A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impac...A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.展开更多
Biofouling on ships and offshore structures has always been a difficult problem to solve,which not only jeopardizes the structural strength but also brings great economic losses.Ultrasonic cavitation is expected to so...Biofouling on ships and offshore structures has always been a difficult problem to solve,which not only jeopardizes the structural strength but also brings great economic losses.Ultrasonic cavitation is expected to solve this problem due to its characteristics of no damage to structures and no pollution.Starting from the phenomenon and mechanism of ultrasonic cleaning,this paper introduces the application of ultrasonic cavitation in ship,pipeline and oil cleaning as well as ballast water treatment.By reviewing the existing studies,limitations such as insufficient ultrasonic parameter studies,lack of uniform cleanliness standards,and insufficient cavitation studies are summarized to provide traceable research ideas for improving ultrasonic cavitation technology and to guide the expansion and improvement of its applications.展开更多
Self-excited oscillating jets(SOJ)are used in several practical applications.Their performances are significantly affected by structural parameters and the target distance.In this study,a geometric model of the SOJ no...Self-excited oscillating jets(SOJ)are used in several practical applications.Their performances are significantly affected by structural parameters and the target distance.In this study,a geometric model of the SOJ nozzle accounting for multiple structural parameters is introduced,then the related cavitation performances and the optimal target distance are investigated using a Large-Eddy Simulation(LES)approach.Results are also provided about an experiment,which was conducted to validate the simulation results.By analyzing the evolution of the vapor volume fraction at the nozzle outlet,a discussion is presented about the effect of the aforementioned structural parameters on the cavitation performances and the target distance.It is shown that the distribution of cavitation clouds at the outlet of the SOJ nozzle displays a non-monotonic trend(first increasing,then decreasing).Under working conditions with an inlet pressure of 4 MPa,a SOJ nozzle outlet/inlet diameter ratio(D_(1)/D_(2))of 1.2,and a chamber diameter ratio(D/L)close to 1.8,the nozzle outlet cavitation performance attains a maximum.The optimal structural parameters correspond to the optimal target distance,which is near 50 mm.The experiments have revealed that the SOJ nozzle with the above parameters displays a good cavitation erosion effect at the target distance of 50 mm,in satisfactory agreement with the numerical simulation results.展开更多
The compressibility of fluids has a profound influence on oscillating bubble dynamics,as characterized by the Mach number.However,current theoretical frameworks for bubbles,whether at the first or second order of the ...The compressibility of fluids has a profound influence on oscillating bubble dynamics,as characterized by the Mach number.However,current theoretical frameworks for bubbles,whether at the first or second order of the Mach number,are primarily confined to scenarios characterized by weak compressibility.Thus,a critical need to elucidate the precise range of applicability for both first-and second-order bubble theories arises.Herein,we investigate the suitability and constraints of bubble theories with different orders through a comparative analysis involving experimental data and numerical simulations.The focal point of our investigation encompasses theories such as the Rayleigh–Plesset,Keller,Herring,and second-order bubble equations.Furthermore,the impact of parameters inherent in the second-order equations is examined.For spherical oscillating bubble dynamics in a free field,our findings reveal that the first-and second-order bubble theories are applicable when Ma≤0.3 and 0.4,respectively.For a single sonoluminescence bubble,we define an instantaneous Mach number,Mai.The second-order theory shows abnormal sensibility when Mai is high,which is negligible when Mai≤0.4.The results of this study can serve as a valuable reference for studying compressible bubble dynamics.展开更多
Cavitation is a common issue in pumps,causing a decrease in pump head,a fall in volumetric efficiency,and an intensification of outlet flow pulsation.It is one of the main hazards that affect the regular operation of ...Cavitation is a common issue in pumps,causing a decrease in pump head,a fall in volumetric efficiency,and an intensification of outlet flow pulsation.It is one of the main hazards that affect the regular operation of the pump.Research on pump cavitation mainly focuses on mixed flow pumps,jet pumps,external spur gear pumps,etc.However,there are few cavitation studies on external herringbone gear pumps.In addition,pumps with different working principles significantly differ in the flow and complexity of the internal flow field.Therefore,it is urgent to study the cavitation characteristics of external herringbone gear pumps.Compared with experimentalmethods,visual research and cavitation area identification are achieved through computation fluid dynamic(CFD),and changing the boundary conditions and shape of the gear rotor is easier.The simulation yields a head error of only 0.003%under different grid numbers,and the deviation between experimental and simulation results is less than 5%.The study revealed that cavitation causes flow pulsation at the outlet,and the cavitation serious area is mainly distributed in the meshing gap and meshing area.Cavitation can be inhibited by reducing the speed,increasing the inlet pressure,and changing the helix angle can be achieved.For example,when the inlet pressure is 5 bar,the maximumgas volume fraction in themeshing area is less than 50%.These results provide a reference for optimizing the design and finding the optimal design parameters to reduce or eliminate cavitation.展开更多
Cavitation is a prevalent phenomenon within the domain of ship and ocean engineering,predominantly occurring in the tail flow fields of high-speed rotating propellers and on the surfaces of high-speed underwater vehic...Cavitation is a prevalent phenomenon within the domain of ship and ocean engineering,predominantly occurring in the tail flow fields of high-speed rotating propellers and on the surfaces of high-speed underwater vehicles.The re-entrant jet and compression wave resulting from the collapse of cavity vapour are pivotal factors contributing to cavity instability.Concurrently,these phenomena significantly modulate the evolution of cavitation flow.In this paper,numerical investigations into cloud cavitation over a Clark-Y hydrofoil were conducted,utilizing the Large Eddy Simulation(LES)turbulence model and the Volume of Fluid(VOF)method within the OpenFOAM framework.Comparative analysis of results obtained at different angles of attack is undertaken.A discernible augmentation in cavity thickness is observed concomitant with the escalation in attack angle,alongside a progressive intensification in pressure at the leading edge of the hydrofoil,contributing to the suction force.These results can serve as a fundamental point of reference for gaining a deeper comprehension of cloud cavitation dynamics.展开更多
