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Amorphous solids are known to fail catastrophically via fracture, and cavitation at nano-metric scales is known to play a significant role in such a failure process. Micro-alloying via inclusions is often used as a means to increase the fracture toughness of amorphous solids. Modeling such inclusions as randomly pinned particles that only move affinely and do not participate in plastic relaxations, we study how the pinning influences the process of cavitation-driven fracture in an amorphous solid. Using extensive numerical simulations and probing in the athermal quasistatic limit, we show that just by pinning a very small fraction of particles, the tensile strength is increased, and also the cavitation is delayed. Furthermore, the cavitation that is expected to be spatially heterogeneous becomes spatially homogeneous by forming a large number of small cavities instead of a dominant cavity. The observed behavior is rationalized in terms of screening of plastic activity via the pinning centers, characterized by a screening length extracted from the plastic-eigenmodes. [ABSTRACT FROM AUTHOR]

The plastic flow of ultra-high molecular weight polyethylene (UHMWPE) at a frictional interface, which is critical to the wear behavior, was investigated by reactive molecular dynamics simulations. The UHMWPE substrate was found to experience various deformations during the friction process. First, some polyethylene (PE) chains could detach from the substrate because of their rapid movement. Second, the frequent motion of PE chains also resulted in the intermittent formation and breaking of cavities between intermolecular PE chains. These deformations were more obvious on a surface with a convex protrusion, where the plowing effect exacerbated the cavitation and elastic deformation of PE chains. Correspondingly, the plastic flow in turn reconstructed the convex protrusion by displacing the surface atoms on the Fe slab. The plastic flow of PE chains broke the C–C bonds, and the carbon moieties were then chemically bonded onto the metal surface. A rapid change of atomic charge, hence, happened when the bonds broke. Meanwhile, PE chains release short alkyl radicals gradually after bond breakage, indicating gradual wear of the substrate during friction. This work provides molecular insight into the evolution of interfacial microstructure under plastic flow on a UHMWPE substrate. [ABSTRACT FROM AUTHOR]

The presented study aims to reveal the effect of liquid temperature on cavitation-induced erosion of an Al-Mg alloy. An experimental work was conducted using a submerged cavitating waterjet to impact the specimen surface. For a certain cavitation number and a given standoff distance, different liquid temperatures were considered. Accordingly, a comprehensive comparison was implemented by inspecting the mass loss and surface morphology of the tested specimens. The results show that the cumulative mass loss increases continuously with the liquid temperature. A cavitation zone with an irregular profile becomes evident as the cavitation treatment proceeds. Increasing the temperature promotes the generation of cavitation bubbles. Large erosion pits are induced after severe material removal. The microhardness increases with the distance from the target surface. At a liquid temperature of 50°C, the microhardness fluctuates apparently with increasing the depth of indentation. [ABSTRACT FROM AUTHOR]

The black-water regulating valve is very easy to be damaged due to the erosion of the key components, such as valve spool and valve seat. This work presents the failure analysis of the spool and seat of regulating valve in the black-water treatment system. Scanning electron microscopy and X-ray energy-dispersive spectrometer were used to detect the morphology and chemical compositions of failure valve samples. The computational fluid dynamics method was also adopted to simulate the medium flow characteristics in black-water regulating valve. The results show that most erosion areas of the valve occur at the spool-seat throttle zone. The erosion profile is mainly manifested in plastic deformation pits, cutting abrasions, furrows, pinhole pits and impact pits. The particles and cavitation bubbles move toward the throttle zone driven by black-water medium, causing particles impact and bubbles collapse. The particle flow velocity in the throttle zone of the valve is between 50 and 175 m/s, while the maximum velocity can reach 175 m/s. The valve suffered severe particle erosion and cavitation erosion under the particle impact and bubble collapse, finally resulting in its failure. [ABSTRACT FROM AUTHOR]

Investigations were carried out in this paper to study the influence of rapid decompression rate on the polyamide 6 (PA6) liner materials through experimental and numerical methods. Firstly, hydrogen permeation tests at different pressures were conducted to obtain the functions representing the trend of permeation parameters with the pressure. Then decompression tests at different decompression rates had been carried out to get whitening specimens which would be observed using scanning electron microscopy (SEM). Cavitation was found and the variety of the number of cavities with the decompression rate was recorded. It was found that the faster the decompression rate was, the higher the number of cavities in the specimen was. Thirdly, to determine the hydrogen concentration throughout the specimen and numerically check if cavitation occurred at various decompression rates, a 2D finite element model was established which introduced the permeation parameters as functions of pressure but not temperature, as another numerical model indicated the temperature field of specimens changed little. Then an approach was proposed to successfully implement the risk assessment of cavitation, and the liner material was considered as elastoplastic neglecting its viscoelasticity-viscoplasticity. Based on the assumptions and experimental conditions in the study, the Mises yield criterion was successful to assess the cavitation risk, and the approach was verified as the analysis results about the cavitation agree well with the SEM observations. In the end, based on the approach, it could be concluded that 11h was the critical safe decompression time for the PA6 material in this study, and the decompression rate was 7.95 MPa/h. The approach in this study can also be used as guidelines for the cavitation risk assessment of other systems and materials undergoing rapid decompression. • Permeation parameters of PA6 material in gaseous hydrogen are measured under 15 MPa, 43.75 MPa, 87.5 MPa. • The effect of pressure on permeation coefficients is considered in the present diffusion model. • Through SEM observations it is found that the number of cavities rises with the increasing decompression rate. • The safety decompression rate is calculated considering the mechanical equilibrium and hydrogen diffusion in cavities. [ABSTRACT FROM AUTHOR]

The cavitation phenomenon presents a significant challenge in pump operation since the losses incurred by cavitation adversely impact pump performance. The many constraints of conventional anti-cavitation techniques have compelled researchers to explore biological processes for innovative alternatives. Consequently, the use of bionanotechnology for anti-cavitation pumping has emerged as a prominent study domain. Despite the extensive publication of publications on biomimetic technology, research concerning the use of anti-cavitation in pumps remains scarce. This review comprehensively summarizes, for the first time, the advancements and applications of bionic structures, bionic surface texture design, and bionic materials in pump anti-cavitation, addressing critical aspects such as blade leading-edge bionic structures, bionic worm shells, microscopic bionic textures, and innovative bionic coatings. Bionic technology may significantly reduce cavitation erosion and improve pump performance by emulating natural biological structures. This research elucidates the creative contributions of biomimetic designs and their anti-cavitation effects, hence boosting the anti-cavitation performance of pumps. This work integrates practical requirements and anticipates future applications of bionic technology in pump anti-cavitation, offering a significant research direction and reference for scholars in this domain. [ABSTRACT FROM AUTHOR]

