Acoustic Cavitation Phenomenon Research Articles

Heat transfer enhancement of water flow over a heating flat plate using 20 kHz ultrasonic waves irradiated from submerged horn-type transducer

The enhancement of heat transfer of water flow over a flat plate under 20 kHz ultrasound irradiated from a submerged horn-type transducer was investigated experimentally in a water tunnel. To examine the ultrasonic effects, the transducer emitted waves perpendicular to the mainstream direction, and the freestream velocity varied between 0.12 and 0.17 m/s. The transducer position was fixed at 0.45 m from the plate leading edge in a streamwise direction. This position was altered in a heightwise direction as dimensionless heightwise distances (Z) that were divided by the diameter of the horn-tip transducer (12 mm) at 1.5, 3.0, and 4.5 from the plate surface. A hot film sensor and thermochromic liquid crystals coated on the test surface were used to demonstrate the hydrodynamic and thermal characteristics, respectively. The maximum temperature reduction of 3.5 °C was observed in the case of Z = 1.5. By employing a horn-type transducer, the acoustic jet and cavitation phenomena played a key role in destabilizing the thermal and velocity boundary layers, which resulted in a decrease in surface temperature. The incident wave shape was triangular, with an enlarging lateral zone along the flow stream. When the waves were released at Z = 1.5, the local Nusselt number was increased up to 2.55 compared to without waves. Under ultrasonic effects, the near-wall flow velocity was detected to be decreasing upstream prior to the incident zone while increasing in the incident region. When waves existed, the highest turbulent intensity was up to 29 times more intense than it was in the absence of waves. Furthermore, a predictive formula for the Nusselt number with ultrasound was established depending on the local Reynolds number and the distance between the ultrasonic source and test surface.

Ultrasonic Decontamination of Chemical Warfare Agents

Abstract Sonochemistry studies the physical and molecular level changes induced by ultrasonic energy on solutions. Sonochemical degradation of the chemical warfare agents (CWA) may occur due to three successive phenomena based on the principles of acoustic cavitation phenomena: nucleation, growth, and implosive collapse of microbubbles. The sonolytic degradation of CWA was quantified by GC-MS technique, considering the variation of some parameters such as frequency of ultrasonic waves, power control, temperature, and addition of nanoparticles as catalysts to the solution.

Real Time Nanoscale Cleaning Phenomenon Observation During Enforcing MHz Wave By Evanescent Field

In recent years, abrasive nanoparticles (sub Φ50 nm) have been applied in Chemical Mechanical Polishing (CMP) process to realize flattened surface of substrate for multilayer wiring structure and fine wiring width to achieve high performance Large Scale Integration Circuit. Definitely, the highly efficient removal of nanoparticles to be cause of the serious defect which remained on/in substrate in Post-CMP cleaning process is required. Therefore, it is indispensable to investigate the cleaning mechanisms by visualizing the cleaning phenomena that considered as nanoparticles’ behaviors during the process to realize optimal and efficient cleaning technology. However, the cleaning phenomena have not already clearly known because the residual contamination on the wafer surface has been usually inspected only before and after the cleaning process in dry condition, not in wet condition due to the surface scanning methods (e.g., scanning electron microscopy).Generally, cleaning phenomenon is considered as abrasive nanoparticles’ behaviors, which are detached from a wafer surface and occasionally reattach to the surface or remain on the surface to be a residual contamination. These behaviors occurred in a few hundred nm range from the substrate surface. Hence, we have established the real-time visualization method to observe the nanoparticles’ behaviors in wet cleaning phenomena by applying an optical evanescent light that localized less than approx. 200 nm from the surface. Experimentally contact and non-contact cleaning phenomena also have been duplicated on an optical microscope that developed ourself.In this paper, we visualized ultrasonic cleaning phenomena considered as Φ30, 50, 70 nm silica particles’ behaviors and/or cavitation effects movement during enforcing MHz wave by applying an evanescent light. Either Silica nanoparticles or cavitation effects that existing in an evanescent field were limitedly scatter to be the propagating light, which can reach to the optically CMOS area sensor of camera in a microscopy (Figure.1).The typically observation results of the Φ30, 50, 70 nm silica particles’ detachment from the silica glass substrate surface during enforcing 1.1 MHz wave by oscillating piezo actuator with a power density of approx. 0.2 watt per square centimeter with the exposure time of 16 milliseconds in 60 frames per second as shown in Figure.2. The time-varying residual rate of silica particles on the surface was also evaluated by counting the Φ30, 50, 70 nm silica particles that attached on the surface in the observation area of 120 × 40 squared micrometers. Some of each silica nanoparticles were randomly intermittently detached from the surface or remained on the surface during the acoustic cavitation repeatedly irregularly occurs and decays near the surface by enforcing the MHz wave. The nanoparticle residual change rate showed trend that silica nanoparticles detached from the surface when the acoustic cavitation irregularly occurred near the surface.The typically phenomenon was found that the residual silica nanoparticles were detached from the surface within 16 milliseconds (≒1/60 seconds) when the acoustic cavitation effects approached near to the surface that shown by background of high scattering light intensity as shown in Figure.3. Repeated occurrence of acoustic cavitation phenomenon seemed to accelerate the detachment of silica nanoparticles. By using the evanescent field, cleaning phenomena near the surface during enforcing MHz wave were visualized in real time. Figure 1

