The cross-section airfoil of a wind turbine blade is very similar to the airfoil of an aircraft wing. The principle is also very similar. When the airflow flows from the wing tip and flows through the upper and lower surfaces of the blade respectively, due to the unequal areas of the upper and lower surfaces and the unequal airflow speeds, a pressure difference is generated on the upper and lower surfaces, which forms lift. The lift force can be decomposed according to two directions, parallel and perpendicular to the blade rotation plane. The force in the parallel direction makes the blade rotate, and the force in the vertical direction makes the blade bend backward. In practice, we can see that the tips of the blades in operation are curved.
The original back (inward) side of your fan is the side facing the wind. It is recommended to use a three-blade fan with a diameter of about 1.5 meters. Are they basically fans like this? The blade shape of the fan used for blowing is different from the blade shape of the fan blade. It should be a leaf shape similar to the wings of an airplane