Diamond wire sawing plays an important role in semiconductor processing. Considering that the cavitation effect can improve the machining quality, a new technology of ultrasonic cavitation–assisted diamond wire sawing (UCAWS) is proposed in this paper. To study the formation process of cavitation in UCAWS and its influence on processing, a simulation and experimental study of cavitation in UCAWS is conducted. The pressure distribution model and cavitation model of two-phase mixed flow around wire sawing in UCAWS are constructed by combining the ideal bubble dynamic theory. The effect of vapor volume fraction (VVF) on cavitation intensity is calculated using computational fluid dynamics (CFD). The simulation results show that transient cavitation and steady-state cavitation exist simultaneously around wire sawing and with the increase of ultrasonic amplitude, the cavitation effect is enhanced. UCAWS experiments are conducted on monocrystalline silicon to study the changes in sawing force and workpiece surface roughness. The experimental results show that the sawing force of the UCAWS decreases by 6.65% on average compared to ultrasonic vibration–assisted diamond wire sawing (UAWS), the surface roughness value is reduced by 6.3% on average, and the surface morphology is improved. Therefore, UCAWS processing technology can be applied in manufacturing to improve the surface quality of the workpiece further. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: High-speed flow of clean water or water with sediment released from aging spillways may cause abrasion and cavitation on the concrete surface gradually. The occurrence of irregularities on the concrete surface can exacerbate the erosion problem. Which might jeopardize the safety of dams constantly, hence the rehabilitation efforts become urgent tasks in dam safety projects. Methods: This study employs a 3D Computational Fluid Dynamics (CFD) model to quantitatively analyze the cavitation risk on the aging concrete surface of the Chay 5 spillway in Ha Giang, Vietnam, under various operation scenarios. There are two standards used to measure cavitation: the cavitation index (σ) which indicates the danger due to the drop of pressure in rapid flow, and the new gasification index (β) which takes into consideration the formation and collapse of bubbles behind asperities. Results: Three extreme flood cases may not result in potential cavitation because both σ and β exceed critical thresholds. Regarding the six controlled gate scenarios with normal water level, the σ profiles are approximated 1,0 showing a low likelihood of cavitation damage while the β values are smaller than 0.8, indicating a considerable risk of cavitation. Besides, the opening height of 100 cm poses the greatest risk of creating severe cavitation erosion in the concave area and slope portion. The flip bucket experienced the most vulnerable cavitation when the opening height is 400 cm. In addition, an approach to spillway surface rehabilitation involving specialized mortars has been presented. Conclusion: For aging conveyance structure, gasification index (β) takes into account irregularities surface, providing a more comprehensive assessment of the likelihood of cavitation damage than cavitation index (σ). After rehabilitation with anti-shrinkage high abrasion resistance mortar, the entire spillway surface is smooth. This allows for reducing the cavitation risk and improvement of life service thereof. [ABSTRACT FROM AUTHOR]

The rapid and accurate recognition of cavitation in centrifugal pumps has become essential for improving production efficiency and ensuring machinery longevity. To address the limitations of existing methods in terms of applicability, accuracy, and efficiency, a new method based on multi-dimensional feature fusion and convolutional gate recurrent unit (MCGN) was proposed. Experimental monitoring of cavitation of centrifugal pumps was conducted. Five signals at different water temperatures and operating frequencies were collected. Key modulating features were extracted by time-frequency analysis and principal component analysis. The multi-dimensional features are fused by one and two dimensional convolutional neural networks. The cavitation state label was used to label the sample set by cavitation number, net positive suction head, and cavitation evolution images captured by high-speed cameras. Finally, the neural network based on the convolutional gate recurrent unit was used to classify the cavitation state of the centrifugal pump. The experimental results demonstrate that the proposed method achieves recognition accuracies exceeding 98% for vibration signals, noise signals, outlet pressure pulsation signals, and torque signals. Compared with the short-time Fourier transform-autoencoder model, MCGN model can improve the recognition accuracy by 4.03%, computation efficiency by 20%, and loss by 87%. These advances underscore the potential of the method in monitoring and maintenance practices for centrifugal pumps. [ABSTRACT FROM AUTHOR]

The complex interaction between shock waves and two-phase interfaces can generate cavitation. In this study, the cavitation induced by the high-speed jet impact on the water surface was investigated. The mixture fluid is modeled using the barotropic equation of state under the framework of the two-phase flow model, which can describe the mixture of air, water, and vapor with any proportion. Through constructing a 1D Riemann problem for the impact-induced cavitation phase transition, it indicates that the coupling effect of multiple rarefaction waves emitted from the two-phase interface is responsible for the cavitation phase transition inside the liquid. Then, a 3D (three-dimensional) simulation regarding the impact of a high-speed jet on the water surface was conducted and validated against previous experiments that captured the cavitation phase transition phenomenon in the central region after the jet impact. The 3D simulation results revealed the spatial structure and development process of shock waves in detail. The coupling effects of shock waves and two-phase interfaces generate a ring-shaped rarefaction wave, which develops radially inward and superimposes, resulting in the formation of acorn-shaped cavitation bubble nuclei inside the water. The 3D simulation can provide spatial shock/rarefaction wave structures and internal flow details that have never been obtained in experiments, such as shock generation and propagation, rarefaction wave generation and center convergence, and the internal structure of acorn-shaped cavitation nucleation. Furthermore, the influence of the jet velocity on the cavitation intensity was analyzed, and a quantitative relationship was provided. [ABSTRACT FROM AUTHOR]

To augment the erosion and corrosion resistance of the additively manufactured Hastelloy C276 coating, it was subjected to ultrasonic shot peening (USP) treatment. Subsequently, cavitation erosion and electrochemical corrosion experiments were conducted. This study explored the influence of USP under various parameters on cavitation erosion/corrosion behavior and erosion mechanism through microhardness testing, analysis of roughness changes, micromorphology observation, microstructure characterization, mass loss monitoring, and measurement of electrochemical parameters. The results show that with an increase in shot peening duration, the hardness of the coating increases by 37.1% due to the refinement of the surface structure, and the depth of the hardened layer reaches 206.9 μm. The mass loss rate of the USP-treated coating is reduced by 43.9% compared to the initial coating. The damage mechanism of cavitation erosion involves cavity growth and crack propagation. The surface layer of the USP-strengthened coating exhibits a smaller grain size and increased hardness, significantly enhancing its resistance to damage. Notably, the cavitation erosion behavior of Hastelloy C276 shows a preferential removal of the Mo element. USP treatment also enhances the coating's performance in electrochemical corrosion experiments, proving to be an effective method for further enhancing the resistance of Hastelloy C276 to cavitation erosion and corrosion. [ABSTRACT FROM AUTHOR]

