A comparison of ultrasonic cavitation intensity in liquids

Cavitation intensity in 37 organic liquids is compared with cavitation intensity in water under the same conditions. Temperature ranges are established over which cavitation intensities in these liquids are at their highest.     

A comparison of two methods for determining ultrasonic intensity for medical transducers

The spatial and temporal average intensity (ISATA) is determined for four diagnostic ultrasound transducers by two methods: (a) direct measurements (beam profiling) with a miniature hydrophone, as described in the AIUM-NEMA standard, and (b) estimating from measurements of total power and assumptions about beam size. The latter method is frequently used by diagnostic ultrasound manufacturers when reporting output levels to users and regulatory agencies. However, due to the conventions for defining beam area, this method actually overestimates the spatial average intensity. For the four transducers tested, the estimated ISATA exceeds the measured ISATA by several hundred percent. The spatial peak, temporal average intensity (ISPTA) was also measured for the four transducers and is less than the estimated ISATA in every case.     

Effect of liquid-phase properties on ultrasound intensity and cavitational activity

The intensity of ultrasound is attenuated due to various properties of the liquid, such as viscosity, density, etc. In this paper, a simple method is proposed to measure the combined attenuation and cavitational activity of ultrasound intensity in various organic liquids using standard KI decomposition reaction. A modified experimental attenuation coefficient is proposed and its dependence on liquid viscosity reasonably matches the theoretical predictions made by Stokes [G.G. Stokes, Trans. Camb. Philos. Soc. 8 (1849) 287]. Exploratory work to determine the effect of other liquid properties on cavitational activity is carried out. Correlations are proposed to explain the dependence of the attenuated cavitational activity on various properties of a liquid.     

Physical facets of ultrasonic cavitational synthesis of zinc ferrite particles

This paper addresses the physical features of the ultrasonic cavitational synthesis of zinc ferrite particles and tries to establish the relationship between cavitation physics and sonochemistry of the zinc ferrite synthesis. A dual approach of coupling experimental results with simulations of radial motion of cavitation bubbles has been adopted. The precursors for the zinc ferrite, viz. ZnO and Fe₃O₄ are produced in situ by the hydrolysis of Zn and Fe(II) acetates stimulated by OH radicals produced from the transient collapse of the cavitation bubbles. Experiments performed under different conditions create significant variation in the production of OH radicals, and hence, the rate of acetate hydrolysis. Correlation of the results of experiments and simulations sheds light on the important facets of the physical mechanism of ultrasonic cavitational zinc ferrite synthesis. It is revealed that too much or too little rate of acetate hydrolysis results in smaller particle size of zinc ferrite. The first effect of a higher rate of hydrolysis leads to excessively large growth of particles, due to which they become susceptible to the disruptive action of cavitation bubbles. Whereas, the second effect of too small rate of hydrolysis of Zn and Fe(II) acetates restricts the growth of particles. It has been observed that the initial reactant concentration does not influence the mean particle size or the size distribution of zinc ferrite particles. The present investigation clearly confirms that the rate-controlling step of zinc ferrite synthesis through ultrasonic cavitational route is the rate of formation of OH radicals from cavitation bubbles.     

Cavity cluster approach for quantification of cavitational intensity in sonochemical reactors

The mechanism involved in the spectacular effects from cavitation phenomenon is very complex and there have been several proposed theories to explain the observed results. The experimental as well as the visual observations indicate that a single collapsing cavity is also influenced by the dynamics of the surrounding cavities, which are very near to the collapsing cavity. The observed effects and erosion patterns cannot be explained properly on the basis of a single cavity collapse and hence in this study a cavity cluster (group of cavities) has been considered to understand the mechanism of cavitational effects. The effect of intensity, frequency of ultrasound, initial size of the cluster and the fraction of energy transferred from the collapsing cavities to the surrounding cavities on the cavitational intensity quantified in terms of the pressure pulse generated at the collapse of cavities as well as the active zone of cavitation has been investigated using bubble/cavity dynamics equations, numerically. On the basis of the trends obtained, empirical correlations estimating the collapse pressure and active volume of cavitation, have been developed.     

