Correcting inflow measurements from hawts using a lifting-surface code

Aerodynamic performance data from a rotating HAWT blade is typically correlated with measurements of a local inflow angle, obtained by flow angle sensors attached to the leading edge of the blade section. In order to provide accurate performance data for 2D blade-element/momentum codes, the 3D field data must be corrected in terms of the section angle of attack. A 3D Lifting-Surface Inflow Correction Method (LSIM) has been developed with the aid of a vortex-panel code in order to calculate the relationship between the local flow angle and the angle of attack. Sets of inflow correction curves were produced for each spanwise station of interest. The method has been tested using hypothetical 3D input data, based on measurements from the Combined Experiment Rotor at the National Renewable Energy Laboratories and wind tunnel tests at Delft University of Technology. The method was shown to successfully produce a converged solution for the inflow correction curves. The results show the importance of using the 3D LSIM correction instead of a 2D correction, particularly at the inboard sections of the blade where the upwash at the sensor is affected by post stall effects and changes in spanwise circulation distribution on the blade.