Prediction of aeroacoustic performance of counter-rotating wind turbine by changing the rotational speed of front rotor

This study aims to investigate the aerodynamic and aeroacoustic performance of a counter-rotating wind turbine (CRWT) to define the effect of rotational wind speed of the front rotor on the sound pressure level of CRWT, using CFD simulation. For this purpose, NREL Phase VI wind turbine was considered as the single rotor, and validation of aerodynamic and aeroacoustic simulation has been carried out for the solver. Then, 3D simulation has been applied on single rotor and counter-rotating wind turbines to scrutinize the acoustic level of CRWT by changing the rotational speed of the front rotor. The unsteady flow simulation was carried out with the realizable k– ε Reynolds-averaged Navier–Stokes turbulence model, and the calculated flow field data were utilized using Ffowcs Williams–Hawkings model for predicting the acoustic level at receiver location, defined based on the IEC61400-11 standard. The results show that increasing the rotational wind speed of the upstream rotor leads to augmenting the noise emitted from CRWT. On the other hand, for tip speed ratios (TSR) ranging from 6 to 12, with increasing the front rotor RPM, the power coefficient of CRWT enhances, while for the TSR more than 12, an inverse behavior has been observed and power coefficient declines along with increasing front rotor’s speed of revolution.