Effect of Wind Shear Profile on Broadband Noise Emissions from Wind Turbines Blades Under Neutral Atmospheric Conditions

The size of utility-scale wind power plants and number of installations are increasing constantly due to growing demand for wind power and to combat climate change. One of key issues posed with large size turbines is longer blades with higher blade tip speeds which generate higher aerodynamic noise levels and cause deleterious health effects such as annoyance and stress for inhabitants near turbines. In this paper, the effect of log-law and power law wind shear profiles on the sound power level is investigated when turbines operate in neutral atmospheric boundary layer conditions. Brooks et al. [1] and Moriarty & Migliore [2] models have been implemented for predicting turbulent boundary layer trailing edge noise and inflow broadband noise levels from blades of 2 MW wind turbine. Results demonstrate that using power law exponent range of 0.05–0.2, inflow noise increased by 2–5 dB for entire frequency spectra, while trailing edge noise increased by 2 dB for f < 1 kHz. With log-law profile, the trailing edge noise showed a change of 10 dB while for inflow noise showed change up to 5 dB when surface roughness varied from 0.01 to 0.1. The overall noise levels predicted by both models using power and log-law have been validated with measured data of GE 1.5sle and Siemens SWT turbines at wind speed of 11 m/s. It was found that overall noise levels obtained using power law agreed with experiment data within 2 dBA, while log-law predictions deviate by 4–7 dBA for f < 1 kHz and within 1 dBA for f > 1 kHz in the frequency spectra.