Description of an 8 MW reference wind turbine

An 8 MW wind turbine is described in terms of mass distribution, dimensions, power curve, thrust curve, maximum design load and tower configuration. This turbine has been described as part of the EU FP7 project LEANWIND in order to facilitate research into logistics and naval architecture efficiencies for future offshore wind installations. The design of this 8 MW reference wind turbine has been checked and validated by the design consultancy DNV-GL. This turbine description is intended to bridge the gap between the NREL 5 MW and DTU 10 MW reference turbines and thus contribute to the standardisation of research and development activities in the offshore wind energy industry

HAWT near-wake aerodynamics, part I : axial flow conditions

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 valida- tion 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 three- dimensional 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. Copyrightpeer-reviewe

An approach for the verification and validation of rotor aerodynamics codes based on free-wake vortex methods

This paper presents an approach to verify and validate a newly developed free-wake lifting line vortex code to model the wake generated by a wind turbine in axial flow conditions. Although the code is intended to simulate wind turbine wakes, it may be readily applied to propellers and helicopter rotors. The Delft University of Technology model wind turbine is used for this case study. Detailed hot-film inflow measurements in the near wake and smoke visualizations of tip vortex cores are used as a basis for validating the free-wake model. A parametric analysis was carried out to investigate how different levels of blade/wake descretizations and viscous modeling influence the accuracy of the inflow results. The tip vortex locations were compared with those predicted by the vortex model. In general very good agreement was obtained. It was found that the middle sections of the blades are rather insensitive to the choice of the viscous modeling parameters. However, high sensitivity to these parameters was observed at the blade tip and root regions.peer-reviewe

Velocity measurements in the near wake of a horizontal axis wind turbine

Single film hot-film measurements in the near wake of a horizontal axis wind turbine are performed in the Delft University of Technology Open Jet Facility in order to capture the blade azimuth dependent velocity vectors. A novel approach to determine the average, blade azimuth dependent, velocity vector is proposed. It makes use of the asymmetric response of hot-films that have the film parallel to its probe. Contrary to the traditional approach in which the direction of velocity components cannot be determined and which poorly predicts relatively small velocity components, the proposed method yields velocity direction as part of the solution and consistently predicts relatively small velocity components. An uncertainty analysis is performed on the velocity magnitude and flow angle, quantifying the data quality. Furthermore, comparisons with previously published data on the same rotor, in the same wind tunnel are made. The comparisons increase confidence in the data and reveal the advantages of the proposed velocity determination method. Qualitatively, the velocity signals derived with the proposed approach are in agreement with expectations from a general vortex wake model, also the relatively small tangential and radial velocity components.peer-reviewe