The near-field of a lab-scale wind turbine in tailored turbulent shear flows

Li, Leon; Hearst, R. Jason; Ferreira, Manuel; Ganapathisubramani, Bharathram

doi:10.1016/j.renene.2019.12.049

Cited by 11 publications

(11 citation statements)

References 27 publications

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“…During the tests here described, the wind tunnel has been equipped with a turbulence-generating active grid, designed to the specifications of Makita (1991), which is able to generate turbulent flows with different levels of shear and free stream turbulence intensities up to 16 % (Hearst & Ganapathisubramani 2017; Li et al. 2020); no shear has been generated for the measurements presented in this study. This grid is composed of 18 stepper motors that independently drive 11 vertical rods and 7 horizontal rods, each moving a set of agitator wings.…”

Section: Experimental Methodsmentioning

confidence: 99%

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The influence of free stream turbulence on the development of a wind turbine wake

Gambuzza

Ganapathisubramani

2023

J. Fluid Mech.

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The wake of an isolated model-scale wind turbine is analysed in a set of inflow conditions having free stream turbulence intensity between 3 % and 12 %, and integral time scales in the range of 0.1–10 times the convective time scale based on the turbine diameter. It is observed that the wake generated by the turbine evolves more rapidly, with the onset of the wake evolution being closer to the turbine, for high turbulence intensity and low integral time scale flows, in accordance with literature, while flows at higher integral time scales result in a slow wake evolution, akin to that generated by low-turbulence inflow conditions despite the highly turbulent ambient condition. The delayed onset of the wake evolution is connected to the stability of the shear layer enveloping the near-wake, which is favoured for low-turbulence or high-integral time scale flows, and to the stability of the helical vortex set surrounding the wake, as this favours interaction events and prevents momentum exchange at the wake boundary which hinder wake evolution. The rate at which the velocity in the wake recovers to undisturbed conditions is instead analytically shown to be a function of the Reynolds shear stress at the wake centreline, an observation that is confirmed by measurements. The rate of production of Reynolds shear stress in the wake is then connected to the power harvested by the turbine to explain the differences between flows at equivalent turbulence intensity and different integral time scales. The wake recovery rate, and by extension the behaviour of the turbine wake in high-integral time scale flows, is seen to be a linear function of the free stream turbulence intensity for flows with Kolmogorov-like turbulence spectrum, in accordance with literature. This relation is seen not to hold for flows with different free stream turbulence spectral distribution; however, this trend is recovered if the contributions of low frequency velocity components to the turbulence intensity are ignored or filtered out from the computation.

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Section: Experimental Methodsmentioning

confidence: 99%

“…2015; Tobin, Zhu & Chamorro 2015; Deskos, Payne & Gaurier 2020; Li et al. 2020; Gambuzza & Ganapathisubramani 2021) and the drag generated by turbine simulators (Blackmore et al. 2014), with turbines being more apt at converting velocity fluctuations into power if those are present as lower-frequency contributions.…”

Section: Introductionmentioning

confidence: 99%

The influence of free stream turbulence on the development of a wind turbine wake

Gambuzza

Ganapathisubramani

2023

J. Fluid Mech.

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“…Due to the higher costs affiliated with experimental setups, the reliance on numerical tools such as Computational Fluid Dynamics (CFD) has seen a rapid increase over the years [11]. Due to unsteady and disrupted wind conditions [12], and higher turbulent flows [13,14] in the urban neighborhood, CFD simulations becomes challenging and requires a careful selection of numerical models and appropriate geometries to obtain realistic estimations [15]. The computational cost becomes the main bottleneck concerning the choice of a particular modeling strategy.…”

Section: Introductionmentioning

confidence: 99%

Parametric Analysis Using CFD to Study the Impact of Geometric and Numerical Modeling on the Performance of a Small Scale Horizontal Axis Wind Turbine

et al. 2022

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The reliance on Computational Fluid Dynamics (CFD) simulations has drastically increased over time to evaluate the aerodynamic performance of small-scale wind turbines. With the rapid variability in customer demand, industrial requirements, economic constraints, and time limitations associated with the design and development of small-scale wind turbines, the trade-off between computational resources and the simulation’s numerical accuracy may vary significantly. In the context of wind turbine design and analysis, high fidelity simulation under full geometric and numerical complexity is more accurate but pose significant demands from a computational standpoint. There is a need to understand and quantify performance deterioration of high fidelity simulations under reduced geometric or numerical approximation on a single small scale turbine model. In the present work, the flow past a small-scale Horizontal Axis Wind Turbine (HAWT) was simulated under various geometric and numerical configurations. The geometric complexity was varied based on stationary and rotating turbine conditions. In the stationary case, simple 2D airfoil, 2.5D blade, 3D blade sections are evaluated, while rotational effects are introduced for the configuration 3D blade, rotor only, and the full-scale wind turbine with and without the inclusion of a nacelle and tower. In terms of numerical complexity, the Single Reference Frame (SRF), Multiple Reference Frames (MRF), and the Sliding Meshing Interface (SMI) is analyzed over Tip Speed Ratios (TSR) of 3, 6, 10. The quantification of aerodynamic coefficients of the blade (Cl, Cd) and turbine (Cp, Ct) was conducted along with the discussion on wake patterns in comparison with experimental data.

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“…One of the main challenges for today's wind turbines is the power generation fluctuations which cause instability in the grid network (Anvari et al, 2016). It has been reported that the effect of the extreme events can get transferred to the grid with even amplification in magnitudes (amount of power generation is related to the cube of wind velocity); the power output of the whole wind farm can change by 50 % in just 2 min (Milan et al, 2013). These turbulent features also induce fatigue loads on the blades (Burton et al, 2011) predominantly for the flapwise loadings (Rezaeiha et al, 2017), which then get transferred to the gearbox (Feng et al, 2013), bearings and then the whole structure.…”

Section: Introductionmentioning

confidence: 99%

“…The effect of the wind shears on wind turbine aerodynamics has been studied by several investigators. The effect of various steady shear flows and turbulence intensities, generated by active grid, on the near-wake region of a small-scale turbine was investigated by Li et al (2020) using particle image velocimetry (PIV) measurements. It has been found that the absolute mean velocity deficit in this region remains symmetric, and it is insensitive to the inflow non-uniformity.…”

Section: Introductionmentioning

confidence: 99%

Investigating the loads and performance of a model horizontal axis wind turbine under reproducible IEC extreme operational conditions

et al. 2021

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Abstract. The power generation and loading dynamic responses of a 2.2 m diameter horizontal axis wind turbine (HAWT) under some of the IEC 61400-1 transient extreme operational conditions, more specifically extreme wind shears (EWSs) and extreme operational gust (EOG), that were reproduced at the WindEEE Dome at Western University were investigated. The global forces were measured by a multi-axis force balance at the HAWT tower base. The unsteady horizontal shear induced a significant yaw moment on the rotor with a dynamic similar to that of the extreme event without affecting the power generation. The EOG severely affected all the performance parameters of the turbine.

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The near-field of a lab-scale wind turbine in tailored turbulent shear flows

Cited by 11 publications

References 27 publications

The influence of free stream turbulence on the development of a wind turbine wake

The influence of free stream turbulence on the development of a wind turbine wake

Parametric Analysis Using CFD to Study the Impact of Geometric and Numerical Modeling on the Performance of a Small Scale Horizontal Axis Wind Turbine

Investigating the loads and performance of a model horizontal axis wind turbine under reproducible IEC extreme operational conditions

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