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Cavitation Inception - DOAJ

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Last Updated: 06 August 2022

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Correlation between Pressure Minima and Cavitation Inception Numbers: Fundamentals and Hydrofoil Flows

Although modern CFD technologies for fully turbulent flows accurately forecast pressure distribution around blade-free blades and with cavities of length comparable to the blade size, blade cavitation inception is a difficult challenge for these devices. With the known pressure distribution along the blade region, there could be the possibility of considering the true 3D flow around the blade edges of blades as a 2D flow; the cavitation inception number is estimated in this 2D cavitation flow; and correlations between this number and the pressure minimum in cavitation-free flow around the same region are established.

Source link: https://doi.org/10.3390/jmse10070871


Cavitation Inception on Hydrokinetic Turbine Blades Shrouded by Diffuser

Diffuser technology embedded within hydrokinetic rotors can enhance the conversion of the fluid's kinetic energy into shaft power, according to Diffuser technology. However, rotor blades are prone to the phenomenon of cavitation, which can reduce overall power quality. The authors are unaware of any other research published in the literature investigating the effects of u03b7 d and C T d on the cavitation of shrouded hydrokinetic blades. The model uses the Blade Element Momentum Theory to find optimized blade geometry in order to minimize or even avoid the occurrence of cavitation. An investigation of the existing model with and without a diffuser was carried out to see the changes in the optimized geometry in terms of chord and twist angle distribution. In addition, the improved optimization system will completely eliminate the cavitation process, making it a good substitute for the manufacture of diffuser-augmented hydrokinetic blades free of cavitation.

Source link: https://doi.org/10.3390/su14127067


Acoustic Detection of Cavitation Inception

An experimental research has been carried out in order to look at the noise generated by various cavitating sources in order to determine the reliability of noise tests for detecting cavitation. Measurements have been conducted to determine the onset of cavitau00action in a water tunnel under a variety of operating conditions. The onu00acset of cavitation was determined visually by a Perspex side of the water tunnel's operational section. Moreover, a theoretical analysis of the pressure radiating from the cavitation nuclei at their critical radii and frequency was presented. Tests showed that, generally, at the time of visual inception, there was a marked rise in the sound pressure level in the high-frequency noise, at least, at the time of visual incepation, although lower-frequency noise inu00acation increased as the cavitation progressed. The results showed that the experimental findings of inception confirm the noise measurements.

Source link: https://doaj.org/article/4051708a40764225a240d4379b94283a


Experimental and Numerical Study of Cavitation Number Limitations for Hydrodynamic Cavitation Inception Prediction

The production, expansion, and subsequent destruction of vapor bubbles in a moving liquid is Hydrodynamic cavitation. The cavitation number is a measure used to estimate cavitation and its potential consequences. In this study, the RANS SST k u2013_u03c9 turbulence model was used to predict turbulent flow in ANSYS Fluent, and RANS SST ku2013u03c9 turbulence model was used. It was found that cavitation inception was sensitive to changes in nozzle geometry, and that, since geometrical parameters are not included in the cavitation number formula, cavitation inception rates can be different at the same cavitation number.

Source link: https://doi.org/10.3390/fluids7060198


Optimization for Cavitation Inception Performance of Pump-Turbine in Pump Mode Based on Genetic Algorithm

Cavitation is a negative factor of hydraulic machinery because of its harmful effects on the operation's stability and safety. The geometry of blade leading edge is determining the local flow separation, which also influences the size and position of pressure drop. Hence, the optimization of leading edge shape is also helpful in the enhancement of cavitation inception results. With the increase of the minimum pressure coefficient, the pressure drop location had moved downstream. Experimental verifications also showed a significant improvement in cavitation inception results, which is evidently enhanced.

