Implosion Of Cavitation Bubbles Research Articles

Development of an Ultrasonic Resonator for Ballast Water Disinfection

Ultrasonic disinfection involves the application of low-frequency acoustic energy in a water body to induce cavitation. The implosion of cavitation bubbles generates high speed microjets >1 km/s, intense shock wave >1 GPa, localized hot spots >1000 K, and free-radicals, resulting in cell rupture and death of micro-organisms and pathogens. Treatment of marine ballast water using power ultrasonics is an energy-intensive process. Compared with other physical treatment methods such as ultraviolet disinfection, ultrasonic disinfection require 2 to 3 orders of magnitude more energy to achieve similar rate of micro-organism mortality. Current technology limits the amount of acoustic energy that can be transferred per unit volume of fluid and presents challenges when it comes to high-flow applications. Significant advancements in ultrasonic processing technology are needed before ultrasound can be recognized as a viable alternative disinfection method. The ultrasonic resonator has been identified as one of the areas of improvement that can potentially contribute to the overall performance of an ultrasonic disinfection system. The present study focuses on the design of multiple-orifice resonators (MOR) for generating a well-distributed cavitation field. Results show that the MOR resonator offers significantly larger vibrational surface area to mass ratio. In addition, acoustic pressure measurements indicate that the MOR resonators are able to distribute the acoustic energy across a larger surface area, while generating 2-4 times higher pressures than existing ultrasonic probes.

Piston slap induced pressure fluctuation in the water coolant passage of an internal combustion engine

Liner cavitation is caused by water pressure fluctuation in the water coolant passage (WCP). When the negative pressure falls below the saturated vapor pressure, the impulsive pressure following the implosion of cavitation bubbles causes cavitation erosion of the wet cylinder liner surface. The present work establishes a numerical model for structural-acoustic coupling between the crankcase and the acoustic field in the WCP considering their dynamic characteristics. The coupling effect is evaluated through mutual interaction terms that are calculated from the mode shapes of the acoustic field and of the crankcase vibration on the boundary. Water pressure fluctuations in the WCP under the action of piston slap forces are predicted and the contributions of the uncoupled mode shapes of the crankcase and the acoustic field to the pressure waveform are analyzed. The influence of sound speed variations on the water pressure response is discussed, as well as the pressure on the thrust sides of the four cylinders.

Investigating the possibility of Sonofusion in Deuterated acetone

In this article, energetic implosion of a single vapor bubble induced by a standing acoustic wave is theoretically studied and the Sonoluminescing bubble parameters involved in Sonofusion in Deuterated acetone (C 3 D 6 O) are investigated. Parameters such as radius, wall velocity, interior temperature and pressure of the bubble influenced by various driving pressure amplitudes in Deuterated acetone at ∼0 °C are investigated. Based on the obtained results, the possibility of thermonuclear fusion inside imploding cavitation bubbles is discussed. The interior pressure of C 3 D 6 O vapor bubbles at the collapse time is extremely high and the increase of the pressure amplitude increases the pressure inside the bubble. Our findings reveal that the maximum temperature inside acoustic-induced cavitation bubble in Deuterated acetone increases with the acoustic pressure amplitude and it is much higher than the maximum temperature inside acoustic induced cavitation bubbles in liquids such as water and acids. Consequently, the calculated temperature at the pressure amplitude of 7.23 bar was about 3.7 × 10 5 K and it is predicted that at the reported experimental condition, the case of a bubble cluster subjected to the pressure amplitude of about 15 bar, the temperature inside the bubble reaches to 1.2 × 10 6 K. • The Sonoluminescing bubble parameters involved in Sonofusion are obtained. • Increasing acoustic pressure amplitude increases maximum temperature inside bubble. • Temperature inside C 3 D 6 O bubble is much higher than the bubbles in other liquids. • Bubble interior temperature at reported experimental condition can be 10 6 K < T < 10 7 K.