Due to the poor surface characteristics of additively manufactured parts, the necessity for post-process surface enhancement is crucial. Among the prevalent post-processing techniques, the acoustic cavitation-based surface finishing technique has recently emerged. Despite a considerable amount of focused research on the material removal mechanisms of this technique, less attention has been devoted to addressing its limitations associated with enhancing the process capability towards achieving a better surface finish. The driving force behind the acoustic cavitation technique is the bubble implosion through cavitation streaming, and the cessation of the acoustic cavitation streaming beyond a certain length is the main limitation. It has restrained the process capability towards finishing both external and internal surfaces. Hence, this research aims to unravel novel ways of employing the acoustic cavitation-generating parameters and achieving better-quality surface finishing of additively manufactured (AM) components. A study has been conducted on different AM materials, including Inconel 625 and aluminum alloy, by introducing various methods associated with acoustic amplitude, working mediums, temperature, and external vibration. The results reveal a significant reduction in average surface roughness for both materials. The topographical and morphological observations confirm the qualitative improvement on the surfaces. In addition, the conical bubble structures that frame the acoustic cavitation streaming are elucidated by implementing high-speed imaging techniques, and their enhancement at different parametric conditions is delineated. Henceforth, the findings suggest a notable insight into the potential of the employed approaches in enhancing the acoustic cavitation streaming for achieving a better surface finish of AM components. [Display omitted] • Surface finishing of AM components by enhanced acoustic cavitation. • Overcoming the limitations of acoustic cavitation for surface quality improvement. • Acoustic cavitation: factors affecting acoustic streaming and AM surface quality. • Thermal effect on bubble structures in free-field and confined acoustic cavitation. • A study on parametric investigation of acoustic cavitation: a different approach. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cavitation erosion, as a mechanical effect of destruction, constitutes a complex and critical problem that affects the safety and efficiency of the functioning of engineering components specific to many fields of work, the most well-known being propellers of ships and maritime and river vessels, seawater desalination systems, offshore oil and gas drilling platforms (including drilling and processing equipment), and the rotors and blades of hydraulic machines. The main objective of the research conducted in this paper is to experimentally investigate the phenomenology of this surface degradation process of maritime ships and offshore installations operating in marine and river waters. To reduce cavitation erosion of maritime structures made from Duplex stainless steels, the study used the deposition by welding of layers of metallic alloys with a high capacity for work hardening. The cavitation tests were conducted in accordance with the American Society for Testing and Materials standards. The response of the deposited metal under each coating condition, compared to the base metal, was investigated by calculating the erosion penetration rate (MDER) through mass loss measurements over the cavitation duration and studying the degraded zones using scanning electron microscopy (SEM), the energy-dispersive X-ray analysis, and hardness measurements. It was revealed that welding hardfacing with austenitic manganese alloy contributes to an approximately 8.5–10.5-fold increase in cavitation erosion resistance. The explanation is given by the increase in surface hardness of the coated area, with 2–3 layers of deposited alloy reaching values of 465–490 HV5, significantly exceeding those specific to the base metal, which range from 260–280 HV5. The obtained results highlighted the feasibility of forming hard coatings on Duplex stainless-steel substrates. [ABSTRACT FROM AUTHOR]

CoCrFeMnNi-XZrO2 (X is a mass percentage, X = 1, 3, 5, and 10) high-entropy alloy composite coatings were successfully prepared on 0Cr13Ni5Mo martensitic stainless steel substrates using laser cladding technology. The phase composition, microstructure, mechanical properties, and cavitation erosion behavior of the composite coatings under different contents of ZrO2 were studied. The mechanism of ZrO2 particle-reinforced cavitation corrosion resistance was studied using ABAQUS2023 finite element software. The results show that the phase structure of the composite coating organization is composed of FCC phase reinforced by ZrO2 phase. The addition of ZrO2 causes lattice distortion. The coatings have typical branch crystals and an equiaxed crystal microstructure. With the increase in ZrO2 content, the microhardness of the composite coatings gradually increases. When X = 10%, the coating's microhardness reached 348 HV, which was 95.53% higher than the high-entropy alloys without ZrO2 added. Adding ZrO2 can prolong the incubation period of high-entropy alloys; the high-entropy alloy composite coating with 5 wt.% ZrO2 exhibited the best cavitation resistance, with a cumulative volume loss rate of only 15.74% of the substrate after 10 h of ultrasonic cavitation erosion. The simulation results indicate that ZrO2 can withstand higher stress and deformation in cavitation erosion, reduce the degree of substrate damage, and generate higher compressive stress on the coating surface to cope with cavitation erosion. [ABSTRACT FROM AUTHOR]

The scientific goal of this study was to investigate the effects of various parameters on cavitation-induced erosion, with the aim to enhance the understanding and assessment of cavitation resistance in hydraulic systems. Cavitation erosion poses significant challenges to the durability and efficiency of hydraulic components, such as those found in hydropower plants and pumping stations. Prompted by the need to improve the reliability of cavitation testing and material assessment, this research conducted a comprehensive sensitivity analysis of a cavitation jet apparatus (CJA). This study employed an experimental platform that consisted of a vertical cylindrical test tank, a submerged nozzle, and an aluminum sample. By examining a range of orifice diameters, this research identified that smaller diameters led to increased erosion intensity, with the most pronounced effects observed at a diameter of 2 mm. Furthermore, various standoff distances (SoDs) were tested, which revealed that shorter distances resulted in greater erosion, with the highest impact noted at an SoD of 5 cm. This study also evaluated different nozzle geometries, where it was found that a 132° conical sharped edges nozzle, combined with an orifice diameter of 2 mm and an SoD of 5 cm, produced the most severe erosion. Conversely, chamfered edges nozzles and a commercial nozzle (MEG2510) with an SoD of 10 cm or greater showed reduced erosion. These results highlight that by standardizing the testing duration to 1200 s, the CJA could reliably assess the cavitation resistance of materials. This study established a clear relationship between increased pressure and higher impact forces, which led to more severe erosion. The findings underscore the effectiveness of the CJA in evaluating material resistance under various cavitation conditions, thus addressing a critical need for reliable cavitation testing tools. [ABSTRACT FROM AUTHOR]

The stability of the plugging zone has a great impact on lost circulation control and gas invasion prevention in fractured reservoirs. In this work, the concept of "cavitation‐induced shear failure" is put forward based on the analysis of the flow field characteristics, and the failure mechanism is discussed. The strength physical model of a fractured plugging zone is formed based on the analysis of the characteristic parameters of LCMs and the failure mechanism. And then the simulation experiments of cavitation‐induced shear failure, gas invasion prevention, pressure bearing, and tight plugging are carried out. The research shows that (1) the fractured plugging zone is a dense granular matter system, and the contact forces and quid bridge force are dominant in its internal; (2) the cavitation‐induced shear failure is one of the main failure modes of the plugging zone in a fractured gas reservoir, and the failure process includes three steps: gas diffusion‐dilution damage, confluence and carry damage, and displacement dislocation shear failure; (3) the strengthening model of the plugging zone, "rigid bridging+elastoplastic filling+lacing wire of fiber+film‐forming seal," is a better model, and experiments prove that it can form a tight pressure‐bearing plugging zone, preventing drill‐in fluid loss. The research results provide a theoretical and technical basis for the lost circulation control of fractured gas formations. [ABSTRACT FROM AUTHOR]

