Stall in Yawed Flow Conditions: A Correlation of Blade Element Momentum Predictions With Experiments

Haans, Wouter; Sant, Tonio; Kuik, Gam Gijs van; Bussel, Gjw Gerard van

doi:10.1115/1.2349545

Cited by 19 publications

(18 citation statements)

References 3 publications

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“…Tuft visualizations on the blade are performed, in conjunction with hotfi lm CTA in the near-wake, to observe dynamically stalled fl ows. 17 Furthermore, the PLA three-dimensional fl ow velocity vectors in the near-wake are determined by means of hot-fi lm CTA. At three downstream planes parallel to the rotor plane, single-sensor hot-fi lm traverses are made.…”

Section: Introductionmentioning

confidence: 99%

HAWT near‐wake aerodynamics, Part I: axial flow conditions

et al. 2008

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An improved physical understanding of the rotor aerodynamics of a horizontal axis wind turbine (HAWT) is required to reduce the uncertainties associated with today's design codes. Wind tunnel experiments contribute to increased knowledge and enable validation and construction of models. The present study focuses on the near-wake of a model HAWT in both axial and yawed flow conditions. At three downstream planes parallel to the rotor plane, single-sensor hot-film traverses are made. The phase-locked unsteady threedimensional flow velocity vector is determined by a novel data reduction method. A series of two papers discusses the near-wake aerodynamics of a model HAWT. The main goals are to obtain a detailed understanding of the near-wake development and to arrive at a base for model construction and validation. The first paper presents the experimental setup, data reduction and the results for the baseline case (axial flow conditions).In the second paper, the results for the yawed flow cases are presented and the effect of yaw misalignment on the near-wake development is discussed.

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Section: Introductionmentioning

confidence: 99%

HAWT near‐wake aerodynamics, Part I: axial flow conditions

et al. 2008

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“…Flow visualization methods have therefore enabled the study of the blades of operational wind turbines during stall. Successful implementations have included surface tufts , flow cones and reflective stall flags to provide indications of near blade surface flow.…”

Section: Introductionmentioning

confidence: 99%

“…Small model turbines such as the 1.2m wind turbine described by Haans et al . have been successfully studied in wind tunnels. In their study, once per revolution images of the tufted wind turbine blade were recorded by a camera positioned downwind of the turbine.…”

Section: Introductionmentioning

confidence: 99%

Digital tuft analysis of stall on operational wind turbines

Swytink-Binnema

Johnson

2015

Wind Energ.

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Operational wind turbines are exposed to dynamic inflow conditions because of, for instance, atmospheric turbulence and wind shear. In order to understand the resulting three-dimensional and transient aerodynamics effects at a site, a 10 m stall-regulated upwind two-bladed wind turbine was instrumented for a novel digital tuft flow visualization study. High definition video of a tufted blade was acquired during wind turbine operation in the field, and a novel digital image processing algorithm calculated the blade stall directly from the video. After processing O.10 5 / sequential images, the algorithm achieved a 5% bias error compared with previous manual analysis methods. With increasing wind speed (5 m/s to 20 m/s) the fraction of tufts exhibiting stalled flow increased from 5% to 40% on the outboard 40% of the blade. The independently measured instantaneous turbine power production correlates highly with the stall fraction. Some azimuthal variation in the stall fraction associated with dynamic stall induced by vertical wind shear was seen with a maximum in the 45-90 ı azimuthal location. The high detail, quantitative image processing method demonstrated good agreement with the expected behaviour for a stall-regulated wind turbine and revealed azimuthal variation because of shear-induced dynamic stall. The amount of reliable blade stall data to be obtained from digital tuft visualization has hereby been vastly increased.

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Section: Objectivesmentioning

confidence: 99%

“…The delta simulations are designed to determine if an method's assumptions regarding complex flow phenomena. Though modifications of the BEM method have been attempted, the inherent assumptions that form the basis of this method's calculations limit its overall accuracy [10].Combinations of BEM based techniques with the more complex full Navier-Stokes equations are typically more successful than pure modifications of the technique in terms of accuracy. In 2002, Sørensen and Shen [11] developed an aerodynamic model for examining the three dimensional flow field surrounding a wind turbine.…”

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Computational Examination of Utility Scale Wind Turbine Wake Interactions

Zhou¹

2015

J Fundam Renewable Energy Appl

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Numerical simulations of small, utility scale wind turbine groupings were performed to determine how wakes generated by upstream turbines affect the performance of the small turbine group as a whole. Specifically, various wind turbine arrangements were simulated to better understand how turbine location influences small group wake interactions. The minimization of power losses due to wake interactions certainly plays a significant role in the optimization of wind farms. Since wind turbines extract kinetic energy from the wind, the air passing through a wind turbine decreases in velocity, and turbines downstream of the initial turbine experience flows of lower energy, resulting in reduced power output. This study proposes two arrangements of turbines that could generate more power by exploiting the momentum of the wind to increase velocity at downstream turbines, while maintaining low wake interactions at the same time. Simulations using Computational Fluid Dynamics are used to obtain results much more quickly than methods requiring wind tunnel models or a large scale experimental test. Computational Examination of Utility Scale Wind Turbine Wake InteractionsTyamo Okosun and Chenn Q Zhou* have performed additional validation studies supporting the accuracy of commercial software. One of the most common commercial CFD codes, ANSYS Fluent ® is used in many projects due to its flexibility and accuracy. Amano et al. [17] used Fluent ® to analyze and improve the design of a wind turbine rotor blade, resulting in the addition of a swept edge to the blade in an effort to extract greater amounts of power from the wind. Palm et al. [18] used Fluent ® to determine basic relations that can be used to predict the power output of a given tidal farm configuration. Department of Mechanical Engineering, Purdue University, Center for Innovation through Visualization and Simulation, Purdue University Calumet, USA Journal of Fundamentals of Renewable Energy and ApplicationsIn 2007, Wußow et al. [19] used ANSYS Fluent ® to model a fullsized wind turbine and determine the aerodynamic flow physics in the wake downstream of the rotor. By using a direct model with a body fitted grid, this simulation aimed to accurately capture the flow physics generated by the interaction of rotating turbine blades with a given wind flow. In this case, the rotor rotational speed was fixed at a value corresponding to the velocity of the oncoming wind at the wind turbine hub height. Although this assumption reduces the computational time required for the simulation, it prevents aerodynamic forces from being accurately modeled on the wind turbine rotor. However, this does not affect the downstream wake aerodynamics, which is the main focus of the project. Using the Large Eddy Simulation (LES) turbulence model, Wußow et al. generated results that matched experimental data closely, albeit representing only the lower range of available data. Thus, simplified CFD simulations can provide accurate results in the small time frames encountered in many ind...

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Stall in Yawed Flow Conditions: A Correlation of Blade Element Momentum Predictions With Experiments

Cited by 19 publications

References 3 publications

HAWT near‐wake aerodynamics, Part I: axial flow conditions

HAWT near‐wake aerodynamics, Part I: axial flow conditions

Digital tuft analysis of stall on operational wind turbines

Computational Examination of Utility Scale Wind Turbine Wake Interactions

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