Experimental investigation of the spatial distribution of the intensity of cavitational processes

We propose an experimental method for distant measurements of the spatial distribution of cavitation intensity. The experimental results are obtained by investigating cavitation on a rigid cylinder and thin wires. The possibility of attaining a higher spatial resolution is shown.Lobachevskii State University, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, Nos. 3–4, pp. 337-xxx, March–April, 1995.     

超声强度定性演示实验

利用超声波在介质中传播使质点产生强烈振动而引起界面的变化。演示了超声场在换能器平面辐射、聚焦系统下焦平面及其以内的横截面上的液包喷泉的变化．     

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

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

High intensity ultrasonic equipment for teaching and research

Colleges now need equipment to demonstrate ultrasonic effects such as cavitation and emulsification to students. The author uses his equipment to do this and also to carry out fundamental research into the applications of high intensity ultrasound     

A comparison of the titanomagnetites produced by several volcanoes in Iceland

Samples of titanomagnetite extracted from the ejecta of volcanoes in Iceland have been separated according to the intensity of their magnetisation and analysed with Mossbauer spectroscopy and electron microprobe analysis. It is shown that the magnetic peaks in the Mossbauer spectra vary widely between different source volcanoes and magnetic fractions, and thus that the Mossbauer spectrum of the titanomagnetite could be a useful fingerprint of the tephra.     

Cavitation intensity of water under practical ultrasonic cleaning conditions

When measuring cavitation during cooling of thermally degassed water cavitation maxima are frequently observed at various temperatures. Relations between this phenomenon and frequency and power of ultrasounds as well as air content in water have been examined. It was found out that the secondary water regassing with air is the reason.     

A high power ultrasonic array based test cell

This paper describes the use of finite element (FE) analysis as a tool in the design process for laboratory based ultrasonic test cells. The system was designed to incorporate an array of ultrasonic transducers to provide a pressure focus in the centre of the cell and importantly, operate both above and below the cavitation threshold of the load medium. Furthermore, the cell incorporates a coolant jacket to accommodate temperature control of the load material associated with the process. A 2D FE model corresponding to a slice through the operational plane of the cell was developed and used to investigate the influence of cell wall material and thickness, transducer configuration, rotation of a metallic stirrer blade and heat transfer fluid on the cell acoustic response. Importantly, experimentally measured pressure field maps demonstrate good correlation with the FE predicted fields. A final manufactured test cell is shown to produce a highly focussed region of cavitation. Finally, the importance in accurately representing the acoustic properties of the constituent materials used in such FE models is demonstrated through an illustrated example.     

Optimisation of 20 kHz sonoreactor geometry on the basis of numerical simulation of local ultrasonic intensity and qualitative comparison with experimental results

The intensity distribution of the ultrasonic energy is, after the frequency, the most significant parameter to characterize ultrasonic fields in any sonochemical experiment. Whereas in the case of low intensity ultrasound the measurement of intensity and its distribution is well solved, in the case of high intensity (when cavitation takes place) the measurement is much more complicated. That is why the predicting the acoustic pressure distribution within the cell is desirable. A numerical solution of the wave equation gave the distribution of intensity within the cell. The calculations together with experimental verification have shown that the whole reactor behaves like a resonator and the energy distribution depends strongly on its shape. The agreement between computational simulations and experiments allowed optimisation of the shape of the sonochemical reactor. The optimal geometry resulted in a strong increase in intensity along a large part of the cell. The advantages of such optimised geometry are (i) the ultrasonic power necessary for obtaining cavitation is low; (ii) low power delivered to the system results in only weak heating, consequently, no cooling is necessary and (iii) the "active volume" is large, i.e. the fraction of the reactor volume with high intensity is large and is not limited to a vicinity close to the horn tip.     

