Broadband noise radiation analysis for an HAWT rotor

The paper demonstrates a computational methodology for the noise prediction of an horizontal axis wind turbine (HAWT) rotor in time domain. The aeroacoustic modeling is based on the Ffowcs Williams and Hawkings equation considering only the surface monopole and dipole noise sources. The accurate solution of the noise problem is strongly influenced by the unsteadiness of the rotor flowfield, the nonuniform inflow effects and the blade aerodynamic parameters which are included in the numerical model. The aerodynamic analysis uses a three-dimensional low-order panel method combined with a boundary layer correction model for the calculation of the blade pressure distribution, obtaining satisfactory agreement with experimental data. Acoustic pressure predictions for the NREL downwind rotor are presented for several cases proving that broadband noise propagation dominates at low- and mid-frequency ranges. Sound pressure level contours occur via Fourier transformations, while the directivity for a single frequency source is also examined.