Estimation Method to Achieve a Noise Reduction Effect of Airfoil with a Serrated Trailing Edge for Wind Turbine Rotor

Abstract

This chapter describes a wind tunnel experiment that was undertaken to investigate the changes in the aerodynamic performance of a wind turbine due to the inclusion of a 2-Dimension (2D) airfoil with a serrated trailing edge designed to reduce the noise caused by a wind turbine rotor blade. The restrictive condition for the serrated trailing edge equipped with the use of a 2D airfoil was examined through the use of a wind tunnel experiment after studying existing restrictive condition and analyzing prior research on serrated trailing edges. The study was conducted according to Howe's theory, which is a cornerstone of the study of noise reduction effects produced by a serrated trailing edge. For the serrated trailing edge equipped on a 2D airfoil, the wake distribution and the relation to noise were analyzed in order to determine the restrictive condition in accordance with Howe's theory. The results indicated that an empirical formula or a theoretical approach should consider changes in the boundary layer thickness of a 2D airfoil, so an empirical noise prediction formula is suggested for the serrated trailing edge. Also, a comparison and an analysis of the prediction and the experimental results for the noise produced by the NACA0012 or the baseline airfoil equipped with a serrated trailing edge suggested a novel formula for a 2D airfoil. Finally, the 2D airfoil noise data are compared with wind tunnel test data by using an empirical formula estimation method.

Serrations as a Passive Solution for Turbomachinery Noise Reduction

“…Ryi and Choi [34] also aimed to reduce noise by modifying the trailing edge, but their application focused on wind turbine rotor airfoils. They used an experimental wind tunnel setup placed in an anechoic chamber to characterize a constant chord (350 mm) and torsion-free wind turbine blade using six different types of greenhouses.…”

“…The reduction increases with increasing channel depth (at f > 500 Hz); the effect is maintained even at high f, up to 10 kHz; a smaller channel width is desirable Umax ~ 80 m/s Higher ΔOASLP with increasing h/λ ratios; Very high h/λ ~ good at high f. Analytical, imposed turbulence, M = 0.1 [34] Ryi & Choi [34], 2018 ⊠…”