SR-AOP(sulfate radical advanced oxidation process)is a novel water treatment method able to eliminate refractory organic pollutants.Hydrodynamic cavitation(HC)is a novel green technology,that can effectively produce s...SR-AOP(sulfate radical advanced oxidation process)is a novel water treatment method able to eliminate refractory organic pollutants.Hydrodynamic cavitation(HC)is a novel green technology,that can effectively produce strong oxidizing sulfate radicals.This paper presents a comprehensive review of the research advancements in these fields and a critical discussion of the principal factors influencing HC-enhanced SR-AOP and the mechanisms of synergistic degradation.Furthermore,some insights into the industrial application of HC/PS are also provided.Current research shows that this technology is feasible at the laboratory stage,but its application on larger scales requires further understanding and exploration.In this review,some attention is also paid to the design of the hydrodynamic cavitation reactor and the related operating parameters.展开更多
In a multi-bubble system, the bubble behavior is modulated by the primary acoustic field and the secondary acoustic field. To explore the translational motion of bubbles in cavitation liquids containing high-concentra...In a multi-bubble system, the bubble behavior is modulated by the primary acoustic field and the secondary acoustic field. To explore the translational motion of bubbles in cavitation liquids containing high-concentration cavitation nuclei,evolutions of bubbles are recorded by a high-speed camera, and translational trajectories of several representative bubbles are traced. It is found that translational motion of bubbles is always accompanied by the fragmentation and coalescence of bubbles, and for bubbles smaller than 10 μm, the possibility of bubble coalescence is enhanced when the spacing of bubbles is less than 30 μm. The measured signals and their spectra show the presence of strong negative pressure, broadband noise,and various harmonics, which implies that multiple interactions of bubbles appear in the region of high-intensity cavitation.Due to the strong coupling effect, the interaction between bubbles is random. A simplified triple-bubble model is developed to explore the interaction patterns of bubbles affected by the surrounding bubbles. Patterns of bubble interaction, such as attraction, repulsion, stable spacing, and rebound of bubbles, can be predicted by the theoretical analysis, and the obtained results are in good agreement with experimental observations. Mass exchange between the liquid and bubbles as well as absorption in the cavitation nuclei also plays an important role in multi-bubble cavitation, which may account for the weakening of the radial oscillations of bubbles.展开更多
A fractal geometric boundary with natural wall features is introduced into a hybrid lattice-Boltzmann-method(LBM)multiphase model. The physical model of cavitation bubble collapse near the irregular geometric wall is ...A fractal geometric boundary with natural wall features is introduced into a hybrid lattice-Boltzmann-method(LBM)multiphase model. The physical model of cavitation bubble collapse near the irregular geometric wall is established to study the thermodynamic characteristics of the bubble collapse. Due to the lack of periodicity, symmetry, spatial uniformity and obvious correlation in the LBM simulation of the bubble collapse near the fractal wall, the morphological analysis based on Minkowski functional is introduced into the thermodynamic investigation of cavitation bubble so as to analyze and obtain the effective information. The results show that the Minkowski functional method can employed to study the temperature information in complex physical fields hierarchically and quantitatively. The high/low temperature region of the cavitation flow is explored, and thermal effect between irregular and fractal geometric wall and cavitation bubble can be revealed. It illustrates that LBM and morphological analysis complement each other, and morphological analysis can also be used as an optional and potential tool in research field of complex multiphase flows.展开更多
Ultrasonic baths and sonochemical reactors are widely used in industrial applications dealing with surface cleaningand chemical synthesis. The processes of erosion, cleaning and structuring of the surface can be typic...Ultrasonic baths and sonochemical reactors are widely used in industrial applications dealing with surface cleaningand chemical synthesis. The processes of erosion, cleaning and structuring of the surface can be typically controlledby changing relevant influential parameters. In particular, in this work, we experimentally investigate theeffect of NaCl concentration (0–5.5 mol/L) on the erosion of an aluminum foil under ultrasonic exposure at afrequency of 28 kHz. Special attention is paid to the determination of cavitation zones and their visualizationusing heat maps. It is found that at low NaCl concentration (0.3 mol/L), the foil destruction rate is higher thanin distilled water. At higher concentrations of salt, cavitation takes place mainly in the upper part of the container.展开更多
The intensification of physicochemical processes in the sonochemical reactor chamber is widely used in problems of synthesis,extraction and separation.One of the most important mechanisms at play in such processes is ...The intensification of physicochemical processes in the sonochemical reactor chamber is widely used in problems of synthesis,extraction and separation.One of the most important mechanisms at play in such processes is the acoustic cavitation due to the non-uniform distribution of acoustic pressure in the chamber.Cavitation has a strong impact on the surface degradation mechanisms.In this work,a numerical calculation of the acoustic pressure distribution inside the reactor chamber was performed using COMSOL Multiphysics.The numerical results have revealed the dependence of the structure of the acoustic pressure field on the boundary conditions for various thicknesses of the piezoelectric transducer.In particular,the amplitude of the acoustic pressure is minimal in the case of absorbing boundaries,and the attenuation becomes more significant as the thickness of the piezoelectric transducer increases.In addition,reflective boundaries play a significant role in the formation and distribution of zones of maximum cavitation activity.展开更多