Plasma spray is a promising technology for surface protection and modification in many industrial application fields. However, the low adhesive or cohesive strength of the plasma sprayed coatings limited their further application. The cohesive strength was enhanced 115% ultra-sonicating the substrate during the plasma spraying process of Ni-10wt.%Al coatings. With the increase of power density from 0 to 1.32 W/cm2, the porosity, residual stress and strain were all decreased. However, when the power was further increased to 2.20 W/cm2, the porosity, residual stress and strain were all increased. Ultrasonic energy and the ultrasonic effects of acoustic pressure, acoustic streaming, heat effect, and cavitation effect would affect the physical processes of wetting, filling and solidification of the molten droplets during the plasma spraying process, affecting the microstructure and cohesive strength of the plasma sprayed coatings. The ultrasonic energy and ultrasonic effects which are affected by the ultrasonic power density affecting the fundamental physical processes is the key to enhance the cohesive strength of the plasma sprayed coatings. [ABSTRACT FROM AUTHOR]

The behaviour of bubbles in cavitation and boiling processes is determined by the thermodynamic parameters of the two-phase medium and the intensity of heat and mass transfer, which affect the final dynamic effects. In this review, we analyse the influences of these factors on bubble behaviour, as described in existing mathematical models. In particular, we analyse the physical processes that govern bubble behaviour, the influence of mass transfer, vapor and liquid temperature, vapour, and liquid pressure on the inertial and dynamic stages of development. In conclusion, we summarize the problems associated with modelling, the accuracy of numerical predictions, and propose directions for further research. [ABSTRACT FROM AUTHOR]

The erosion process of a 4 μm monolayer CrN coating deposited on 316L stainless steel due to cavitation was investigated using finite element analysis (FEA). To estimate load parameters from cavitation pit geometry resulting from high impact velocity and high strain rate, the explicit dynamic solver was employed. Water microjet impacts at velocities of 100, 200 and 500 m/s were simulated to recreate different cavitation erosion intensities observed in the experiment. The resulting damage characteristics were compared to previous studies on uncoated 316L steel. The relationship between impact velocity and postimpact geometry was examined. Simulations revealed that only impact at 500 m/s can exceed the maximum yield stress of the substrate without penetrating the coating. Subsequent impacts on the same zone deepen the impact pit and penetrate the coating, leading to direct substrate degradation. The influence of impact velocity on the coating degradation process is discussed. [ABSTRACT FROM AUTHOR]

Laser beam remelting is a relatively simple and highly effective technique for the physical modification of surfaces to improve resistance to cavitation erosion. In this study, we investigated the effect of laser remelting on the surface of cast stainless steel with 0.40% C, 25% Cr, 20% Ni, and 1.5% Si on cavitation erosion behavior in tap water. The investigation was conducted using a piezoceramic crystal vibrator apparatus. Base laser beam parameters were carefully selected to result in a defect-free surface (no porosity, material burn, cracks) with hardness capable of generating better resistance to cavitation erosion. The experimental results were compared with those of the reference material. Surface morphology and microstructure evolution after cavitation tests were analyzed using an optical metallographic microscope (OM), scanning electron microscope (SEM), and hardness tests to explore the mechanism of improving surface degradation resistance. The conducted research demonstrated that surfaces modified by laser remelting exhibit a 4.8–5.1 times greater increase in cavitation erosion resistance due to the homogenization of chemical composition and refinement of the microstructure, while maintaining the properties of the base material. [ABSTRACT FROM AUTHOR]

Experimental investigations into acoustic cavitation and ultrasound-assited emulsification process between highly viscous liquids were systematically conducted in a laboratory-built ultrasonic microreactor. Under ultrasound irradiation, four cavitation modes were observed simultaneously in soybean oil, including volume, shape, transient collapse and cavitation clouds. Influenced by the intense oscillation of cavitation bubbles, emulsification between viscous liquids was initiated through a dispersion and migration mode. The effects of varying parameters, such as input power, residence time, channel size, HLB value, surfactant concentration and volume ratio between aqueous and oil phase, on the size and polydispersity of prepared emulsion were investigated using water-soybean oil two-phase system as a model. The emulsion size was reduced to 75.60 nm through optimization of experimental parameters. Based on these findings, the ultrasonic microreactor was successfully employed in the preparation of Vitamin E-enriched nano-emulsions. A fine emulsion with low average size (47.69 nm) and good storage stability (60 days) was prepared within 2 min, further indicating the potential application of ultrasonic microreactor in the beverage and pharmaceutical industries. Article Highlights: Emulsification between viscous liquids was realized through a dispersion and migration mode. Effects of varying parameters on size and polydispersity of prepared emulsion were investigated. Vitamin E-enriched nano-emulsion with low average size and good storage stability was prepared within 2 min. [ABSTRACT FROM AUTHOR]

[Display omitted] • An method of high-density ultrasound for enhanced mass transfer in liquid-liquid interfacial reaction was proposed. • The mass transfer coefficient in liquid-liquid interfacial reaction systems was enhanced by 252 %. • Iron doping rate of prepared Fe-CDs reached 20.9 %. • Photocatalytic oxidation efficiency of prepared Fe-CDs on 1,4-DHP reached 98.2 %. • Ultrasonically regulated particle size, size distribution and fluorescence of prepared Fe-CDs. The precise and controllable preparation of carbon nanomaterials under mild conditions poses a great challenge, especially for metal-catalysed multiphase preparation. This work proposes an efficient method that utilizing high-density ultrasound to enhance the liquid-liquid interfacial reaction system. Iron-doped carbon dots (Fe-CDs) are successfully synthesized in such a normal temperature and atmospheric-pressure reaction condition. It is shown that transient cavitation provides a high-temperature and high-pressure microenvironment for the preparation of Fe-CDs. Moreover, the size of the reactant droplets is reduced from 200.0 ± 17.3 μm to 8.1 ± 2.9 μm owing to the acoustic flow and cavitation effects, which increases the specific surface area of the two reacting phases and improves the mass transfer coefficient by more than 252.0 %. As a result, the yield increases by more than an order of magnitude (from 0.7 ± 0.1 % to 11.9 ± 0.2 %) and the Fe doping rate reaches 20.9 %. The photocatalytic oxidation conversion of 1,4-Dihydropyridine (1,4-DHP) using the obtained Fe-CDs is as high as 98.2 %. This research gives a new approach for the efficient and safe production of Fe-CDs, which is promising for industrial applications. [ABSTRACT FROM AUTHOR]

