Identifying the flap side-edge noise contribution of a wind turbine blade section with an adaptive trailing edge

Abstract

Active trailing-edge technology is a promising application for localized load alleviation of large-diameter wind turbine rotors, accomplished using one or more control surfaces in the rotor blade's outer region. This work focuses on identifying noise contributions from the flap side-edge and the trailing edge in a laboratory condition. Measurements were conducted in the Acoustic Wind Tunnel Braunschweig (AWB) at the German Aerospace Center's (DLR) Braunschweig site. The small-scale model has a span of 1,200 mm and a chord length of 300 mm. The control surface, a plain flap, has a span of 400 mm and a chord length of 90 mm. Far-field noise was measured using a phased-microphone array for various flow speeds, angles of attack, and flap deflection angles. Due to the size of the model and assumed closeness of the sound sources, two noise reduction addons were installed interchangeably: trailing-edge brush and flap side-edge porous foam for sound source identification. Analysis of the far-field noise reveals that, while changes to the flap deflection angle alter the far-field noise spectra, the trailing-edge noise remains the predominant noise source at deflection angles (Formula presented.) and (Formula presented.). No additional noise level was observed from the flap side edge within the measurable frequency range at these angles. The flap side-edge noise has an increased role for frequency larger than 2 kHz for the larger flap deflection angles of (Formula presented.) and (Formula presented.).