Hydraulic jetting is a form of fracturing that involves using a high-pressure jet of water to create fractures in the reservoir rock with a nozzle serving as the central component of the hydraulic sandblasting perfora...Hydraulic jetting is a form of fracturing that involves using a high-pressure jet of water to create fractures in the reservoir rock with a nozzle serving as the central component of the hydraulic sandblasting perforation tool.In this study,the flow behavior of the nozzle is simulated numerically in the framework of a SST k-ωturbulence model.The results show that the nozzle structure can significantly influence the jet performance and related cavitation effect.Through orthogonal experiments,the nozzle geometric parameters are optimized,and the following configuration is found accordingly:contraction angle 20°,contraction segment length 6 mm,cylindrical segment diameter 6 mm,cylindrical segment length 12 mm,spread segment length 10 mm,and spread angle 55°.展开更多
The corrosion behavior of 304L stainless steel(SS)in 3.5wt%NaCl solution after different cavitation erosion(CE)times was mainly evaluated using electrochemical noise and potentiostatic polarization techniques.It was f...The corrosion behavior of 304L stainless steel(SS)in 3.5wt%NaCl solution after different cavitation erosion(CE)times was mainly evaluated using electrochemical noise and potentiostatic polarization techniques.It was found that the antagonism effect resulting in the passivation and depassivation of 304L SS had significant distinctions at different CE periods.The passive behavior was predominant during the incubation period of CE where the metastable pitting initiated at the surface of 304L SS.Over the rising period of CE,the 304L SS experienced a transition from passivation to depassivation,leading to the massive growth of metastable pitting and stable pitting.The depassivation of304L SS was found to be dominant at the stable period of CE where serious localized corrosion occurred.展开更多
Cavitating jet is a promising drilling rate improvement technology in both the marine natural gas hydrate (NGH) fluidization exploitation method and the integrated radial jet drilling and completion method. In present...Cavitating jet is a promising drilling rate improvement technology in both the marine natural gas hydrate (NGH) fluidization exploitation method and the integrated radial jet drilling and completion method. In present study, we aim to improve the efficiency of jet erosion and extracting NGH. With a computational fluid dynamics (CFD) method, the pressure, velocity and cavitation field characteristics of organ-pipe cavitating jet (OPCJ) are analysed. The divergent angle, throat length, and divergent length of OPCJ nozzle are preferred to obtain stronger jet cavitation erosion effect. Laboratory experiments of gas hydrate-bearing sediments (GHBS) erosion by OPCJ and conical jet (CJ) are conducted to compare and validate the jet erosion performance. The impinging models of OPCJ and CJ are constructed to study the impact characteristics. Results show that the preferred values of divergent angle, throat length, and divergent length are 15°, 1d, and 3d, respectively, in present simulation conditions. For GHBS, the OPCJ possesses the advantages of high efficiency and low energy consumption. Moreover, the OPCJ has higher penetration efficiency, while showing equivalent penetration ability compared to CJ. During the impinging process, the OPCJ can induce stronger impact pressure and turbulence effect, and also shows stronger chambering effect and bottom cleaning ability compared to CJ. This study presents the erosion performance of OPCJ and CJ on GHBS, and provides preliminary insights on the potential field applications in NGH exploitation.展开更多
To investigate the improvement in the fatigue strength of magnesium alloy by peening methods,magnesium alloy AZ31 was treated by submerged laser peening(SLP),cavitation peening(CP),and shot peening(SP),and the fatigue...To investigate the improvement in the fatigue strength of magnesium alloy by peening methods,magnesium alloy AZ31 was treated by submerged laser peening(SLP),cavitation peening(CP),and shot peening(SP),and the fatigue properties were evaluated by a plane bending fatigue test.In the case of SLP,both the impact induced by laser ablation(LA)and that caused by laser cavitation(LC),which developed after LA,were used.In the present study,the fatigue life at a constant bending stress was examined to determine the suitable coverage.It was found that the fatigue strengths at N=10^(7)for the SLP,CP,and SP specimens treated by each optimum condition were 56%,18%,and 16%higher,respectively,than that of the non-peened(NP)specimen,which was 97 MPa.The key factors in the improvement of fatigue strength by peening methods were work hardening and the introduction of compressive residual stress.展开更多
Cavitation generation methods have been used in multifarious directions because of their diversity,and numerous studies and discussions have been conducted on cavitation generation methods.This study aims to explore t...Cavitation generation methods have been used in multifarious directions because of their diversity,and numerous studies and discussions have been conducted on cavitation generation methods.This study aims to explore the generating mechanism and evolution law of volume alternate cavitation(VAC).In the VAC,liquid water is placed in an airtight container with a variable volume.As the volume alternately changes,the liquid water inside the container continues to cavitate.Then,the mixture turbulence model and in-cylinder dynamic grid model are adopted to conduct computational fluid dynamics simulation of volume alternate cavitation.In the simulation,the cloud images at seven heights on the central axis are monitored,and the phenomenon and mechanism of height and eccentricity are analyzed in detail.By employing the cavitation flow visualization method,the generating mechanism and evolution law of cavitation are revealed.The synergistic effects of experiments and high-speed camera capturing confirm the correctness of the simulation results.In the experiment,the volume change stroke of the airtight container is set to 20 mm,the volume change frequency is 18 Hz,and the shooting frequency of the high-speed camera is set to 10000 FPS.The experimental results indicate that the position of the cavitation phenomenon has a reasonable law during the whole evolution cycle of the cavitation cloud.Also,the volume alternation cycle corresponds to the generation,development,and collapse stages of cavitation bubbles.展开更多
