Numerical prediction on the effect of free surface vortex on intake flow characteristics for tidal power station

Ahn, Soo-Hwang; Xiao, Yexiang; Wang, Zhengwei; Zhou, Xuezhi; Luo, Yongyao

doi:10.1016/j.renene.2016.09.021

Cited by 67 publications

(10 citation statements)

References 29 publications

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“…Turbulence was modelled using the k-ω shear stress transport (SST). SST k-ω had been found to be suitable for numerical modelling of free-surface vortices [16,17]. This turbulence model exhibits better performance in predicting flows at walls and adverse pressure gradients as compared to other eddyviscosity models [18].…”

Section: Computational Domain and Boundary Conditionsmentioning

confidence: 99%

Numerical Investigation of the Performance of a Submersible Pump: Prediction of Recirculation, Vortex Formation, and Swirl Resulting from Off-Design Operating Conditions

et al. 2021

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Like any other turbomachinery, it is essential that the hydraulic behavior and performance of mixed-flow pumps are evaluated way in advance prior to manufacturing. Pump performance relies heavily on the proper design of the intake structure. Intake structures should be accurately designed in order to minimize and avoid unnecessary swirl and vortex formations. Ensuring the optimum performance condition as well as predicting how a particular intake structure affects the efficiency of the pump often requires either physical model studies or theoretical evaluations. Unfortunately, physical models are costly, time-consuming, and site-specific. Conversely, design and performance predictions using a theoretical approach merely gives performance values or parameters, which are usually unable to determine the root cause of poor pump performance. This study evaluates the viability of using Computational Fluid Dynamics (CFD) as an alternative tool for pump designers and engineers in evaluating pump performance. A procedure for conducting CFD simulations to verify pump characteristics such as head, efficiency, and flow as an aid for preliminary pump design is presented. Afterwards, a multiphase simulation using the VOF approach is applied to compare the fluid dynamics between four different pump intake structures. A full-sized CFD model of the pump sump complete with the pump’s active components was used for the intake structure analysis in order to avoid scaling issues encountered during the reduced-scale physical model test. The results provided a clear illustration of the hydraulic phenomena and characteristic curves of the pump. A performance drop in terms of reduction in TDH was predicted across the various intake structure designs. The CFD simulation of intake structure provided a clear insight on the varying degree of swirl, flow circulation, and effect on pump efficiency between all four cases.

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Section: Computational Domain and Boundary Conditionsmentioning

confidence: 99%

Numerical Investigation of the Performance of a Submersible Pump: Prediction of Recirculation, Vortex Formation, and Swirl Resulting from Off-Design Operating Conditions

et al. 2021

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“…Turbulence was modelled using the k − ω shear-stress transport (SST). SST k − ω had been found to be suitable for numerical modelling of free-surface vortices [19,20] and exhibits better performance in predicting flows at walls and adverse pressure gradients as compared to other eddy-viscosity models [21]. The pressure-based coupled solver was applied.…”

Section: Boundary Condition and Solver Parametersmentioning

confidence: 99%

Reduction of Entrained Vortices in Submersible Pump Suction Lines Using Numerical Simulations

et al. 2020

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Pump intake structure design is one area where physical models still remain as the only acceptable method that can provide reliable engineering results. Ensuring the amount of turbulence, entrained air vortices, and swirl are kept within acceptable limits requires site-specific, expensive, and time-consuming physical model studies. This study aims to investigate the viability of Computational Fluid Dynamics (CFD) as an alternative tool for pump intake design thus reducing the need for extensive physical experiments. In this study, a transient multiphase simulation of a 530 mm wide rectangular intake sump housing a 116 m3/h pump is presented. The flow conditions, vortex formation and inlet swirl are compared to an existing 1:10 reduced scaled physical model test. For the baseline test, the predicted surface and submerged vortices agreed well with those observed in the physical model. Both the physical model test and the numerical model showed that the initial geometry of the pump sump is unacceptable as per ANSI/HI 9.8 criteria. Strong type 2 to type 3 submerged vortices were observed at the floor of the pump and behind the pump. Consequently, numerical simulations of proposed sump design modification are further investigated. Two CFD models with different fillet-splitter designs are evaluated and compared based on the vortex formation and swirl. In the study, it was seen that a trident-shaped splitter design was able to prevent flow separation and vortex suppression as compared to a cross-baffle design based on ANSI/HI 9.8. CFD results for the cross-baffle design showed that backwall and floor vortices were still present and additional turbulence was observed due to the cross-flow caused by the geometry. Conversely, CFD results for the trident-shaped fillet-splitter design showed stable flow and minimized the floor and wall vortices previously observed in the first two models.

