rate of liquid hydrogen is much larger, and the peak value is about ninety times as high as water at room temperature. Furthermore, a parametric study of cavitating flows on hydrofoil is conducted by considering different cavitation number and dimensionless thermodynamic coefficient. The obtained results provide an insight into the thermodynamic effect on the cavitating flows.

  16. U-shaped Vortex Structures in Large Scale Cloud Cavitation

    Cao, Yantao; Peng, Xiaoxing; Xu, Lianghao; Hong, Fangwen


    The control of cloud cavitation, especially large scale cloud cavitation(LSCC), is always a hot issue in the field of cavitation research. However, there has been little knowledge on the evolution of cloud cavitation since it is associated with turbulence and vortex flow. In this article, the structure of cloud cavitation shed by sheet cavitation around different hydrofoils and a wedge were observed in detail with high speed camera (HSC). It was found that the U-shaped vortex structures always existed in the development process of LSCC. The results indicated that LSCC evolution was related to this kind of vortex structures, and it may be a universal character for LSCC. Then vortex strength of U-shaped vortex structures in a cycle was analyzed with numerical results.

  17. Comminution of Mica by Cavitation Abrasive Water Jet

    GUO Chu-wen; LIU Lin-sheng; HAN Dong-tai; LI Ai-min; ZHANG Dong-hai


    The comminution of mica with an abrasive water jet is mainly based on three knids of effects, that is, high-speed collision, cavitating effect and shearing effect. Cavitation abrasive water jet was applied for the comminution of mica because cavitation abrasive water jet can make full use of the three effects mentioned above. Besides high speed impacting among particles,cavitation and shearing were also enhanced due to the divergent angle at the outlet of the cavitation nozzle.A JME-200CX transmission electron microscope was used for observing the size distribution of particles.Variance analysis on the experimental results indicates that the effect of cavitation is much more significant than that of collision.The effect of pressure on comminution results becomes less with the decrease of the particle size.

  18. Cavitation erosion behavior of nickel-aluminum bronze weldment

    李小亚; 闫永贵; 许振明; 李建国


    Cavitation erosion behavior of nickel-aluminum bronze(NAB)weldment in 3.5% NaCl aqueous solution was studied by magnetostrictive vibratory device for cavitation erosion.The results show that cavitation erosion resistance of the weld zone(WZ)of the weldment is superior to that of the base metal.SEM observation of eroded specimens reveals that the phases undergoing selective attack by the stress of cavitation erosion at the early stage of cavitation erosion are:martensite in the WZ,α phase in the heat-affected zone(HAZ)and eutectoidal phase in the base metal; the microcracks causing cavitation damage initiate at the phase boundaries.

  19. Cavitation measurement during sonic and ultrasonic activated irrigation.

    Macedo, Ricardo; Verhaagen, Bram; Rivas, David Fernandez; Versluis, Michel; Wesselink, Paul; van der Sluis, Luc


    The aims of this study were to quantify and to visualize the possible occurrence of transient cavitation (bubble formation and implosion) during sonic and ultrasonic (UAI) activated irrigation. The amount of cavitation generated around several endodontic instruments was measured by sonochemiluminescence dosimetry inside 4 root canal models of human dimensions and varying complexity. Furthermore, the spatial distribution of the sonochemiluminescence in the root canal was visualized with long-exposure photography. Instrument oscillation frequency, ultrasonic power, and file taper influenced the occurrence and amount of cavitation. In UAI, cavitation was distributed between the file and the wall extending beyond the file and inside lateral canals/isthmuses. In sonic activated irrigation, no cavitation was detected. Cavitation was shown to occur in UAI at clinically relevant ultrasonic power settings in both straight and curved canals but not around sonically oscillating instruments, driven at their highest frequency. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  20. Detached eddy simulation of unsteady cavitation and pressure fluctuation around 3-D NACA66 hydrofoil

    Zhang De-Sheng


    Full Text Available The unsteady cavitating flow and pressure fluctuation around the 3-D NACA66 hydrofoil were simulated and validated based on detached eddy simulation turbulence model and a homogeneous cavitation model. Numerical results show that detached eddy simulation can predict the evolution of cavity inception, sheet cavitation growth, cloud cavitation shedding, and breakup, as well as the pressure fluctuation on the surface of hydrofoil. The sheet cavitation growth, detachment, cloud cavitation shedding are responsible for the features of the pressure fluctuation.

  1. L-Area Cavitation Tests Final Analysis - Limits Application

    Wood, D.C.


    The L-Area cavitation test was designed to better define the onset of cavitation in the reactor system. The onset of gas evolution in the effluent piping and pump cavitation was measured using state-of-the-art equipment to provide data with a high confidence and low uncertainty level. The limits calculated from the new data will allow an approximate two percent increase in reactor power if the reactor is effluent temperature-limited with no compromise in reactor safety.

  2. Preparation of graphene by jet cavitation

    Shen, Zhigang; Li, Jinzhi; Yi, Min; Zhang, Xiaojing; Ma, Shulin


    Despite its bright prospects, graphene faces challenges including issues concerning mass production. Here we present a totally green approach whereby common crystal graphite can be exfoliated into graphene sheets in aqueous solution by jet cavitation. This is possible mainly because the tensile stress caused by graphite-solution interfacial reflection of compressive waves acts an intensive 'suction disk' on the graphite flakes. We confirm the presence of graphene sheets by diverse characterizations. The graphene yield by our method is estimated as ~ 4 wt%, which could potentially be improved by further processing. The method, of a mechanical nature, is powerful compared to the traditional low-throughput micromechanical cleavage. Our work here illustrates jet cavitation as a facile, low cost, timesaving and laborsaving route, which can potentially be scaled up to mass production of graphene.

  3. Cavitation-based hydro-fracturing simulator

    Wang, Jy-An John; Wang, Hong; Ren, Fei; Cox, Thomas S.


    An apparatus 300 for simulating a pulsed pressure induced cavitation technique (PPCT) from a pressurized working fluid (F) provides laboratory research and development for enhanced geothermal systems (EGS), oil, and gas wells. A pump 304 is configured to deliver a pressurized working fluid (F) to a control valve 306, which produces a pulsed pressure wave in a test chamber 308. The pulsed pressure wave parameters are defined by the pump 304 pressure and control valve 306 cycle rate. When a working fluid (F) and a rock specimen 312 are included in the apparatus, the pulsed pressure wave causes cavitation to occur at the surface of the specimen 312, thus initiating an extensive network of fracturing surfaces and micro fissures, which are examined by researchers.

  4. Cavitated Bifurcation for Incompressible Hyperelastic Material

    任九生; 程昌钧


    The spherical cavitated bifurcation for a hyperelastic solid sphere made of the incompressible Valanis-Landel material under boundary dead-loading is examined. The analytic solution for the bifurcation problem is obtained. The catastrophe and concentration of stresses are discussed. The stability of solutions is discussed through the energy comparison.And the growth of a pre-existing micro-void is also observed.

  5. Photoacoustic cavitation for theranostics: mechanism, current progress and applications

    Feng, Y.; Qin, D.; Wan, M.


    As an emerging cavitation technology, photoacoustic cavitation (PAC) means the formation of bubbles in liquids using focused laser and pre-established ultrasound synchronously. Its significant advantages include the decreased threshold of each modality and the precise location of cavitation determined by the focused laser. In this paper, a brief review of PAC is presented, including the physical mechanism description, the classic experimental technology, the representative results in variety of media, and its applications in biomedical imaging and therapy. Moreover, some preliminary results of PAC in perfluoropentane (PFP) liquid and PFP droplets investigated by passive cavitation detection (PCD) in our group are also presented.

  6. Understanding Cavitation Intensity through Pitting and Pressure Pulse Analysis

    Jayaprakash, A.; Singh, S.; Choi, J.-K.; Chahine, G.


    Cavitation erosion is of interest to the designers of ship propulsion devices because of its detrimental effects. One of the difficulties of predicting cavitation erosion is that the intensity of cavitation is not well predicted or defined. In this work we attempt to define the intensity of a cavitation erosion field through analysis of cavitation induced erosion pits and pressure pulses. In the pitting tests, material samples were subjected to cavitation field for a short duration of time selected within the test sample's incubation period, so that the test sample undergoes plastic deformation only. The sample material reacts to these cavitation events by undergoing localized permanent deformation, called pits. The resulting pitted sample surfaces were then optically scanned and analyzed. The pressure signals under cavitating jets and ultrasonic horns, for different conditions, were experimentally recorded using high frequency response pressure transducers. From the analysis of the pitting data and recorded pressure signals, we propose a model that describes the statistics, which in the future can be used to define the cavitation field intensity. Support for this work was provided by Office of Naval Research (ONR) under contract number N00014-08-C-0450, monitored by Dr. Ki-Han Kim.