Resin materials feature exceptional physical properties and inexpensive cost, but unfavorable surface characteristics, such as low wear resistance and poor erosion wear performance, render them tough to satisfy greater demands. The potential option is to prepare supersonic plasma sprayed Al 2 O 3 -13 wt%TiO 2 /Al 2 O 3 -phenolic resin (AT13/Al 2 O 3 -PF) coating on the surface of the resin matrix. AT13 feedstocks are classified into two types: Al 2 O 3 -13 wt%TiO 2 powder prepared by the agglomeration granulation process (AT13-1) and the mixture of spherical Al 2 O 3 and TiO 2 (approximately 13 wt%) powder (AT13-2). The effect of component dispersion on mechanical and tribological characteristics of coatings was thoroughly investigated, as well as the solid particle erosion wear behavior of coatings. The results illustrated that the evenly dispersed TiO 2 phase in AT13-1 coating was prone to homogenize the coating structure, resulting in better tribological characteristics than AT13-2 coating, although erosion wear performance was inferior to AT13-2 coating. The wear rate of AT13-1 coating was 1.36 × 10−5 mm3 (N m)−1, which was 1/21 times that of AT13-2 coating. At the 60° erosion angle, the high porosity of AT13-1 coating resulted in hard phase cracking or hard phase debonding. The high microhardness of AT13-2 coating reduced erosion wear at the 90° erosion angle. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) and TiO 2 - doped YSZ (TiYSZ) coatings were prepared using Atmospheric Plasma Spraying (APS) at different power levels to protect of flow passage components from cavitation erosion. We analyzed, the effects of TiO 2 doping and spraying power on the coatings' phase structure, microstructure and mechanical properties using XRD, Raman spectroscopy, SEM, Vickers hardness and nano-indentation. We tested the cavitation erosion behavior of TiYSZ coatings and YSZ coatings (as a reference) in a laboratory setting employing vibration-induced cavitation in accordance with ASTM standard G32-16. The results showed that the YSZ coating contained 50% c-phase and 50% t-phase, while the TiYSZ coating contained approximately 78 % c-phase. Spraying power hadlittle effect on the phase structure of either coating. However, higher spraying power increased the density of the coating, leading to greater microhardness. TiYSZ coatings were denser than YSZ at any power level and did not exhibit a distinct microcolumnar grain structure, unlike YSZ. Additionally, TiYSZ coatings displayed better mechanical properties, including higher hardness, elastic modulus, toughness, and fracture strength compared to YSZ. As a result, the cavitation resistance of TiYSZ coatings improved by about 50% compared to YSZ. Furhermore, we found that chemical degradation of YSZ-based ceramics under cavitation erosion conditions plays a role in cavitation erosion. We also observed that cavitation-induced amorphization is a key mechanism contributing to this degradation. [ABSTRACT FROM AUTHOR]

The circulation pump in a distillation column is a core device in a material circulation system, and its stable operation is crucial for the production process. The impeller of the circulation pump is prone to failure due to long-term contact with corrosive media, and subjected to a large amount of material erosion, which severely challenges the safety control of the distillation reaction system. Focusing on the corrosion failure phenomenon of circulation pump impellers, the failure mechanism was studied by means of macroscopic inspection, chemical composition analysis, metallographic examination, scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). Results indicated that the corrosion of circulation pump impellers was the result of the combined effects of surface wear, cavitation, and halogen element corrosion. The medium in contact with the impeller contained chloride ions, fluoride ions, and solid particles. During circulation pump operation, a low-pressure zone formed at the inlet, generating numerous water vapor bubbles. These bubbles burst in the high-pressure zone, creating highly localized impact forces. Combined with the abrasive action of solid particles on the impeller surface, this led to the destruction of the passivation film and the formation of numerous small pits. These corrosion pits and the surrounding environment formed micro-galvanic corrosion cells with small anodes and large cathodes. Under the accelerated corrosion caused by fluoride and chloride ions, the corrosion process towards the inner wall of the impeller intensified, ultimately leading to impeller failure. This study clarified the corrosion failure mechanism and its root causes in the 2507 duplex stainless steel circulation pump impeller and proposes corresponding improvement recommendations, providing a scientific basis for preventing similar issues from occurring in the future. [ABSTRACT FROM AUTHOR]

A large-scale physical model was used to determine the hydrodynamic load on the radial gates of a diversion tunnel. The conditions for closing the emergency-repair slide gates were studied as well. The optimal dimensions of the structures for supplying air to the chamber of radial gates are substantiated. [ABSTRACT FROM AUTHOR]

In order to study the feasibility of forming microtexture at the surface of 7050 aluminum alloy by laser-induced cavitation bubble, and how the density of microtexture influences its tribological properties, the evolution of the cavitation bubble was captured by a high-speed camera, and the underwater acoustic signal of evolution was collected by a fiber optic hydrophone system. This combined approach was used to study the effect of the cavitation bubble on 7050 aluminum alloy. The surface morphology of the microtexture was analyzed by a confocal microscope, and the tribological properties of the microtexture were analyzed by a friction testing machine. Then the feasibility of the preparation process was verified and the optimal density was obtained. The study shows that the microtexture on the surface of a sample is formed by the combined results of the plasma shock wave and the collapse shock wave. When the density of microtexture is less than or equal to 19.63%, the diameters of the micropits range from 478 μm to 578 μm, and the depths of the micropits range from 13.56 μm to 18.25 μm. This shows that the laser-induced cavitation bubble is able to form repeatable microtexture. The friction coefficient of the sample with microtexture is lower than that of the untextured sample, with an average friction coefficient of 0.16. This indicates that the microtexture formed by laser-induced cavitation bubble has a good lubrication effect. The sample with a density of 19.63% is uniform and smooth, having the minimum friction coefficient, with an average friction coefficient of 0.14. This paper provides a new approach for microtexture processing of metal materials. [ABSTRACT FROM AUTHOR]

The flow field of a low specific speed centrifugal pump is investigated in the present work based on numerical simulation to establish the effect of circumferential positions of balance holes on cavitation behaviour and cavitation erosion of the centrifugal pump. The distribution of the pressure around balance holes is studied, the initiation and development of cavitation at different balance hole schemes are compared, and the distribution of cavitation erosion for the original pump and the ideal scheme is also predicted. The results show that when the NPSHa is high, there is low pressure zone in balance hole, which leads to cavitation in the pump. The cavitation performance of pump is improved by gradually moving balance holes away from blade suction surface, as this reduces low pressure zones around the balance hole and incipient cavitation. Under critical cavitation conditions, the cavitation shows a tendency to collapse as the angle (φ) of circumferential position of balance holes decreases, and the proportion of the higher vapor volume fraction in cavitation core zones also decreases. The cavitation erosion zones on blade surfaces are predicted by using the Erosive Power Method (EPM). The erosion impact of the original pump is more pronounced in the comparative results.

