Cavitation Action Research Articles

Study on Dynamic Evolution and Erosion Characteristics of Cavitation Clouds in Submerged Cavitating Water Jets

The dynamic evolution behavior of submerged water jet cavitation clouds was studied by combining experiments and simulation. The formation, development, shedding, and collapsing process of a void cloud was analyzed by high-speed camera technology, and the influence of jet pressure was studied. Cavitation water jet erosion experiments were carried out on AL6061 specimens with standard cylindrical nozzles, and the correlation between cavitation cloud evolution and material erosion was studied by surface analysis. The results showed that the evolution of a cavitation cloud has obvious periodicity, that one period is about 0.8 ms, and its action region can be divided according to the attenuation rate of the jet velocity of the nozzle axis. The attenuation rate of the jet velocity at the nozzle axis in the central jet action zone is less than or equal to 82.5%, in the mixed action zone greater than 82.5% and less than 96%, and in the cavitation action zone greater than or equal to 96%. The erosion damage characteristics in different regions of the mixed action zone are significantly different.

A COMPARATIVE STUDY OF ALUMINUM OXIDE NANOPARTICLES SYNTHESIZED IN PLASMA DISCHARGE UNDER ULTRASONIC CAVITATION AND BY LASER ABLATION FOR CREATION OF COMPOSITE MATERIALS

In this work, aluminum oxide nanoparticles were fabricated by two physical methods: laser ablation in liquid medium and plasma discharge under the action of intensive ultrasonic cavitation. Dynamic light scattering, scanning electron microscopy, and electrokinetic potential measurements were employed to comparatively examine the nanoparticles obtained by both methods. It was found that the synthesized particles had spherical shapes with a size range of about 50-70 nm and relatively narrow particle size distributions and were stable to aggregation and sedimentation. The electrokinetic potential values of the pure particles and the effects of the presence of water-soluble polymer polyethylene glycol were used to examine the surface properties of the nanoparticles. This study demonstrates the effect of ultrasonic action on particle surface activity.

Elastification of the arterial wall by high-intensity low-frequency ultrasound

A significant increase in the elasticity of the femoropopliteal artery segments in vitro was found as a result of the action of cavitation generated by powerful low-frequency (24–26 kHz) ultrasound introduced into the vessel by a flexible waveguide. The vessel elasticity was evaluated both by the deflection under the action of an external force and by the degree of its expansion vasodilatation by the internal pressure created by the expanding balloon. The possibility of achieving a more than two-fold decrease in the vascular wall elasticity modulus after 30-s exposure to an ultrasound intensity of 31 W/cm2 was shown. It has been established that at the 10 μm amplitude of ultrasonic vibrations, vascular wall damage occurs in the form of small foci of detachment and rupture of the intima accompanied by delamination in the media layer, when polymorphic slit-like cavities are formed with an increase in the amplitude of oscillations above 23 μm.

Evaluation of ultrasonic-assisted pickling with different frequencies on NaCl transport, impedance properties, and microstructure in pork

The effects of ultrasonic curing with various frequencies on sodium chloride (NaCl) mass transfer in pork muscle and its potential mechanisms were investigated. The results showed that ultrasound curing dramatically increased the NaCl content in pork compared to static curing, especially curing at 26.8 kHz. The binarized images of NaCl penetration in pork visually confirmed that ultrasound enhanced the efficiency of mass transfer. Energy dispersive spectroscopy showed that the distribution of NaCl in pork tissue cured by ultrasound was the densest compared to the static curing. According to impedance analysis and microstructure observation, the structure of cell membranes was damaged to different extents during ultrasound treatments. The potential mechanisms of low-frequency ultrasound accelerated curing are mainly attributed to the action of acoustic cavitation and the sponge effect. Overall, the low-frequency ultrasound is a promising revolutionary technology in the food industry that can speed up the curing process of meat.

Получение полимерных композиционных материалов на основе наночастиц оксида цинка, синтезированных в плазменном разряде под действием ультразвука

Zinc oxide nanoparticles were synthesized and samples of films of polymer composite materials on their basis were obtained and studied. Zinc oxide nanoparticles were synthesized in a plasma discharge under the action of ultrasonic cavitation. To create composites with a homogeneous distribution of nanoparticles, solution technology was used, and then melt compounding technology. Composite materials based on a copolymer of polyethylene and vinyl acetate and zinc oxide nanoparticles were obtained, and not sonicated and sonicated nanoparticles were used. The obtained samples of composite materials were studied by X-ray phase analysis, X-ray fluorescence analysis and scanning electron microscopy. It was shown that there are differences between the samples: in the case of nanoparticles without ultrasonic treatment, the particles are more strongly aggregated inside the composite material and their average size is visually larger than in the case of a sample with nanoparticles subjected to ultrasonic treatment.