  7. Modeling Unsteady Cavitation Effects and Dynamic Loads in Cryogenic Systems Project

    National Aeronautics and Space Administration — There currently are no analytical or CFD tools that can reliably predict unsteady cavitation dynamics in liquid rocket turbopumps. Cavitation effects, particularly...

  8. LDV survey of cavitation and resonance effect on the precessing vortex rope dynamics in the draft tube of Francis turbines

    Favrel, A.; Müller, A.; Landry, C.; Yamamoto, K.; Avellan, F.


    The large-scale penetration of the electrical grid by intermittent renewable energy sources requires a continuous operating range extension of hydropower plants. This causes the formation of unfavourable flow patterns in the draft tube of turbines and pump-turbines. At partial load operation, a precessing cavitation vortex rope is formed at the Francis turbine runner outlet, acting as an excitation source for the hydraulic system. In case of resonance, the resulting high-amplitude pressure pulsations can put at risk the stability of the machine and of the electrical grid to which it is connected. It is therefore crucial to understand and accurately simulate the underlying physical mechanisms in such conditions. However, the exact impact of cavitation and hydro-acoustic resonance on the flow velocity fluctuations in the draft tube remains to be established. The flow discharge pulsations expected to occur in the draft tube in resonance conditions have for instance never been verified experimentally. In this study, two-component Laser Doppler Velocimetry is used to investigate the axial and tangential velocity fluctuations at the runner outlet of a reduced scale physical model of a Francis turbine. The investigation is performed for a discharge equal to 64 % of the nominal value and three different pressure levels in the draft tube, including resonance and cavitation-free conditions. Based on the convective pressure fluctuations induced by the vortex precession, the periodical velocity fluctuations over one typical precession period are recovered by phase averaging. The impact of cavitation and hydro-acoustic resonance on both axial and tangential velocity fluctuations in terms of amplitude and phase shift is highlighted for the first time. It is shown that the occurrence of resonance does not have significant effects on the draft tube velocity fields, suggesting that the synchronous axial velocity fluctuations are surprisingly negligible compared to the velocity

  9. Anisotropic hydrodynamics -- basic concepts

    Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael


    Due to the rapid longitudinal expansion of the quark-gluon plasma created in relativistic heavy ion collisions, potentially large local rest frame momentum-space anisotropies are generated. The magnitude of these momentum-space anisotropies can be so large as to violate the central assumption of canonical viscous hydrodynamical treatments which linearize around an isotropic background. In order to better describe the early-time dynamics of the quark gluon plasma, one can consider instead expanding around a locally anisotropic background which results in a dynamical framework called anisotropic hydrodynamics. In this proceedings contribution we review the basic concepts of the anisotropic hydrodynamics framework presenting viewpoints from both the phenomenological and microscopic points of view.

  10. Visualization of cavitation in flanged poppet valve; Tsubatsuki popetto bennai no cavitation no kashika

    Iijima, A.; Tsukiji, T. [Ashikaga Institute of Technology, Tochigi (Japan); Sumita, T. [Tokimec Inc., Tokyo (Japan)


    Only half-cut models are dealt with in reports made available so far about experiments on the visualization of cavitation in what is called a flanged poppet valve, which is a valve whose cone-shaped poppet is provided with flanges at its end and periphery for reduction in fluid force. In the present report, a valve is drilled from three directions in an experiment for visualizing flows near the poppet valve flanges, which is for three-dimensional model visualization. The shapes of the poppet valve flanges are changed in various ways for the study of cavitation generation limits. (translated by NEDO)

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

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


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

  12. Dispersive hydrodynamics: Preface

    Biondini, G.; El, G. A.; Hoefer, M. A.; Miller, P. D.


    This Special Issue on Dispersive Hydrodynamics is dedicated to the memory and work of G.B. Whitham who was one of the pioneers in this field of physical applied mathematics. Some of the papers appearing here are related to work reported on at the workshop "Dispersive Hydrodynamics: The Mathematics of Dispersive Shock Waves and Applications" held in May 2015 at the Banff International Research Station. This Preface provides a broad overview of the field and summaries of the various contributions to the Special Issue, placing them in a unified context.

  13. Acoustic cloaking and transformation acoustics

    Chen Huanyang [School of Physical Science and Technology, Soochow University, Suzhou, Jiangsu 215006 (China); Chan, C T, E-mail: kenyon@ust.h, E-mail: phchan@ust.h [Department of Physics and the William Mong Institute of NanoScience and Technology, The Hong Kong University of Science and Technology, Clear Water Bay (Hong Kong)


    In this review, we give a brief introduction to the application of the new technique of transformation acoustics, which draws on a correspondence between coordinate transformation and material properties. The technique is formulated for both acoustic waves and linear liquid surface waves. Some interesting conceptual devices can be designed for manipulating acoustic waves. For example, we can design acoustic cloaks that make an object invisible to acoustic waves, and the cloak can either encompass or lie outside the object to be concealed. Transformation acoustics, as an analog of transformation optics, can go beyond invisibility cloaking. As an illustration for manipulating linear liquid surface waves, we show that a liquid wave rotator can be designed and fabricated to rotate the wave front. The acoustic transformation media require acoustic materials which are anisotropic and inhomogeneous. Such materials are difficult to find in nature. However, composite materials with embedded sub-wavelength resonators can in principle be made and such 'acoustic metamaterials' can exhibit nearly arbitrary values of effective density and modulus tensors to satisfy the demanding material requirements in transformation acoustics. We introduce resonant sonic materials and Helmholtz resonators as examples of acoustic metamaterials that exhibit resonant behaviour in effective density and effective modulus. (topical review)

  14. Prediction of Hydrodynamic Noise of Open Cavity Flow

    GENG Donghan; WANG Yu


    In this paper, the hydrodynamically generated noise by the flow over an open cavity is studied. First, aeroacoustic theories and computational aeroacoustic(CAA)methodologies are reviewed in light of hydrodynamic acoustics, based on which, a hybrid method is presented. In the coupling procedure, the unsteady cavity flow field is computed using large-eddy simulation(LES), while the radiated sound is calculated by the Ffowcs Williams-Hawkings(FW-H)acoustic analogy with acoustic source terms extracted from the time-dependent solutions of the unsteady flow. The hybrid LES-FW-H acoustic analogy method is tested with an open cavity flow at Mach number of 0.006 and Reynolds number of 105. Following the reflection theorem of Powell, the contributions from different source terms are quantified, and the terms involving wall-pressure fluctuations are found to account for most of the radiated intensity. The radiation field is investigated in the frequency domain. For the longitudinal direction, the sound propagates with a dominant radiation downstream the cavity in the near-field and a flatter directivity in the far-field, while for the spanwise direction, the acoustic waves have a similar propagation along +z and-z directions, with no visible directivity.

  15. Droplet actuation by surface acoustic waves: an interplay between acoustic streaming and radiation pressure

    Brunet, Philippe; Baudoin, Michael; Matar, Olivier Bou; Zoueshtiagh, Farzam


    Surface acoustic waves (SAW) are known to be a versatile technique for the actuation of sessile drops. Droplet displacement, internal mixing or drop splitting, are amongst the elementary operations that SAW can achieve, which are useful on lab-on-chip microfluidics benches. On the purpose to understand the underlying physical mechanisms involved during these operations, we study experimentally the droplet dynamics varying different physical parameters. Here in particular, the influence of liquid viscosity and acoustic frequency is investigated: it is indeed predicted that both quantities should play a role in the acoustic-hydrodynamic coupling involved in the dynamics. The key point is to compare the relative magnitude of the attenuation length, i.e. the scale within which the acoustic wave decays in the fluid, and the size of the drop. This relative magnitude governs the relative importance of acoustic streaming and acoustic radiation pressure, which are both involved in the droplet dynamics.


    CHEN Xin; YAO Yan; LU Chuan-jing; CHEN Ying; CAOJia-yi


    To apply the measurements of model experiment in water tunnel to the actual sailing condition,it is necessary to know accurately the strut effect and its rule.In the present work,the corresponding interferences of one-side strut and two-side strut on the natural cavitating flows around a submerged vehicle in water tunnel were investigated numerically,using the homogeneous equilibrium two-phase model coupled with a natural cavitation model.The numerical simulation results show that the strut types have distinct effects on the hydrodynamic properties.For the same given upstream velocity and downstream pressure,the existence of the strut leads to an increment of natural cavitation number,reduces the low-pressure region and depresses the pressure on the vehicle surface near the sides of strut.In the case of given cavitaiton number,the influences of the two-side strut on the drag and lift coefficients are both enhanced along with the increment of attack angle,however the influence of the one-side strut gradually gets stronger on the drag coefficient but weaker on the lift coefficient contrarily.In addition,based on the present numerical results,a correction method by introducing the sigmoidal logistic function is proposed to eliminate the interference from the foil-shaped strut.

