Cavitating Water Jet Research Articles

Experimental study on the breaking of A-IX-2 explosive by submerged cavitation water jet

It was investigated to break A-IX-2 explosive using the submerged cavitation water jet for emptying scrapped ammunitions charged A-IX-2 explosives. The Split Hopkinson pressure bar (SHPB) tests were firstly accomplished for A-IX-2 explosive to obtain its stress-strain mechanical properties. The breaking effect and its mechanism of the submerged cavitation water jet were investigated. The broken A-IX-2 explosives were tested by scanning electron microscope (SEM) to analyze the mesoscopic mode of cavitation water jet breaking A-IX-2 explosive. Finally, the internal temperatures of A-IX-2 explosive during the whole impact process were detected. The results showed that A-IX-2 explosive exhibits strain rate effect. The submerged cavitation water jet is available to use to empty ammunition charged A-IX-2 explosive and the maximum particle size is no more than 3cm. The fragmentation of the explosive by the submerged cavitation water jets is mainly caused by the combined action of micro-jets and shock waves generated by the collapse of cavitation bubbles. The mesoscopic mode is mainly the separation of crystals from binder and aluminum powder. The temperature change of A-IX-2 explosive in the whole process is about 20 °C.

Effect of Processing Degree and Nozzle Diameter on Multifunction Cavitation

The bubbles of water jet cavitation and of multifunction cavitation (MFC) generated by nozzles with diameters of 0.1, 0.2 and 0.8 mm were investigated for the collapse pressure of microjets, the nozzle-specimen distance, the degree of processing, the photocatalyst characteristics for titanium oxide particles, and the multi-bubble sonoluminescence. The dependence of these characteristics on the nozzle diameter was clarified. The nozzle-specimen distance became shorter as the nozzle diameter decreased. The titanium oxide powder was processed with MFC using 0.8, 0.2 and 0.1 mm water jet nozzles. More hydrogen was generated with a nozzle diameter of 0.8 mm than with a 0.1 mm nozzle. A 0.2 mm nozzle generated less hydrogen than a 0.1 mm nozzle because the water jet pressure from a 0.2 mm nozzle was lower. A 0.1 mm nozzle produced the same luminous intensity from cavitation bubbles as a 0.8 mm nozzle. These results mean that the bubble temperature attained by 0.1 and 0.8 mm nozzles is relatively high. The smaller the nozzle diameter becomes, the smaller the bubble diameter and the lower the collapse pressure of the microjet, which leads to a lower degree of processing and reduced influence on photocatalytic properties.

Water-jet cavitation shocking as a novel array micro-forming technique

Micro-feature arrays and large-area complex microscopic features on thin metallic sheet play an important role in micro-components. A novel technique-submerged water-jet cavitation shocking-is presented to generate micro-feature arrays on 304 stainless foils in this paper. High-speed camera shadowgraph images of the cavitation cloud were employed to analyze the impact zone. Then the forming depth, uniformity of forming depth and the thickness distribution of the micro-feature arrays were also studied. The results show that the forming region can be categorized into the jet-impact-zone, the bubble-impact-zone and the periphery-impact-zone radially. Bubble-impact-zone peaks in the depth of array micro-forming. The forming depth increases with time while the uniformity decreases with time. The forming parts have a uniform thickness distribution.

Surface Characteristics and Cavitation Damage in 8090Al–Li Alloy by Using Cavitation Water Jet Peening Processing

The cavitation strengthening test of Aluminum lithium Alloy (8090Al–Li) was carried out with different pressure process parameters. The roughness, residual stress, and morphology of the treated samples were studied. A high dislocation density was formed in the cavitation area of the workpiece, which resulted in surfacing hardening. The cavitation effect occurred in the collapse area. It was beneficial for the process to be the right choice for the surface treatment of metal materials. The results confirmed that surface roughness, grain size, micro-strain, erosive effect, and micro-hardness of the alloy were significantly affected by different cavitation peening pressures. In this case, surface roughness increased as the impact pressure increased. Besides, the microcrystalline structure decreased in the cavitation treatment area. The study showed on how the impact of the different cavitation peening pressure could suppress the material surfaces, the compressive residual stress, attained the maximum values of −137 MPa to −162 MPa, which increased from 7.87 to 27.56%, as compared to the original sample. In contrast, the corresponding surface roughness average increased to 3.04 μm. Experimental observation shows that the cavitation collapse boundaries obtained by the proposed sample surface and metallographic images were highly complete and accurate.