The Ultrasonic cavitation effect has been widely used in mechanical engineering,chemical engineering,biomedicine,and many other fields.The quantitative characterization of ultrasonic cavitation intensity has always be...The Ultrasonic cavitation effect has been widely used in mechanical engineering,chemical engineering,biomedicine,and many other fields.The quantitative characterization of ultrasonic cavitation intensity has always been a difficulty.Based on this,a fluorescence analysis method has been adopted to explore ultrasonic cavitation intensity in this paper.In the experiment of fluorescence intensity measurement,terephthalic acid(TA)was used as the fluorescent probe,ultrasonic power,ultrasonic frequency,and irradiation time were independent variables,and fluorescence intensity and fluorescence peak area were used as experimental results.The collapse of cavitation bubble will cause molecular bond breakage and release·OH,and the non-fluorescent substance TA will form the strong fluorescent substance TAOH with·OH.The spectra of the treated samples were measured by a F-7000 fluorescence spectrophotometer.The results showed that the fluorescence intensity and fluorescence peak area increased rapidly after ultrasonic cavitation treatment,and then increased slowly with the increase of ultrasonic power,which gradually increased with the increase of irradiation time.They first decreased and then increased with the increase of ultrasonic frequency from 20 kHz to 40 kHz.The irradiation time was the most influential factor,and the cavitation intensity of low frequency was higher overall.The fluorescence intensity and fluorescence peak area of the samples increased by 2-20 times after ultrasonic treatment,which could increase from 69 and 5238 to 1387 and 95451,respectively.After the irradiation time exceeded 25 min,the growth rate of fluorescence intensity slowed down,which was caused by the decrease of gas content and TA concentration in the solution.The study quantitatively characterized the cavitation intensity,reflecting the advantages of fluorescence analysis,and provided a basis for the further study of ultra-sonic cavitation.展开更多
In this study,we designed a new,semi-balanced,twisted rudder to reduce the surface cavitation problem of medium-high-speed surface warships.Based on the detached eddy simulation(DES)with the Spalart-Allmaras(SA)model(...In this study,we designed a new,semi-balanced,twisted rudder to reduce the surface cavitation problem of medium-high-speed surface warships.Based on the detached eddy simulation(DES)with the Spalart-Allmaras(SA)model(SA-DES)and the volume of fluid(VOF)method,the hydrodynamic and cavitation performances of an ordinary semi-balanced rudder and semi-balanced twisted rudder at different rudder angles were numerically calculated and compared using the commercial computational fluid dynamics(CFD)software STAR-CCM+with the whole-domain structured grid.The calculation results showed that,under the same working conditions,the maneuverability of the semi-balanced twisted rudder basically remained unchanged compared with that of the ordinary semi-balanced rudder.Furthermore,the surface cavitation range of the semi-balanced twisted rudder was much smaller,and the inception rudder angle of the rudder surface cavitation increased by at least 5°at the maximum speed.In conclusion,the semi-balanced twisted rudder effectively reduced the cavitation of the rudder surface without reducing the rudder effect and exhibited excellent anti-cavitation performance.展开更多
In this paper,after the successful applications to open water propeller performance estimations,the influence of transition sensitive and modified mass transfer models tuned to account for the laminar flow in the pred...In this paper,after the successful applications to open water propeller performance estimations,the influence of transition sensitive and modified mass transfer models tuned to account for the laminar flow in the prediction of the cavitation inception of marine propulsors is investigated from the point of view of the unsteady functioning and induced pressure pulses.The VP1304(also known as PPTC)test case,for which dedicated data were collected during several workshops,is considered first.After preliminary analyses using RANS,also Detached Eddy Simulations(DES)are included to better account for the vortex dynamics and its influence on pressure pulses.Similarly to what observed in uniform inflow,results show a better agreement with the available measurements of propeller performances and confirm the reliability of the proposed approaches for unsteady,non-cavitating,model scale propeller predictions.The overall cavitation pattern is improved too by the application of the transition sensitive correction to the mass transfer model,but the complex dynamics of bubble cavitation observed in experiments prevents quantitatively better predictions in terms of thrust/torque breakdown and induced pressure pulses levels regardless the use of RANS or DES methods.展开更多
Previous investigation on side channel pump mainly concentrates on parameter optimization and internal unsteady vortical flows.However,cavitation is prone to occur in a side channel pump,which is a challenging issue i...Previous investigation on side channel pump mainly concentrates on parameter optimization and internal unsteady vortical flows.However,cavitation is prone to occur in a side channel pump,which is a challenging issue in promoting performance.In the present study,the cavitating flow is investigated numerically by the turbulence model of SAS combined with the Zwart cavitation model.The vapors inside the side channel pump firstly occur in the impeller passage near the inlet and then spread gradually to the downstream passages with the decrease of NPSHa.Moreover,a strong adverse pressure gradient is presented at the end of the cavity closure region,which leads to cavity shedding from the wall.The small scaled vortices in each passage reduce significantly and gather into larger vortices due to the cavitation.Comparing the three terms of vorticity transport equation with the vapor volume fraction and vorticity distributions,it is found that the stretching term is dominant and responsible for the vorticity production and evolution in cavitating flows.In addition,the magnitudes of the stretching term decrease once the cavitation occurs,while the values of dilatation are high in the cavity region and increase with the decreasing NPSHa.Even though the magnitude of the baroclinic torque term is smaller than vortex stretching and dilatation terms,it is important for the vorticity production along the cavity surface and near the cavity closure region.The pressure fluctuations in the impeller and side channel tend to be stronger due to the cavitation.The primary frequency of monitor points in the impeller is 24.94 Hz and in the side channel is 598.05 Hz.They are quite corresponding to the shaft frequency of 25 Hz(fshaft=1/n=25 Hz)and the blade frequency of 600 Hz(fblade=Z/n=600 Hz)respectively.This study complements the investigation on cavitation in the side channel pump,which could provide the theoretical foundation for further optimization of performance.展开更多
基金supported by the Program for National Defense Science and Technology Foundation Strengtheningthe Youth Foundation of Rocket Force University of Engineering(Grant No.2021QN-B014)。
文摘A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.