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“…In the present research, simulation of the vortex and the flow pattern in the reservoir was carried out by solving 3D Navier-Stokes fluid motion equations based on the finite volume method by the STAR-CCM + Software. Continuity and Navier-Stokes equations in the two-phase flow conditions, assuming homogeneity, are as follows [31,32]:…”

Section: Numerical Modelmentioning

confidence: 99%

Elimination of vortices by wave generation as a hydraulic anti-vortex method

Pakdel

Tabatabai

Sarkardeh

et al. 2020

J Braz. Soc. Mech. Sci. Eng.

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Free-surface vortex formation is one of the undesirable hydraulic phenomena that may occur at intakes during the dewatering reservoir. This research is meant to investigate the effect of waves on formed vortices in vertical intakes numerically by applying STAR-CCM + software. The simulation was conducted to model the free surface and turbulence by volume of fluid and large eddy simulation methods, respectively. Sensitivity analysis was undertaken on different mesh sizes to select appropriate mesh dimensions. Then, verification was performed by Sun and Liu (J Hydraul Res 53:787-796, 2015) experimental data. Results showed that waves reduce or eliminate hydraulic parameters of the formed vortices such as vortex strength, tangential, radial, and axial velocity components. The reduction appeared by average values of 32%, 30%, 22%, and 25% in vortex strength, tangential, radial, and axial velocity components, respectively. Waves also led to decrement in the length and diameter of air-core of vortices about 45% for the former and more than 50% for the latter. In addition, it was concluded that the smaller the waves, the greater their effects would appear on the elimination of the vortex phenomenon. Finally, a relationship between the wave properties, as a hydraulic approach to anti-vortex, and vortex parameters was developed. Keywords Vertical intake • Surface wave • Free-surface vortex • Numerical simulation • STAR-CCM+ List of symbols P Pressure (kgm −1 s −2) u Velocity (ms −1) f i External force (kgms −2) g Gravity force (ms −2) V e Tangential velocity (ms −1) V r Radial velocity (ms −1) V z Axial velocity (ms −1) r Vortex radius (ms −1) Z Height from free surface (m) k T Turbulence kinematic energy σ Coefficient of surface tension Density (kgm −3) Dynamic viscosity (kgm −1 s −1) Reynolds-stress tensor (kgm −1 s −2) Kinematic viscosity (m 2 s −1) Eddy viscosity (m 2 s −1) e Effective viscosity (m 2 s −1) Γ Circulation (m 2 /s) ⃗ Angular velocity (rads −1) 2 r m V Γ in max Dimensionless parameter of tangential velocity (−Vrrm) e max Dimensionless parameter of radial velocity (V z r 2 m e z) max Dimensionless parameter of axial velocity

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Numerical prediction on the effect of free surface vortex on intake flow characteristics for tidal power station

Cited by 67 publications

References 29 publications

Numerical Investigation of the Performance of a Submersible Pump: Prediction of Recirculation, Vortex Formation, and Swirl Resulting from Off-Design Operating Conditions

Numerical Investigation of the Performance of a Submersible Pump: Prediction of Recirculation, Vortex Formation, and Swirl Resulting from Off-Design Operating Conditions

Reduction of Entrained Vortices in Submersible Pump Suction Lines Using Numerical Simulations

Elimination of vortices by wave generation as a hydraulic anti-vortex method

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