Extraction of the wake induction and angle of attack on rotating wind turbine blades from PIV and CFD results

Herráez, Iván; Daniele, Elia; Schepers, J.G.

doi:10.5194/wes-3-1-2018

Cited by 26 publications

(27 citation statements)

References 10 publications

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“…The local tangential velocity extracted from the radial traverse corresponds to the local tangential wake induction after changing its sign. It is demonstrated in Ref [39] that this method can predict the AoA satisfactorily from the root until at least 92% of the blade length. For larger spanwise positions, other methods, like e.g.…”

Section: Control Point Locusmentioning

confidence: 97%

“…• Herráez Method: This method obtains the undisturbed flow rotor velocity by extracting them directly from a position in the rotor plane where the influence of the blade bound circulation from each blade is canceled out by the other blades [39]. In the case of axi-symmetric, homogeneous inflow, this position corresponds to the bisectrix of the angle between two arbitrary blades.…”

Section: Control Point Locusmentioning

confidence: 99%

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Evaluation of different methods for determining the angle of attack on wind turbine blades with CFD results under axial inflow conditions

et al. 2018

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This work presents an investigation on different methods for the calculation of the angle of attack and the underlying induced velocity on wind turbine blades using data obtained from three-dimensional Computational Fluid Dynamics (CFD). Several methods are examined and their advantages, as well as shortcomings, are presented. The investigations are performed for two 10MW reference wind turbines under axial inflow conditions, namely the turbines designed in the EU AVATAR and INNWIND.EU projects. The results show that the evaluated methods are in good agreement with each other at the mid-span, though some deviations are observed at the root and tip regions of the blades. This indicates that CFD results can be used for the calibration of induction modeling for Blade Element Momentum (BEM) tools. Moreover, using any of the proposed methods, it is possible to obtain airfoil characteristics for lift and drag coefficients as a function of the angle of attack. Nomenclature ρ Air density [kg m −3 ] Γ Circulation [m 2 s −1 ]

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Section: Control Point Locusmentioning

confidence: 97%

Section: Control Point Locusmentioning

confidence: 99%

Evaluation of different methods for determining the angle of attack on wind turbine blades with CFD results under axial inflow conditions

et al. 2018

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“…Despite the possible validation for force and pressure coefficient, the proposal of an alternative model for rotational augmentation necessitates the capture of aerodynamic coefficient, thus, the AoA, or alternatively, the determination of the local velocity in the rotor plane without bound circulation [22], i.e. axial and angular induction factors.…”

Section: Validation Of the Simulationsmentioning

confidence: 99%

“…Clearly, deducing the value of the aerodynamic forces from both experiments or simulations required the estimation of the angle of attack (AoA). In a rotating blade, this aspect is directly connected with the determination of the local inflow velocity in the rotor plane which is free of bound circulation (local undisturbed velocity) [22]. There are several methods for calculating the angle of attack at the rotor, thus, the analyses of this work are restricted to three proposals: average azimuthal technique (AAT) [23], three-point (3P) [24] and zero gamma (ZG) [22].…”

Section: Introductionmentioning

confidence: 99%

“…In a rotating blade, this aspect is directly connected with the determination of the local inflow velocity in the rotor plane which is free of bound circulation (local undisturbed velocity) [22]. There are several methods for calculating the angle of attack at the rotor, thus, the analyses of this work are restricted to three proposals: average azimuthal technique (AAT) [23], three-point (3P) [24] and zero gamma (ZG) [22]. Since there is no common agreement within the research community on which method should represent the most suitable option, for the remaining of this work the indication of the AoA from threedimensional CFD simulation refers always to an averaged value of the results obtained by applying the three aforementioned methods.…”

Section: Introductionmentioning

confidence: 99%

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On the calibration of rotational augmentation models for wind turbine load estimation by means of CFD simulations

et al. 2020

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In this work the improved version of an engineering model which accounts for rotational augmentation effects by means of computational fluid dynamics (CFD) calibration is explored and discussed. Based on an analysis of the NREL Phase VI wind turbine, the novel modeling is presented, which uses as base line the formulation proposed by Chaviaropoulos and Hansen. The model is calibrated based on CFD simulations using OpenFOAM. The corresponding correction of the two dimensional polars is straightforward implemented within MoWiT, an in-house software for load calculation. The novel formulation results in improved lift and drag coefficients prediction in all considered cases, reducing the deviation with respect to the rotating CFD cases down to few percent. The optimal configuration including the correction for tip effects of Shen shows better agreements at the very tip of the blade. Furthermore the range of applicability for large wind turbine rotor blades based on a virtual 10 MW rotor model is discussed.

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Extracting angles of attack from blade‐resolved rotor CFD simulations

2020

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The distribution of the angles of attack over the span of a rotor blade, together with blade element theory, provides a useful framework to understand forces, performance and other fluid dynamic phenomena of axial‐flow rotors. However, the angle of attack is not straightforward to define for a three‐dimensional rotor, where the flow is perturbed by the blade circulation, shed vorticity and wake development.This paper evaluates six methods to extract the angles of attack from blade‐resolved CFD simulations of axial‐flow turbines. Simulations of two different rotors are presented: a low solidity rotor designed for wind and a higher solidity rotor designed for tidal stream energy conversion. Of the analysed methods, five were obtained from the literature and are tested in terms of their internal parameters. The remaining method is named the streamtube analysis method (SAM) and is presented as an improvement on analysis methods that azimuthally average the flow data on the rotor plane, referred to as azimuthal averaging techniques (AATs). The SAM method accounts for the expansion of the streamtubes in flow‐field velocity sampling and exhibits improved convergence on the internal parameters compared with AAT.The six methods are benchmarked in terms of the angles of attack, axial induction factors and the local lift and drag coefficients, identifying that most perform well and converge with each other despite the different underlying assumptions or modelling approaches. However, given the limitations and inherent dependency on internal parameters, the line averaging and SAM are suggested for general flow analysis application.

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Extraction of the wake induction and angle of attack on rotating wind turbine blades from PIV and CFD results

Cited by 26 publications

References 10 publications

Evaluation of different methods for determining the angle of attack on wind turbine blades with CFD results under axial inflow conditions

Evaluation of different methods for determining the angle of attack on wind turbine blades with CFD results under axial inflow conditions

On the calibration of rotational augmentation models for wind turbine load estimation by means of CFD simulations

Extracting angles of attack from blade‐resolved rotor CFD simulations

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