Review of Underwater Ship Hull Cleaning Technologies

This paper presents a comprehensive review and analysis of ship hull cleaning technologies. Various cleaning methods and devices applied to dry-dock cleaning and underwater cleaning are introduced in detail, including rotary brushes, high-pressure and cavitation water jet technology, ultrasonic technology, and laser cleaning technology. The application of underwater robot technology in ship cleaning not only frees divers from engaging in heavy work but also creates safe and efficient industrial products. Damage to the underlying coating of the ship caused by the underwater cleaning operation can be minimized by optimizing the working process of the underwater cleaning robot. With regard to the adhesion technology mainly used in underwater robots, an overview of recent developments in permanent magnet and electromagnetic adhesion, negative pressure force adhesion, thrust force adhesion, and biologically inspired adhesion is provided. Through the analysis and comparison of current underwater robot products, this paper predicts that major changes in the application of artificial intelligence and multirobot cooperation, as well as optimization and combination of various technologies in underwater cleaning robots, could be expected to further lead to breakthroughs in developing next-generation robots for underwater cleaning.

Sonoluminescence from Ultra-High-Temperature and High-Pressure Cavitation and its Effect on Surface Modification of Cr-Mo Steel

Sonoluminescence from various types of cavitation bubbles, namely those of water jet cavitation (WJC), water jet cavitation with a swirl flow nozzle (SFN-WJC), multifunction cavitation (MFC), ultrasonic cavitation (UC), and ultrahigh-temperature and highpressure cavitation (UTPC), wasinvestigated. The sonoluminescence measurements were compared with the surface modification characteristics imparted to Cr-Mo steel. The luminescence intensity of the various types of cavitation was measured using two types of photon counting head, whose detection sensitivity depends on the wavelength range. 2 UTPC had the highest light intensity, followed by MFC, UC, SFN-WJC, and WJC. The temperature inside the bubbles from the various types of cavitation could be estimated using the black-body emission method based on Planck’s law and the emission intensity, which was corrected for the sensitivity of the detector. UTPC, which had high luminosity and could treat surfaces at high temperatures, was found to increase compressive residual stress and decrease surface roughness compared to WJC and SFN-WJC, which had low luminosity and are forms of cold working. At higher cavitation temperature, more corrosion-resistant and oxidation-resistant films form on a steel surface. The magnitude of luminescence intensity for a cavitation process corresponds to the magnitude of corrosion potential (surface potential), which indicates corrosion resistance

Characteristics of Waterjet Cavitation Erosion of 304 Stainless Steel After Corrosion in NaCl Solution

Characteristics of Waterjet Cavitation Erosion of 304 Stainless Steel After Corrosion in NaCl Solution

Effects of nozzle lip geometry on the cavitation erosion characteristics of self-excited cavitating waterjet

The cavitation erosion characteristics of self-excited cavitating waterjet produced by a nozzle with various lip geometries were investigated. The cavitation erosive intensity was estimated by the mass loss of pure aluminum specimens and the sound press level of under the optimum standoff distance. The power spectrum density of noise and the surface profiles of the specimens were studied to uncover the influencing mechanism. The variables of lip geometries include: straight length (L1/d = 0.15–0.75), expansion angles (0–40°), expansion length (L2/d = 0.5–3). It is shown that the nozzle lip geometry can produce a significant influence on the cavitation erosion characteristics. The cavitation erosive ability can be affected by the straight length based on the vena contracta and pressure fluctuation feedback. The expansion structure can influence the jet’s cavitation erosive characteristic from two different aspects: the jet’s structuring frequency and the periodic behavior of the cavitation cloud. Moreover, it is possible to define an optimal geometry under this condition where the erosion mass loss is at a relative maximum, that is straight length L1/d around 0.35, expansion angle 10°<θ<25°, length 1.0<L2/d<2.5.