Effect of ultrasound pre-treatment on carbonaceous copper-bearing shale flotation

Although numerous studies have been implemented on identifying the impact of acoustic waves on mineral beneficiation, its fundamental aspects remain unclear in the literature. The present work, for the first time, systematically investigates the role of ultrasound pre-treatment (UPT) in the carbonaceous copper-bearing shale flotation. To this end, conditioning was carried out at different powers of applied ultrasound. Non-treated and UPT shale flotation tests were performed in the presence of frother (MIBC) and collector (KEX). To analyse particle surface charge variation and collector adsorption properties after application of UPT, zeta potential and ultraviolet–visible spectroscopy measurements were implemented, respectively. The generation of sub-micron bubbles due to the acoustic cavitation was characterised by laser-based particle size measurements. Shale hydrophobicity was determined using the sessile drop and captive bubble techniques.The micro-flotation results showed that the mass recovery increased by 40% at 20 W of applied ultrasonic power. The positive effect of UPT on the copper-bearing shale flotation was related to: i) generation of ultrafine bubbles due to the acoustic cavitation phenomenon and ii) the cleaning effect through transient bubble collapse. However, rigorous ultra-sonication diminished the recoverability of the sample owing to the less intensified number of ultrafine bubbles on the particle surfaces and formation of free H and OH radicals, which led to the oxidation of particle surfaces. These statements were correlated well with the observations of the zeta potential, particle size analysis and quantified ultrafine bubbles. Finally, we briefly highlighted fundamental knowledge gaps in flotation and ultrasound-related issues for future work.

CFD Analysis of Journal Bearing by Modifying The Roughness Surface

A journal bearing is a machine part that is used to ensure that the shaft always rotates in the opposite direction of the axis. Journal bearings are chosen because they are well-suited for use in mechanical systems that demand precision, speed, and a high load capacity. Recent years have seen an increase in research on how to improve the tribological performance of bearings by considering the design/architecture of these bearings. Numerous scientists have developed numerous methods for measuring pressure distribution, load-carrying capacity, acoustic power level, force friction, and cavitation phenomena in order to improve the performance of tribology, particularly in journal bearings. As a result, hydrodynamic lubrication was used in the investigation. The investigation was conducted using a computational fluid dynamics (CFD) three-dimensional journal bearing model that took cavitation into account. Additionally,the location of the heterogeneous rough/smooth bearing pattern was modified, as was the shaft rotational speed. The results of this study indicate that when the surface roughness is applied to journal bearings in a variety of locations with heterogeneous rough/smooth bearing patterns, the tribological performance of journal bearings is significantly improved, and that high shaft rotational speed has a significant effect on the tribological performance of journal bearings.

