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RISS 인기검색어
- 검색키워드
- 저자 : Renfang Huang (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Renfang Huang,Xianwu Luo,Bin Ji 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.6
This paper presents the implementation and assessment of a modified Partially averaged Navier-Stokes (PANS) turbulence modelwhich can successfully predict the transient cavitating turbulent flows. The proposed model treats the standard k-e model as the parentmodel, and its main distinctive features are to (1) formulate the unresolved-to-total kinetic energy ratio (fk) based on the local grid size aswell as turbulence length scale, and (2) vary the fk-field both in space and time. Numerical simulation used the modified PANS model forthe sheet/cloud cavitating flows around a three-dimensional Clark-Y hydrofoil. The available experimental data and calculations of thestandard k-e model, the fk = 0.8 PANS model, the fk = 0.5 PANS model are also provided for comparisons. The results show that themodified PANS model accurately captures the transient cavitation features as observed in experiments, namely, the attached sheet cavitygrows in the flow direction until to a maximum length and then it breaks into a highly turbulent cloud cavity with three-dimensionalstructures in nature. Time-averaged drag/lift coefficients together with the streamwise velocity profiles predicted by the proposed modelare in good agreement with the experimental data, and improvements are shown when compared with results of the standard k-e model,the fk = 0.8 PANS model and the fk = 0.5 PANS model. Overall, the modified PANS model shows its encouraging capability of predictingthe transient cavitating turbulent flows.
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Numerical investigation of cavitation-vortex interaction in a mixed-flow waterjet pump
Renfang Huang,Bin Ji,Xianwu Luo,Zhihong Zhai,Jiajian Zhou 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.9
Turbulent cavitating flows in a mixed-flow waterjet pump were numerically investigated using the k-w SST turbulence model and themass transfer cavitation model based on the Rayleigh-Plesset equation to provide a comprehensive understanding of the cavitation-vortexinteraction mechanism. The predicted hydraulic performance, as well as the cavitation performance, exhibits a reasonable agreement withthe experimental results. The vorticity distributions under three operation conditions were illustrated together. Based on the illustration,cavitation development enhances vorticity production and flow unsteadiness in a mixed-flow waterjet pump. Vortices are basically locatedat the cavity interface, particularly at the downstream interface, during cavitation. Further analyses using the relative vorticity transportequation in cavitating turbulent flows indicate that vortex dilation and baroclinic torque exhibit a steep jump as cavitation occurs. Inaddition, vortex stretching contributes mainly to large-scale vortex generation.
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Instability analysis under part-load conditions in centrifugal pump
Weixiang Ye,Renfang Huang,Zhiwu Jiang,Xiaojun Li,ZuChao Zhu,Xianwu Luo 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1
In this study, a centrifugal pump with a specific speed of 39.12 m×min -1 ×m 3 s -1 is treated to analyze the flow instability under part-load conditions by numerical simulation and experimental test. For calculations, the RANS method, coupled with the k-ω SST turbulence model, is adopted. Numerical results at different operation points are compared with available experimental data, such as hydraulic performance and flow field information by particle image velocimetry. The numerical and experiment results agree well. The flow simulation indicates a strong reverse flow at the passage upstream impeller inlet, and the energy loss in the impeller is the largest under partload conditions among all flow components in the pump. In one impeller revolution, one blade-to-blade flow passage is always nearly blocked off by the rotating stall occurring at the impeller inlet for each instant, and the blockage induces a jet flow with large velocity at the next blade-to-blade flow passage along the rotational direction of the impeller. The blockage and the jet flow in the blade-to-blade flow passages will make the flow unstable inside the impeller and cause performance breakdown and pressure vibration under part-load conditions for the pump.
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