Coarse-resolution numerical prediction of small wind turbine noise with validation against field measurements

The noise emission and the power output from a small horizontal axis wind turbine is investigated using coarse-resolution computational fluid dynamics (CFD) simulations conducted with the commercial software STAR-CCM+®. The steady Reynolds-averaged Navier-Stokes (RANS) and transient delayed detached-eddy simulation (DDES) methodologies were used for the prediction of the flow field around the wind turbine. It is found that the DDES method with the Spalart-Allmaras turbulence model provides predictions of the wind turbine power that are in good conformance with available field measurements. The aeroacoustic calculations were performed using both the STAR-CCM+® acoustic model and an in-house code. The in-house code implemented both the permeable and impermeable formulations of the Ffowcs Williams and Hawkings (FW-H) equation. The predicted A-weighted sound pressure level (SPL) spectra, as well as the apparent SPL, obtained from the permeable formulation of the FW-H equation agree well with the wind turbine acoustic field measurements. It is found that the presence of the tower slightly decreases the wind turbine power output at all simulated incident wind speeds. It is also found that the presence of the tower leads to modifications of the SPL spectra at frequencies between about 300 and 1500 Hz.