Tailoring the crystalline phase and size of the MoO3 quantum dots via sonication induced modified top-down method

In this paper, a modified top-down method is adopted to synthesize highly stable and water-soluble Molybdenum trioxide quantum dots (MoO3 QDs) without any surfactants. In this sonication induced modified method, commercial Molybdenum Oxide powder and Hydrochloric acid were used as the precursor and etchant, respectively. The impact of sonication bath temperature on the morphological, microstructural, size, crystal-structural, and optical properties of MoO3 QDs have been systematically investigated. The controlled sonication bath temperature during the synthesis process results in the tunability of the QDs. The mechanism behind the controlled size of the QDs deeply rooted in the acoustic cavitation phenomenon. The synthesized QDs exhibit poly-crystallinity with mixed phases: orthorhombic (α-MoO3) and hexagonal (h-MoO3). Interestingly, the complete elimination of the hexagonal phase from the QDs has been observed as a function of sonication bath temperature.

Ultrasound Applied in the Reduction of Viscosity of Heavy Crude Oil

Reducing the viscosity of heavy oil through upgrading techniques is crucial to maintaining the demand for oil, which is growing at an annual rate of 1.8%. The phenomenon of acoustic cavitation occurs when ultrasound is applied in the treatment of heavy crudes. This is an emerging technology that is being developed to improve the physical and chemical properties of highly viscous crudes, which facilitates handling, increases the proportion of light factions, and improves their price in the market. Taking into account that it does not yet operate on an industrial scale, a bibliographic review of the advances in acoustic cavitation technology with ultrasound for the improvement of heavy crude is justified, to contribute to the development of its industrial application by identifying new approaches and research guidelines in engineering and science. The objective of this article is to show the advance of said technology and describe the experiments carried out by various authors. For this purpose, a literature review was conducted with documents published from 1970 to 2020, which were compiled through a systematic search in academic databases. As a result of this review, some conceptual gaps and deficiencies in the phenomenological foundation were found, which explain the current difficulties to implement experimental tests and design the process at larger scales. These deficiencies limit the quality and repeatability of the results. A need was also identified to focus the efforts on a systematic experimentation that fulfills the laboratory and pilot plant phases, which are essential to take these technologies to an industrial scale.

Sonochemical dissolution of nanoscale ThO2 and partial conversion into a thorium peroxo sulfate

The influence of the sample morphology and experimental conditions towards the sonochemical dissolution of nanoscale ThO2 samples in sulfuric acid media is described. Significant sonochemical dissolution rates and yields are observed at 20 kHz under Ar/O2 atmosphere in dilute 0.5 M H2SO4 at room temperature, contrasting with the generally-reported high refractory behavior for ThO2. The dissolution of ThO2 combines the physical effects driven by acoustic cavitation phenomenon, the complexing affinity of Th(IV) in sulfuric medium and the sonochemical generation of H2O2. These sonochemical conditions further allow the observation of the partial conversion of ThO2 into a scarce Th(IV) peroxo sulfate with 1D morphology resulting from one or both following processes: dissolution/reprecipitation or formation of an intermediate Th(IV) surface complex.

Numerical and Experimental Studies on the Effect of Surface Roughness and Ultrasonic Frequency on Bubble Dynamics in Acoustic Cavitation

With many emerging applications such as chemical reactions and ultrasound therapy, acoustic cavitation plays a vital role in having improved energy efficiency. For example, acoustic cavitation results in substantial enhancement in the rates of various chemical reactions. In this regard, an applied acoustic field within a medium generates acoustic streaming, where cavitation bubbles appear due to preexisting dissolved gas in the working fluid. Upon cavitation inception, bubbles can undergo subsequent growth and collapse. During the last decade, the studies on the effects of different parameters on acoustic cavitation such as applied ultrasound frequency and power have been conducted. The bubble growth and collapse mechanisms and their distribution within the medium have been classified. Yet, more research is necessary to understand the complex mechanism of multi-bubble behavior under an applied acoustic field. Various parameters affecting acoustic cavitation such as surface roughness of the acoustic generator should be investigated in more detail in this regard. In this study, single bubble lifetime, bubble size and multi-bubble dynamics were investigated by changing the applied ultrasonic field. The effect of surface roughness on bubble dynamics was presented. In the analysis, images from a high-speed camera and fast video recording techniques were used. Numerical simulations were also done to investigate the effect of acoustic field frequency on bubble dynamics. Bubble cluster behavior and required minimum bubble size to be affected by the acoustic field were obtained. Numerical results suggested that bubbles with sizes of 50 µm or more could be aligned according to the radiation potential map, whereas bubbles with sizes smaller than 10 µm were not affected by the acoustic field. Furthermore, it was empirically proven that surface roughness has a significant effect on acoustic cavitation phenomena.

