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Unformatted text preview: April 1999 • NREL/CP-500-26337 Horizontal Axis Wind Turbine Aerodynamics: ThreeDimensional, Unsteady, and Separated Flow Influences M.C. Robinson, M.M. Hand, D.A. Simms, S.J. Schreck Presented at the 3rd ASME/JSME Joint Fluids Engineering Conference San Francisco, California July 18-23, 1999 National Renewable Energy Laboratory 1617 Cole Boulevard Golden, Colorado 80401-3393 NREL is a U.S. Department of Energy Laboratory Operated by Midwest Research Institute • Battelle • Bechtel Contract No. DE-AC36-98-GO10337 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Available to DOE and DOE contractors from: Office of Scientific and Technical Information (OSTI) P.O. Box 62 Oak Ridge, TN 37831 Prices available by calling 423-576-8401 Available to the public from: National Technical Information Service (NTIS) U.S. Department of Commerce 5285 Port Royal Road Springfield, VA 22161 703-605-6000 or 800-553-6847 or DOE Information Bridge http://www.doe.gov/bridge/home.html Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste Proceedings of FEDSM99 rd 3 ASME/JSME Joint Fluids Engineering Conference July 18-23, 1999, San Francisco, CA FEDSM99-S295-01 HORIZONTAL AXIS WIND TURBINE AERODYNAMICS: THREE-DIMENSIONAL, UNSTEADY, AND SEPARATED FLOW INFLUENCES M. C. Robinson National Renewable Energy Laboratory 1617 Cole Blvd., Golden, CO 80401 [email protected] D. A. Simms National Renewable Energy Laboratory 1617 Cole Blvd., Golden, CO 80401 [email protected] M. M. Hand National Renewable Energy Laboratory 1617 Cole Blvd., Golden, CO 80401 [email protected] S. J. Schreck National Renewable Energy Laboratory 1617 Cole Blvd., Golden, CO 80401 [email protected] ABSTRACT Surface pressure data from the National Renewable Energy Laboratory’s “Unsteady Aerodynamics Experiment” were analyzed to characterize the impact of threedimensionality, unsteadiness, and flow separation effects observed to occur on downwind horizontal axis wind turbines (HAWT). Surface pressure and strain gage data were collected from two rectangular planform blades with S809 airfoil crosssections, one flat and one twisted. Both blades were characterized by the maximum leading edge suction pressure and by the azimuth, velocity, and yaw at which it occurred. The occurrence of dynamic stall at all but the inboard station (30% span) shows good quantitative agreement with the theoretical limits on inflow velocity and yaw that should yield dynamic stall events. A full three-dimensional characterization of the surface pressure topographies combined with flow visualization data from surface mounted tufts offer key insights into the three-dimensional processes involved in the unsteady separation process and may help to explain the discrepancies observed with force measurements at 30% span. The results suggest that quasi-static separation and dynamic stall analysis methods relying on purely two-dimensional flow characterizations may not be capable of simulating the complex three-dimensional flows observed with these data. INTRODUCTION Wind turbine aerodynamic loads routinely exhibit startling spatial and temporal complexities, driven by the combined influences of three-dimensionality, unsteadiness, and dynamic separat...
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