Acoustic measurements of a DU96-W-180 airfoil with flow-misaligned serrations at a high Reynolds number in a closed-section wind tunnel
R. Merino-Martinez (TU Delft - Aircraft Noise and Climate Effects)
Wouter C.P. van der Velden (TU Delft - Aerodynamics)
F. Avallone (TU Delft - Wind Energy)
D. Ragni (TU Delft - Wind Energy)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
Trailing-edge serrations are passive noise reduction add-ons widely used in wind-turbine applications. This study presents acoustic beamforming results of microphone array measurements of a cambered airfoil (DU96-W-180) in a closed-section wind-tunnel at a Reynolds number of industrial interest. Two different serration geometries with different lengths were tested and compared with the straight-edge baseline airfoil. The serrations were set at a flap angle of 6 degrees. Several flow velocities and angles of attack were tested at three chord-based Reynolds numbers ranging from 5105 to 1.5106. A phased microphone array was used to obtain source maps of the trailing-edge noise; Particle Image Velocimetry (PIV) was employed to obtain information about the turbulent boundary layer approaching the trailing edge; further, a numerical simulation using the Lattice Boltzmann Method (LBM) was performed for comparison. Far-field noise from the experimental data and computations shows a satisfactory agreement. Noise reductions of several dB were obtained, especially at lower frequencies. An increase in high-frequency noise is observed after a crossover frequency, which is assumed to be due to the set flap angle.