Validation of the AeroDyn subroutines using NREL unsteady aerodynamics experiment data



Completion of the full-scale wind tunnel tests of the NREL Unsteady Aerodynamics Experiment (UAE) phase VI allowed validation of the AeroDyn wind turbine aerodynamics software to commence. Detailed knowledge of the inflow to the UAE was the bane of prior attempts to accomplish any in-depth validation in the past. The wind tunnel tests permitted unprecedented control and measurement of inflow to the UAE rotor. The data collected from these UAE tests are currently under investigation as part of an effort to better understand wind turbine rotor aerodynamics in order to improve aeroelastic modelling techniques. Preliminary results from this study using the AeroDyn subroutines are presented, pointing to several avenues towards improvement. Test data indicate that rotational effects cause more static stall delay over a larger portion of the blades than predicted by current methods. Despite the relatively stiff properties of the UAE, vibration modes appear to influence the aerodynamic forces and system loads. AeroDyn adequately predicts dynamic stall hysteresis loops when appropriate steady, 2D aerofoil tables are used. Problems encountered include uncertainties in converting measured inflow angle to angle of attack for the UAE phase VI. Future work is proposed to address this angle-of-attack problem and to analyse a slightly more complex dynamics model that incorporates some of the structural vibration modes evident in the test data. Copyright © 2002 John Wiley & Sons, Ltd.