Experimental and numerical investigation of two-phase flow and mass transfer in a self-excited oscillation pulse jet pump

The pulse water jet pump is widely used for many industrial purposes owing to the presence of pressure fluctuations that can considerably improve the erosive action of a jet. However, literature regarding the cavitating water jet flow patterns and underlaying mass transfer mechanisms remains relatively scarce due to existing measurement obstacles. To reveal underlying relationships between pump geometrical configuration and its performance, this study presents an experimental and numerical investigation of a self-excited oscillation water jet pump. Firstly, an experimental rig was built, and the performance of the pump was assessed against various operating conditions. Then, a numerical model based on the same pump geometry and operation conditions was developed to provide detailed predictions of the internal cavitating flow patterns. Reasonably good agreements were found between the numerical predictions and experimental measurements, which indicate that the developed numerical model can accurately predict the flow entrainment process in the self-excited oscillation pulse jet pump. Internal cavitating flow patterns in terms of streamlines, pressure contours, and velocity profiles were explored for different pump geometric configurations by adjusting the nozzle-throat distance. Relationships between these influential factors and pump mixing capacity were provided. This paper presents an in-depth understanding of the self-excited oscillation pulse water jet and systematically explores the impacts of pump geometries and operating conditions on its performance.

Effects of Organ-Pipe Chamber Geometry on the Frequency and Erosion Characteristics of the Self-Excited Cavitating Waterjet

Erosion experiments were performed to uncover the impact of organ-pipe chamber geometry on the frequency and erosion characteristics of self-excited cavitating waterjets. Jets emanating from self-excited nozzles with various organ-pipe geometries were investigated. The upstream and downstream contraction ratios of the organ-pipe resonator were changed respectively from 1.5 to 6 and 2 to 12. Pressure sensors and hydrophone were used to characterize jets’ frequency characteristics. Mass loss was also obtained in each of the configurations to assess the erosion performance. By tuning the self-excited frequency, the peak resonance was achieved using the nozzles with different geometries. Accordingly, the acoustic natural frequencies of various chamber geometries were obtained precisely. Results show that with increasing upstream and downstream contraction ratio of the organ-pipe chamber, the acoustic natural frequency increases monotonically due to the reduction of equivalent length, while the resonance amplitude and mass loss first increase and then decrease. There are optimum geometric parameters to reach the largest resonance amplitude and erosion mass loss: the upstream contraction ratio being between two and four, and downstream ratio being between four and seven. The effective length of the organ pipe can be calculated by the sum of the physical length and equivalent length to accurately obtain the acoustic natural frequency. Under the optimized parameters, the equivalent length can be estimated as 0.35D.

The Dynamic Evolution of Cavitation Vacuolar Cloud with High-Speed Camera

The dynamic model of a single cavitation bubble in the submerged cavitation water jet was established and solved by MATLAB to obtain its motion characteristics and pressure pulse change rules. Numerical simulation based on FLUENT to closer wall, empty bubble breaking form then influences the law of mechanics effect, with the increase in empty bubble, and the breaking time is reduced, but the maximum jet velocity and pressure increase gradually, on the mechanism of action of the solid wall by the fact that the combination of microfluidic and shock wave gradually plays a leading role, while plastic deformation and basic cavitation erosion are avoided. The maximum pressure and maximum jet velocity increase little, and the collapse time of cavitation is reduced. By comparing the grayscale images of the two combinations of jets, it can be found that the brightness of the vacuolar clouds in diameter (d) = 1.6 mm and pressure (P) = 15 MPa is slightly less than that in d = 1.2 mm and P = 30 MPa, indicating that the density of the vacuolar clouds and the dispersion is relatively high, while the increase in nozzle diameter leads to the increase in flow rate, which increases the shear layer of high-speed submerged jet in a static water. The pressure pulse generated by cavitating water jet hollow bubble failure is far greater than the linear superposition value of a single cavitation bubble. But the high-pressure shock wave value on the fixed wall and water hammer pressure are generated by microjet. The conclusion is also corresponding to the simulation results.