  17. Smoothed Particle Hydrodynamic Simulator


    This code is a highly modular framework for developing smoothed particle hydrodynamic (SPH) simulations running on parallel platforms. The compartmentalization of the code allows for rapid development of new SPH applications and modifications of existing algorithms. The compartmentalization also allows changes in one part of the code used by many applications to instantly be made available to all applications.

  18. Hydrodynamic aspect of caves

    Franci Gabrovsek


    Full Text Available From a hydrological point of view, active caves are a series of connected conduits which drain water through an aquifer. Water tends to choose the easiest way through the system but different geological and morphological barriers act as flow restrictions. The number and characteristics of restrictions depends on the particular speleogenetic environment, which is a function of geological, geomorphological, climatological and hydrological settings. Such a variety and heterogeneity of underground systems has presented a challenge for human understanding for many centuries. Access to many underground passages, theoretical knowledge and recent methods (modeling, water pressure-resistant dataloggers, precise sensors etc. give us the opportunity to get better insight into the hydrodynamic aspect of caves. In our work we tried to approach underground hydrodynamics from both theoretical and practical points of view. We present some theoretical background of open surface and pressurized flow in underground rivers and present results of some possible scenarios. Moreover, two case studies from the Ljubljanica river basin are presented in more detail: the cave system between Planinsko polje and Ljubljansko barje, and the cave system between Bloško polje and Cerkniško polje. The approach and methodology in each case is somewhat different, as the aims were different at the beginning of exploration. However, they both deal with temporal and spatial hydrodynamics of underground waters. In the case of Bloško polje-Cerkniško polje system we also explain the feedback loop between hydrodynamics and Holocene speleogenesis.

  19. Acoustical Imaging

    Litniewski, Jerzy; Kujawska, Tamara; 31st International Symposium on Acoustical Imaging


    The International Symposium on Acoustical Imaging is a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. This interdisciplinary Symposium has been taking place continuously since 1968. In the course of the years the proceedings volumes in the Acoustical Imaging Series have become a reference for cutting-edge research in the field. In 2011 the 31st International Symposium on Acoustical Imaging was held in Warsaw, Poland, April 10-13. Offering both a broad perspective on the state-of-the-art as well as  in-depth research contributions by the specialists in the field, this Volume 31 in the Series contains an excellent collection of papers in six major categories: Biological and Medical Imaging Physics and Mathematics of Acoustical Imaging Acoustic Microscopy Transducers and Arrays Nondestructive Evaluation and Industrial Applications Underwater Imaging

  20. Observation of Self-Cavitating Envelope Dispersive Shock Waves in Yttrium Iron Garnet Thin Films.

    Janantha, P A Praveen; Sprenger, Patrick; Hoefer, Mark A; Wu, Mingzhong


    The formation and properties of envelope dispersive shock wave (DSW) excitations from repulsive nonlinear waves in a magnetic film are studied. Experiments involve the excitation of a spin wave step pulse in a low-loss magnetic Y_{3}Fe_{5}O_{12} thin film strip, in which the spin wave amplitude increases rapidly, realizing the canonical Riemann problem of shock theory. Under certain conditions, the envelope of the spin wave pulse evolves into a DSW that consists of an expanding train of nonlinear oscillations with amplitudes increasing from front to back, terminated by a black soliton. The onset of DSW self-cavitation, indicated by a point of zero power and a concomitant 180° phase jump, is observed for sufficiently large steps, indicative of the bidirectional dispersive hydrodynamic nature of the DSW. The experimental observations are interpreted with theory and simulations of the nonlinear Schrödinger equation.

  1. Compressible Turbulent Flow Numerical Simulations of Tip Vortex Cavitation

    Khatami, F.; Weide, van der E.T.A.; Hoeijmakers, H.W.M.


    For an elliptic Arndt’s hydrofoil numerical simulations of vortex cavitation are presented. An equilibrium cavitation model is employed. This single-fluid model assumes local thermodynamic and mechanical equilibrium in the mixture region of the flow, is employed. Furthermore, for characterizing the

  2. Pressure and velocity dependence of flow-type cavitation erosion

    Auret, JG


    Full Text Available of underpressure expands for the higher velocity vOz. Thus cavitation bubbles leave this region farther downstream and the erosion zone shifts down- stream. At the same time, cavitation damage will in- crease because of the larger...

  3. Cavitation Measurement during Sonic and Ultrasonic Activated Irrigation

    Macedo, R.G.; Verhaagen, B.; Fernandez Rivas, David; Versluis, Andreas Michel; Wesselink, P.R.; van der Sluis, L.W.M.


    Introduction The aims of this study were to quantify and to visualize the possible occurrence of transient cavitation (bubble formation and implosion) during sonic and ultrasonic (UAI) activated irrigation. Methods The amount of cavitation generated around several endodontic instruments was measured

  4. Cavitation measurement during sonic and ultrasonic activated irrigation

    Macedo, R.; Verhaagen, B.; Fernandez Rivas, D.; Versluis, M.; Wesselink, P.; van der Sluis, L.


    Introduction The aims of this study were to quantify and to visualize the possible occurrence of transient cavitation (bubble formation and implosion) during sonic and ultrasonic (UAI) activated irrigation. Methods The amount of cavitation generated around several endodontic instruments was measured

  5. Cavitation-aided grain refinement in aluminium alloys

    Atamanenko, T.V.


    This thesis deals with grain refinement under the influence of ultrasonic-driven cavitation in aluminium casting processes. Three major goals of this research were: (1) to identify the mechanism of the cavitation-aided grain refinement at different stages of solidification; (2) to reveal the

  6. Cavitation-aided grain refinement in aluminium alloys

    Atamanenko, T.V.


    This thesis deals with grain refinement under the influence of ultrasonic-driven cavitation in aluminium casting processes. Three major goals of this research were: (1) to identify the mechanism of the cavitation-aided grain refinement at different stages of solidification; (2) to reveal the conditi

  7. Suppression of Fatigue Crack Propagation of Duralumin by Cavitation Peening

    Hitoshi Soyama


    Full Text Available It was demonstrated in the present paper that cavitation peening which is one of the mechanical surface modification technique can suppress fatigue crack propagation in duralumin. The impacts produced when cavitation bubble collapses can be utilised for the mechanical surface modification technique in the same way as laser peening and shot peening, which is called “cavitation peening”. Cavitation peening employing a cavitating jet in water was used to treat the specimen made of duralumin Japanese Industrial Standards JIS A2017-T3. After introducing a notch, fatigue test was conducted by a load-controlled plate bending fatigue tester, which has been originally developed. The fatigue crack propagation behavior was evaluated and the relationship between the fatigue crack propagation rate versus stress intensity factor range was obtained. From the results, the fatigue crack propagation rate was drastically reduced by cavitation peening and the fatigue life of duralumin plate was extended 4.2 times by cavitation peening. In addition, the fatigue crack propagation can be suppressed by 88% in the stable crack propagation stage by cavitation peening.

  8. Examples of oil cavitation erosion in positive displacement pumps

    Halat, J. A.; Ellis, G. O.


    The effects of cavitation flow on piston type, positive displacement, hydraulic pumps are discussed. The operating principles of the pump and the components which are most subject to erosion effects are described. The mechanisms of cavitation phenomena are identified from photographic records. Curves are developed to show the solubility of air in water, oil-water emulsion, and industrial hydraulic oil.

  9. Progress in numerical simulation of cavitating water jets

    PENG Guoyi; SHMIZU Seiji


    This paper reviews recent progress made toward modeling of cavitation and numerical simulation of cavitating water jets.Properties of existing cavitation models are discussed and a compressible mixture flow method for the numerical simulation of highspeed water jets accompanied by intensive cavitation is introduced.Two-phase fluids media of cavitating flow are treated as a homogeneous bubbly mixture and the mean flow is computed by solving Reynolds-Averaged Navier-Stokes (RANS) equations for compressible fluid.The intensity of cavitation is evaluated by the gas volume fraction,which is governed by the compressibility of bubble-liquid mixture corresponding to the status of mean flow field.Numerical results of cavitating water jet issuing from an orifice nozzle are presented and its applicability to intensively cavitating jets is demonstrated.However,the effect of impact pressure caused by collapsing of bubbles is neglected,and effectively coupling of the present compressible mixture flow method with the dynamics of bubbles remains to be a challenge.

  10. Real-Time Two-Dimensional Imaging of Microbubble Cavitation

    Vignon, F.; Shi, W.T.; Powers, J.E.; Liu, J.; Drvol, L.; Lof, J.; Everbach, C.; Gao, S.; Xie, F.; Porter, T.


    Ultrasound cavitation of microbubble contrast agents has a potentialfor therapeutic applications, including sonothrombolysis in acute ischemic stroke. For safety, efficacy, and reproducibility of treatment, it is critical to evaluate the cavitation state (e.g. stable versus inertial forms of cavitat

  11. Cavitation Measurement during Sonic and Ultrasonic Activated Irrigation

    Macedo, R.G.; Verhaagen, B.; Fernandez-Rivas, D.; Versluis, M.; Wesselink, P.R.; Sluis, van der L.W.M.