Fluid dynamic-based Engineering design of a Full-Scale Device for the improvement of Extra Virgin Olive Oil Yield and Quality by means of Combined Acoustic Cavitation and Thermal Conditioning

After some hesitations, the scientific community is jointly converging on the benefits due to the ultrasound treatment by means of mechanical effects generated by acoustic cavitation phenomena occurring into the olive oil paste proposed initially by Amirante and Clodoveo. In recent works, many authors have now confirmed that this promising emerging technology produces relevant beneficial effects if applied to the extraction process under well-controlled conditions. In the last years, the industrial applications of ultrasound (US) in the Extra-Virgin Olive Oil (EVOO) extraction process are changing the paradigm of the knowledge in this field of interest due to a great effort of the research activity. In the present work, the design of the device by means a Three-Dimensional (3D) Multiphase Computational Fluid Dynamic (CFD) analysis was performed, which describes the ultrasound effects in the olive paste, necessary to control the US waves propagation. Thus, fluid dynamic analysis allowed to predict the flow path in the ultrasound devices, to evaluate the flow parameters of the olive paste inside the SHE and the cavitation phenomenon, with the aim to find an optimal design, capable to ensure the best ultrasounds and mixing effects. Moreover, experimental results demonstrated that the machine can guarantee an actual simultaneous improvement of the olive oil extraction yield, as well as of the product quality. Finally, the results from sensory evaluations are summarized confirming the goodness of EVOO obtained by means of US.

Room-Temperature Synthesis of High-Entropy Perovskite Oxide Nanoparticle Catalysts through Ultrasonication-Based Method.

In the present study, a sonochemical-based method for one-pot synthesis of entropy-stabilized perovskite oxide nanoparticle catalysts with high surface area was developed. The high-entropy perovskite oxides were synthesized as monodispersed, spherical nanoparticles with an average crystallite size of approximately 5.9 nm. Taking advantage of the acoustic cavitation phenomenon in the ultrasonication process, BaSr(ZrHfTi)O3 , BaSrBi(ZrHfTiFe)O3 and Ru/BaSrBi(ZrHfTiFe)O3 nanoparticles were crystallized as single-phase perovskite structures through ultrasonication exposure without calcination. Notably, the entropically-driven stability of Ru/BaSrBi(ZrHfTiFe)O3 with excellent dispersion of Ru in the perovskite phase bestowed the nanoparticles of Ru/BaSrBi(ZrHfTiFe)O3 with good catalytic activity for CO oxidation.

How to Interpret the Ultrasound Output Display Standard for Diagnostic Ultrasound Devices: Version 3.

How to Interpret the Ultrasound Output Display Standard for Diagnostic Ultrasound Devices: Version 3.

Mechanisms of effective gold shell on Fe3O4 core nanoparticles formation using sonochemistry method.

Sonochemical synthesis (sonochemistry) is one of the most effective techniques of breaking down large clusters of nanoparticles (NPs) into smaller clusters or even individual NPs, which ensures their dispersibility (stability) in a solution over a long duration. This paper demonstrates the potential of sonochemistry becoming a valuable tool for the deposition of gold (Au) shell on iron oxide nanoparticles (Fe3O4 NPs) by explaining the underlying complex processes that control the deposition mechanism. This review summarizes the principles of the sonochemistry method and highlights the resulting phenomenon of acoustic cavitation and its associated physical, chemical and thermal effects. The effect of sonochemistry on the deposition of Au NPs on the Fe3O4 surface of various sizes is presented and discussed. A Vibra-Cell ultrasonic solid horn with tip size, frequency, power output of ½ inch, 20 kHz and 750 W respectively was used in core@shell synthesis. The sonochemical process was shown to affect the surface and structure of Fe3O4 NPs via acoustic cavitation, which prevents the agglomeration of clusters in a solution, resulting in a more stable dispersion. Deciphering the mechanism that governs the formation of Au shell on Fe3O4 core NPs has emphasized the potential of sonication in enhancing the chemical activity in solutions.