Numerical Prediction of Erosive Potential of Unsteady Cavitating Flow around Hydrofoil

The paper attempts to assess the erosive potential of cavitation bubbles in unsteady flow of liquid over a prismatic hydrofoil using two-way coupling of the URANS and the Rayleigh-Plesset equations. The erosive potential of the cavitating flow is evaluated from the energy dissipated during the collapses of imploding cavitation bubbles near the solid surface of the hydrofoil. The bubbles are assumed spherical and the phase slip is neglected. Bubble fission is modelled using a simple break-up model. The interaction between bubbles is considered by superposing the pressure change due to pressure waves generated by collapsing bubbles and propagated in the computational domain over the local pressure in the liquid (external to the bubble). The rate of erosion of the solid material is not studied in this work. The flow is analysed using the in-house three-dimensional solver for unsteady turbulent flow with bubble dynamics. The results are demonstrated on the NACA 2412 hydrofoil with the incidence angle of 8 degrees and the cavitation number 1.37, which corresponds to the regime of oscillating partial cavity with periodic shedding of bubble cloud downstream of the cavity.

Character of the cavitation erosion on selected metallic materials

It's well known, that the imploding cavitation bubbles causes the damage on the solid surfaces. This process is then dangerous for the mechanical parts of the hydraulic machines. Proposed article dealing with the analysis of the type of the damage caused by the cavitation erosion according to the selected metallic material of the specimen. As is shown in the article, the type of the damage has a realtion to the hydraulic parameters of the flow (velocity, cavitation number). The optical and weight measerument methods will be used for the anlysis.

Reaction of Ferricyanide and Methyl Viologen with Free Radicals Produced by Ultrasound in Aqueous Solutions

The redox reactions of organic radicals, with Fe(CN)63− and methyl viologen, generated from the sonochemical decomposition of aliphatic alcohols in aqueous solutions, have been studied. The number of radicals produced was found to relate to the amount of adsorbed alcohol molecules (Gibbs surface excess) at the gas−aqueous solution interface for any bulk solution concentration of the alcohol. The majority of the radicals produced stem from the thermal degradation of the alcohol molecules that have entered imploding cavitation bubbles. The maximum rate of reduction at 355 kHz, of Fe(CN)63−, was 2.6 ± 0.3 μM min−1, whereas for methyl viologen, it was 1.2 ± 0.3 μM min−1 under the conditions used.The difference in the rates is attributed to the reaction of various pyrolytically produced organic radicals with the methyl viologen radical cation. The possible reactions occurring in the sonolysis of alcohol/water systems are discussed in detail.

Cavitation damage incubation with typical fluids applied to a scroll expander system

During the operation of a scroll expander system overpressure may occur resulting in cavitation damage. Impacts due to implosion of cavitation bubbles near to suction ports can result in damage to the scroll plate in the expander. The accumulation of cavitation pits across the scroll plate leads to cavitation erosion hence efficiency drop. An experimental analysis to identify the mechanical damage of the cavitation on various steel surfaces with different liquid environments was conducted. Three liquid environments and four steel grades were utilised experimentally. The liquids used for the tests were distilled water, used as a reference liquid, and the two working fluids of the scroll expander a synthetic lubricant and a high molecular refrigerant. The steel grades were a high carbon (AISI 1085) and low carbon (AISI 1010) martensitic steel with retained austenite, a chromium martensitic steel (AISI 52100) and a martensitic scroll plate (SP) sample. An ultrasonic transducer was utilised to produce cavitation conditions using a 5 mm diameter probe. The comparison of the results revealed the most hostile liquid environment according to the morphology evaluation of the incubation pits. The cavitation mechanisms are discussed and the cavitation resistance of the steel grades is evaluated. The best performing steel material against cavitation is determined for the conditions described.