    Introduction The aims of this study were to quantify and to visualize the possible occurrence of transient cavitation (bubble formation and implosion) during sonic and ultrasonic (UAI) activated irrigation. Methods The amount of cavitation generated around several endodontic instruments was measure

  12. Cavitation measurement during sonic and ultrasonic activated irrigation

    Macedo, R.; Verhaagen, B.; Fernandez Rivas, D.; Versluis, M.; Wesselink, P.; van der Sluis, L.


    Introduction The aims of this study were to quantify and to visualize the possible occurrence of transient cavitation (bubble formation and implosion) during sonic and ultrasonic (UAI) activated irrigation. Methods The amount of cavitation generated around several endodontic instruments was measured

  13. Rudder gap cavitation: Fundamental understanding and its suppression devices

    Rhee, Shin Hyung, E-mail: [Department of Naval Architecture and Ocean Engineering, Research Institute of Marine Systems Engineering, Seoul National University, 599 Gwanangno, Gwanak-ku, Seoul 151-744 (Korea, Republic of); Lee, Changmin; Lee, Hee Bum [Department of Naval Architecture and Ocean Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Oh, Jungkeun [Jungseok Research Institute of International Logistics and Trade, Inha University, Incheon 402-751 (Korea, Republic of)


    With the increasing size and speed of cargo ships, which results in high speed flow in propeller slipstream, cavitation is frequently observed on and around the rudder system. Among the various types of cavitation on the rudder system, the rudder gap cavitation is the most difficult one to control and suppress. For the development of rudder gap cavitation suppression devices, both experimental and numerical analyses of the physical phenomenon are warranted. In the present study, experiments of the incipient cavitation and pressure measurement were carried out for typical cargo ship rudder sections with and without the suppression devices, which were suggested by the author. The experiments were simulated using computational fluid dynamics tools and the results were compared in terms of the cavitation inception and surface pressure distribution. Fundamental understanding of the rudder gap cavitation inception was obtained along with its relevance to the surface pressure distribution. It is confirmed that the gap flow blocking devices effectively suppress the rudder gap cavitation and, at the same time, augment lift.

  14. Acoustic biosensors

    Fogel, Ronen; Limson, Janice; Seshia, Ashwin A.


    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of ...

  15. Acoustic textiles

    Nayak, Rajkishore


    This book highlights the manufacturing and applications of acoustic textiles in various industries. It also includes examples from different industries in which acoustic textiles can be used to absorb noise and help reduce the impact of noise at the workplace. Given the importance of noise reduction in the working environment in several industries, the book offers a valuable guide for companies, educators and researchers involved with acoustic materials.

  16. Hydrodynamics of the Dirac spectrum

    Liu, Yizhuang, E-mail: [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Warchoł, Piotr, E-mail: [M. Smoluchowski Institute of Physics, Jagiellonian University, PL-30348 Krakow (Poland); Zahed, Ismail, E-mail: [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)


    We discuss a hydrodynamical description of the eigenvalues of the Dirac spectrum in even dimensions in the vacuum and in the large N (volume) limit. The linearized hydrodynamics supports sound waves. The hydrodynamical relaxation of the eigenvalues is captured by a hydrodynamical (tunneling) minimum configuration which follows from a pertinent form of Euler equation. The relaxation from a phase of unbroken chiral symmetry to a phase of broken chiral symmetry occurs over a time set by the speed of sound.



    A computational modeling for the sheet cavitating flows is presented. The cavitation model is implemented in a viscous Navier-Stokes solver. The cavity interface and shape are determined using an iterative procedure matching the cavity surface to a constant pressure boundary. The pressure distribution, as well as its gradient on the wall, is taken into account in updating the cavity shape iteratively. Numerical computations are performed for the sheet cavitating flows at a range of cavitation numbers across the hemispheric headform/cylinder body with different grid numbers. The influence of the relaxation factor in the cavity shape updating scheme for the algorithm accuracy and reliability is conducted through comparison with other two cavity shape updating numerical schemes.The results obtained are reasonable and the iterative procedure of cavity shape updating is quite stable, which demonstrate the superiority of the proposed cavitation model and algorithms.

  18. Analysis on Velocity Characteristics of Cavitation Flow Around Hydrofoil

    LI Xiang-bin; LIU Shu-yan; WANG Guo-yu; ZHANG Bo; ZHANG Min-di


    The time-averaged velocity distributions in flows around a hydronautics hydrofoil were measured by using a digit-al particle image velocimeter (DPIV) system. The results show that the velocity distribution in the whole flow field depends on the development of cavitation structures with the decreasing of cavitation number. The high-fluctuation region with lower velocity relates to the cavitation area. The lowest velocity distribution in the cavity core becomes more uniform, and its in-fluence becomes smaller gradually as moving to downstream. The main-stream velocity distribution is even, then fluctuate and even at last. In the supercavitation stage, the fluid velocity in the cavitation region, corresponding to the front of the hydrofoil's suction surface, has a distribution close to the main stream, while the fluid velocity in other cavitation area is lower.

  19. Study of the cavitating instability on a grooved Venturi profile

    Danlos, Amélie; Ravelet, Florent; Coutier-Delgosha, Olivier; Bakir, Farid


    Cavitation is a limiting phenomenon in many domains of fluid mechanics. Instabilities of a partial cavity developed on an hydrofoil, a converging-diverging step or in an inter-blade channel in turbomachinery, have already been investigated and described in many previous works. The aim of this study is to evaluate a passive control method of the sheet cavity. According to operating conditions, cavitation can be described by two different regimes: an unstable regime with a cloud cavitation shedding and a stable regime with only a pulsating sheet cavity. Avoiding cloud cavitation can limit structure damages since a pulsating sheet cavity is less agressive. The surface condition of a converging-diverging step, like a Venturi-type obstacle, is here studied as a solution for a passive control of the cavitation. This study discusses the effect of an organized roughness, in the shape of longitudinal grooves, on the developed sheet cavity. Analyzes conducted with Laser Doppler Velocimetry, visualisations and pressure ...


    De-Min Liu


    Full Text Available Cavitation is not only related with pressure, but also affected by temperature. Under high temperature, temperature depression of liquids is caused by latent heat of vaporization. The cavitation characteristics under such condition are different from those under room temperature. The paper focuses on thermodynamic cavitation based on the Rayleigh-Plesset equation and modifies the mass transfer equation with fully consideration of the thermodynamic effects and physical properties. To validate the modified model, the external and internal flow fields, such as hydrofoil NACA0015 and nozzle, are calculated, respectively. The hydrofoil NACA0015's cavitation characteristic is calculated by the modified model at different temperatures. The pressure coefficient is found in accordance with the experimental data. The nozzle cavitation under the thermodynamic condition is calculated and compared with the experiment.

  1. Cavitation characteristics of pit structure in ultrasonic field

    BAI LiXin; XU WeiLin; ZHANG FaXing; LI NaiWen; ZHANG YiChi; HUANG DeFa


    Bubble collecting, bubble holding and micro-bubble ejecting characteristics of pit structure and the influence of cavitation bubble on the development of erosion pit are investigated by means of highspeed photography experiments. Pits tend to collect and hold wandering cavitation bubbles. The air holding phenomenon of pits can be a destination of the incubation period in the process of cavitation erosion. The holding bubble tends to eject micro-bubbles from the top of holding cavitation bubble,making the pit a source of nuclei. With bubbles being held in pits, the diameters of pits increase rapidly.But in the given experiment condition, there is a specific stable value beyond which the diameter of pits will not increase. This characteristic will be helpful in understanding and predicting the cavitation erosion process.

  2. Effect of cavitation bubble collapse on hydraulic oil temperature

    沈伟; 张健; 孙毅; 张迪嘉; 姜继海


    Cavitation bubble collapse has a great influence on the temperature of hydraulic oil. Herein, cone-type throttle valve experiments are carried out to study the thermodynamic processes of cavitation. First, the processes of growth and collapse are analysed, and the relationships between the hydraulic oil temperature and bubble growth and collapse are deduced. The effect of temperature is then considered on the hydraulic oil viscosity and saturated vapour pressure. Additionally, an improved form of the Rayleigh–Plesset equation is developed. The effect of cavitation on the hydraulic oil temperature is experimentally studied and the effects of cavitation bubble collapse in the hydraulic system are summarised. Using the cone-type throttle valve as an example, a method to suppress cavitation is proposed.