Pulse pressure loading and erosion pattern of cavitating jet

Various erosion patterns generated through the cavitating water jet impacts under ambient pressure conditions were investigated in experiments and numerical simulations. A series of normalized stand-off distances ∈ [2.5 13.5] were studied during the erosion acceleration period. Two ring-like erosion areas were observed for comparatively low ∈ [2.5 6.5]. To gain insight into the pulse pressure loading on the erosion area, numerical calculations were performed using the volume of fluid (VOF) interface capturing methodology combined with the large-eddy simulation turbulence model. The erosion patterns are clarified based on the mass loss and distribution features of the eroded regions. The first ring, generated by the cavitation clouds impingement outside the central stagnation area, mainly contributes to the mass loss. The second ring moves inward, merges into the inner ring and eventually vanishes with increasing . High pressure pulsation is found around the locations of the maximum erosion and the approximate intermediate radius of the second ring. The pressure pulsation in the first ring area are dominated by the frequency of the vortices shedding from the jet nozzle. Several higher frequencies are found as the spectral features of the eroded regions in each pattern.

Effects of surface roughness on self-excited cavitating water jet intensity in the organ-pipe nozzle: Numerical simulations and experimental results

This study was conducted to investigate effects of surface roughness on self-excited cavitating water jet intensity in an organ-pipe nozzle. Roughness average (Ra) values are 0.8, 1.6, 3.2, 6.3, 12.5, and 25 [Formula: see text]m, respectively. Numerical simulation results indicate that at inlet pressure of 10 MPa, the maximum, minimum, and real-time pressures in the self-excited oscillation chamber reach their respective peak values. The turbulent kinetic energy intensity in the external flow region is also most intense at this point, the vapor volume fraction in orifice is the highest, the vortex distribution scope in the orifice is the largest under [Formula: see text], and the self-excited cavitating water jet intensity is the strongest. The opposite variations emerge at [Formula: see text] compared to those of [Formula: see text], where the intensity is weakest. Pressure varies only slightly as Ra varies from 0.8 [Formula: see text]m to 6.3 [Formula: see text]m. Turbulent kinetic energy intensity behaves similarly as Ra increases from 0.8 [Formula: see text]m to 3.2 [Formula: see text]m. At [Formula: see text], it was weaker than at Ra = 0.8–3.2 [Formula: see text]m. Similarly, there are only slight differences in vapor volume fraction and vortex distribution scope with Ra from 0.8 [Formula: see text]m to 6.3 [Formula: see text]m. The intensities at Ra = 0.8–3.2 [Formula: see text]m are similar, and weaker at Ra = 6.3 [Formula: see text]m. Pressure values are maximal at inlet pressure of 20 MPa, turbulent kinetic energy intensity is most intense, vapor volume fraction is highest, vortex distribution scope is largest under [Formula: see text] [Formula: see text]m, and intensity is strongest. Distinctions among pressure, turbulent kinetic energy intensity, vapor volume fraction, and vortex distribution scope values with Ra from 0.8 [Formula: see text]m to 3.2 [Formula: see text]m are slight. Differences in the corresponding intensities are also slight; all decrease with Ra from 12.5 [Formula: see text]m to 25 [Formula: see text]m as the intensity gradually weakens. Numerical simulation results were validated by comparison against corresponding experimental phenomena.

