Aeroacoustic analysis of a wind turbine airfoil and blade on icing state condition

An influences of iced airfoils on aerodynamic and aeroacoustic properties were studied to predict of the wind turbine noise on icing state. In order to validate the aerodynamic performance, the experimental results and iced airfoils, which were studied by Jasinski et al. ["Wind turbine performance under icing state conditions," AIAA Paper No. 97-0977, 1997], were used. Ice accretions on the two S809 wind turbine airfoils were predicted using the NASA LEWICE code. For analysis of boundary layer properties, the computational fluid dynamics was used when the Reynolds number is 1 x 10(6). To validate aerodynamic performances, lift coefficients were compared to the experimental result. The aeroacoustic analysis is estimated by summating the Turbulent inflow (TI) noise and the airfoil self-noise. The airfoil self-noise is obtained using aerodynamics data such as a boundary layer thickness. Semi-empirical method proposed by Brooks et al. [Airfoil Self-Noise and Prediction (NASA reference publication 1218, 1989)] was used. The TI noise is a dominant noise source because of a complicated shape of leading edge on the iced airfoil. For considering leading edge shapes, therefore, TI noise modeling proposed by Moriarty et al. [" Recent improvement of a semi-empirical aeroacoustic prediction code for wind turbines," AIAA Paper 2004-3041, 2004; " Prediction of turbulent inflow and trailing-edge noise for wind turbines," AIAA Paper 2005-2881, 2005] was used. As a result, lift coefficients of the iced airfoils matched well experimental data by Jasinski et al. The sound pressure level was increased 2-4 dB from the clean airfoils. The analysis of wind turbine blades on icing state was conducted using the same method. The NREL Phase VI rotor was used as the baseline. Ice accretions on the two wind turbine blades were predicted using the LEWICE code. The overall sound pressure level was increased up to 2.6 dB from the clean wind turbine blade. (C) 2014 AIP Publishing LLC.