  3. Characteristic analysis of unsteady viscous flow around a cavitating propeller


    Based on viscous multiphase flow theory, this paper presents some recent validation results with a hybrid grid and sliding mesh solving Unsteady Navier-Stokes (N-S) and Bubble Dynamics equations as applied to prediction of pressure, velocity and vapor volume fraction in the wake in an uniform inflow. Comparable to experimental results, numerical predictions of sheet cavitation, tip vortex cavitation and hub vortex cavitation are in agreement with the corresponding experimental data, the same as numerical predictions of pressure in wake. Tip vortex cavitation is the most important to generate the pressure fluctuation within the near wake. The characteristics such as blade and shaft rate frequency of propeller pressure in wake coincide with its geometric model and parameters. With increasing distance from propeller disk, the pressure signals at blade frequency de-crease. The process of attenuation becomes fast with the decreased advance coefficient and cavitation number.

  4. Flow and cavitation characteristics of water hydraulic poppet valves

    廖义德; 刘银水; 黄艳; 李壮云


    Two types of poppet valves were tested, one is a poppet with a sharp-edged seats, and the other is that with a chamfered seat. During the tests, the effects of backpressure and poppet lift on flow characteristics were considered. Cavitation inception was detected by the appearance and rapid growth of a particular low frequency component of the outlet pressure fluctuation of valve when cavitation occurs. Experimental results show cavitation, back pressure, valve opening and its geometrical shape have significant effects on the flow characteristics of valve. The flow coefficient of throttle with water used as working medium is 0. 85~0. 95 when there is no cavitation. The pressure drop of flow saturation decreases with the increasing of poppet lift. The sharp-edged throttle has stronger anti-cavitation ability than the chamfered one.


    ZHANG Ling-xin; ZHAO Wei-guo; SHAO Xue-ming


    A pressure-based algorithm for the prediction of cavitating flows is presented. The algorithm employs a set of equations including the Navier-Stokes equations and a cavitation model explaining the phase change between liquid and vapor. A pressure-based method is used to construct the algorithm and the coupling between pressure and velocity is considered. The pressure correction equation is derived from a new continuity equation which employs a source term related to phase change rate instead of the material derivative of density Dp/Dt.Thispressure-based algorithm allows for the computation of steady or unsteady,2-Dor 3-D cavitating flows. Two 2-D cases, flows around a flat-nose cylinder and around a NACA0015 hydrofoil, are simulated respectively, and the periodic cavitation behaviors associated with the re-entrant jets are captured. This algorithm shows good capability of computating time-dependent cavitating flows.

  6. Combined experimental and computational investigation of the cavitating flow in an orifice plate with special emphasis on surrogate-based optimization method

    Li, XianLin; Huang, Biao; Chen, Tairan; Liu, Ying; Qiu, Si Cong [School of Mechanical and Vehicular Engineering, Beijing Institute of Technology, Beijing (China); Zhao, Jing [China Academy of Launch Vehicle Technology, Beijing (China)


    We investigated the influence of geometrical parameters of the orifice plate on the cavitation structures, and optimized these parameters by using a surrogate-based model with special emphasis on the concentration of hydroxyl radical released. The results show that for the orifice plate of the hydrodynamic cavitation system, the possible location of the inception of the cavity spreads to throat and divergent section of the venturi geometry. Based on the surrogate model and global sensitivity assessment, the diameter of throat Dt and diameter of inlet Din significantly influenced the size of the cavity, while the length of throat Lt had little effect on both cavitation intensity and flow rate. It should be noted that when Lt is decreased, the size of cavity would be slightly decreased but the flow rate increased clearly. The increase of the diverging section is in favor of the size of cavity. By comparing the experimental measurements on the concentration of Methylene blue, the optimum geometry of the orifice plate for best cavitational activity is proposed.

  7. Cavitation instability in bulk metallic glasses

    Dai L.H.


    Full Text Available Recent experiments have shown that fracture surfaces of bulk metallic glasses (BMGs usually exhibit an intriguing nanoscale corrugation like fractographic feature mediated by nanoscale void formation. We attribute the onset of this nanoscale corrugation to TTZs (tension transformation zones mediated cavitation. In our recent study, the spall experiments of Zr-based BMG using a single-stage light gas gun were performed. To uncover the mechanisms of the spallation damage nucleation and evolution, the samples were designed to be subjected to dynamic tensile loadings of identical amplitude but with different durations by making use of the multi-stress pulse and the double-flyer techniques. It is clearly revealed that the macroscopic spall fracture in BMGs originates from the nucleation, growth and coalescence of micro-voids. Then, a microvoid nucleation model of BMGs based on free volume theory is proposed, which indicates that the nucleation of microvoids at the early stage of spallation in BMGs is resulted from diffusion and coalescence of free volume. Furthermore, a theoretical model of void growth in BMGs undergoing remote dynamic hydrostatic tension is developed. The critical condition of cavitation instability is obtained. It is found that dynamic void growth in BMGs can be well controlled by a dimensionless inertial number characterizing the competition between intrinsic and extrinsic time scales. To unveil the atomic-level mechanism of cavitation, a systematic molecular dynamics (MD simulation of spallation behaviour of a binary metallic glass with different impact velocities was performed. It is found that micro-void nucleation is determined TTZs while the growth is controlled by shear transformation zones (STZs at atomic scale.

  8. Peripapillary intrachoroidal cavitation in pathological myopia.

    Marticorena-Álvarez, P; Clement-Fernández, F; Iglesias-Ussel, L


    A 54 year old woman with pathological myopia, presented with an elevated, yellowish-white lesion at the inferior border of the myopic conus in her left eye. The optical coherence tomography (OCT) demonstrated an intrachoroidal hyporeflective space. The fluorescein angiography examination (FA) showed early hypofluorescence with delayed staining, with no leakage of contrast. Recognition of «peripapillary intrachoroidal cavitation» as an own entity associated with pathological myopia is important to avoid confusion with other possible retinal lesions which require further investigation and treatment. Copyright © 2012 Sociedad Española de Oftalmología. Published by Elsevier Espana. All rights reserved.

  9. Cavitation erosion of copper and aluminium in water at elevated-temperature

    Auret, JG


    Full Text Available Cavitation erosion tests were carried out in tap water on aluminium and copper samples in a rotating disk cavitations test apparatus, to study the effect of water temperature on cavitation dynamics and cavitation erosion. A shift in the position...

  10. 超声空化气泡动力学仿真及其影响因素分析%Dynamic simulation of ultrasonic cavitation bubble and analysis of its influencing factors

    崔方玲; 纪威


      为获得最佳的超声空化效果,构建了空化气泡运动的动力学模型,并对模型方程进行数值仿真,探讨了超声频率、声压、空化泡初始半径、反应体系主体温度和绝热指数对空化气泡运动的影响。模拟结果表明,随着超声频率的增加,空化效应减弱;随着声压幅值的增大,空化泡最大振幅增加,崩溃时的最高温度和最大压力先增大后减小;气泡的初始半径较小,并且反应体系温度较低时,空化效果较好;绝热指数取值的不同会导致空化模拟计算结果有所差异,该研究为超声空化技术的广泛应用提供参考。%Ultrasonic waves can be found in many different areas such as chemistry, biology, cleaning, medicine, etc. The mechanical interaction between ultrasonic waves and bubbles in liquids leads to a phenomenon described as ultrasonic acoustic cavitation. A cavitation bubble in a liquid undergoes cycles of growth, rapid collapse, and damped rebounds in response to ultrasonic sound waves. Due to the very short lifetime of an ultrasonic cavitation bubble, the high temperature and pressure from its collapse haven’t hitherto been measurable, but the cavitation process can be simulated by constructing a dynamic model of a cavitation bubble. This paper explores physical conditions under which the best ultrasonic cavitation effect can be obtained and provides theoretical guidance for extensive applications of ultrasonic cavitation. Based on the Rayleigh-Plesset equation, we perfected bubble dynamic motion in an ultrasonic cavitation model by considering viscosity, surface tension, vapour pressure, adiabatic exponent, and acoustic radiation damping as dynamic factors. Since temperature variations influence physical properties of water, physical models of water saturation vapor pressure, surface tension, sound velocity and viscosity with temperature changing were also built. Thus, influences of ultrasonic frequency

  11. Numerical 3D analysis of cloud cavitation shedding frequency on a circular leading edge hydrofoil with a barotropic cavitation model

    Blume, M.; Skoda, R.


    A compressible density-based time-explicit low Mach number consistent viscous flow solver is utilised in combination with a barotropic cavitation model for the analysis of cloud cavitation on a circular leading edge (CLE) hydrofoil. For 5° angle of attack, cloud structure and shedding frequency for different cavitation numbers are compared to experimental data. A strong grid sensitivity is found in particular for high cavitation numbers. On a fine grid, a very good agreement with validation data is achieved even without explicit turbulence model. The neglect of viscous effects as well as a two-dimensional set-up lead to a less realistic prediction of cloud structures and frequencies. Comparative simulations with the Sauer-Schnerr cavitation model and modified pre-factors of the mass transfer terms underestimate the measured shedding frequency.

