Integration of Beddoes-Leishman aerodynamic model into Double Streamtube thoery for vertical axis wind turbine simulation

Wind power generation plays today a fundamental role in the frame of renewable energies and the wind turbine design and optimization is an even more important task for the wind energy manufacturer industry. On a general basis wind turbines can be classified as Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT) whether the wind direction is parallel or perpendicular to the axis of rotation. Moreover the aerodynamic behavior of these two typologies of turbines is very different, as the HAWT is mainly characterized by steady blade load while the VAWT is characterized by a strong aerodynamic unsteadiness on the blade, which results to be very complicated to be predicted and modeled. In this paper we propose a numerical methodology for the prediction of aerodynamics of VAWT, coupling the Beddoes-Leishman (BL) model for the airfoil´s unsteady aerodynamic coefficients prediction with the Paraschivoiu Double Streamtube (DS) aerodynamic model for VAWT. The proposed model couples the rotational dynamics of the wind turbine modeled by DS, with the aerodynamic coefficients degradation due to the local flow unsteadiness on the blade modeled by BL. The results achieved were compared with a set of experimental data available in literature and with CFD simulation, showing the importance of the non-stationary BL model for the blade´s aerodynamic coefficients prediction. Furthermore the coupled DSBL model is able to provide key information about the non-stationary aerodynamic conditions experienced on the blade for design and optimization purposes.