Influence of Wind Shear on Far-field Sound Propagation From Wind Turbine

Acoustics from wind turbines is a cause of annoyance to neighbors. The low-frequency noise that travels to the far-field is an increasing concern with growing numbers of onshore wind turbines. This work discusses the noise generation and propagation from a wind turbine under four vertical atmospheric wind shear conditions. Firstly, the flow characteristics (specifically the trailing-edge boundary layer thickness) around a NACA0012 aerofoil are determined using CFD simulations for an angle of attack of 6 degrees. These results are used in the BPM model to estimate the trailing-edge noise generated from the blades. The resulting broadband noise signal is then propagated to the far-field using a ray model. The sound pressure level for distances up to 5km in the downwind direction is evaluated, and the spectral distribution of the noise at different locations analyzed using Fourier Transform. Low-frequency fluctuations are observed to persist even at large distances from the wind turbine blades. The spatial locations corresponding to constructive and destructive interference of the acoustic signals appear to be strongly influenced by the vertical wind shear profile.