The wind tests were performed to represent the correct mean wind
thrust or drag forces on the turbine. The wind thrust curve of the NREL
5MW turbine is shown in Fig. 4. With the wind speed larger than the
cutout speed 25 m/s, the wind turbine will be parked and the blades
will be feathered into the wind, so there is only wind drag on the
blade, and there is no centrifugal force and gyro moment. At the rated
wind speed of 11.4 m/s, the thrust force on the rotor reached the maximum
value. Two disks of different diameters were used to model the
two different thrust forces based on the drag formulation on the flat