Degradation of Azo Dye by Ultrasound in Rotating Flow Field

Azo dyes such as Congo red can easily cause cancer when they come into contact or are absorbed by the human body, so it is urgent to find a fast and simple method for degrading Congo red. In order to better achieve this research goal, an ultrasonic method was used to degrade Congo red solution in a rotating flow field. The concentration of hydroxyl radical in the solution was significantly increased under the action of ultrasonic cavitation, chemical action of zero valent iron, and mechanochemistry. Under the strong oxidation of hydroxyl radical and the reduction of nano zero valent iron peeled off in the reaction process, the reaction speed is significantly accelerated and should promote the reaction. The effect of increasing stirring and adding iron powder particles on ultrasonic cavitation was studied by numerical simulation, and the yield of hydroxyl radical in the system was measured by fluorescence analysis. The experimental results show that, first, the rotating field formed by mixing increases the uniformity of ultrasonic sound field distribution and the amplitude of sound pressure, and it improves the cavitation intensity. In the effective dispersion area, the strong ultrasonic wave can form a temporary high-energy microenvironment in the suspension through cavitation, generate high strength shockwaves and micro jets, and thus significantly deagglomerate the iron powder aggregates. The addition of iron powder particles then provides a complementary Fenton reagent for the degradation reaction. The concentration of hydroxyl radicals in the solution was significantly increased by the synergy of the two actions. The degradation rate of Congo red reached more than 99% after 30 min of reaction.

Sono-electrolysis performance based on indirect continuous sonication and membraneless alkaline electrolysis: Experiment, modelling and analysis

In the present study, experiments of membraneless alkaline sono-electrolysis are combined to a mathematical model describing the performance of a sono-electrolyzer based on the electrochemical resistances and overpotentials (activation, Ohmic and concentration) and the oscillation of the acoustic cavitation bubble, and its related sono-physical and sonochemical effects, as a single unit and within population. The study aims to elucidate the mechanism of action of acoustic cavitation when coupled to alkaline electrolysis, using a membraneless H-cell configuration and indirect continuous sonication (40 kHz, 60 We). The calorimetric characterization constituted the bridge between experimental results and the numerical and simulation approach, while the quantification of the rate of produced hydrogen both experimentally and numerically highlighted the absence of the contribution of sonochemistry, and explained the role of ultrasounds by the action of shockwaves and microjets. Finally, the energetic sono-physical approach allowed an estimation of the predominance of the shockwaves and microjets effects according to the bubble size distribution within the population corresponding to the acoustic conditions of the study. The resulting macroscopic effect in sono-electrolysis process has been assessed considering the induced degassing. A reduction in the fraction of electrodes’ coverage by bubbles from 76% to 42% has been recorded, corresponding to a decrease of 7.2% in Ohmic resistance and 62.35% in bubble resistance.

Determination of the influence of the sound capillary effect on the process of soaking vegetable raw materials in the acoustic extractor

The object of research is the process of liquid movement in capillaries during the extraction of biologically active substances (BAS) from plant raw materials under the action of the sound capillary effect. A characteristic feature of vegetable raw materials is a large number of pores of the capillary type. Penetration of the extractant into the raw material occurs through capillaries and leads to the filling of cells and voids in it. The process of filling the capillaries and cell voids with the extractant can be quite long and significantly increase the extraction time as a whole. It was established that the penetration of the extractant into the capillaries of plant raw materials is affected by ultrasonic vibrations that cause cavitation. Under the action of cavitation, which occurs in the ultrasonic field, the penetration of the extractant into narrow cavities and crevices is accelerated and deepened. This phenomenon is called the sound capillary effect. The analysis of literary sources showed that there are no data on the study of the conditions for the occurrence of the sound capillary effect and the effect on the speed of movement of liquid in the capillaries of ultrasonic pressure during the BAS extraction from plant raw materials. Numerical modeling was used to study the movement of liquid (extractant) in capillaries during the BAS extraction from plant raw materials under the conditions of ultrasound. As a result of the conducted research, the conditions for the occurrence of ultrasonic cavitation in the process of BAS extraction from plant raw materials with the most common extractants, such as water and ethanol solutions, were found. The values of the amplitude of the sound pressure of the extractant, which occurs under the conditions of the sound capillary effect directly at the entrance to the capillary, were also found. The dependences of the sound capillary pressure on the diameter of the capillary for the most common extractants have been established. The influence of the sound-capillary effect on the speed of movement of the most common extractants in capillaries of different sizes is determined. The obtained research results allow to quantitatively evaluate the influence of the sound-capillary effect on the movement of extractants in the capillaries of plant raw materials, on the rate of wetting of plant raw materials and the speed of mass exchange processes during extraction. These results can be used when choosing operating modes of existing and designing new equipment for the BAS extraction from plant raw materials under ultrasound conditions.