基金Supported by the National Natural Science Foundation of China(No.52101373)Shenzhen Science and Technology Program(No.CYJ20230807145621043)+2 种基金Postdoctoral Science Foundation of China(No.2021M692629)Young Talent Fund of the University Association for Science and Technology in Shaanxi,China(No.20210417)Fundamental Research Funds for the Central Universities(No.3102021HHZY030009).
文摘Biofouling on ships and offshore structures has always been a difficult problem to solve,which not only jeopardizes the structural strength but also brings great economic losses.Ultrasonic cavitation is expected to solve this problem due to its characteristics of no damage to structures and no pollution.Starting from the phenomenon and mechanism of ultrasonic cleaning,this paper introduces the application of ultrasonic cavitation in ship,pipeline and oil cleaning as well as ballast water treatment.By reviewing the existing studies,limitations such as insufficient ultrasonic parameter studies,lack of uniform cleanliness standards,and insufficient cavitation studies are summarized to provide traceable research ideas for improving ultrasonic cavitation technology and to guide the expansion and improvement of its applications.
基金supported by Key Projects of the Joint Fund of the National Natural Science Foundation of China(U20A20292)The Fundamental Research Funds for the Central Universities(No.JZ2021HGB0090)+2 种基金Key R&D Program of Zhenjiang City(GY2020015)Technology Support Plan(Research on Key Industrial Technologies)(TG202251)Shandong Province Science and Technology SMES Innovation Ability Improvement Project(2023TSGC0005).
文摘Self-excited oscillating jets(SOJ)are used in several practical applications.Their performances are significantly affected by structural parameters and the target distance.In this study,a geometric model of the SOJ nozzle accounting for multiple structural parameters is introduced,then the related cavitation performances and the optimal target distance are investigated using a Large-Eddy Simulation(LES)approach.Results are also provided about an experiment,which was conducted to validate the simulation results.By analyzing the evolution of the vapor volume fraction at the nozzle outlet,a discussion is presented about the effect of the aforementioned structural parameters on the cavitation performances and the target distance.It is shown that the distribution of cavitation clouds at the outlet of the SOJ nozzle displays a non-monotonic trend(first increasing,then decreasing).Under working conditions with an inlet pressure of 4 MPa,a SOJ nozzle outlet/inlet diameter ratio(D_(1)/D_(2))of 1.2,and a chamber diameter ratio(D/L)close to 1.8,the nozzle outlet cavitation performance attains a maximum.The optimal structural parameters correspond to the optimal target distance,which is near 50 mm.The experiments have revealed that the SOJ nozzle with the above parameters displays a good cavitation erosion effect at the target distance of 50 mm,in satisfactory agreement with the numerical simulation results.
基金Supported by the Natural Science Foundation of China under Grant No.12372239the Natural Science Foundation of Heilongjiang Province under Grant No.YQ2022E017。
文摘The compressibility of fluids has a profound influence on oscillating bubble dynamics,as characterized by the Mach number.However,current theoretical frameworks for bubbles,whether at the first or second order of the Mach number,are primarily confined to scenarios characterized by weak compressibility.Thus,a critical need to elucidate the precise range of applicability for both first-and second-order bubble theories arises.Herein,we investigate the suitability and constraints of bubble theories with different orders through a comparative analysis involving experimental data and numerical simulations.The focal point of our investigation encompasses theories such as the Rayleigh–Plesset,Keller,Herring,and second-order bubble equations.Furthermore,the impact of parameters inherent in the second-order equations is examined.For spherical oscillating bubble dynamics in a free field,our findings reveal that the first-and second-order bubble theories are applicable when Ma≤0.3 and 0.4,respectively.For a single sonoluminescence bubble,we define an instantaneous Mach number,Mai.The second-order theory shows abnormal sensibility when Mai is high,which is negligible when Mai≤0.4.The results of this study can serve as a valuable reference for studying compressible bubble dynamics.
基金supported by a Grant(2024-MOIS35-005)of Policy-linked Technology Development Program on Natural Disaster Prevention and Mitigation funded by Ministry of Interior and Safety(MOIS,Korea).
文摘Cavitation is a common issue in pumps,causing a decrease in pump head,a fall in volumetric efficiency,and an intensification of outlet flow pulsation.It is one of the main hazards that affect the regular operation of the pump.Research on pump cavitation mainly focuses on mixed flow pumps,jet pumps,external spur gear pumps,etc.However,there are few cavitation studies on external herringbone gear pumps.In addition,pumps with different working principles significantly differ in the flow and complexity of the internal flow field.Therefore,it is urgent to study the cavitation characteristics of external herringbone gear pumps.Compared with experimentalmethods,visual research and cavitation area identification are achieved through computation fluid dynamic(CFD),and changing the boundary conditions and shape of the gear rotor is easier.The simulation yields a head error of only 0.003%under different grid numbers,and the deviation between experimental and simulation results is less than 5%.The study revealed that cavitation causes flow pulsation at the outlet,and the cavitation serious area is mainly distributed in the meshing gap and meshing area.Cavitation can be inhibited by reducing the speed,increasing the inlet pressure,and changing the helix angle can be achieved.For example,when the inlet pressure is 5 bar,the maximumgas volume fraction in themeshing area is less than 50%.These results provide a reference for optimizing the design and finding the optimal design parameters to reduce or eliminate cavitation.