Effect of the sonication and coating time on the photocatalytic degradation of TiO2, TiO2-Ag, and TiO2-ZnO thin film photocatalysts

Today, the ultrasound utilizing for material synthesis has been extensively investigated. The unusual acoustic cavitation phenomenon caused by ultrasonic waves has created a new world for the production of high efficiency photocatalysts with new structures. In this study, TiO2, TiO2-Ag, and TiO2-ZnO thin film photocatalysts were prepared using titanium isopropoxide Ti[OCH(CH3)2]4, zinc acetate dehydrates (CH3COO)2Zn·2H2O, and silver nitrate AgNO3 by a sol–gel method under the ultrasonic irradiation. The prepared photocatalysts were characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), and energy dispersive spectroscopy. The SEM images showed that the Ag and ZnO particles were evenly dispersed in the photocatalysts due to the ultrasonic irradiation, and Ag particles were approximately 90 nm, which is relatively small compared to the photocatalysts which is not treated with ultrasonic irradiation. The catalytic activity of the photocatalysts was determined using Acid Red 27 dye. The most excellent catalytic degradation was obtained with TiO2-ZnO thin film photocatalyst. In comparison to the conventional photocatalyst, the efficiency of photocatalytic activity of the photocatalyst produced under ultrasonication has been increased due to the reduced size of Ag and ZnO and its uniform dispersion.

Effect of acoustic cavitation phenomenon on bioactive compounds release from Eryngium caucasicum leaves

This study investigated the effect of acoustic cavitation phenomenon generated by ultrasonic waves on bioactive compounds release from Eryngium caucasicum leaves into the surrounding medium. Peleg’s model was implemented to provide a clearer insight into the kinetics modeling during 60 min sonication at different temperatures (30–60 °C) and ultrasonic power (50–150 W). The experimental data were successfully fitted employing Peleg’s model with the high coefficient of determination (0.95), low root mean square error (0.003%) and mean relative percentage deviation modulus (6.40%). Then, the optimal conditions, using response surface methodology (RSM), were determined as ultrasonic power of 112.10 W, temperature of 50.00 °C and 33.53 min sonication time. Spectrophotometric analysis revealed that extract was a potential source of phenolics (64.00 ± 0.13 mg GAE g−1) with high scavenging ability of DPPH˙, ABTS˙+ and HO˙ (78.18 ± 0.12, 74.19 ± 0.14 and 49.38 ± 0.18%, respectively). The high-performance liquid chromatography (HPLC) revealed that gallic acid, chlorogenic acid, p-coumaric acid, ferulic acid, and apigenin were the main phenolics existed in the product. The process efficiency was enhanced significantly (p < 0.05) via performing preliminary static time (PST, 60 min). The quantity and quality of extracts improved using PST, where gallic acid had the highest concentration (24.59 ± 0.12 mg g−1). Scanning electron microscopy (SEM) images confirmed the dramatic effect of acoustic cavitation on cells structure.

Entropy‐Maximized Synthesis of Multimetallic Nanoparticle Catalysts via a Ultrasonication‐Assisted Wet Chemistry Method under Ambient Conditions

AbstractA facile ultrasonication‐assisted wet chemistry method for preparing multicomponent alloy nanoparticles (NPs) including high‐entropy alloys (HEAs) is reported. PtAuPdRhRu alloy (HEA), quaternary PtAuPdRh alloy, and ternary PtAuPd alloy NPs are produced with ≈3 nm in diameter. Taking advantage of the acoustic cavitation phenomenon in ultrasonication process, noble metal precursors could be co‐reduced by chemical reductants and transform to alloy structures under operation at room conditions. The instantaneous massive energy (≈5000 °C, 2000 atm) occurring in momentary timespans (≤10−9 s) contributes to the formation of multimetallic mixed nanomaterials driven by entropy maximization. Owing to strong synergistic effects, the catalysts with the HEA NPs supported on carbons exhibit prominent electrocatalytic activities for hydrogen evolution reaction.

