1 Risø National Laboratory for Sustainable Energy, Technical University of Denmark2 Department of Wind Energy, Technical University of Denmark3 unknown
This report contains 2D measurements of the NACA 63-415 and a NACA 63-415 airfoil with modified leading edge called NACA 63-415-Risø-D. The aerodynamic properties were derived from pressure measurements on the airfoil surface and in the wake. The VELUXopen jet wind tunnel was used having a background turbulence intensity of 1%, an inlet flow velocity of 40 m/s which resulted in a Reynolds number of 1.6×106. The airfoil sections had a chord of 0.600 m and 0.606 m for NACA 63-415 and NACA 63-415-Risø-D,respectively. The span was 1.9 m and end plates were used to minimise 3D flow effects. The measurements comprised both static and dynamic inflow where dynamic inflow was obtained by pitching the airfoil in a harmonic motion. We tested the influence ofleading edge roughness, stall strips and vortex generators. For smooth surface conditions the modified airfoil showed an increase in lift-drag ratio before stall at a=8° from 67 to 72. Furthermore, the maximum lift increased from 1.33 to 1.37 while theminimum drag was maintained. Double stall was observed on the NACA 63-415 airfoil, but not on the modified airfoil. This was reflected in the standard deviation of both lift and drag in stall which was significantly lower for the modified airfoilindicating smooth and stable stall conditions. No significant differences were observed for dynamic stall. Test on both airfoil sections with zigzag tape at the leading edge towards the pressure side showed that the insensitivity to roughness was improvedsignificantly for the modified airfoil. However, if zigzag tape was mounted at the leading edge towards the suction side less improvement was observed. Mounting of stall strips at and near the leading edge showed that only if they were mounted at the veryvicinity of the leading edge the airfoil characteristics were affected significantly. If the stall strips were mounted on the pressure side downstream of approximately 1 % chord length only little influence was seen for positive angles of attack. TheDanish Energy Agency funded the present work under the contract, ENS-1363/99-0011.
Vindenergi og atmosfæriske processer; Risø-R-1193; Risø-R-1193(EN)