Breaking through Barriers: Ultrafast Microbullet Based on Cavitation Bubble.

Micromotors hold great promise for extensive practical applications such as those in biomedical domains and reservoir exploration. However, insufficient propulsion of the micromotor limits its application in crossing biological barriers and breaking reservoir boundaries. In this study, an ultrafast microbullet based on laser cavitation that can utilize the energy of a cavitation bubble and realize its own hurtling motion is reported. The experiments are performed using high-speed photography. A boundary integral method is adopted to reveal the motion mechanism of a polystyrene (PS)/magnetic nanoparticle (MNP) microbullet under the action of laser cavitation. Furthermore, the influence of certain factors (including laser intensity, microbullet size, and ambient temperature) on the motion of the microbulletwasexplored. For the PS/MNP microbullet driven by laser cavitation, the instantaneous velocity obtained can reach 5.23 m s-1 . This strategy of driving the PS/MNP microbullet provides strong penetration ability and targeted motion. It is believed that the reported propulsion mechanism opens up new possibilities for micromotors in a wide range of engineering applications.

Kinetics of fibrin clots destruction under ultrasonic cavitation

We studied the kinetic features of fibrin clot destruction in vitro under the action of ultrasonic cavitation generated by low-frequency (36 kHz) ultrasound (US) with the intensity I0 of 4.4–51.2 W/cm2, using a flexible waveguide concentrator. It was established that the rate of US destruction of clots immersed in saline at the initial stage of the process is proportional to I0 in the range of 12–51 W/cm2, corresponds to first-order kinetics, and is determined by the erosive processes without the formation of D-dimers and other fibrinolysis products at a minimum contribution of sonochemical reactions. The clot destruction rate is maximum at the initial time moment and decreases with increasing the US exposure duration (by 35 % in 1 min and by 72 % by the end of the second minute at I0 = 51.2 W/cm2). It was shown that in order to increase the completeness of clot destruction at a minimum administered US dose, it is advisable to minimize the US exposure time when using the highest values of the US intensity limited by the level of safe cavitation exposure to the vascular wall, hemostasis, and blood cells.

Theoretical and experimental investigation of cavitation number limits

Cavitation remains a popular field of scientific research due to the generated effects and a wide range of possible applications. At the same time, despite the active development of technologies for treatment of liquid materials by cavitation action, the equipment used for initiation of cavitation action has not fundamentally changed. In this regard, the main direction of development of efficiency of technological processes based on cavitation impact should be the search for ways to improve the efficiency of existing equipment, which will form the basis for the development of new types of devices. For development of devices it is necessary to understand how to increase the efficiency of created cavitation in various devices. To date, in the analysis of the degree of intensity and the threshold of creation of cavitation is used dimensionless cavitation number, which due to a number of limitations is not able to fully reflect all the parameters of the process of creation of hydrodynamic cavitation. In this paper we present a theoretical and experimental study using two types of hydrodynamic cavitation generators, to assess the limitations of the dimensionless cavitation number.

Design of process equipment exposure sources for ultrasonic absorption of greenhouse gases

The work aims at improving the efficiency of greenhouse gas utilisation processes, namely carbon dioxide. The principle of operation of the designed equipment is to realise the process of ultrasonic absorption (absorption of gas by liquid) when carbon dioxide is fed over the surface of the liquid, in which cavitation occurs. The source of the cavitation action is a plate that oscillates with a given frequency and amplitude. The efficiency of the ultrasonic gas absorption process is determined by the parameters of plate oscillations. In particular, to ensure the necessary and sufficient amplitude of plate oscillations and uniformity of its distribution along the plate, it is proposed to solve the problem of optimal placement of the required number of ultrasonic emitters of a given size. As a criterion of optimality, it is proposed to use the integral power of oscillations of the whole plate, formed by a certain number of emitters. The proposed and developed numerical model of oscillation formation in the plate is based on the solution of the biharmonic equation for the distribution of amplitudes of oscillations, taking into account the finiteness of its thickness and provides the choice of the number, location, and size of ultrasonic emitters required to solve a particular problem. The simulation results allowed us to establish that the optimal location of the emitters depends on specific characteristics that must be taken into account when solving the problem of optimising the size and location of ultrasonic emitters for each particular plate. The calculations showed high efficiency of the created model and the possibility of its practical application for solving the problems of utilisation of greenhouse gas emissions in agriculture.