Source link: https://doi.org/10.1155/2014/234615


Improved Prediction of Sheet Cavitation Inception Using Bridged Transition Sensitive Turbulence Model and Cavitation Model

Laminar boundary layer flow separation under Reynolds numbers systems with transitional flow can be influenced by sheet cavitation inception. The local correlation based transition model, u03b3 R e u03b8 transition model, has been shown to predict laminar separation and subsequent boundary layer transition for non-cavitating flows. The predicted laminar separation of a U03B3 e U2312 R e u03b8 transition model is expanded in this report to increase sheet cavitation results on hydrofoils and model scale marine propellers, according to the present study. The open case of the PPTC VP1304 model scale marine propeller tested on an inclined shaft is investigated as a reference case.

Source link: https://doi.org/10.3390/jmse9121343


Optimization of the critical overlap length of hudraulic distributors regarding cavitation inception

Abstract of the present paper The aim of this paper is to increase the overlap length in various types of hydraulic valves. The intention of the present study was to generalize the frequency length modeling of the overlap length to various manufacturers and to determine the minimum length at cavitation inception. The results reveal that the pressure losses in rotating distributors and other types of distributors are similar, including the slide-valves that are the overwhelming majority of hydraulic distributors. The overlap length has a greater effect on the cavitation formation than the distributor rotation speed, according to the manufacturer. Article Highlights The pressure losses in a rotary distributor and a slide-valve can be described in a similar way. The overlap length has a significant effect on the cavitation formation, more than rotation speed.

Source link: https://doi.org/10.1007/s42452-021-04756-5


The Cavitation Nuclei Transient Characteristics of Lennard-Jones Fluid in Cavitation Inception

We used mathematical modeling and molecular dynamics simulation to investigate Lennard-Jones fluid with different initial cavitation nuclei under the NVT-constant ensemble in this paper, since cavitation nuclei transient characteristics in cavitation inception. The results revealed that the liquid molecules would enter the cavitation nuclei, which contributed to the formation of cavitation nuclei in cavitation inception, owing to decrease in liquid local pressure. The molecular potential energy of the cavitation nuclei part was higher in the cavitation nuclei portion, according to the study, though liquid molecular potential energy rises at a rapid rate at the start of the cavitation nuclei rise. The consistency of the liquid and the surface layer changes more apparent, but the amount of vapor in the bubble changes insignificantly.

Source link: https://doi.org/10.2478/pomr-2018-0077


Numerical Study on Tip Vortex Cavitation Inception on a Foil

The initiation of tip vortex cavitation in shallow water has been predicted by a numerical simulation in this paper, and a new scaling scheme with variable exponent has also been suggested for the cavitation inception index. Models in the turbulence layer of the tip region, where the tip vortex is grown, behaved differently, resulting in different pressure and velocity fields in the vortex region. The tip vortex cavitation inception numbers for the foil, which were predicted using both wetted and cavitating flow simulation methods, were estimated using both wetted and cavitation flow simulation methods, indicating a good correlation. The new cavitation scaling exponents were also found to have new empirical connections as a result of the Reynolds number substitutable for the two common constant scaling exponents. This scaling model explained how the scaling law evolves with the Reynolds number and produced a more accurate scaling number for any given Reynolds number under turbulent flow conditions, as shown in the scaling model.

Source link: https://doi.org/10.3390/app11167332


Stability of Air Nucleus in Liquid Water and Cavitation Inception on Marine Engineering

The computational domain of water molecules with air nucleus was investigated using molecular dynamics simulation, and the transient characteristics of air nucleus in liquid water were determined in order to investigate air nucleus stability in seawater and cavitation. The results revealed that an air nucleus of a particular mass would maintain the dynamic equilibrium in liquid water. When the nuclei radius was stable in water, the internal density of air nuclei was positively correlated with the nuclei radius.

Source link: https://doi.org/10.2478/pomr-2018-0119

* Please keep in mind that all text is summarized by machine, we do not bear any responsibility, and you should always check original source before taking any actions

* Please keep in mind that all text is summarized by machine, we do not bear any responsibility, and you should always check original source before taking any actions