  12. Experimental investigation of the flow-induced vibration of hydrofoils in cavitating flows

    Wang, Guoyu; Wu, Qin; Huang, Biao; Gao, Yuan


    The objective of this paper is to investigate the correlation between fluid induced vibration and unsteady cavitation behaviours. Experimental results are presented for a modified NACA66 hydrofoil, which is fixed at α=8°. The high-speed camera is synchronized with a single point Laser Doppler Vibrometer to analyze the transient cavitating flow structures and the corresponding structural vibration characteristics. The results showed that, with the decreasing of the cavitation number, the cavitating flows in a water tunnel display several types of cavitation patterns, such as incipient cavitation, sheet cavitation and cloud cavitation. The cavity shedding frequency reduces with the decrease of the cavitation number. As for the cloud cavitation regime, the trend of the vibration velocity goes up with the growth of the attached cavity, accompanied with small amplitude fluctuations. Then the collapse and shedding of the large-scale cloud cavities leads to substantial increase of the vibration velocity fluctuations.

  13. Scalability of Hydrodynamic Simulations

    Tang, Shikui


    Many hydrodynamic processes can be studied in a way that is scalable over a vastly relevant physical parameter space. We systematically examine this scalability, which has so far only briefly discussed in astrophysical literature. We show how the scalability is limited by various constraints imposed by physical processes and initial conditions. Using supernova remnants in different environments and evolutionary phases as application examples, we demonstrate the use of the scaling as a powerful tool to explore the interdependence among relevant parameters, based on a minimum set of simulations. In particular, we devise a scaling scheme that can be used to adaptively generate numerous seed remnants and plant them into 3D hydrodynamic simulations of the supernova-dominated interstellar medium.

  14. Relativistic Hydrodynamics with Wavelets

    DeBuhr, Jackson; Anderson, Matthew; Neilsen, David; Hirschmann, Eric W


    Methods to solve the relativistic hydrodynamic equations are a key computational kernel in a large number of astrophysics simulations and are crucial to understanding the electromagnetic signals that originate from the merger of astrophysical compact objects. Because of the many physical length scales present when simulating such mergers, these methods must be highly adaptive and capable of automatically resolving numerous localized features and instabilities that emerge throughout the computational domain across many temporal scales. While this has been historically accomplished with adaptive mesh refinement (AMR) based methods, alternatives based on wavelet bases and the wavelet transformation have recently achieved significant success in adaptive representation for advanced engineering applications. This work presents a new method for the integration of the relativistic hydrodynamic equations using iterated interpolating wavelets and introduces a highly adaptive implementation for multidimensional simulati...

  15. Communication Acoustics

    Blauert, Jens

    the book a source of valuable information for those who want to improve or refresh their knowledge in the field of communication acoustics - and to work their way deeper into it. Due to its interdisciplinary character Communication Acoustics is bound to attract readers from many different areas, such as......Communication Acoustics deals with the fundamentals of those areas of acoustics which are related to modern communication technologies. Due to the advent of digital signal processing and recording in acoustics, these areas have enjoyed an enormous upswing during the last 4 decades. The book...... chapters represent review articles covering the most relevant areas of the field. They are written with the goal of providing students with comprehensive introductions. Further they offer a supply of numerous references to the relevant literature. Besides its usefulness as a textbook, this will make...

  16. Radiation acoustics

    Lyamshev, Leonid M


    Radiation acoustics is a developing field lying at the intersection of acoustics, high-energy physics, nuclear physics, and condensed matter physics. Radiation Acoustics is among the first books to address this promising field of study, and the first to collect all of the most significant results achieved since research in this area began in earnest in the 1970s.The book begins by reviewing the data on elementary particles, absorption of penetrating radiation in a substance, and the mechanisms of acoustic radiation excitation. The next seven chapters present a theoretical treatment of thermoradiation sound generation in condensed media under the action of modulated penetrating radiation and radiation pulses. The author explores particular features of the acoustic fields of moving thermoradiation sound sources, sound excitation by single high-energy particles, and the efficiency and optimal conditions of thermoradiation sound generation. Experimental results follow the theoretical discussions, and these clearl...

  17. Burst Mechanisms in Hydrodynamics

    Knobloch, E


    Different mechanisms believed to be responsible for the generation of bursts in hydrodynamical systems are reviewed and a new mechanism capable of generating regular or irregular bursts of large dynamic range near threshold is described. The new mechanism is present in the interaction between oscillatory modes of odd and even parity in systems of large but finite aspect ratio, and provides an explanation for the bursting behavior observed in binary fluid convection. Additional applications of the new mechanism are proposed.

  18. Relativistic cosmological hydrodynamics

    Hwang, J


    We investigate the relativistic cosmological hydrodynamic perturbations. We present the general large scale solutions of the perturbation variables valid for the general sign of three space curvature, the cosmological constant, and generally evolving background equation of state. The large scale evolution is characterized by a conserved gauge invariant quantity which is the same as a perturbed potential (or three-space curvature) in the comoving gauge.

  19. Inertial cavitation to non-invasively trigger and monitor intratumoral release of drug from intravenously delivered liposomes.

    Graham, Susan M; Carlisle, Robert; Choi, James J; Stevenson, Mark; Shah, Apurva R; Myers, Rachel S; Fisher, Kerry; Peregrino, Miriam-Bazan; Seymour, Len; Coussios, Constantin C


    The encapsulation of cytotoxic drugs within liposomes enhances pharmacokinetics and allows passive accumulation within tumors. However, liposomes designed to achieve good stability during the delivery phase often have compromised activity at the target site. This problem of inefficient and unpredictable drug release is compounded by the present lack of low-cost, non-invasive methods to measure such release. Here we show that focused ultrasound, used at pressures similar to those applied during diagnostic ultrasound scanning, can be utilised to both trigger and monitor release of payload from liposomes. Notably, drug release was influenced by liposome composition and the presence of SonoVue® microbubbles, which provided the nuclei for the initiation of an event known as inertial cavitation. In vitro studies demonstrated that liposomes formulated with a high proportion of 1,2 distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) released up to 30% of payload following ultrasound exposure in the presence of SonoVue®, provided that the exposure created sufficient inertial cavitation events, as characterised by violent bubble collapse and the generation of broadband acoustic emissions. In contrast a 'Doxil'-like liposome formulation gave no such triggered release. In pre-clinical studies, ultrasound was used as a non-invasive, targeted stimulus to trigger a 16-fold increase in the level of payload release within tumors following intravenous delivery. The inertial cavitation events driving this release could be measured remotely in real-time and were a reliable predictor of drug release.

  20. Hydrodynamics of insect spermatozoa

    Pak, On Shun; Lauga, Eric


    Microorganism motility plays important roles in many biological processes including reproduction. Many microorganisms propel themselves by propagating traveling waves along their flagella. Depending on the species, propagation of planar waves (e.g. Ceratium) and helical waves (e.g. Trichomonas) were observed in eukaryotic flagellar motion, and hydrodynamic models for both were proposed in the past. However, the motility of insect spermatozoa remains largely unexplored. An interesting morphological feature of such cells, first observed in Tenebrio molitor and Bacillus rossius, is the double helical deformation pattern along the flagella, which is characterized by the presence of two superimposed helical flagellar waves (one with a large amplitude and low frequency, and the other with a small amplitude and high frequency). Here we present the first hydrodynamic investigation of the locomotion of insect spermatozoa. The swimming kinematics, trajectories and hydrodynamic efficiency of the swimmer are computed based on the prescribed double helical deformation pattern. We then compare our theoretical predictions with experimental measurements, and explore the dependence of the swimming performance on the geometric and dynamical parameters.

  1. Hydrodynamics of fossil fishes.

    Fletcher, Thomas; Altringham, John; Peakall, Jeffrey; Wignall, Paul; Dorrell, Robert


    From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms.

  2. Cavitation and contrast: the use of bubbles in ultrasound imaging and therapy.

    Stride, E P; Coussios, C C


    Microbubbles and cavitation are playing an increasingly significant role in both diagnostic and therapeutic applications of ultrasound. Microbubble ultrasound contrast agents have been in clinical use now for more than two decades, stimulating the development of a range of new contrast-specific imaging techniques which offer substantial benefits in echocardiography, microcirculatory imaging, and more recently, quantitative and molecular imaging. In drug delivery and gene therapy, microbubbles are being investigated/developed as vehicles which can be loaded with the required therapeutic agent, traced to the target site using diagnostic ultrasound, and then destroyed with ultrasound of higher intensity energy burst to release the material locally, thus avoiding side effects associated with systemic administration, e.g. of toxic chemotherapy. It has moreover been shown that the motion of the microbubbles increases the permeability of both individual cell membranes and the endothelium, thus enhancing therapeutic uptake, and can locally increase the activity of drugs by enhancing their transport across biologically inaccessible interfaces such as blood clots or solid tumours. In high-intensity focused ultrasound (HIFU) surgery and lithotripsy, controlled cavitation is being investigated as a means of increasing the speed and efficacy of the treatment. The aim of this paper is both to describe the key features of the physical behaviour of acoustically driven bubbles which underlie their effectiveness in biomedical applications and to review the current state of the art.

