Noise Reduction Technologies for Wind Turbines

Abstract

Results from a numerical and experimental aeroacoustic assessment of 2D wind turbine blade sections are presented. CFD/CAA-based predictions using a synthetic turbulence method were conducted at a NACA 64-618 profile as well as at a new low-noise airfoil design RoH-W-18%c37. Validation experiments were performed in DLR's Acoustic Wind-Tunnel Braunschweig (AWB) for varying transition locations. A trailing-edge noise reduction benefit of 2-4 dB in overall sound pressure level was predicted for the new airfoil under design conditions. A large laminar extent of the boundary layer significantly reduces the noise emission (by up to 8~dB) compared to equivalent cases with forced transition at the leading edge. An additional noise reduction (with realistic reductions of the peak levels by 4-6 dB) was accomplished by flow-permeable trailing-edge extensions which were successfully transferred to the two profiles from forerunner aerospace-related studies.