基金supported by the National Natural Science Foundation of China(Nos.12202011,12332014)China Postdoctoral Science Foundation(No.2022M710190).
文摘Cavitation is a prevalent phenomenon within the domain of ship and ocean engineering,predominantly occurring in the tail flow fields of high-speed rotating propellers and on the surfaces of high-speed underwater vehicles.The re-entrant jet and compression wave resulting from the collapse of cavity vapour are pivotal factors contributing to cavity instability.Concurrently,these phenomena significantly modulate the evolution of cavitation flow.In this paper,numerical investigations into cloud cavitation over a Clark-Y hydrofoil were conducted,utilizing the Large Eddy Simulation(LES)turbulence model and the Volume of Fluid(VOF)method within the OpenFOAM framework.Comparative analysis of results obtained at different angles of attack is undertaken.A discernible augmentation in cavity thickness is observed concomitant with the escalation in attack angle,alongside a progressive intensification in pressure at the leading edge of the hydrofoil,contributing to the suction force.These results can serve as a fundamental point of reference for gaining a deeper comprehension of cloud cavitation dynamics.
文摘SR-AOP(sulfate radical advanced oxidation process)is a novel water treatment method able to eliminate refractory organic pollutants.Hydrodynamic cavitation(HC)is a novel green technology,that can effectively produce strong oxidizing sulfate radicals.This paper presents a comprehensive review of the research advancements in these fields and a critical discussion of the principal factors influencing HC-enhanced SR-AOP and the mechanisms of synergistic degradation.Furthermore,some insights into the industrial application of HC/PS are also provided.Current research shows that this technology is feasible at the laboratory stage,but its application on larger scales requires further understanding and exploration.In this review,some attention is also paid to the design of the hydrodynamic cavitation reactor and the related operating parameters.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974232 and 12374441)the Fund from the Yulin Science and Technology Bureau,China(Grant No.CXY-2022-178).
文摘In a multi-bubble system, the bubble behavior is modulated by the primary acoustic field and the secondary acoustic field. To explore the translational motion of bubbles in cavitation liquids containing high-concentration cavitation nuclei,evolutions of bubbles are recorded by a high-speed camera, and translational trajectories of several representative bubbles are traced. It is found that translational motion of bubbles is always accompanied by the fragmentation and coalescence of bubbles, and for bubbles smaller than 10 μm, the possibility of bubble coalescence is enhanced when the spacing of bubbles is less than 30 μm. The measured signals and their spectra show the presence of strong negative pressure, broadband noise,and various harmonics, which implies that multiple interactions of bubbles appear in the region of high-intensity cavitation.Due to the strong coupling effect, the interaction between bubbles is random. A simplified triple-bubble model is developed to explore the interaction patterns of bubbles affected by the surrounding bubbles. Patterns of bubble interaction, such as attraction, repulsion, stable spacing, and rebound of bubbles, can be predicted by the theoretical analysis, and the obtained results are in good agreement with experimental observations. Mass exchange between the liquid and bubbles as well as absorption in the cavitation nuclei also plays an important role in multi-bubble cavitation, which may account for the weakening of the radial oscillations of bubbles.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11874140 and 12174085)Basic Science (Natural Science) Research Project for the Universities of Jiangsu Province (Grant No. 23KJD140002)the Natural Science Foundation of Nantong (Grant No. JC2023081)。
文摘A fractal geometric boundary with natural wall features is introduced into a hybrid lattice-Boltzmann-method(LBM)multiphase model. The physical model of cavitation bubble collapse near the irregular geometric wall is established to study the thermodynamic characteristics of the bubble collapse. Due to the lack of periodicity, symmetry, spatial uniformity and obvious correlation in the LBM simulation of the bubble collapse near the fractal wall, the morphological analysis based on Minkowski functional is introduced into the thermodynamic investigation of cavitation bubble so as to analyze and obtain the effective information. The results show that the Minkowski functional method can employed to study the temperature information in complex physical fields hierarchically and quantitatively. The high/low temperature region of the cavitation flow is explored, and thermal effect between irregular and fractal geometric wall and cavitation bubble can be revealed. It illustrates that LBM and morphological analysis complement each other, and morphological analysis can also be used as an optional and potential tool in research field of complex multiphase flows.
文摘Ultrasonic baths and sonochemical reactors are widely used in industrial applications dealing with surface cleaningand chemical synthesis. The processes of erosion, cleaning and structuring of the surface can be typically controlledby changing relevant influential parameters. In particular, in this work, we experimentally investigate theeffect of NaCl concentration (0–5.5 mol/L) on the erosion of an aluminum foil under ultrasonic exposure at afrequency of 28 kHz. Special attention is paid to the determination of cavitation zones and their visualizationusing heat maps. It is found that at low NaCl concentration (0.3 mol/L), the foil destruction rate is higher thanin distilled water. At higher concentrations of salt, cavitation takes place mainly in the upper part of the container.
文摘The intensification of physicochemical processes in the sonochemical reactor chamber is widely used in problems of synthesis,extraction and separation.One of the most important mechanisms at play in such processes is the acoustic cavitation due to the non-uniform distribution of acoustic pressure in the chamber.Cavitation has a strong impact on the surface degradation mechanisms.In this work,a numerical calculation of the acoustic pressure distribution inside the reactor chamber was performed using COMSOL Multiphysics.The numerical results have revealed the dependence of the structure of the acoustic pressure field on the boundary conditions for various thicknesses of the piezoelectric transducer.In particular,the amplitude of the acoustic pressure is minimal in the case of absorbing boundaries,and the attenuation becomes more significant as the thickness of the piezoelectric transducer increases.In addition,reflective boundaries play a significant role in the formation and distribution of zones of maximum cavitation activity.
