Effects of yawed inflow and blade-tower interaction on the aerodynamic and wake characteristics of a horizontal-axis wind turbine

The aerodynamic characteristics of a wind turbine change dramatically under the influence of complex inflow and interaction between blade and tower. In this study, detailed full-scale CFD models of NREL 5 MW wind turbine are developed to investigate the specific aerodynamic characteristics with varying yaw angles and wind speeds based on OpenFOAM tool box. The total and local blade aerodynamic loads are analyzed by incorporating the effects of yawed inflow and tower. It is clearly noted that the blade load fluctuation amplitude and influence range due to the presence of tower gradually increase when the yaw angle becomes larger. Moreover, the threepoint method is employed to extract the angle of attack (AOA) and induce factor of different blade sections within a rotation period. Generally, the fluctuation amplitudes of AOA and induce factor increase with the increase of yaw angle by ignoring the abrupt change induced by the tower shadow effect. Subsequently, the effects of blade rotation on the aerodynamic force of tower for varying wind speeds and yaw angles are considered, and a "negative pressure" state is observed when the blade passes in front of the tower. Finally, the wake effect under yawed inflow is revealed in details.