Investigating the Effects of Tip Modification on High-Frequency Noise Emission of CART II Wind Turbine using a Hybrid Computational Aeroacoustic Approach

Abstract

This study carries out computational aeroacoustic calculations around the tip region of the CART II wind turbine blade. Additionally, two modified tip designs, namely; tip O and tip R, are further investigated to determine how the geometry of the tip region affects the noise emission characteristics of the wind turbine. The study focuses on the tip vortex noise mechanism using hybrid computational aeroacoustic to tackle the issue of the enormous computational power required for direct noise simulation. Improved Delayed Detached Eddy Simulation (IDDES) technique is used to calculate the instantaneous turbulent flow field near the sound source region, and the noise prediction in far-field is performed using the Ffowcs Williams and Hawking’s (FW-H) acoustic analogy. The method visualizes the flow field near the blades’ tip, assisting researchers to have an accurate understanding of aerodynamically induced noise mechanisms in that highly complex flow region, thus being able to modify tip design in a way that contributes to lower overall noise emission. The results for the outboard section of the CART II wind turbine’s blade are validated with experimental data. Broadband noise sources such as turbulent-boundary-layer trailing-edge (TBL-TE) noise and the tip vortex noise mechanisms are investigated for the base case as well as tip O and tip R. The results show that the overall sound pressure level (OASPL) and the generated torque of tip R and tip O, are 2.0 %, 5.0 % and 0.8 %, 2.2 % lower than the base case, respectively.

Keywords

• horizontal axis wind turbine
• aerodynamic noise
• turbulence
• ffowcs williams and hawkings acoustic analogy
• improved delayed detached eddy simulation