基金The authors gratefully acknowledge the financial support by the Marine Economy Development Foundation of Guangdong Province“Technical Support for Stimulation and Testing of Gas Hydrate Reservoirs”(GDNRC[2022]44).
文摘Hydraulic jetting is a form of fracturing that involves using a high-pressure jet of water to create fractures in the reservoir rock with a nozzle serving as the central component of the hydraulic sandblasting perforation tool.In this study,the flow behavior of the nozzle is simulated numerically in the framework of a SST k-ωturbulence model.The results show that the nozzle structure can significantly influence the jet performance and related cavitation effect.Through orthogonal experiments,the nozzle geometric parameters are optimized,and the following configuration is found accordingly:contraction angle 20°,contraction segment length 6 mm,cylindrical segment diameter 6 mm,cylindrical segment length 12 mm,spread segment length 10 mm,and spread angle 55°.
基金financially supported of the National Natural Science Foundation of China (Nos.52101105 and 51975263)。
文摘The corrosion behavior of 304L stainless steel(SS)in 3.5wt%NaCl solution after different cavitation erosion(CE)times was mainly evaluated using electrochemical noise and potentiostatic polarization techniques.It was found that the antagonism effect resulting in the passivation and depassivation of 304L SS had significant distinctions at different CE periods.The passive behavior was predominant during the incubation period of CE where the metastable pitting initiated at the surface of 304L SS.Over the rising period of CE,the 304L SS experienced a transition from passivation to depassivation,leading to the massive growth of metastable pitting and stable pitting.The depassivation of304L SS was found to be dominant at the stable period of CE where serious localized corrosion occurred.
基金financially supported by National Natural Science Foundation of China(No.52174009 and No.51827804)Marine Economy Development Foundation of Guangdong Province(GDNRC[2022]44)“Technical Support for Stimulation and Testing of Gas Hydrate Reservoirs”.
文摘Cavitating jet is a promising drilling rate improvement technology in both the marine natural gas hydrate (NGH) fluidization exploitation method and the integrated radial jet drilling and completion method. In present study, we aim to improve the efficiency of jet erosion and extracting NGH. With a computational fluid dynamics (CFD) method, the pressure, velocity and cavitation field characteristics of organ-pipe cavitating jet (OPCJ) are analysed. The divergent angle, throat length, and divergent length of OPCJ nozzle are preferred to obtain stronger jet cavitation erosion effect. Laboratory experiments of gas hydrate-bearing sediments (GHBS) erosion by OPCJ and conical jet (CJ) are conducted to compare and validate the jet erosion performance. The impinging models of OPCJ and CJ are constructed to study the impact characteristics. Results show that the preferred values of divergent angle, throat length, and divergent length are 15°, 1d, and 3d, respectively, in present simulation conditions. For GHBS, the OPCJ possesses the advantages of high efficiency and low energy consumption. Moreover, the OPCJ has higher penetration efficiency, while showing equivalent penetration ability compared to CJ. During the impinging process, the OPCJ can induce stronger impact pressure and turbulence effect, and also shows stronger chambering effect and bottom cleaning ability compared to CJ. This study presents the erosion performance of OPCJ and CJ on GHBS, and provides preliminary insights on the potential field applications in NGH exploitation.
基金This work was partly supported by JSPS KAKENHI,Grant Numbers 20H02021 and 22KK0050.
文摘To investigate the improvement in the fatigue strength of magnesium alloy by peening methods,magnesium alloy AZ31 was treated by submerged laser peening(SLP),cavitation peening(CP),and shot peening(SP),and the fatigue properties were evaluated by a plane bending fatigue test.In the case of SLP,both the impact induced by laser ablation(LA)and that caused by laser cavitation(LC),which developed after LA,were used.In the present study,the fatigue life at a constant bending stress was examined to determine the suitable coverage.It was found that the fatigue strengths at N=10^(7)for the SLP,CP,and SP specimens treated by each optimum condition were 56%,18%,and 16%higher,respectively,than that of the non-peened(NP)specimen,which was 97 MPa.The key factors in the improvement of fatigue strength by peening methods were work hardening and the introduction of compressive residual stress.
基金Supported by National Nature Science Foundation of China(Grant No.51575245)Jiangsu Provincial Key research and development program(Grant No.BE2015134)Zhenjiang Municipal Key Research and Development Project(Grant No.KZ2020001).
文摘Cavitation generation methods have been used in multifarious directions because of their diversity,and numerous studies and discussions have been conducted on cavitation generation methods.This study aims to explore the generating mechanism and evolution law of volume alternate cavitation(VAC).In the VAC,liquid water is placed in an airtight container with a variable volume.As the volume alternately changes,the liquid water inside the container continues to cavitate.Then,the mixture turbulence model and in-cylinder dynamic grid model are adopted to conduct computational fluid dynamics simulation of volume alternate cavitation.In the simulation,the cloud images at seven heights on the central axis are monitored,and the phenomenon and mechanism of height and eccentricity are analyzed in detail.By employing the cavitation flow visualization method,the generating mechanism and evolution law of cavitation are revealed.The synergistic effects of experiments and high-speed camera capturing confirm the correctness of the simulation results.In the experiment,the volume change stroke of the airtight container is set to 20 mm,the volume change frequency is 18 Hz,and the shooting frequency of the high-speed camera is set to 10000 FPS.The experimental results indicate that the position of the cavitation phenomenon has a reasonable law during the whole evolution cycle of the cavitation cloud.Also,the volume alternation cycle corresponds to the generation,development,and collapse stages of cavitation bubbles.