Simple quantification of ultrasonic intensity using aqueous solution of phenolphthalein

Aqueous phenolphthalein solution under sonication was investigated for use as a chemical dosimeter. The fading time of aqueous phenolphthalein solution under sonication depended on the concentration of phenolphthalein and the pH values of solutions. The fading time was correlated to the ultrasonic intensity in a reaction vessel that is estimated on the basis of decomposition of porphyrin. The relation between the fading time and the ultrasonic intensity for different frequencies is expressed by a single curve. From these results, it is indicated that aqueous solutions of phenolphthalein is useful for simple quantification of ultrasonic intensity for practical use, and one can regard it as one of the ultrasonic intensity indicators.     

Observations of water cavitation intensity under practical ultrasonic cleaning conditions

In the industrial cleaning processes either organic solvents or water solutions are used as the cleaning media. The primary causative factor of ultrasonic cleaning is cavitation. Below are presented results of investigations into the influence of temperature, gas content and the solution level in an ultrasonic cleaner on cavitation intensity in the tap water. Previous investigations have revealed a great deal of information on the influence of the above factors on the cavitation intensity and these are confirmed. It has now been found that the tap water reaches the highest cavitation intensity at temperatures below 20 degrees C but during heating at higher temperatures (20-40 degrees C) a second peak of cavitation intensity may appear-depending on the height of water in the bath and air content.     

Cryptanalysis and improvement of several quantum private comparison protocols

Recently, Wu et al(2019 Int. J. Theor. Phys. 58 1854) found a serious information leakage problem in Ye and Ji's quantum private comparison protocol(2017 Int. J. Theor. Phys. 561517), that is, a malicious participant can steal another's secret data without being detected through an active attack means. In this paper, we show that Wu et al's active attack is also effective for several other existing protocols, including the ones proposed by Ji et al and Zha et al(2016 Commun. Theor. Phys. 65 711; 2018 Int. J. Theor. Phys. 57 3874). In addition,we propose what a passive attack means, which is different from Wu et al's active attack in that the malicious participant can easily steal another's secret data only by using his own secret data after finishing the protocol, instead of stealing the data by forging identities when executing the protocol. Furthermore, we find that several other existing quantum private comparison protocols also have such an information leakage problem. In response to the problem, we propose a simple solution, which is more efficient than the ones proposed by Wu et al, because it does not consume additional classical and quantum resources.     

The comparison of ultrasonic disintegration in laboratory and technical scale disintegrators

The study was aimed at finding the impact of the construction of two disintegration instruments (laboratory and technical scale) on the effects of ultrasonic disintegration. The tests were carried out on excess sewage sludge and an increase in soluble COD in the sludge after ultrasonic disintegration was determined. In both types of disintegrators, the sludge was subjected to ultrasounds at the same level of energy density, but the disintegration effects were about three times higher in the case of the technical module application.     

Sonoluminescence intensity and ultrasonic cavitation temperature in organic solvents: Effects of generated radicals

Ultrasonic cavitation in organic solvents remains poorly understood in contrast with aqueous systems, largely because of complexities related to solvent decomposition. In this study, we sonicated different types of organic solvents (i.e. linear alkanes, aliphatic alcohols, aromatic alcohols, and acetate esters) under argon saturation. The average temperature of the cavitation bubbles was estimated using the methyl radical recombination method. We also discuss the effects of the physical properties of the solvents, such as vapor pressure and viscosity, on the cavitation temperature. The average cavitation bubble temperature and sonoluminescence intensity were higher in organic solvents with lower vapor pressure; for aromatic alcohols, these values were particularly high. It was found that the specific high sonoluminescence intensities and average cavitation temperatures exhibited in aromatic alcohols are caused by the highly resonance-stable generated radicals. The results obtained in this study are very useful for acceleration of sonochemical reaction in organic solvents, which are indispensable for organic synthesis and material synthesis.     

Model of cell membrane in ultrasonic field

A model of cell membrane as a viscous plate is studied. It is subjected to an ultrasonic field. The influence of the field on the membrane is compared for two cases: purely viscous plate and plate containing gold nanoparticles. It is shown that nanoparticles lead to increasing the influence of the acoustic waves. Its impact is sensitive to membrane’s physical properties and it was observed in recent experiments. In principle, this effect can be used for selective cancer cells killing.