Estimating the angle of attack from blade pressure measurements on the National Renewable Energy Laboratory phase VI rotor using a free wake vortex model: yawed conditions

Sant, Tonio; Kuik, Gijs van; Bussel, G.J.W. Van

doi:10.1002/we.280

Cited by 33 publications

(16 citation statements)

References 21 publications

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“…Towards the tip region, the reduced frequency is low and the flow can be assumed to be steady. Tip effects cause a reduction in lift as was also observed in the NREL Phase VI experiment as shown in [8] and [9]. This can also be observed with the IFW result.…”

Section: Conditions At the Rotor Planesupporting

confidence: 79%

Validating BEM, Direct and Inverse Free Wake Models with the MEXICO Experiment.

Micallef

Kloosterman

Ferreira

et al. 2010

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to generate experimental data for validation of models for wind turbines. Kulite c pressure sensors were used for pressure measurements while Particle Image Velocimetry was used with the aim of tracking the tip vortex trajectory. The pressure measurements were carried out for both axial and yawed flow conditions with yaw angles of 15 o , 30 o and 45 o . For the Particle Image Velocimetry measurements data was gathered for axial flow and for the ±30 o yaw cases at a single tip speed ratio. In this work, an inverse free wake lifting line model, a direct free wake model and a BEM model are validated with the MEXICO data. Particular emphasis is placed on the study of yawed flow conditions. The inverse free-wake model makes use of the experimental loads as input in order to find the distribution of inductions and angle of attack. The predictive capability of BEM may therefore be assessed based on this. Validation of the inverse free-wake model was performed by investigating the stagnation pressure prediction as well as the vortex trajectory prediction. This was done by means of the PIV data gathered from the MEXICO experiment. This PIV data was also used for validation purposes of the direct free-wake model. The differences in the angle of attack distributions in yawed flow with these models was studied in order to assess the difference in results between the use of 2D and 3D airfoil data.

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Section: Conditions At the Rotor Planesupporting

confidence: 79%

Validating BEM, Direct and Inverse Free Wake Models with the MEXICO Experiment.

Micallef

Kloosterman

Ferreira

et al. 2010

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

Self Cite

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“…To put to try again the ability of the model to predict effective angle of attack distributions at arbitrarily yawed flow conditions, just departing from the known induction factors at zero yaw angle, the rest of the section presents a comparison to angle of attack distributions obtained iteratively by a free wake vortex model. The method, presented by Sant et al to determine angle of attack distributions from experimental data, is a free wake vortex model reconstructed from the bound circulation estimated by the Kutta–Joukowsky law, combining measured blade loads and assumed angle of attack distributions. From the wake structure, a new angle of attack distribution is re‐estimated.…”

Section: Application Of the Methodsmentioning

confidence: 99%

Angle of attack distribution on wind turbines in yawed flow

Morote

2015

Wind Energ.

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This paper presents a new approach to model the induction for wind turbines in yawed flow to find the effective angle of attack distribution along the blades. There is an inherent difficulty in determining the angle of attack required by aeroelastic codes as input to tabulated airfoil data. Unlike two-dimensional (2D) conditions where the angle of attack is the angle between the unperturbed flow and the airfoil chord, for the rotating blade, the incoming flow is bended because of rotation and affected by the induction of the blade circulation and the tip and root vortices, making the definition of the angle of attack uncertain.In this work, the analogy with 2D potential flows suggests that a coupling term between the unperturbed geometric angle of attack and the unitary velocity in the radial direction should be included to calculate the effective angle of attack seen by the blade strips. The model introduces two radially dependent interferences on the geometric angle, obtained from axial flow conditions that give the effective angle of attack under arbitrarily yawed flow conditions. The model gives a uniform treatment to the radial flows associated with yawed conditions or coned rotors and can be applied directly to calculate the effective angle of attack distribution on coned rotors in yawed flow. The accuracy of the method compares with results obtained from conventional or higher degree of complexity methods. The model can be incorporated into blade element momentum theory codes as an option to calculate angle of attack distributions.

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“…It is of great importance to develop advanced tools to predict and improve wind turbine performance in order to capture the energy more efficiently from the wind. Today, designers of wind turbines have a large number of different aerodynamic predictive tools to their disposal, including blade element momentum based methods, fixed/free vortex wake models, actuator disk/line/surface models and full Navier–Stokes methods. However, the validity and range of applicability of the various methods are still not fully settled.…”

Section: Introductionmentioning

confidence: 99%

Actuator line/Navier–Stokes computations for the MEXICO rotor: comparison with detailed measurements

2011

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In the European collaborative MEXICO (Model Experiments in Controlled Conditions) project, a series of experiments was carried out on a 4.5 m diameter wind turbine rotor to validate numerical diagnostics tools. Here, some of the measured data are compared with computations of the combined actuator line/Navier-Stokes (AL/NS) model developed at the Technical University of Denmark. The AL/NS model was combined with a large eddy simulation technique and used to compute the flow past the MEXICO rotor in free air and in the DNW German-Dutch wind tunnel for three commonly defined test cases at wind speeds of 10, 15 and 24 m s 1 . Two sets of airfoil data were used. Comparisons of blade loadings showed that the AL/NS technique with the modified airfoil data is in better agreement with the measurements than with the original 2D airfoil data. Comparisons of detailed near-wake velocities showed good agreement with the measurements. Computations including the influence of the geometry of the wind tunnel showed that tunnel effects are not significant and the effect of the geometry of the wind tunnel only results in a speedup of 3% at a thrust coefficient of C T D 1.The AL/NS model developed at DTU consists of a Navier-Stokes solver and an actuator line model. The Navier-Stokes solver EllipSys2D/3D was originally developed at DTU 28 and Risø National Laboratory. 29 To take into account turbulence, 812 Wind Energ. 2012; 15:811-825

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Estimating the angle of attack from blade pressure measurements on the National Renewable Energy Laboratory phase VI rotor using a free wake vortex model: yawed conditions

Abstract: Wind turbine design codes for calculating blade loads are usually based on a blade element momentum (BEM) approach. Since wind turbine rotors often operate in off-

Cited by 33 publications

References 21 publications

Validating BEM, Direct and Inverse Free Wake Models with the MEXICO Experiment.

Validating BEM, Direct and Inverse Free Wake Models with the MEXICO Experiment.

Angle of attack distribution on wind turbines in yawed flow

Actuator line/Navier–Stokes computations for the MEXICO rotor: comparison with detailed measurements

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