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The purpose of this paper is to investigate the effects of surface topography, including surface roughness, waviness and taper, on the cavitation of liquid film lubricated mechanical seals (LFL-MS).

A universal governing equation considering cavitation is established, and an equivalent relative density is defined to characterize the cavitation degree. The equation is discretized by the finite volume method and solved by the Gauss–Seidel relaxation scheme.

Results indicate that both radial length and a circumferential width of the cavitation zone and cavitation degree are affected significantly by the waviness amplitude and taper, but the effect of surface roughness is limited.

Effect mechanism of surface topography on the cavitation of LFL-MS is investigated and cavitation degree is reflected by an equivalent relative density. The results further help to comprehensively explore the cavitation mechanism.

The purpose of this paper is to study the effects of operating conditions including process coefficient, lubricant viscosity and cavitation pressure on the cavitation of spiral groove liquid-film seal (SG-LFS).

A mathematical model of SG-LFS is established based on the JFO boundary and a relative density is introduced. The universal governing equation after a coordinate transformation is discretized by the FVM method and solved by the Gauss-Seidel relaxation scheme.

The results indicate that the two-dimensional size of cavitation and cavitation degree are affected significantly by the process coefficient and lubricant viscosity but the effect of cavitation pressure can be ignored.

The effect mechanisms of operating conditions on the cavitation of SG-LFS are studied by the JFO boundary and cavitation degree characterized by a relative density. The results presented are helpful to perfect and deeply understand the cavitation mechanism of liquid-film seal.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2020-0083/

The purpose of this paper is to accurately predict the cavitation performance of a cryogenic pump and reveal the influence of the inlet pressure, the surface roughness and the flow rate on the cavitation performance.

Firstly, the Zwart cavitation model was modified by considering the thermodynamic effect. Secondly, the feasibility of the modified model was validated by the cavitation test of a hydrofoil. Thirdly, the effects of the inlet pressure, the surface roughness and the flow rate on cavitation flow in the cryogenic pump were studied by using the modified cavitation model.

The modified cavitation model can predict the cavitation performance of the cryogenic pump more accurately than the Zwart cavitation model. The thermodynamic effect inhibits cavitation development to a certain extent. The higher the vapor volume fraction, the lower the pressure and the lower the temperature. At the initial stage of the cavitation, the head increases first and then decreases with the increase of the roughness. When the cavitation develops to a certain degree, the head decreases with the increase of the roughness. With the decrease of the flow rate, the hydraulic loss increases and the cavitation at the impeller intensifies.

A cavitation model considering the thermodynamic effect is proposed. The mechanism of the influence of the roughness on the performance of the cryogenic pump is revealed from two aspects. Taking the hydraulic loss as a bridge, the relationships among flow rates, vapor volume fractions, streamlines, temperatures and pressures are established.

The purpose of this paper is to study the transient cavitation process in torque converters with a particular focus on cavitation suppression with a passive flow control technique.

The transient fluid field in a torque converter was simulated by RANS-based computational fluid dynamics (CFD) in a full three-dimensional (3D) model. A homogeneous Rayleigh–Plesset cavitation model was used to simulate the transient cavitation process and the results were validated with test data. Various secondary flow passages (SFP) were applied to the stator blade. The cavitation behavior and hydrodynamic performance were simulated and compared to investigate the effect of SFP geometries on cavitation suppression.

Presented results show that cavitation in the torque converter is highly unstable at stall operating condition because of the combination of a high incidence angle and high flow velocity. The addition of an SFP to the stator blade produces a disruption of the re-entrant jet and reduces the overall degree of cavitation, consequently inhibiting the unstable cavitation and reducing performance degradation.

This paper provides unique insights into the complicated transient cavitation flow patterns found in torque converters and introduces effective passive flow control techniques useful to researchers and engineers in the areas of fluid dynamics and turbomachinery.

This paper aims to study the influence of microparticles on the surface cavitation behavior of 2Cr3WMoV steel; microparticle suspensions of different concentration, particle size, material and shape were prepared based on ultrasonic vibration cavitation experimental device.

2Cr3WMoV steel was taken as the research object for ultrasonic cavitation experiment. The morphology, quantity and distribution of cavitation pits were observed and analyzed by metallographic microscope and scanning electron microscope.

The study findings showed that the surface cavitation process produced pinhole cavitation pits on the surface of 2Cr3WMoV steel. High temperature in the process led to oxidation and carbon precipitation on the material surface, resulting in the “rainbow ring” cavitation morphology. Both the concentration and size of microparticles affected the number of pits on the material surface. When the concentration of microparticles was 1 g/L, the number of pits reached the maximum, and when the size of microparticles was 20 µm, the number of pits reached the minimum. The microparticles of Fe3O4, Al2O3, SiC and SiO2 all increased the number of pits on the surface of 2Cr3WMoV steel. In addition, the distribution of pits of spherical microparticles was more concentrated than that of irregularly shaped microparticles in turbidity.

Most of the current studies have not systematically focused on the effect of each factor of microparticles on the cavitation behavior when they act separately, and the results of the studies are more scattered and varied. At the same time, it has not been found to carry out the study of microparticle cavitation with 2Cr3WMoV steel as the research material, and there is a lack of relevant cavitation morphology and experimental data.