Mechanical Surface Treatments of AISI 304 Stainless Steel: Effects on Surface Microrelief, Residual Stress, and Microstructure

The surface roughness, residual stress, and microstructure of AISI 304 stainless steel specimens after laser shock peening (LSP), water jet cavitation peening (WjCP), water jet shot peening (WjSP), and multi-pin ultrasonic impact treatment (UIT) were studied in this work. Compared to the initial state, the surface roughness (Ra) was, respectively, decreased by approx. 5.5, 7.8, 38.2, and 91.1% after the LSP, WjCP, WjSP, and UIT processes. The volume fraction of e-martensite of ~ 3-5% was observed in all treated specimens except for the LSP-treated ones. The volume fraction of α′-martensite was increased in the following sequence: WjCP (~ 5%), LSP (~ 5%), WjSP (~ 25%), UIT (~ 50%). The studied mechanical surface treatments promote a significant reduction in grains size of both austenite (~ 15-20 nm) and martensite (~ 20-37 nm) leading to essential hardening. All studied processes result in the formation of compressive residual stresses (− 377…693 MPa) and the improvement in the bearing curve parameters. The microhardness estimated accounting for the contributions of different hardening mechanisms to the yield strength magnitude correlates well with the experimental data. The grain boundary hardening and dislocation hardening are concluded to be the most influential mechanisms.

Research on cavitation gain induced by nanosecond pulsed laser based on microparticles

The cavitation gain refers to the phenomenon of increasing the number and intensity of cavitation by lowering the threshold of cavitation. Microparticles play a direct and critical role in the cavitation process. Laser cavitation gain based on microparticles has been found. To study the mechanism of cavitation gain, the finite-difference time-domain simulation model is established to analyze the field enhancement effect around the microparticle under laser irradiation. A laser-induced cavitation experiment platform is built, and the pulsation process of cavitation is recorded by a high-speed camera. Combined with FLUENT bubble collapse vector model, the impact of the cavitation water jet on the wall is analyzed. The result shows that microparticles reduce the cavitation threshold of liquid. Owing to the field enhancement effect at the bottom of microparticles, the number of primary cavitation bubbles in the mixed solution is greater than that in distilled water under the same experimental conditions, and the dominant cavitation bubble has a larger radius and a longer pulsation period. The bubble collapse near the wall produces an obvious water jet and wall-leaning effect, and the pressure on the wall in the microparticles mixture is higher than that in distilled water. Cavitation gain of microparticles in the laser-induced cavitation processing is helpful in revealing the mechanism of cavitation erosion and solving the problem of cavitation damage. The behavior of cavitation gain can help us rationally utilize water jet force produced by laser-induced cavitation in microparticle mixtures, which has a profound influence on the innovative development of material surface micromachining.

Surface hardening of metals at room temperature by nanoparticle-laden cavitating waterjets

Reported in this paper is a novel and facile room-temperature surface-hardening technique, capable of providing five-fold increase in the hardness of an aluminum alloy, by utilizing a cavitating waterjet laden with hard nanoparticles. Microstructural and composition analyses reveal several mechanisms responsible for surface hardening: strain hardening, grain refinement, and dispersion strengthening. The hardened alloy surface also exhibits about 50% reduction in friction in a series of microscale friction measurements. Without the need to treat the alloy at elevated temperatures, this technique obviates such problems as additional energy usage, part distortion, microstructural and composition changes, and thermal shock-induced cracking. Equally important, this new method could be further tailored to impart metals, polymers, composites, etc. with different surface functional properties.

Dynamic behaviour of cavitation clouds: visualization and statistical analysis

High-speed visualization and subsequent statistical analysis of a high-speed cavitating water jet were performed with a custom image acquisition and processing system. In a cavitating water jet, cavity clouds form and collapse with an unsteady, periodic tendency where the frequency depends on the flow conditions. The aim of the presented investigations was to examine and analyse the dynamic behaviour of these cavity clouds to understand the effect of the influencing experimental working conditions, such as injection pressure, nozzle geometry and shape (convergent or divergent) on the size, integrity and life cycle of the clouds. The results show oscillation patterns in the geometry of the clouds (thickness, length, area, etc.), through shedding, growing, shrinking, which are related to upstream pressure fluctuations caused by the plunger pump and the interaction between the jet and the surroundings. The corresponding characteristic oscillation frequencies of the cavitating jets were also determined through cloud shape analysis.