  3. Cell-Type-Selective Effects of Intramembrane Cavitation as a Unifying Theoretical Framework for Ultrasonic Neuromodulation.

    Plaksin, Michael; Kimmel, Eitan; Shoham, Shy


    Diverse translational and research applications could benefit from the noninvasive ability to reversibly modulate (excite or suppress) CNS activity using ultrasound pulses, however, without clarifying the underlying mechanism, advanced design-based ultrasonic neuromodulation remains elusive. Recently, intramembrane cavitation within the bilayer membrane was proposed to underlie both the biomechanics and the biophysics of acoustic bio-effects, potentially explaining cortical stimulation results through a neuronal intramembrane cavitation excitation (NICE) model. Here, NICE theory is shown to provide a detailed predictive explanation for the ability of ultrasonic (US) pulses to also suppress neural circuits through cell-type-selective mechanisms: according to the predicted mechanism T-type calcium channels boost charge accumulation between short US pulses selectively in low threshold spiking interneurons, promoting net cortical network inhibition. The theoretical results fit and clarify a wide array of earlier empirical observations in both the cortex and thalamus regarding the dependence of ultrasonic neuromodulation outcomes (excitation-suppression) on stimulation and network parameters. These results further support a unifying hypothesis for ultrasonic neuromodulation, highlighting the potential of advanced waveform design for obtaining cell-type-selective network control.

  4. Catastrophic Cracking Courtesy of Quiescent Cavitation

    Daily, D Jesse; Thomson, Scott L; Truscott, Tadd T


    A popular party trick is to fill a glass bottle with water and hit the top of the bottle with an open hand, causing the bottom of the bottle to break open. We investigate the source of the catastrophic cracking through the use of high-speed video and an accelerometer attached to the bottom of a glass bottle. Upon closer inspection, it is obvious that the acceleration caused by hitting the top of the bottle is followed by the formation of bubbles near the bottom. The nearly instantaneous acceleration creates an area of low pressure on the bottom of the bottle where cavitation bubbles form. Moments later, the cavitation bubbles collapse at roughly 10 times the speed of formation, causing the bottle to break. The accelerometer data shows that the bottle is broken after the bubbles collapse and that the magnitude of the bubble collapse is greater than the initial impact. The fluid dynamics video highlights that this trick will not work if the bottle is empty nor if it is filled with a carbonated fluid because the...

  5. Cavitation and pore blocking in nanoporous glasses.

    Reichenbach, C; Kalies, G; Enke, D; Klank, D


    In gas adsorption studies, porous glasses are frequently referred to as model materials for highly disordered mesopore systems. Numerous works suggest that an accurate interpretation of physisorption isotherms requires a complete understanding of network effects upon adsorption and desorption, respectively. The present article deals with nitrogen and argon adsorption at different temperatures (77 and 87 K) performed on a series of novel nanoporous glasses (NPG) with different mean pore widths. NPG samples contain smaller mesopores and significantly higher microporosity than porous Vycor glass or controlled pore glass. Since the mean pore width of NPG can be tuned sensitively, the evolution of adsorption characteristics with respect to a broadening pore network can be investigated starting from the narrowest nanopore width. With an increasing mean pore width, a H2-type hysteresis develops gradually which finally transforms into a H1-type. In this connection, a transition from a cavitation-induced desorption toward desorption controlled by pore blocking can be observed. Furthermore, we find concrete hints for a pore size dependence of the relative pressure of cavitation in highly disordered pore systems. By comparing nitrogen and argon adsorption, a comprehensive insight into adsorption mechanisms in novel disordered materials is provided.

  6. Characterization of the cavitating flow in converging-diverging nozzle based on experimental investigations

    Rudolf Pavel


    Full Text Available Cavitation phenomena occuring in converging-diverging nozzle (Venturi tube are described in the paper. A closed test circuit with possibility to control both flow rate and static pressure level were used. Loss coefficient was evaluated for different sigma numbers resulting in full „static“ characterization of the nozzle. Visualizations of the cavitation pattern development were acquired and matched with evolution of the loss coefficient. Three cavitation regimes are described: partial cavitation, fully developed cavitation, supercavitation.

  7. Experimental evaluation of numerical simulation of cavitating flow around hydrofoil

    Dular, M.; Bachert, R.; Stoffel, B. [Darmstadt Univ. of Technology, Lab. for Turbomachinery and Fluid Power (Germany); Sirok, B. [Ljubljana Univ., Lab. for Water and Turbine Machines (Slovenia)


    Cavitation in hydraulic machines causes different problems that can be related to its unsteady nature. An experimental and numerical study of developed cavitating flow was performed. Until now simulations of cavitating flow were limited to the self developed 'in house' CFD codes. The goal of the work was to experimentally evaluate the capabilities of a commercial CFD code (Fluent) for simulation of a developed cavitating flow. Two simple hydrofoils that feature some 3D effects of cavitation were used for the experiments. A relatively new technique where PIV method combined with LIF technique was used to experimentally determine the instantaneous and average velocity and void ratio fields (cavity shapes) around the hydrofoils. Distribution of static pressure on the hydrofoil surface was determined. For the numerical simulation of cavitating flow a bubble dynamics cavitation model was used to describe the generation and evaporation of vapour phase. An unsteady RANS 3D simulation was performed. Comparison between numerical and experimental results shows good correlation. The distribution and size of vapour structures and the velocity fields agree well. The distribution of pressure on the hydrofoil surface is correctly predicted. The numerically predicted shedding frequencies are in fair agreement with the experimental data. (authors)


    ZHAO Wei-guo; ZHANG Ling-xin; SHAO Xue-ming


    The numerical simulation of cavitation flow on a 2D NACA0015 hydrofoil under high pressure and temperature is performed. The Singhal's cavitation model is adopted combined with an improved RNG k-ε turbulence model to study the cavitation flow. The thermal effect in the cavitation flow is taken into account by introducing the energy equation with a source term based on the latent heat transfer. The code is validated by a case of a hydrofoil under two different temperatures in a comparison between the simulation and the experiment. Computational results show that the latent heat of vaporization has a significant impact on the cavitation process in the high temperature state, and the cavity in the high temperature state is thinner and shorter than that in a normal state with the same cavitation number, due to the fact that the heat absorption in the cavitation area reduces the local temperature and the saturated vapor pressure. This numerical study provides some guidance for the design of machineries in the High Pressure and Temperature (HPT) state.

  9. Numerical research on unsteady cavitating flow over a hydrofoil

    Homa, D.; Wróblewski, W.


    Cavitation is a widely known phenomenon in pumps and water turbines installations. It can lead to significant damage of blades and walls of the rotor therefore it is crucial during pump designing and exploitation to avoid working in flow conditions, that enabled cavitation to occur. Nowadays numerical simulations of flow can provide valuable information concerning pressure and velocity distribution and can indicate if there is a risk of cavitating flow appearance. There are a few mathematical models which describe cavitating flow. In the paper Schnerr & Sauer model was chosen for simulation. Aim of the paper is to verify its utility in case of different cavitating flow regimes over Clark-Y hydrofoil. After performing the grid independence study four different cavitation regimes were investigated. The vapour areas appearance, their shapes and changes in time were observed. The assumption of isothermal, two - phase flow was made. The calculations were performed using OpenFOAM and were compared to the available measurements data. The presented results concerned sheet and cloud cavitation regimes.

  10. Detecting cavitation in vivo from shock-wave therapy devices

    Matula, Thomas J.; Yu, Jinfei; Bailey, Michael R.


    Extracorporeal shock-wave therapy (ESWT) has been used as a treatment for plantar faciitis, lateral epicondylitis, shoulder tendonitis, non-unions, and other indications where conservative treatments have been unsuccessful. However, in many areas, the efficacy of SW treatment has not been well established, and the mechanism of action, particularly the role of cavitation, is not well understood. Research indicates cavitation plays an important role in other ultrasound therapies, such as lithotripsy and focused ultrasound surgery, and in some instances, cavitation has been used as a means to monitor or detect a biological effect. Although ESWT can generate cavitation easily in vitro, it is unknown whether or not cavitation is a significant factor in vivo. The purpose of this investigation is to use diagnostic ultrasound to detect and monitor cavitation generated by ESWT devices in vivo. Diagnostic images are collected at various times during and after treatment. The images are then post-processed with image-processing algorithms to enhance the contrast between bubbles and surrounding tissue. The ultimate goal of this research is to utilize cavitation as a means for optimizing shock wave parameters such as amplitude and pulse repetition frequency. [Work supported by APL internal funds and NIH DK43881 and DK55674.