Role of ultrasonic oscillation in chemical processes in microreactors: A mesoscale issue

The integration of microreactor and ultrasound represents an emerging area for process intensification and has attracted considerable attention in recent years. One of the most important meso-scientific issues in ultrasound techniques is acoustic cavitation, which plays a vital role in the macroscopic performance of an ultrasonic microreactor. In this review, we first briefly summarize the latest research on acoustic cavitation phenomena in microreactors. The effects of channel configuration, solvent properties, and ultrasound parameters are systematically reviewed. In addition, the role of acoustic cavitation in various chemical processes (e.g., mixing, absorption, emulsification, and particle synthesis) is presented from a mesoscale perspective, which in turn provides guidance for ultrasound applications. A thorough understanding of the ultrasound intensification mechanism will contribute to the future development of this promising technology.

Modelling pressure distribution in sonicated ethanol solution using COMSOL simulation

Ultrasound application has been reported to assist chemical processes as a result of various physiochemical effects during acoustic cavitation phenomena in a liquid. In this study, acoustic pressure distribution in ethanol solution induced by ultrasonic waves in a sonoreactor was investigated using COMSOL Multiphysics software. The variations of acoustic pressure distribution in ethanol liquid were investigated through a single-phase incompressible model developed by varying the frequency of an ultrasonic transducer. The simulation in COMSOL Multiphysics shows that the acoustic wave emitted from the bottom of the sonoreactor generated multiple layers of high acoustic pressure distribution. The fluctuating pressure magnitude along the sonoreactor shows that constructive interference produced high acoustic pressure region whereas destructive interference resulted in low acoustic pressure. Meanwhile, the distance over sound wave can travel before attenuation occurs is much further at 60 kHz. These results support the theory that wave attenuation is strongly frequency dependent.

Designing the ultrasonic system used in industrial air filtration based on the ultrasonic cavitation phenomenon

The paper presents the activity developed developed in the field of polluted air purification from industrial shop (paint shops, foundries, welding constructions, forging, etc.). The advantages of using ultrasounds in the pollutant air filtration and purification process and an ultrasonic filter designed are presented considering the ultrasonic cavitation phenomenon. The main computational and construction elements of the ultra-acoustic system used in the design of the air filter are presented in the paper. The work focuses in the design of the main part of the ultrasonic system represented by ultrasonic transducer. In this case, the transducer network that is used in ultrasonic cavitation method consists of ten ultrasonic transducers. Each one of them consists of asymmetrical passive elements (reflector and radiant element).The design steps and the use of FEM as working method will provide the theoretical basis of the operation of the ultrasonic system so that it allows air filtration based on the ultrasonic acoustic cavitation phenomenon.

Study on separation characteristics of water in oil (W/O) emulsion under ultrasonic standing wave field

The separation characteristics of W/O emulsion were investigated under ultrasonic standing wave field in this paper. The effects of the irradiation time, acoustic intensity, frequency, oil viscosity, and oil-water interfacial tension on the separation characteristics of emulsion were studied in details. It was proved that there existed an optimal irradiation time, acoustic intensity and oil-water interfacial tension to achieve the maximum separation efficiency in ultrasonic treatment process. Excessive long irradiation time had little effect on improving the dehydration rate of emulsion but rather increased unnecessary processing time. Excessive high acoustic intensity caused the occurrence of acoustic cavitation phenomenon. The acoustic cavitation would cause the aggregated droplets to be dispersed by oscillating bubbles or even emulsified again by high speed micro jets. The acoustic cavitation threshold is effectively and accurately obtained by a spectral analysis method. The micro acoustic streaming which resulted from the attenuation of acoustic energy occurred with the increase of frequency. It sheared the aggregated droplets, destroyed the stable droplets banding and reduced the separation efficiency of emulsion. The excess surfactant adsorbed on the oil-water interface resulted in the increase of the interfacial film strength, which hindered the coalescence process of droplets and reduced the separation efficiency.