In-situ experimental observation cannot be an effective method in the impact process of metal cavitation erosion, and the impact damage energy prediction theory has not been established based on a detailed mathematical and physical model. Research has shown that the metal material can be regarded as a sensor to reflect the impact parameters. Soft metal materials such as industrial pure copper with a single α-phase microstructure can be a suitable sensor to detect cavitation erosion effects, revealing the impact behaviors of the cavitation jet through the depth, width and spatial distribution of cavitation pits on the surface. In this scenario, volume loss of cavitation pits on a macro/mesoscale are obtained by three-dimensional surface measurement. A coupled fluid-solid simulation model calculating the impact damage energy on a macro/mesoscale is established based on the Smoothed Particle Hydrodynamics (SPH) and the Crystal Plasticity Finite Element Method (CPFEM). Python programming is used to set the trajectory of SPH particles to determine the macro cavitation flow field. IFEM methods were used to construct the prediction theory of cavitation impact energy in a relatively simple exponential equation, establishing the quantitative relationship between cavitation impact damage energy and measured volume of cavitation pits. Compared with conventional measurement and simulation, the present multiscale approaches are assumed as a further step advancement towards calculating the impact damage energy of cavitation water jet.

This paper investigates the impregnation of Japanese cedar (Cryptomeria japonica D. Don) with water using ultrasound irradiation, followed by immersion in water containing bulk nanobubbles (NBs). Cavitation bubbles generated during ultrasound irradiation mechanically remove extractives from the wood surface, enhancing the mass transfer of water into the wood. Water containing bulk NBs has a lower surface tension compared to pure water, enabling superior permeability into narrow spaces. However, the application of water containing NBs for wood impregnation post-sonication remains underexplored. In this study, wood was subjected to ultrasound irradiation at 38 kHz, followed by immersion in water containing bulk NBs, to determine the optimal sonication time and NB concentration for efficient impregnation. The results indicate that water uptake by the wood initially increases and then decreases with increasing NB concentration and sonication time. Optimal sonication time and NB concentration resulted in highly efficient impregnation. [ABSTRACT FROM AUTHOR]

This research is focused on studying the behavior of bubbles in one-dimensional nozzle flows. The study delves into the complex flow of cavitating bubbles within geometries of varying cross-sectional areas, using a second-grade fluid. The cavitation phenomenon poses a potential threat, as it can harm surfaces upon bubble collapse or interaction with adjacent boundaries. Thus, the proposed model unveils the intricate behavior of cavitating bubbles in response to nozzle shape and fluid properties. The governing equations are first modeled using the Rayleigh–Plesset equation along with continuity and momentum equations for bubbly liquids. They are then simplified and nondimensionalized to solve by means of the RK method. The influence of several nondimensional parameters, including the Reynolds number, fluid parameter, cavitation number and the number of bubbles, on the flow behavior of second-grade fluid through various channels is illustrated using graphs. To validate the results, the Newtonian formulation was applied in the current setting, and it was found that the obtained results matched the available literature. Also, critical values of void fractions for the radius of the bubble are presented. The non-Newtonian properties of the fluid are observed a significant outcome for the reduction of cavitation damage and noise. [ABSTRACT FROM AUTHOR]

Microelectrochemical systems (MEMSs) have important applications in electronic information, aerospace, national defense and other fields. The microhemispherical concave die is the manufacturing foundation for the MEMS system. To clarify the forming mechanism of microhemispherical concave dies machined by microultrasonic machining with ceramic whole ball tools, a material removal model was presented. Furthermore, the kinetic energy model of a spherical abrasive under the action of microultrasonic and whole ball ceramic tools was also established. The model of the brittle-plastic transition removal mode is correlated with the kinetic energy of the abrasive model. The surface morphology of miniature molds exhibits significant variations attributed to the altered material removal mode, the removal mechanism was analyzed. The theoretical model is verified by experiments. Experiments were performed with lower and higher viscosity polishing fluids. The surface roughness of the plastic removal area in each group was 96.4 and 60.1 nm. Due to the high viscosity polishing fluid eliminating some of the cavitation phenomena, the overall surface quality is improved; hence, the surface roughness decreases by 37.6% under the same processing conditions. In the low-viscosity experimental group, the surface roughness was 113.61, 302.28 and 367.24 nm, respectively. The experimental verification confirmed that variations in surface morphology occur, even with the same removal mode applied at different locations on the microconcave die. The reasons for the surface roughness variation in different areas of the microconcave die are analyzed and reveal the influence of ultrasonic cavitation on the material removal mode in microultrasonic machining. [ABSTRACT FROM AUTHOR]

The atomic‐scale response of inhomogeneous fluids at interfaces and surrounding solute particles plays a critical role in governing chemical, electrochemical, and biological processes. Classical molecular dynamics simulations have been applied extensively to simulate the response of fluids to inhomogeneities directly, but are limited by the accuracy of the underlying interatomic potentials. Here, we use neural network potentials (NNPs) trained to ab initio simulations to accurately predict the inhomogeneous responses of two distinct fluids: liquid water and molten NaCl. Although NNPs can be readily trained to model complex bulk systems across a range of state points, we show that to appropriately model a fluid's response at an interface, relevant inhomogeneous configurations must be included in the training data. In order to sufficiently sample appropriate configurations of such inhomogeneous fluids, we develop protocols based on molecular dynamics simulations in the presence of external potentials. We demonstrate that NNPs trained on inhomogeneous fluid configurations can more accurately predict several key properties of fluids—including the density response, surface tension and size‐dependent cavitation free energies—for liquid water and molten NaCl, compared to both empirical interatomic potentials and NNPs that are not trained on such inhomogeneous configurations. This work therefore provides a first demonstration and framework to extract the response of inhomogeneous fluids from first principles for classical density‐functional treatment of fluids free from empirical potentials. [ABSTRACT FROM AUTHOR]

In the paper, we present the results of an experimental study of a hydrophobic liquid flow between non-concentric cylinders. In the region of flow expansion, gas cavitation of the dissolved gas can be observed depending on the gap size between the cylinders. If the liquid contains water, steam cavitation of the impurity can be also observed. Steam cavitation of water occurs when the surfaces of the cylinders with a small gap slide between each other. Water vapor condenses into microdroplets when the flow stops. Three-phase gas bubbles with water microdroplets are formed at the gas-liquid interface. This gas bubble design is shown to have its own electric field. When a bubble rises, its water microdroplet moves along the gas-liquid interface and occupies a minimal distance from the surface of the neighboring bubble. In the case of several three-phase bubbles located nearby, the water microdroplets in them split, indicating the direction of the neighboring electric field sources. A patent for a method of registering sources of quasi-static electric fields was obtained based on the performed research. [ABSTRACT FROM AUTHOR]