Cavitation erosion resistance parameter of hard CAVD coatings

Nowadays the most machining tools are coated with hard coatings to prolong their lifetime and to improve their working efficiency. They are very often used for high wear applications, where they are subjected to cyclic impact loading. Main benefits of hard coatings are based on the combination of high hardness and toughness, properties that are especially important in the conditions of dynamic impact wear when high cyclic local loading is the main cause of coating degradation. A cavitation test can be a useful tool for studies of plastic deformation, crack initiation and propagation in thin hard coatings. Cavitation damage is caused by repeating action of imploding cavitation bubbles in the vicinity of solid surface. Because TiN and Cr–N coatings are the most popular coatings for commercial applications, their cavitation erosion resistance were tested. TiN and Cr–N coatings with various thicknesses were deposited on stainless steel, by means of the cathodic arc evaporation (CAVD) method at various temperatures and bias voltages. All tests were performed in the same cavitation conditions in the cavitation chamber with a system of barricades. Obtained results have showed very good correlation between the mass loss and the new parameter. Analysis of degradation mechanism of thin nanocrystalline coatings under the impact degradation results in the obtainment of a new parameter to assess the resistance of hard coating against cavitation. The cavitation tests showed that plastic properties and adhesion play the main role in the coatings resistance, as well as the structure of a given material and its thermal properties.

MTBE degradation by hydrodynamic induced cavitation

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

Kinetics of Nanotube and Microfiber Scission under Sonication

Carbon nanotubes are commonly dispersed in liquid solvents by means of sonication. This has the disadvantage, however, that it can induce the scission of the particles that are near imploding cavitation bubbles. Nanotube scission arises from the fluid friction at the surface of the nanotubes in the radial elongational flow field that forms around a cavitation bubble. An understanding of the kinetics of this phenomenon is of critical importance for controlling the length of the nantoubes in their applications yet remains elusive. We investigate this kinetics quantitatively in the present work. The strain rate of the elongational flow around a cavitation bubble is estimated experimentally using carbon microfibers of known mechanical properties. The average length L(t) of the nanotubes is measured by means of dynamic light scattering as a function of time t, and we observed that L(t) scales as t−n, with n ≅ 0.2. This scaling differs from the one predicted theoretically in the literature for the scission of f...

The effect of high power ultrasound on an aqueous suspension of graphite

Ultrasound treatment was used to study the decrease of the granulometry of graphite, due to the cavitation, which allows the erosion by separating grains. At a smaller scale, cavitation bubble implosion tears apart graphite sheets as shown by HRTEM, while HO and H radicals produced from water sonolysis, generate oxidative and reductive reactions on these sheet fragments. Such reactions form smaller species, e.g. dissolved organic matter. The methodology proposed is very sensitive to unambiguously identifying the in situ composition of organic compounds in water. The use of the atmospheric pressure chemical ionization (APCI) Fourier transform mass spectrometry (FTMS) technique minimizes the perturbation of the organic composition and does not require chemical treatment for analysis. The structural features observed in the narrow range ( m/ z < 300) were mainly aromatic compounds (phenol, benzene, toluene, xylene, benzenediazonium, etc.), C 4–C 6 alkenes and C 2–C 10 carboxylic acids. Synthesis of small compounds from graphite sonication has never been reported and will probably be helpful to understand the mechanisms involved in high energy radical reactions.

Development of a Novel Oil Cavitation Jet Peening System and Cavitation Jet Erosion in Aluminum Alloy, AA 6063-T6

Compressive residual stresses that improve fatigue strength of material are obtained by peening the surface. Unlike traditional processes, a novel process of oil cavitation jet peening was developed. The process is based on implosion generated by the oil cavitation jet that plastically deforms the surface, imparting compressive residual stresses. The process developed involves injection of a high-speed oil jet (∼230 m/s) through a suitably designed nozzle, into an oil-filled chamber containing the specimen to be peened. The region of cavitation generation, growth, and collapse, at the various cavitation numbers, was recorded using high-speed photography. To optimize the process parameters, a simple erosion test was performed in aluminum alloy, AA 6063-T6, specimens. The impact pressure generated during the implosion of cavitation bubbles causes plastic deformation and erosion of the surface. The surface deformation and cavitation jet erosion in the exposed specimens were characterized using optical and scanning electron microscopies. The standoff distance, which measures jet impact zone of the specimen from nozzle, was optimized at 15 mm in a cavitation number (which is a measure of pressure ratio across the nozzle) of 0.0017. The surface deformation produced by collapse of the oil bubble was similar to impact of oil droplet on the surface. The material removal mechanism during implosion of the bubble is predominately by ductile shear deformation.