The purpose of this study is to determine the cavitation flow characteristics of the high-pressure differential control valve. The relationship between cavitation, flow coefficient and spool angle is obtained. By analyzing the relationship between different spool angles and energy loss, the energy loss at different spool angles is predicted.

A series of numerical simulations were performed to study the cavitation problem of a high-pressure differential control valve using the RNG k–e turbulence model and the Zwart cavitation model. The flow states and energy distribution at different spool angles were analyzed under specific working conditions.

The cavitation was the weakest when the spool angle was 120° or the outlet pressure was 8 MPa. The pressure and speed fluctuations of the valve in the throttle section were greater than those at other locations. By calculating the entropy production rate, the reason and location of valve energy loss are analyzed. The energy loss near the throttling section accounts for about 92.7% of the total energy loss. According to the calculated energy loss relationship between different regions of the spool angle, the relationship between any spool angle and energy loss in the [80,120] interval is proposed.

This study analyzes the cavitation flow characteristics of the high-pressure differential control valve and provides the law of energy loss in the valve through the analysis method of entropy. The relationship between spool angle and energy loss under cavitation is finally proposed. The research results are expected to provide a theoretical basis for the optimal design of valves.

Cavitation erosion has always been a common technical problem in a hydraulic discharging structure. This paper aims to investigate the cavitation erosion behavior of hydraulic concrete under high-speed flow.

A high-speed and high-pressure venturi cavitation erosion generator was used to simulate the strong cavitation. The characteristics of hydrodynamic loads of cavitation bubble collapse zone, the failure characteristics and the erosion development process of concrete were investigated. The main influencing factors of cavitation erosion were discussed.

The collapse of the cavitation bubble group produced a high frequency, continuous and unsteady pulse load on the wall of concrete, which was more likely to cause fatigue failure of concrete materials. The cavitation action position and the main frequency of impact load were greatly affected by the downstream pressure. A power exponential relationship between cavitation load, cavitation erosion and flow speed was observed. With the increase of concrete strength, the degree of damage of cavitation erosion was approximately linearly reduced.

After cavitation erosion, a skeleton structure was formed by the accumulation of granular particles, and the relatively independent bulk structure of the surface differed from the flake structure formed after abrasion.

The purpose of this paper is to study the cavitation erosion stages of AA5083 by electrochemical noise (EN).

EN technology including noise resistance and fast Fourier transform were used to characterize the electrochemical process during the cavitation erosion process.

AA5083 suffers from uniform corrosion during the cavitation erosion process. The whole cavitation erosion process can be divided into three stages: incubation stage, acceleration stage and steady-state stage. EN signals showed obvious differences in different stages of cavitation erosion.

EN technique is a suitable method that can be used to study cavitation erosion mechanism and identify cavitation erosion stages.

Hydroelectric power is widely used because it is environmental friendly, renewable and green. The cavitation is an inevitable phenomenon during the operation of hydro turbine, which is related to the efficiency and service life of the unit. This paper aims to discriminate the phenomenon of the incipient cavitation, prevent the early destruction and avoid the irreversible damage to hydro turbine.

The paper tries to find out the characteristics of cavitation entirely through a variety of features. The method comprises collection of the signals using a hydrophone, acceleration sensor and acoustic emission sensor; analyzing cavitation signal by using the way of wavelet time-frequency, peak factor and power spectral density; and comparing the different wavelet basis for analyzing signals and find the most suitable one.

The analyzed results show that the wavelet basis of morlet is more suitable for the cavitation signals. The hydrophone can distinguish the different operating conditions and discriminate the difference between the phenomenon of incipient cavitation and the other state of cavitation. The results show that when the hydrophone and acceleration sensors are used, the accuracy rate goes up to 75 per cent, which meets the requirements for the detection for incipient cavitation.

This paper focuses on finding the best sensor to discriminate the operating state of incipient cavitation to prevent early destruction.

The purpose of this paper is to study the mechanism and suppression of instabilities induced by cavitating flow around a three-dimensional hydrofoil with a particular focus on cavitation control with a slot.

The transient cavitating flow around a Clark-Y hydrofoil was investigated using a transport-equation-based cavitation model and the stress-blended eddy simulation model was used to capture the flow turbulence. A homogeneous Rayleigh–Plesset cavitation model was used to model the transient cavitation process and the results were validated with test data. A slot was applied to the hydrofoil to suppress cavitation instabilities, and various slot widths and exit locations were applied to the blade and the cavitation behavior, as well as drag/lift forces, were simulated and compared to investigate the effects of slot geometries on cavitation suppression.

The large eddy simulation based turbulence model was able to capture the interactions between the cavitation and turbulence. Moreover, the simulation revealed that the re-entrant jet was responsible for the periodic shedding of cavities. The results indicated that a slot was able to mitigate or even suppress cavitation-induced instabilities. A jet flow was generated at the slot exit and disturbed the re-entrant jet. If the slot geometry was properly designed, the jet could block the re-entrant jet and suppress the unsteady cavitation behavior.

This study provides unique insights into the complicated transient cavitation flows around a three-dimensional hydrofoil and introduces an effective passive cavitation control technique useful to researchers and engineers in the areas of fluid dynamics and turbomachinery.