Unsubmerged cavitating abrasive waterjet (UCAWJ) has been shown to artificially create a submerged environment that produces shear cavitation, which effectively enhances rock-breaking performance. The shear cavitation generation and collapse intensity depend on the pressure difference between the intermediate high-speed abrasive waterjet and the coaxial low-speed waterjet. However, the effect of the pressure of the coaxial low-speed waterjet is pending. For this purpose, the effect of low-speed waterjet pressure on rock-breaking performance at different standoff distances was experimentally investigated, and the effects of erosion time and ruby nozzle diameter on erosion performance were discussed. Finally, the micromorphology of the sandstone was observed at different locations. The results show that increased erosion time and ruby nozzle diameter can significantly improve the rock-breaking performance. At different standoff distances, the mass loss increases first and then decreases with the increase of low-speed waterjet pressure, the maximum mass loss is 10.4 g at a low-speed waterjet pressure of 0.09 MPa. The surface morphology of cavitation erosion was measured using a 3D profiler, the increase in both erosion depth and surface roughness indicated a significant increase in the intensity of the shear cavitation collapse. At a low-speed waterjet pressure of 0.18 MPa, the cavitation erosion surface depth can reach 600 mm with a roughness of 127 mm. [ABSTRACT FROM AUTHOR]

Submersible drainage pumps are used around the world both residentially and industrially for draining water and sewage. However, these pumps are prone to wear and clogging when the flows inward contain particles and air bubbles, and the combined effects of cavitation and erosion directly affect the performance of such pumps and degrade their efficiency. Therefore, it is essential to design a submersible pump that mitigates the adverse effects of cavitation and erosion. Reported here is an energy-efficient submersible drainage pump for use in emergency response. The combined cavitation–erosion effects are established in order to reduce their adverse impact on the pump, and how erosion wear affects the cavitation characteristics of the water in the pump is investigated. An experiment was conducted to verify the numerical results pump, and then, the influences of particle concentration and size on two-stage existing and altered model submersible pumps were analyzed using computational fluid dynamics. The results show that the performance of the altered model pump increased by 4.34%, with the cavitation–erosion effects reduced significantly. In addition, higher particle concentration induced higher erosion rates at both the leading and trailing edges of the impeller blades. Furthermore, the altered model significantly reduced the cavitation–erosion impact on the pump impeller blades compared to the existing model. [ABSTRACT FROM AUTHOR]

Coal seam cavitation is one of the most effective techniques for gas disaster control in low-permeability coal. Due to the difference in cavitation method and process, the damage degree and fracture development range of the coal body around the cavern are greatly different, and the effect of increasing the permeability of the coal body is further changed. In order to further understand the permeability enhancement mechanism of cavitation technology on low-permeability coal and effectively guide engineering applications, this paper conducted experimental research on the unloading damage and permeability evolution characteristics of coal under different cavitation paths using a coal-rock "adsorption-percolation-mechanics" coupling test system. Through the analysis of coal strength and deformation characteristics, coal damage characteristics, and the evolution law of coal permeability combined with the macroscopic damage characteristics of coal, the strength degradation mechanism of unloaded coal and the mechanism of increased permeability and flow were revealed. The results show that unloading can significantly reduce the strength of coal, and the greater the unloading rate, the more obvious the reduction. The essence of this is that unloading reduces the cohesion and internal friction angle of coal—damage and breakage are the most effective ways to improve the permeability of the coal body. Unloading damaged coal bodies not only significantly improves the permeability of the coal body but also improves the diffusion ability of gas, and finally, shows a remarkable strengthening effect of gas extraction. [ABSTRACT FROM AUTHOR]

The current research investigates the effects of materials and riblets on cavitation-induced erosion morphology, depth, and cross-sectional area through experimental approaches. To achieve these aims, the erosion of pure aluminum (1xxxAl or Al) and alpha brass (CuZn37 or CZ108), in the presence and absence of bio-inspired sawtooth riblets, was examined after exposure to multiple collapses of single cavitation bubbles with a wall distance of 1.8 (dimensionless). The results indicate that the erosion morphology resembles a rounded cone with a circular cross-section. Brass provides 21.6% more erosion resistance compared to that of Al in terms of material properties. Furthermore, the erosion for both Al (depth by 3.8% and width by 18.3%) and brass (depth by 7.9% and width by 27.4%) decreases in the presence of riblets compared to the results for flat surfaces. The greater erosion resistance of brass compared to Al is attributed to the superior mechanical stability of brass, making it a potentially suitable alloy for use in propellers and hulls in the shipping industry. In summary, the results reveal that riblet-equipped materials with high mechanical durability are promising erosion-resistant materials for the shipping industry. However, the potential for chemical reactions in a cathodic environment should be addressed to provide a comprehensive perspective in regards to reducing corrosion intensity. [ABSTRACT FROM AUTHOR]

This study investigates cloud cavitation suppression around a model-scale NACA66 hydrofoil using active water injection and explores the effect of multiple injection parameters. Numerical simulations and a mixed-level orthogonal test method are employed to systematically analyze the impact of jet angle αjet, jet location Ljet, and jet velocity Ujet on cavitation suppression efficiency and hydrofoil energy performance. The study reveals that jet location has the greatest influence on cavitation suppression, while jet angle has the greatest influence on hydrofoil energy performance. The optimal parameter combination (Ljet = 0.30C, αjet = +60 degrees, Ujet = 3.25 m/s) effectively balances energy performance and cavitation suppression, reducing cavitation volume by 49.34% and improving lift–drag ratio by 8.55%. The study found that the jet's introduction not only enhances vapor condensation and reduces the intensity of the vapor–liquid exchange process but also disrupts the internal structure of cavitation clouds and elevates pressure on the hydrofoil suction surface, thereby effectively suppressing cavitation. Further analysis shows that positive-going horizontal jet components enhance the lift–drag ratio, while negative-going components have a detrimental effect. Jet arrangements near the trailing edge negatively impact both cavitation suppression and energy performance. These findings provide a valuable reference for selecting optimal injection parameters to achieve a balance between cavitation suppression and energy performance in hydrodynamic systems. [ABSTRACT FROM AUTHOR]

In the field of power ultrasonic vibration processing, the thin liquid layer nestled between the tool head and the material serves as a hotbed for cavitation shock wave emissions that significantly affect the material's surface. The precise manipulation of these emissions presents a formidable challenge, stemming from a historical deficit in the quantitative analysis of both the ultrasonic enhancement effect and the shock wave intensity within this niche environment. Our study addresses this gap by innovatively modifying the Gilmore-Akulichev equation, laying the groundwork for a sophisticated bubble dynamics model and a pioneering shock wave propagation model tailored to the thin liquid layer domain. Firstly, our study investigated the ultrasound enhancement effect under various parameters of thin liquid layers, revealing an amplification of ultrasound pressure in the thin liquid layer area by up to 7.47 times. The mathematical model was solved using the sixth-order Runge–Kutta method to examine shock wave velocity and pressure under different conditions. our study identified that geometric parameters of the tool head, thin liquid layer thickness, ultrasonic frequency, and initial bubble radius all significantly influenced shock wave emission. At an ultrasonic frequency of 60 kHz, the shock wave pressure at the measurement point exhibited a brief decrease from 182.6 to 179.5 MPa during an increase. Furthermore, rapid attenuation of the shock wave was found within the range of R0-3R0 from the bubble wall. This research model aims to enhance power ultrasonic vibration processing technology, and provide theoretical support for applications in related fields. [ABSTRACT FROM AUTHOR]