基金Supported by National Natural Science Foundation of China(Grant Nos.52005455,51975540)Shanxi Provincial Central Guidance on Local Science and Technology Development Fund of China(Grant No.YDZJSX2022C005).
文摘The Ultrasonic cavitation effect has been widely used in mechanical engineering,chemical engineering,biomedicine,and many other fields.The quantitative characterization of ultrasonic cavitation intensity has always been a difficulty.Based on this,a fluorescence analysis method has been adopted to explore ultrasonic cavitation intensity in this paper.In the experiment of fluorescence intensity measurement,terephthalic acid(TA)was used as the fluorescent probe,ultrasonic power,ultrasonic frequency,and irradiation time were independent variables,and fluorescence intensity and fluorescence peak area were used as experimental results.The collapse of cavitation bubble will cause molecular bond breakage and release·OH,and the non-fluorescent substance TA will form the strong fluorescent substance TAOH with·OH.The spectra of the treated samples were measured by a F-7000 fluorescence spectrophotometer.The results showed that the fluorescence intensity and fluorescence peak area increased rapidly after ultrasonic cavitation treatment,and then increased slowly with the increase of ultrasonic power,which gradually increased with the increase of irradiation time.They first decreased and then increased with the increase of ultrasonic frequency from 20 kHz to 40 kHz.The irradiation time was the most influential factor,and the cavitation intensity of low frequency was higher overall.The fluorescence intensity and fluorescence peak area of the samples increased by 2-20 times after ultrasonic treatment,which could increase from 69 and 5238 to 1387 and 95451,respectively.After the irradiation time exceeded 25 min,the growth rate of fluorescence intensity slowed down,which was caused by the decrease of gas content and TA concentration in the solution.The study quantitatively characterized the cavitation intensity,reflecting the advantages of fluorescence analysis,and provided a basis for the further study of ultra-sonic cavitation.
基金Supported by the National Natural Science Foundation of China under Grant No.51579243.
文摘In this study,we designed a new,semi-balanced,twisted rudder to reduce the surface cavitation problem of medium-high-speed surface warships.Based on the detached eddy simulation(DES)with the Spalart-Allmaras(SA)model(SA-DES)and the volume of fluid(VOF)method,the hydrodynamic and cavitation performances of an ordinary semi-balanced rudder and semi-balanced twisted rudder at different rudder angles were numerically calculated and compared using the commercial computational fluid dynamics(CFD)software STAR-CCM+with the whole-domain structured grid.The calculation results showed that,under the same working conditions,the maneuverability of the semi-balanced twisted rudder basically remained unchanged compared with that of the ordinary semi-balanced rudder.Furthermore,the surface cavitation range of the semi-balanced twisted rudder was much smaller,and the inception rudder angle of the rudder surface cavitation increased by at least 5°at the maximum speed.In conclusion,the semi-balanced twisted rudder effectively reduced the cavitation of the rudder surface without reducing the rudder effect and exhibited excellent anti-cavitation performance.
文摘In this paper,after the successful applications to open water propeller performance estimations,the influence of transition sensitive and modified mass transfer models tuned to account for the laminar flow in the prediction of the cavitation inception of marine propulsors is investigated from the point of view of the unsteady functioning and induced pressure pulses.The VP1304(also known as PPTC)test case,for which dedicated data were collected during several workshops,is considered first.After preliminary analyses using RANS,also Detached Eddy Simulations(DES)are included to better account for the vortex dynamics and its influence on pressure pulses.Similarly to what observed in uniform inflow,results show a better agreement with the available measurements of propeller performances and confirm the reliability of the proposed approaches for unsteady,non-cavitating,model scale propeller predictions.The overall cavitation pattern is improved too by the application of the transition sensitive correction to the mass transfer model,but the complex dynamics of bubble cavitation observed in experiments prevents quantitatively better predictions in terms of thrust/torque breakdown and induced pressure pulses levels regardless the use of RANS or DES methods.
基金National Natural Science Foundation of China(Grant No.52279086)Yunnan Provincial Ranking the Top of the List for Science and Technology Projects of China(Grant No.202204BW050001)。
文摘Previous investigation on side channel pump mainly concentrates on parameter optimization and internal unsteady vortical flows.However,cavitation is prone to occur in a side channel pump,which is a challenging issue in promoting performance.In the present study,the cavitating flow is investigated numerically by the turbulence model of SAS combined with the Zwart cavitation model.The vapors inside the side channel pump firstly occur in the impeller passage near the inlet and then spread gradually to the downstream passages with the decrease of NPSHa.Moreover,a strong adverse pressure gradient is presented at the end of the cavity closure region,which leads to cavity shedding from the wall.The small scaled vortices in each passage reduce significantly and gather into larger vortices due to the cavitation.Comparing the three terms of vorticity transport equation with the vapor volume fraction and vorticity distributions,it is found that the stretching term is dominant and responsible for the vorticity production and evolution in cavitating flows.In addition,the magnitudes of the stretching term decrease once the cavitation occurs,while the values of dilatation are high in the cavity region and increase with the decreasing NPSHa.Even though the magnitude of the baroclinic torque term is smaller than vortex stretching and dilatation terms,it is important for the vorticity production along the cavity surface and near the cavity closure region.The pressure fluctuations in the impeller and side channel tend to be stronger due to the cavitation.The primary frequency of monitor points in the impeller is 24.94 Hz and in the side channel is 598.05 Hz.They are quite corresponding to the shaft frequency of 25 Hz(fshaft=1/n=25 Hz)and the blade frequency of 600 Hz(fblade=Z/n=600 Hz)respectively.This study complements the investigation on cavitation in the side channel pump,which could provide the theoretical foundation for further optimization of performance.