Horizontal Axis Wind Turbine Aerodynamics: Three-Dimensional, Unsteady, and Separated Flow Influences

Research output: Contribution to conferencePaper


Surface pressure data from the National Renewable Energy Laboratory's 'Unsteady Aerodynamics Experiment' were analyzed to characterize the impact of three-dimensionality, 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 airfoilcross-sections, 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 fullthree-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 stallanalysis methods relying on purely two-dimensional flow characterizations may not be capable of simulating the complex three-dimensional flows observed with these data.
Original languageAmerican English
Number of pages13
StatePublished - 1999
Event3rd ASME/JSME Joint Fluids Engineering Conference - San Francisco, California
Duration: 18 Jul 199923 Jul 1999


Conference3rd ASME/JSME Joint Fluids Engineering Conference
CitySan Francisco, California

NREL Publication Number

  • NREL/CP-500-26337


Dive into the research topics of 'Horizontal Axis Wind Turbine Aerodynamics: Three-Dimensional, Unsteady, and Separated Flow Influences'. Together they form a unique fingerprint.

Cite this