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

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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

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

To assess a modified PANS model, the cloud cavitating flow around a Clark-y hydrofoil was investigated. The original PANS turbulence model was modified by introducing a density function into turbulence viscosity coefficient considering the vapor and liquid densities in the cavitating region. By simulating the cavitating flow with different values of controls parameter fk in the modified model, the time evolutions of the cloud cavities, and the lift force of the hydrofoil were obtained and compared with experimental results. The simulation results shown that similar to the original PANS model, the modified one can resolve more turbulent vortex scales with decreasing fk and predict the unsteady characteristics of cloud cavitating flow well. Moreover, the modified model can accurately obtain the interaction between the cavity and re-entrant jet to capture the process of cavity break-off and shedding with various scales. And the fluctuation of the lift force got from the simulation is close to the experimental data. [ABSTRACT FROM AUTHOR]

The unsteady cavitating flows around a Clark-Y hydromantic hydrofoil is studied by using particle imaging velocimetry (PIV) system. It is used to measure the cavity shapes and velocity and vorticity fields. The experiment results show that, firstly, with the decrease of the cavitation number, different flow structure characteristics can be observed in the cavitating flows, for unsteady cloud cavitating, a selfoscillation behavior of the whole sheet cavitation is obtained, with large length fluctuations and vapor cloud shedding; as the flow structure changes, there are obvious differences between the velocity distributions of cavitation flows, the high-fluctuating region with lower velocity gradually expands with the decrease of cavitation number, and the lower velocity area relates to the cavitation area. In various stages of cavitation, the vorticity concentrated in the rear vortex separation region. In cloud cavitation stage, more vortices structures can be seen in the cavitation area due to the frequently mass and momentum transformation, for vorticity gathering area, the original vortex changed into a large group of scattered distribution of vorticity, and also, the vortex regions expanded significantly [ABSTRACT FROM AUTHOR]

Cavitating flows around a two-dimensional NACA66 hydrofoil with an angle of attack of 6. 5° are studied using the mixture multiphase model and cavitation model. The Singhal's full cavitation model (FCM) and the Zwart-Gerber-Belamri (Z-G-B) cavitation model are applied, and based on experimental data, results obtained from the two models are compared in terms of pressure distribution coefficient on the surface of the hydrofoil, lift and drag coefficients and flow field structures. The experimental results show that for the FCM, the value of mass fraction of noncondensible gases has some effects on computational results. The length of cavitation zone becomes smaller with the mass fraction of noncondensible gases decreasing. For the Z-G-B model, both vaporization and condensation coefficients have influence on results. In general, both cavitation models give satisfactory prediction results by choosing reasonable empirical coefficients. [ABSTRACT FROM AUTHOR]

To assess a density modify based turbulence model,the unsteady cloud cavitating flow around a Clark-y hydrofoil is investigated by coupled experimental and numerical methods. A high speed camera is used to visualize the flow structures, and laser Doppler velocity (LDV) is employed for velocity measurement. The numerical simulations are conducted on the two dimensional hydrofoil section, the different turbulence models including the density modify based turbulence model are used for computation. It is shown that the new model can predict successively the characteristic of cavitation and the detail process of the cavitation shedding through adjusting the eddy viscosities. The average flow velocity values accord basically with the experimental results. [ABSTRACT FROM AUTHOR]

The dynamics of cavitating flow around a hydrofoil and a cascade hydrofoil are investigated comparatively by numerical method. The Kubota cavitation model which is based on the equation of Rayleigh-Plesset and the fiher-based turbulence model are used in numerical computation. The results show that the low pressure region of the suction side and the high pressure region of the pressure side of the cascade hydrofoil are reduced, compared with the hydrofoil, the average lift coefficient becomes smaller. The changing period of lift and drag force about the cascade hydrofoil is longer and the fluctuation range is bigger than the hydrofoil. [ABSTRACT FROM AUTHOR]

Cloud cavitation flows around a hydrofoil are simulated to address issues in the cavitation model applications in the computation of cloud cavitating flows. Four cavitation models, including the Kubota model, Singhal model, Merkle model and Kunz model are evaluated in the present study. Numerical results are compared with experimental ones. It is shown that all different cavitation models can predict successively the characteristics of cavitation and the detailed process of the cavitation development. Influences of cavitation models on the length of cavity, velocity and the lift and drag force are evaluated, but no significant effect on the frequency distribution of the dynamics around the foil is observed. [ABSTRACT FROM AUTHOR]

To evaluate the application of the filter-based model(FBM), the modified RNGκ-ε, the FBM model with different filter sizes are used to simulate the cloud cavitating flows around a cascade hydrofoil. The calculation results are compared with the experimental data. It is shown that the fit filter size FBM turbulence model can capture the detail process of the vortex shedding in the rear part of the cavitating region better, while considering the effect of the turbulence in the cavitation model. The lift force and the drag force are more accordant with the experiment with a suitable filter size. [ABSTRACT FROM AUTHOR]

To assess a modified RNG κ - ε turbulence model, the cloud cavitating flow around a Clark-y hydrofoil is investigated using RNG κ - ε turbulence model with a modified turbulence viscosity coefficient, and the coefficient is related to the vapor and liquid densities in the cavitating region. The time evolutions of the shape of cloud cavities, the lift and drag force around the hydrofoil have been obtained, and compared with experimental results. It is shown that the modified model can predict successfully the characteristics of cavitation and the detailed process of the cavitation shedding. Values of n in the modified coefficient are found to have a strong influence on the cavity length, the vapor volume, the lift and drag force, but no significant effect on the frequency distribution of the dynamics around the foil is observed. [ABSTRACT FROM AUTHOR]

Supercavitating flows around a hydrofoil is simulated to grasp the unsteady behaviour numerically. To evaluate the application of turbulence models in the computations of supercavitating flows, three different models are implemented: standard κ-ε model, RNG κ-ε model and SSG Reynolds stress model. And then, numerical results were compared to experimental ones. The results showed that the standard κ-ε model can only simulate the steady supercavitating behavior. However, both the RNG κ-ε model and SSG Reynolds stress model can obtain two-phase mixture characteristics in the cavity area, especially the reverse fluctuating processes of the interface between the vapor phase and water-vapor mixture phase. It is also noted that the maximum cavity length simulated by the RNG κ-ε model agrees well with the experimental one. [ABSTRACT FROM AUTHOR]