Ultrasonic Preparation of Coating Surfaces

For various methods of obtaining coatings, the general stage of technology is the preparation of the surface for the application of the coating material. The properties of the resulting coating directly depend on the quality of preparation. In the process of obtaining coatings, the most common application of ultrasonic treatment to clean the surface from all kinds of contaminants. However, with a sufficient intensity of processing, ultrasound has a significant effect on the geometric properties of the surfaces of products. Prolonged cavitation action leads to changes in the roughness and sub-roughness of the metal surface. The article discusses the effectiveness of the use of ultrasonic liquid treatment in the preparation of surfaces for coating. The results of studies on the effect of cavitation on the change in roughness, sub-roughness and oil absorption are presented. Revealed an improvement in the adhesion properties of surfaces after ultrasonic liquid treatment.

Plasma-Chemical Synthesis of Nanosized Bactericidal Particles under the Action of Ultrasonic Cavitation

Plasma-Chemical Synthesis of Nanosized Bactericidal Particles under the Action of Ultrasonic Cavitation

Synthesis of gaseous hydrogen and nanoparticles of silicon and silicon oxide by pyrolysis of tetraethoxysilane in an electric discharge under the action of ultrasound

In this work, we studied the process of synthesis of gaseous hydrogen, as well as silicon and silica nanoparticles under the action of intensive ultrasonic cavitation in a plasma discharge in a tetraethoxysilane medium.It is shown that a new form of plasma discharge arising in a liquid in an intensive ultrasonic field above the cavitation threshold, characterized by a volumetric glow in the entire space between the electrodes and falling volt-ampere characteristics, can be effectively used to initiate various physical and chemical processes. It was shown that ultrasonic action in combination with an electric discharge is capable to decompose tetraethoxysilane molecules with the formation of hydrogen, carbon oxides, and also solid-phase products - silicon and silica nanoparticles.Experiments on the production of hydrogen and nanoparticles were carried out on a special experimental setup for the implementation of a plasma discharge in liquid-phase media. The setup consists of an ultrasonic generator, a piezoceramic transducer, a discharge power source, a reaction chamber, and discharge electrodes.The results of the analysis of gaseous reaction products by gas chromatography show that during the pyrolysis of liquid tetraethoxysilane, hydrogen with a content of about 90% and carbon oxides are formed. The synthesized silicon and silica nanoparticles were isolated and studied using the methods of physicochemical analysis - infrared spectroscopy, X-ray phase analysis and transmission electron microscopy to determine the composition, shape and size of nanoparticles.The study of nanoparticles by electron microscopy showed that particles of a corner shape are obtained during the synthesis. The size of the synthesized nanoparticles is 50–100 nm. It was also shown by electron microscopy that, upon aggregation, the particles do not become larger in size, but form composite associates. It is also important to note that the advantage of this method for the synthesis of nanoparticles is their activated surface, which has a high reactivity as a result of exposure to intense ultrasound.The resulting nanoparticles and their agglomerates can also be used as functional materials, fillers, and components of composite materials.

MODEL OF DESTRUCTION OF FASTENING PINS OF HYDRAULIC UNIT NO. 2 SAYANO-SHUSHENSKAYA HPP

The paper [1] presents a new model of erosive destruction of materials associated with the formation of high - frequency micro - spirals in the studied materials under the action of cavitation. In the focused channels along the axis of the spirals, significant energy is released that can cause the destruction of the materials under study. Spiral structures are sources of microcracks formed along focused channels. Parts and assemblies of hydraulic units are in a complex stressed state (internal pressure, vibrations, tension of pins). Under the influence of these stresses, microcracks open, which leads to the destruction of the fastening pins.

Obtaining of gaseous hydrogen and silver nanoparticles by decomposition of hydrocarbons in ultrasonically stimulated low-temperature plasma

