Study on the Accuracy of RANS Modelling of the Turbulent Flow Developed
                        in a Kaplan Turbine Operated at BEP. Part 2 - Pressure Fluctuations

Iovănel, Raluca Gabriela; Dunca, Georgiana; Cervantes, Michel

doi:10.29252/jafm.12.05.29705

Cited by 7 publications

(4 citation statements)

References 23 publications

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“…In terms of prediction and simulation, high-precision numerical simulation methods such as Computational Fluid Dynamics (CFD) are widely utilized to predict pressure pulsations, including Direct Numerical Simulation (DNS), Large Eddy Simulation (LES) and models based on Reynolds Averaged Navier-Stokes (RANS). Among them, RANSbased models have limitations in predicting pressure fluctuations [5], while LES and DNS are especially suitable for the study of pressure fluctuations due to their high accuracy in simulating turbulence and complex flow structures. However, these two methods usually require higher computational resources.…”

Section: Introductionmentioning

confidence: 99%

Inner Flow Analysis of Kaplan Turbine under Off-Cam Conditions

Yan,

Luo,

Zhao

et al. 2024

Energies

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Kaplan turbines are widely utilized in low-head and large flow power stations. This paper employs Computational Fluid Dynamics (CFD) to complete numerical calculations of the full flow channel under different blade angles and various guide vane openings, based on 25 off-cam experimental working conditions. The internal flow characteristics of the runner blade and draft tube are analyzed, and a discriminant number for quantitatively assessing the flow uniformity of the draft tube is proposed. The results indicate that low-frequency and high-amplitude pressure pulsations occur on the high- and low-pressure edge of the blade when the opening is small, with pulsations decreasing as the opening increases. The inner flow line of the draft tube is disturbed when both the blade angle and opening are small. Additionally, the secondary frequency of the draft tube inlet is double that of the vane passing frequency. The discriminant number of the flow inhomogeneity approaches 0 under optimal flow conditions. The number increases continuously with the decrease in efficiency, and the flow in the three piers of draft tube becomes more nonuniform. The research results provide a reference for enhancing performance and ensuring the operational stability of Kaplan turbines.

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Section: Introductionmentioning

confidence: 99%

Inner Flow Analysis of Kaplan Turbine under Off-Cam Conditions

Yan,

Luo,

Zhao

et al. 2024

Energies

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“…e typical structure of Kaplan turbines is shown in Figure 1. e excitation forces of Kaplan turbine runners can be both static and dynamic pressures [10][11][12][13][14][15]. e dynamic pressure mostly comes from the rotor-stator interaction (RSI).…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of the Trailing Edge Shape on the Added Damping of a Kaplan Turbine Runner

Zhang

Mbango-Ngoma

et al. 2021

Mathematical Problems in Engineering

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Hydraulic turbine runners experience high excitation forces in their daily operations, and these excitations may cause resonances to runners, which may induce high vibrations and shorten the runner's lifetimes. Increasing the added damping of runners in water can be helpful to reduce the vibration level during resonances. Some studies have shown that the modification of the trailing edge shape can be helpful to increase added damping of hydrofoils in water. However, the influence of blade trailing edge shape on the added damping of hydraulic turbine runners has been studied in a limited way before. Due to the difficulties to study this problem experimentally, the influence of blade trailing edge shape on a Kaplan turbine runner has been studied numerically in this paper and the one-way FSI method was implemented. The performances of three different turbulence models, including the k − ϵ , k − ω SST , and transition SST models, in the added damping simulation of the NACA 0009 hydrofoil were evaluated by comparing with the available results of the two-way FSI simulation in the references. Results show that, unlike the significantly different performances in the two-way FSI method, the performances of all the turbulence models are very close in the one-way FSI method. Then, the k − ϵ turbulence model was applied to the added damping simulation of a Kaplan turbine runner, and results show that the modification of the blade trailing edge shape can be helpful to increase the added damping to some extent.

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“…They concluded that both captured the tip vortex, hub vortices, blades' wakes, and on‐axis structure, and also showed that the dynamics of tip runner vortices is affected by the rotation and shroud boundary layer. Based on flow simulations in the same Kaplan turbine model, Iovănel discussed the advantages and limitations of RANS and URANS modeling, while several turbulence models were used. Most of the researches focused on the pressure fluctuations caused by RSI and the torque fluctuation and vibration induced by the asymmetric pressure loadings were of great concern.…”

Section: Introductionmentioning

confidence: 99%

Simulation of steady and unsteady flows through a small‐size Kaplan turbine

Ghenaiet

Bakour

2020

Engineering Reports

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The increasing demand for electric energy has pushed to rely on the microhydropower as one of the most cost‐effective technologies to improve the grid stability in rural localities. This article investigates the steady and unsteady flows in a complete small Kaplan turbine by means of the solver ANSYS‐CFX. Examination of the basic design parameters in terms of blade setting, vane opening, and interdistance has revealed the best operating parameters and the potentiality of performance improvement. Moreover, the Fast Fourier Transform of static pressure fluctuations recorded at different monitor points allowed analyzing the flow unsteadiness arising from the stator‐rotor interactions (RSI). The prevailing harmonics coinciding with the modes of RSI were determined and compared with the analytically predicted main diametrical modes and frequencies of the pressure waves. The found results in this category of low‐head small Kaplan turbine may serve in developing similar hydroturbines suitable for the microhydropower.

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Study on the Accuracy of RANS Modelling of the Turbulent Flow Developed in a Kaplan Turbine Operated at BEP. Part 2 - Pressure Fluctuations

Cited by 7 publications

References 23 publications

Inner Flow Analysis of Kaplan Turbine under Off-Cam Conditions

Inner Flow Analysis of Kaplan Turbine under Off-Cam Conditions

Numerical Investigation of the Trailing Edge Shape on the Added Damping of a Kaplan Turbine Runner

Simulation of steady and unsteady flows through a small‐size Kaplan turbine

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