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Numerical Modeling of Compound Channels for Determining Kinetic Energy and Momentum Correction Coefficients Using the OpenFOAM Software

Mehranfar Nariman, Ghanbari-Adivi Elham

Archives of Hydro-Engineering and Environmental Mechanics

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2022

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Vol. 69, nr 1

27--43

EN

The non-uniformity of the flow velocity distribution in each section of compound channels and in the main channel-floodplain interface area causes errors in estimating water surface profile, flood routing, pollution transfer, and so on. To reduce the impacts of non-uniformity on the exact calculation of kinetic energy and momentum, α and β correction coefficients are used, respectively. However, the determination method of these coefficients is a challenging issue in river engineering. This study used the OpenFOAM Software to determine these coefficients numerically for two laboratory models of compound open channels of which the data are available, using the single-phase pimpleFoam solver to do modeling in the mentioned software and the k-ωSST turbulence model to calculate the flow characteristics. Based on the results, the highest difference (13%) between the results estimated by the software and those obtained from the lab experiments was seen in the low flow depth where the flow left the main channel and entered the floodplain of a very shallow depth, possibly due to the grid generation of this area. This difference decreased as the flow depth increased, and its average was 6.65% for α coefficient and 2.32% for β coefficient in all cases, which means the results of numerical modeling and the experimental data conformed well, and the OpenFOAM software can be successfully used in flow modeling and analyzing flow characteristics in compound channels.

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Numerical analysis of cavitation phenomena with variable speed centrifugal pump

Rakibuzzaman M., Kim K., Suh S.-H.

Journal of Power Technologies

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2016

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Vol. 96, nr 4

306--311

EN

Cavitation is an abnormal physical phenomenon which can be generated in relatively low pressure regions in centrifugal pumps. In predicting and understanding cavitation in the pumps, it is important to secure their efficiency and reliability. The purpose of this study is to analyze the cavitation flows in centrifugal pumps with variable speeds through numerical methods. The Rayleigh–Plesset cavitation model was adapted as the source term for inter-phase mass transfer in order to predict and understand the cavitation performances. The Reynolds-average Navier-Stokes (RANS) equations were discretized by the finite volume method. The two-equation SST turbulence model was accounted for turbulent flows. The numerical analysis results were validated with experimental data and it was found that both results were in good accordance. The cavitation performances were obtained for variable speeds with different temperatures and the effects on cavitation were described according to different cavitation numbers. Cavitation performances were also observed for different centrifugal pump stages (1st and 2nd). The performances of cavitation decreased with the increase of rotational speed. In addition, the development of cavitation is elucidated according to the different temperatures, and the effects of water vapor volume fraction are discussed.

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Modelowanie rozkładu energii kinetycznej burzliwości i jej szybkości dyssypacji podczas wytwarzana zawiesiny lekkiej

Kacperski Ł., Karcz J.

Inżynieria i Aparatura Chemiczna

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2013

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Nr 3

189--190

PL

Przedstawiono wyniki modelowania numerycznego energii kinetycznej burzliwości i szybkości jej dyssypacji w zbiorniku z mieszadłem do wytwarzania zawiesiny lekkiej. Uzyskano kontury oraz proﬁ le tych wielkości dla burzliwego ruchu płynu w mieszalniku i trzech modeli burzliwości k-ε, k-ω, lub SST. Zidentyﬁkowano strefy, w których modelowane zmienne przyjmują największe wartości i w których rozpraszanie cząstek ciała stałego jest najbardziej efektywne.

XX

Results of numerical modeling of turbulence kinetic energy and its dissipation rate in mechanically agitated floating particles’ suspension are presented. Contours and profiles of these quantities were found for turbulent fluid flow in an agitated vessel and three turbulence 'models k-ε, k-ω or SST. The agitated vessel zones in which modeled quantities took the greatest values and where the best dispersion of floating particles was obtained were identified.