In this work, experimental studies of the process of obtaining hydrogen and silver nanoparticles using intense ultrasonic cavitation affecting a plasma discharge in liquid hydrocarbons were carried out.It was shown that ultrasonic action above the cavitation threshold intensifies heat and mass transfer processes in the treated medium, and in combination with an electric discharge, which contributes to the appearance of an ionized state of matter (plasma), such action is capable of decomposing complex hydrocarbon molecules to an atomic state with subsequent recombination and formation simple molecules.Experiments on the production of hydrogen and nanoparticles were carried out on a special installation for the implementation of an acoustoplasmic discharge in a liquid. The installation includes an ultrasonic generator, a piezoceramic transducer, a plasma discharge power source, a reaction chamber, and discharge electrodes.The results of the analysis of gaseous reaction products by gas chromatography show that during the acoustoplasmic decomposition of hydrocarbons, the formation of almost pure hydrogen (90–95%); the composition of the released gas also includes pairs of initial hydrocarbons.Simultaneously with the production of a hydrogen-containing gas, the decomposition of hydrocarbons in a plasma discharge under the action of ultrasonic cavitation results in the formation of silver nanoparticles. The synthesized nanoparticles were isolated and studied using the method of transmission electron microscopy to determine the shape and size of the nanoparticles.The study of the nanoparticles by electron microscopy showed that during the synthesis, particles are obtained, mainly spherical in shape. The size of the synthesized nanoparticles is 30–40 nm. It was also shown by electron microscopy that, upon aggregation, the particles do not become larger in size, but form compound associates. It is also important to note that the advantage of this method for the synthesis of nanoparticles is their activated surface, which has a high reactivity as a result of exposure to intense ultrasound.The resulting nanoparticles and their agglomerates can also be used as functional materials, fillers, and components of composite materials.

Quantitative Analysis of Acoustic Pressure for Sonophoresis and Its Effect on Transdermal Penetration.

Ultrasound facilitates the penetration of macromolecular compounds through the skin and offers a promising non-invasive technique for transdermal delivery. However, technical difficulties in quantifying ultrasound-related parameters have restricted further analysis of the sonophoresis mechanism. In this study, we devise a bolt-clamped Langevin transducer-based sonophoresis device that enables us to measure with a thin lead zirconate titanate (PZT) sensor. One-dimensional acoustic theory accounting for wave interaction at the skin interface indicates that the acoustic pressure and cavitation onset on the skin during sonophoresis are sensitive to the subcutaneous support, meaning that there is a strong need to perform the pressure measurement in an experimental environment replacing the human body. From a series of the experiments with our new device, the transdermal penetration of polystyrene, silica and gold nanoparticles is found to depend on the size and material of the particles, as well as the hardness of the subcutaneous support material. We speculate from the acoustic pressure measurement that the particles' penetration results from the mechanical action of cavitation.

Removal of Fe3+ from ammonium dihydrogen phosphate solution in an impact-jet hydraulic cavitation extractor

The impurity of Fe 3+ in ammonium dihydrogen phosphate (MAP) solution has a significant influence on the morphology and quality of products. The removal of Fe 3+ from the MAP solution by Di-(2-ethylhexyl) phosphoric acid (D2EHPA) was investigated in an impact-jet hydraulic cavitation (HC) extractor. The organic phase and aqueous phase can be highly mixed under the action of hydraulic cavitation. The extraction efficiency of 80% can be achieved when the extraction reaction was carried out for only 5 min. It was found that the extraction of Fe 3+ with D2EHPA was an exothermic reaction, and the equilibrium equation of extraction was obtained by slope method as follows: F e ( a q u ) 3 + + 8 HD 2 ( o r g ) = Fe D 3 · 13 H D ( o r g ) + 3 H ( a q u ) + After the two-stage extraction, the extraction efficiency of up to 96.7% can be reached (only 3.4 ∼ 4 ppm Fe 3+ remained in the aqueous phase), and the MAP crystals with regular polyhedral structure, single phase nature, and high optical transmittance were obtained.

Cavitation erosion behavior of hydraulic concrete under high-speed flow

PurposeCavitation erosion has always been a common technical problem in a hydraulic discharging structure. This paper aims to investigate the cavitation erosion behavior of hydraulic concrete under high-speed flow.Design/methodology/approachA high-speed and high-pressure venturi cavitation erosion generator was used to simulate the strong cavitation. The characteristics of hydrodynamic loads of cavitation bubble collapse zone, the failure characteristics and the erosion development process of concrete were investigated. The main influencing factors of cavitation erosion were discussed.FindingsThe collapse of the cavitation bubble group produced a high frequency, continuous and unsteady pulse load on the wall of concrete, which was more likely to cause fatigue failure of concrete materials. The cavitation action position and the main frequency of impact load were greatly affected by the downstream pressure. A power exponential relationship between cavitation load, cavitation erosion and flow speed was observed. With the increase of concrete strength, the degree of damage of cavitation erosion was approximately linearly reduced.Originality/valueAfter cavitation erosion, a skeleton structure was formed by the accumulation of granular particles, and the relatively independent bulk structure of the surface differed from the flake structure formed after abrasion.