Characteristics of the aerodynamic force on the blades of a horizontal-axis wind turbine under wind shear and tower interference

The aerodynamic forces on the full-size National Renewable Energy Laboratory 5 MW wind turbine are numerically investigated, considering the effects of wind shear and tower interference. During the operation of wind turbine, the aerodynamic forces on the blade fluctuate periodically, with the frequency quite close to the natural frequency of the blade. As the blade enters the region of high oncoming flow velocity, there is a notable blade stall near the suction surface of the airfoil, which results in a remarkable increase in drag coefficient on the blade and a plateau of lift coefficient. This significantly impacts the thrust and torque on the turbine. In addition, as the blade approaches to the tower, there is a distinct increase in pressure on the leeward surface near the root of the blade. Consequently, the interference of tower will contribute to a larger fluctuation of the thrust and torque during the blade operation. Finally, a formula model is derived to accurately predict the thrust and torque on the blade under a power-law wind profile and tower disturbance.