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

Summary 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 1200 mm and a chord 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. For sound source identification, two noise reduction addons were installed interchangeably: trailing-edge brush and flap side-edge porous foam. 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 − 5 ◦ and 5 ◦ . 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 − 10 ◦ and 10 ◦ . Furthermore, numerical reproduction of the results will also be presented using the FMCAS (Fast Multipole Code for Acoustic Shielding) toolchain developed at DLR.