An experimental study of the effects of the sodium salt of poly(methacrylic acid) (Na-PMAA) on non-photochemical laser-induced nucleation (NPLIN) of sodium acetate crystals is presented. Seeding of supersaturated aqueous solutions with anhydrous (AH) seeds always produced trihydrate (TH) crystals, with or without polymer additive. Using NPLIN, with no Na-PMAA and at low Na-PMAA concentrations (0.25% w/w) AH sodium acetate was produced, firstly as plate-like form IV, but subsequently growing needles, likely to be form I. At high Na-PMAA concentrations (0.73% w/w) we observe formation mostly of stable bubbles. In all samples at low laser peak power densities (<26 MW cm−2) we show for the first time using NPLIN that both crystals and bubbles can be nucleated with a single laser pulse. Measurements of the dependence of bubble or crystal count on laser pulse power indicate a common mechanistic origin for nucleation, which is cavitation due to laser heating of impurity nanoparticles. The bubbles observed are attributed to laser heating of the nanoparticles to high temperatures, resulting in gas formed by thermochemical reactions or gas that was previously dissolved in the solution. Our results provide new insight into the particle-heating mechanism for NPLIN, but whether stable bubbles play a defining role in the nucleation of crystals remains to be resolved. [ABSTRACT FROM AUTHOR]

Single-crystal SiC nanoporous structure has important applications in the field of micro electromechanical systems, chemical sensors and biomedical devices. However, SiC exhibits a strong chemical inertness due to the short interatomic distance and high binding energy, making it significantly challenging to fabricate nanoporous structure. Electrolytic plasma-assisted chemical etching (EPACE) based on electrochemical anodic oxidation and high-activity electrolytic plasma etching is an ideal method for SiC nanoporous structure etching. In which, the spatial distribution of electrolytic plasma has an important impact on EPACE performance, such as etching efficiency and stability. In order to analyze the impact mechanism, this paper studies EPACE in tool electrode mounting posture of vertical and horizontal types by visual observation, real-time recording of voltage-current waveforms during processing, and the morphology analysis of SiC nanoporous structure after etching. It can be found that in the vertical etching type, EPACE can proceed stably because the workpiece immersion depth is greater than the bubble accumulation thickness. However, in the horizontal etching type, bubbles accumulate seriously between the workpiece and the liquid surface, which may cause bubble cavitation and abnormal discharge, leading to damage to the etching surface. The etching current in the vertical etching type is about 1.3 times that of the horizontal etching type, indicating that the bubble mass transfer in the vertical etching type is faster and the etching impedance is smaller, which is beneficial to improve the etching efficiency and obtain a uniform nanoporous structure. Finally, a SiC nanoporous layer with a thickness of 10.6 μm was prepared at etching time t = 50 min in vertical etching type, and the etching efficiency was 212 nm/min. In addition, the prepared nanoporous structure (nanofiber) was connected to the SiC substrate, indicating that it has a good bonding strength. [ABSTRACT FROM AUTHOR]

The presence of gas in transmission fluid can disrupt the flow continuity, induce cavitation, and affect the transmission characteristics of the system. In this work, a gas void fraction model of gas–liquid two-phase flow in a transmission tube is established by taking ISO 4113 test oil, air, and vapor to accurately predict the occurrence, development, and end process of the cavitation zone as well as the transient change in gas void fraction. This model is based on the conservative homogeneous flow model, considering the temperature change caused by transmission fluid compression, and cavitation effects including air cavitation, vapor cavitation, and pseudo-cavitation. In this model, the pressure term is connected by the state equation of the gas–liquid mixture and can be applied to the closed hydrodynamic equations. The results show that in the pseudo-cavitation zone, the air void fraction decreases rapidly with pressure increasing, while in the transition zone from pseudo-cavitation to air cavitation, the air void fraction grows extremely faster and then increases slowly with decreasing pressure. However, in the vapor cavitation zone, the vapor void fraction rises slowly, grows rapidly, and then decreases, which is consistent with the explanation that rarefaction waves induce cavitation and compression waves reduce cavitation. [ABSTRACT FROM AUTHOR]

A renowned hard coating material (WC–Co) has the potential to overcome cavitation erosion (CE) in hydromachinery components. Hydro turbines that employ silt-filled water for electricity generation create a lot of metal waste due to erosion and cavitation caused by the particles. There is an urgent need for repair of hydropower components that have undergone damage due to cavitation. In this investigation, tungsten carbide composite coatings were produced on 13Cr4Ni (CA6NM) stainless steel substrates using the cold spray method. In order to create high-quality coatings, nitrogen was used as the propellant gas. The coating microstructures were characterized by EDS, SEM XRD, and microhardness tests. Cold-sprayed WC–Co-based coatings were exposed to enhance the cavitation erosion resistance of CA6NM steel. Cold spray coating prepared with WC-12/17Co powder has shown excellent wear-resistant properties due to higher hardness and lower porosity. [ABSTRACT FROM AUTHOR]

A pumped storage unit is a crucial guarantee in the pursuit of increased clean energy, especially in the progressively severe circumstances of low energy utilization and poor coordination of the integration of volatile renewable energy. However, due to their bidirectional operation design, pumped turbines possess an S-characteristic attribution, wherein the unsteady phenomena of unit vibration, pressure pulsation, and cavitation erosion happen during the start-up process and greatly impact the stable connection to the power grid. Therefore, a systematic study concentrating on an optimal unified paradigm of a start-up strategy for a pumped storage plant is conducted. Model construction, effective analysis, controller design, and collaborative optimization are sequentially expounded. Firstly, a refined start-up nonlinear model of a pumped storage plant with complex boundary conditions is constructed, wherein the delay time of frequency measurement, saturation, and dead zone features are comprehensively taken account. Furthermore, a variable universe fuzzy PID controller and its operation laws are proposed and specifically designed for the speed governing system of the pumped storage plant; the control quality and anti-disturbance performance are verified by a no-load frequency disturbance experiment. On this basis, taking speed overshoot for stationarity and speed rising time for rapidity, a novel open–close loop collaborative fuzzy control strategy is proposed with rotational speed feedback and a variable universe fuzzy PID control. The experiment results show that the proposed unified paradigm has better control performance in various performance indexes, and more balanced control quality and dynamic performance under various complex start-up conditions, which has great application value for ensuring the unit's timely response to the power grid regulation task and improving the operating stability of the power system. [ABSTRACT FROM AUTHOR]