•OH Inactivation of Cyanobacterial Blooms and Degradation of Toxins in Drinking Water Treatment System

Cyanobacterial blooms continue to serve as one of the most serious global issues threatening water supply and human health. During cyanobacterial bloom season, a large •OH-yield equipment was developed and installed after coagulation settling in a 12000 ton/day drinking water treatment system in Xiamen, China. An •OH concentration of 7.76∼57.8 μmol/L was formed by using the oxygen activated species generated by strong ionisation discharge combining with the effect of water jet cavitation. •OH pre-treatment at a dose of 1.0 mg/L inactivated cyanobacterial blooms in the process of conveying bloom water within only 20s, which were then removed by sand filtration. Under SEM observation, dominant Microcystis sp. colonies connected by mucilage were dispersed into individuals that still retained the cell integrity, indicating no release of intracellular organic matter (IOM). According to a flow cytometry analysis, the main cause of •OH inactivation was the breakage of DNA strands. Meanwhile, the •OH-mineralized microcystin-LR was by breaking the C=C conjugated diene bond and crucial opening the persistent benzene ring to carboxylic acid m/z 158.0. During •OH pre-treatment of 1.0 mg/L and NaClO disinfection of 0.5 mg/L, all water quality indexes and disinfection by-product (DBP) contents complied with the Chinese Sanitary Standards for Drinking Water. Therefore, the •OH based on the strong ionisation discharge showed great prospect for large-scale drinking water treatment in the removal of cyanobacterial blooms while retaining cell integrity as well as the degradation of toxins.

Rad]OH mineralization of norfloxacin in the process of algae bloom water treatment in a drinking water treatment system of 12,000 m3 per day

The accumulation of antibiotics in river watersheds and lakes could induce the spread of antibiotic-resistance genes in drinking water, causing damage to human health. An OH equipment, that produces OH by strong ionization discharge combined with water jet cavitation effect, was installed in a drinking water treatment system of 12,000 m3 per day in Xiang’an water plant, Xiamen of China. The NFX as a model antibiotic was mixed into a branched pipe at a flow rate of 1.0 m3 h−1 for OH mineralization. As a result, the OH after coagulation sedimentation at 1.0 mg L−1 and after sand filtration at 0.5 mg L−1 degraded NFX to not detected within only 20 s. Moreover, the OH mineralizes the NFX into CO2 and H2O by breaking the CF bond, and opening the piperizine, nalidixic, and benzene rings, while NaClO only opens the piperizine ring and adversely forms chlorinated intermediates. By OH disinfection at 0.5 mg L−1 in the main pipe of 500 m3 h−1, all algae blooms were inactivated; the tests of 106 drinking water quality indicators satisfied the Chinese Standards; any disinfection by-products, such as bromate and trihalomethanes (THMs) were not be detected. By NaClO disinfection, the total THMs increased to 190 μg L−1, which is 2.4 times higher than the limit regulated by Environmental Protection Agency (80 μg L−1). To prevent the spread of antibiotic-resistance genes in humans, OH advanced oxidation based on strong ionization discharge could be apply to mineralize antibiotics during practical drinking water treatment.

Residual Stress Modification and Mechanisms of Bearing Steel with Different Microstructures during Water-Jet Cavitation Peening

Abstract Water-jet cavitation peening (WCP) is used to increase the hardness and induce the formation of a compressive residual stress layer on the surface through the shock wave pressure, which is produced by the collapse of small bubbles of a cavitation jet at the surface of materials. In this article, a pressure sensitive paper is applied to determine the pressure field distribution of WCP. WCP is carried out on the bearing steel 100Cr6 with different microstructures, which are heat-treated differently. The hardness, residual stress distribution, and microstructure of bearing steels at the same observation points are compared, respectively, before and after WCP. The research indicates that both the hardness and residual stress are increased with the peening time. It also proves that this method has different strengthening limits for materials with different microstructures because of the different mechanisms of WCP.