VELOCITIES IN THE ROTOR PLANE

 
The wind speed "V" is slowed down in the rotor plane. Energy is extracted. The wind speed after the rotor is apx. 1/3 x V (max. efficiency).The blade, however, does not "see" the wind from the direction, it actually comes, because the blades rotates through

the air with a tip speed "V tip". This creates the resulting wind

speed "V res". You can construct "V res" as shown in the vector drawing above