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

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

Effect of Nozzle-Traveling Velocity on Oil Cavitation Jet Peening of Aluminum Alloy, AA 6063-T6

A new surface modification process was developed to introduce compressive residual stresses at the surface of components. In this process, instead of oil droplets a high-velocity cavitation jet (cloud of oil bubbles) impinges on the surface of the component to be peened. The impact pressure generated during implosion of cavitation bubbles causes severe plastic deformation at the surface. Consequently, beneficial compressive stresses are developed at the surface. In order to find the potential of this process, aluminum alloy AA6063-T6 specimens were peened at a constant cavitation number with various nozzle-traveling velocities. Residual stress induced by oil jet cavitation peening was measured using X-ray diffraction. Oil cavitation jet peening results in a smooth and hard surface. The developed compressive residual stresses at the peened surface are about 52%, 42%, and 35% of yield strength in samples for peened at nozzle traveling velocities of 0.05mm∕s, 0.10mm∕s, and 0.15mm∕s, respectively.

High-speed observation of the effects of ultrasound on liquid mixing and agglomerated crystal breakage processes

A Kodak Ektapro Hs motion analyzer is applied to observe the ultrasonic effect on the mixing and breakage processes of agglomerated crystals suspended in ethanol. Mixing processes with stirring and with ultrasound are investigated by the dispersion of ink in the ethanol and by the motion of small crystals. The vessel is divided into several sections to investigate the local mixing process. Velocity variance is used to indicate the difference of turbulence when ultrasound and impeller stirring are applied respectively. The cavitation distribution in different sections is also recorded, and the effects on particles of different sizes are investigated. Observation of the breakage processes in different sections shows that both collisions between crystals and the vibration and implosion of cavitation bubbles contribute to the breakage process of agglomerated crystals. Finally, the effect of ultrasonic treatment is also compared with impeller stirring and with mechanical grinding.

Theory of supercompression of vapor bubbles and nanoscale thermonuclear fusion

This paper provides the theoretical basis for energetic vapor bubble implosions induced by a standing acoustic wave. Its primary goal is to describe, explain, and demonstrate the plausibility of the experimental observations by Taleyarkhan et al. [Science 295, 1868 (2002); Phys. Rev. E 69, 036109 (2004)] of thermonuclear fusion for imploding cavitation bubbles in chilled deuterated acetone. A detailed description and analysis of these data, including a resolution of the criticisms that have been raised, together with some preliminary HYDRO code simulations, has been given by Nigmatulin et al. [Vestnik ANRB (Ufa, Russia) 4, 3 (2002); J. Power Energy 218-A, 345 (2004)] and Lahey et al. [Adv. Heat Transfer (to be published)]. In this paper a hydrodynamic shock (i.e., HYDRO) code model of the spherically symmetric motion for a vapor bubble in an acoustically forced liquid is presented. This model describes cavitation bubble cluster growth during the expansion period, followed by a violent implosion during the compression period of the acoustic cycle. There are two stages of the bubble dynamics process. The first, low Mach number stage, comprises almost all the time of the acoustic cycle. During this stage, the radial velocities are much less than the sound speeds in the vapor and liquid, the vapor pressure is very close to uniform, and the liquid is practically incompressible. This process is characterized by the inertia of the liquid, heat conduction, and the evaporation or condensation of the vapor. The second, very short, high Mach number stage is when the radial velocities are the same order, or higher, than the sound speeds in the vapor and liquid. In this stage high temperatures, pressures, and densities of the vapor and liquid take place. The model presented herein has realistic equations of state for the compressible liquid and vapor phases, and accounts for nonequilibrium evaporation/condensation kinetics at the liquid/vapor interface. There are interacting shock waves in both phases, which converge toward and reflect from the center of the bubble, causing dissociation, ionization, and other related plasma physics phenomena during the final stage of bubble collapse. For a vapor bubble in a deuterated organic liquid (e.g., acetone), during the final stage of collapse there is a nanoscale region (diameter ∼100nm) near the center of the bubble in which, for a fraction of a picosecond, the temperatures and densities are extremely high (∼108K and ∼10g∕cm3, respectively) such that thermonuclear fusion may take place. To quantify this, the kinetics of the local deuterium/deuterium (D∕D) nuclear fusion reactions was used in the HYDRO code to determine the intensity of the fusion reactions. Numerical HYDRO code simulations of the bubble implosion process have been carried out for the experimental conditions used by Taleyarkhan et al. [Science 295, 1868 (2002); Phys. Rev. E 69, 036109 (2004)] at Oak Ridge National Laboratory. The results show good agreement with the experimental data on bubble fusion that was measured in chilled deuterated acetone.