  11. Effects of fluid thermophysical properties on cavitating flows

    Chen, Tairan; Huang, Biao; Wang, Guoyu; Wang, Kun [Beijing Institute of Technology, Beijing (China)


    We studied the thermo-fluid cavitating flows and evaluated the effects of physical properties on cavitation behaviors. The thermo-fluid (including liquid nitrogen, liquid hydrogen and hot water) cavitating flows around a 2D hydrofoil were numerically investigated. The Favre-averaged Navier-Stokes equations with the enthalpy-based energy equation, transport equation-based cavitation model, and the k- ω SST turbulence model were applied. The thermodynamic parameter ∑, defined as ∑=(P{sub v}{sup 2}L{sup 2})/(P{sub l}{sup 2}C{sub v}T{sub ∞} √ε{sub I}) was used to assess the thermodynamic effects on cavitating flows. The results manifest that the thermal energy solution case yields a substantially shorter and mushier cavity attached on the hydrofoil due to the thermodynamic effects, which shows better agreement with the experimental data. The temperature drop inside the cavity decreases the local saturated vapor pressure and hence increases the local cavitation number; it could delay or suppress the occurrence and development of the cavitation behavior. The thermodynamic effects can be evaluated by thermophysical properties under the same free-stream conditions; the thermodynamic parameter ∑ is shown to be critical in accurately predicting the thermodynamic effects on cavitating flows. The surrogate-based global sensitivity analysis of liquid nitrogen cavitating flow suggests that ρ{sub v}, C{sub l} and L could significantly influence temperature drop and cavity structure in the existing numerical framework, while ρv plays the dominant role on temperature drop when properties vary with changing temperature. The liquid viscosity ml slightly affects the flow structure but hardly affects the temperature distribution.

  12. Numerical investigation of tip clearance cavitation in Kaplan runners

    Nikiforova, K.; Semenov, G.; Kuznetsov, I.; Spiridonov, E.


    There is a gap between the Kaplan runner blade and the shroud that makes for a special kind of cavitation: cavitation in the tip leakage flow. Two types of cavitation caused by the presence of clearance gap are known: tip vortex cavitation that appears at the core of the rolled up vortex on the blade suction side and tip clearance cavitation that appears precisely in the gap between the blade tip edge and the shroud. In the context of this work numerical investigation of the model Kaplan runner has been performed taking into account variable tip clearance for several cavitation regimes. The focus is put on investigation of structure and origination of mechanism of cavitation in the tip leakage flow. Calculations have been performed with the help of 3-D unsteady numerical model for two-phase medium. Modeling of turbulent flow in this work has been carried out using full equations of Navier-Stokes averaged by Reynolds with correction for streamline curvature and system rotation. For description of this medium (liquid-vapor) simplification of Euler approach is used; it is based on the model of interpenetrating continuums, within the bounds of this two- phase medium considered as a quasi-homogeneous mixture with the common velocity field and continuous distribution of density for both phases. As a result, engineering techniques for calculation of cavitation conditioned by existence of tip clearance in model turbine runner have been developed. The detailed visualization of the flow was carried out and vortex structure on the suction side of the blade was reproduced. The range of frequency with maximum value of pulsation was assigned and maximum energy frequency was defined; it is based on spectral analysis of the obtained data. Comparison between numerical computation results and experimental data has been also performed. The location of cavitation zone has a good agreement with experiment for all analyzed regimes.

  13. Numerical 3D flow simulation of attached cavitation structures at ultrasonic horn tips and statistical evaluation of flow aggressiveness via load collectives

    Mottyll, S.; Skoda, R.


    A compressible inviscid flow solver with barotropic cavitation model is applied to two different ultrasonic horn set-ups and compared to hydrophone, shadowgraphy as well as erosion test data. The statistical analysis of single collapse events in wall-adjacent flow regions allows the determination of the flow aggressiveness via load collectives (cumulative event rate vs collapse pressure), which show an exponential decrease in agreement to studies on hydrodynamic cavitation [1]. A post-processing projection of event rate and collapse pressure on a reference grid reduces the grid dependency significantly. In order to evaluate the erosion-sensitive areas a statistical analysis of transient wall loads is utilised. Predicted erosion sensitive areas as well as temporal pressure and vapour volume evolution are in good agreement to the experimental data.


    Wang Tian-kui; Lu Fang; Fan Xiao-bing; Shi Xiao-jun


    After about 10 years' runing of the LCC(DTRC,USA) and the HYKAT(HSVA,Germany), another new large cavitation channel with low background noise is to be in operation in China Ship Scientific Research Center(CSSRC),Wuxi,China. The important specific properties of the channel are the large test section (2.0 m in height, 2.2 m in width and 10.5 m in length), the maximum speed of more than 15 m/s, the low turbulence level, the low background noise of the whole facility, togother with the new noise measurement system. So large scale models can be tested with only minor wall effects and at high Renolds numbers, and the pretentious acoustical measurements can be performed. This paper describes the features of the new channel and the first test results obtained during extensive calibration and validation.


    WU Lei; LU Chuan-jing; LI Jie; CHEN Xin


    A two-phase mixture model was established to study unsteady cavitating flows. A local compressible system of equations was derived by introducing a density-pressure function to account for the two-phase flow of water/vapor and the transition from one phase to the other. An algorithm for solving the variable-density Navier-Stokes equations of cavitating flow problem was put forward. The numerical results for unsteady characteristics of cavitating flows on a 2D NACA hydrofoil coincide well with experimental data.


    ZHANG Jian-min; YANG Qing; WANG Yu-rong; XU Wei-lin; CHEN Jian-gang


    For sudden expansion pipes, experiments were carried out to study the cavitation inception for various enlargement ratios in high speed flows.The flow velocity of the prototype reaches 50 m/s in laboratory.The relationship between the expansion ratio and the incipient cavitation number is obtained.The scale and velocity effects are revealed.It is shown that Keller's revised formula should be modified to calculate the incipient cavitation number when the forecasted velocity of the flows in the prototype exceeds the experimental velocity.



    An approach of modeling viscosity, unsteady partially cavitating flows around lifting bodies is presented. By employing an one-fluid Navier-Stokers solver, the algorithm is proved to be able to handle two-dimensional laminar cavitating flows at moderate Reynolds number. Based on the state equation of water-vapor mixture, the constructive relations of densities and pressures are established. To numerically simulate the cavity wall, different pseudo transition of density models are presumed. The finite-volume method is adopted and the algorithm can be extended to three-dimensional cavitating flows.

  18. Cavitation in dielectric fluid in inhomogeneous pulsed electric field

    Shneider, M N


    This paper proposes a method for studying the early stages of the cavitation development in arbitrary, non-stationary conditions. This method is based on the comparison of the results of calculations in the framework of a theoretical model of the liquid dielectrics motion in a strong non-uniform electric field and experiments with controlled parameters. This approach allows us to find the critical negative pressure, at which cavitation begins to develop, and to determine the values of the constants in the classical models of cavitation.

  19. Ultrasound-induced inertial cavitation from gas-stabilizing nanoparticles.

    Kwan, J J; Graham, S; Myers, R; Carlisle, R; Stride, E; Coussios, C C


    The understanding of cavitation from nanoparticles has been hindered by the inability to control nanobubble size. We present a method to manufacture nanoparticles with a tunable single hemispherical depression (nanocups) of mean diameter 90, 260, or 650 nm entrapping a nanobubble. A modified Rayleigh-Plesset crevice model predicts the inertial cavitation threshold as a function of cavity size and frequency, and is verified experimentally. The ability to tune cavitation nanonuclei and predict their behavior will be useful for applications ranging from cancer therapy to ultrasonic cleaning.


    LEE Jeung-Hoon; JUNG Jae-Kwon; LEE Kyung-Jun; HAN Jae-Moon; PARK Hyung-Gil; SEO Jong-Soo


    Tip vortex cavitation noise of marine propeller became primary concerns to reduce hazardous environmental impacts from commercial ship or to keep the underwater surveillance of naval ships.The investigations of the tip vortex and its induced noise are normally conducted through the model test in a water cavitation tunnel.However the Reynolds number of model-test is much smaller than that of the full-scale,which subsequently results in the difference of tip vortex cavitation inception.Hence,the scaling law between model- and full-scales needs to be identified prior to the prediction and assessment of propeller noise in full scale.From previous researches,it is generally known that the incipient caivtation number of tip vortex can be represented as a power of the Reynolds number.However,the power exponent for scaling,which is the main focus of this research,has not been clearly studied yet.This paper deals with the estimation of scaling exponent based on tip vortex cavitation inception test in both full- and model-scale ships.Acoustical measurements as well as several kind of signal processing technique for an inception criterion suggest the scaling exponent as 0.30.The scaling value proposed in this study shows slight difference to the one of most recent research.Besides,extrapolation of model-ship noise measurement using the proposed one predicts the full-scale noise measurement with an acceptable discrepancy.