Nano-scale thermonuclear fusion in imploding vapor bubbles

This paper presents the specific features of violent vapor cavitation bubble implosion induced by an energetic acoustic standing wave in the Oak Ridge National Laboratory (ORNL) experiments performed using deuterated acetone [Taleyarkhan, R.P., West, C.D., Cho, J.S., Lahey Jr., R.T., Nigmatulin, R.I., Block, R.C., 2002. Evidence for nuclear emissions during acoustic cavitation. Science 295, 1868; Taleyarkhan, R.P., West, C.D., Cho, J.S., Lahey Jr., R.T., Nigmatulin, R.I., Block, R.C., 2004. Additional evidence of nuclear emissions during acoustic cavitation. Phys. Rev. E 69, 036109]. A detailed description and analysis of these data, including a resolution of the criticisms that have been raised, has been given by Nigmatulin et al. [Nigmatulin, R.I., Taleyarkhan, R.P., Lahey Jr., R.T., 2002. The evidence of thermonuclear fusion D + D during acoustic cavitation. In: Vestnik ANRB, No. 4. Ufa, Bashkortostan, Russia; Nigmatulin, R.I., Taleyarkhan, R.P., Lahey Jr., R.T., 2004. The evidence for nuclear emissions during acoustic cavitation revisited. J. Power Energy 218-A, 345] and Lahey et al. [Lahey Jr., R.T., Taleyarkhan, R.P., Nigmatulin, R.I., Akhatov, I.S. Sonoluminescence and the search for sonofusion. In: Advances in Heat Transfer, vol. 39. Academic Press, in press]. The results presented in this paper are found based on the numerical simulations of the bubble implosion phenomena. A more detailed description of the equations for the mathematical modeling of the phenomena has been given by Nigmatulin et al. (2005).

On the maximum D+– D+ fusion rate by the implosion of cavitation bubble

On the maximum D+– D+ fusion rate by the implosion of cavitation bubble

Flash test development using ultrasonics for fast qualification of the mechanical resistance of industrial organic coatings: Part I. Methodological approach

A flash test based on the use of ultrasonics in water is developed in order to qualify industrial organic coatings toughness. It has been applied to samples of paint films used for protection against corrosion. The relevance of this test and the reliability of the results have been demonstrated. After reviewing the physical mechanisms associated with ultrasound waves, it has been shown that the implosion of cavitation bubbles on the organic surface is the predominant phenomenon responsible for the organic coating damages. This theoretical approach seems to be confirmed by the experiments on numerous samples.

Processes and key properties of pool materials for “bubble fusion”

The key properties of pool materials have been studied for intense implosion of cavitation bubble in order to give rise to the nuclear emission. The past studies treated this “bubble fusion” for a couple of special cases, while this paper takes the systematic searches, and clarifies the important roles of absorption efficiency of ultrasound wave, compressibility, surface tension, viscosity, number of D-ions, ionization energy. It is pointed out also that the dipole moment, the molecular structure (mass and size), and the vapor pressure are essential. The selection principles as well as the candidacies for the better materials are proposed. The reason why heavy water does not give rise to the nuclear emission is discussed. It is concluded that the phenomenon of “bubble fusion” is very rare to observe unless the matching contrivance between the irradiated ultrasound wave and the adiabatic bubble growth is undertaken.