The performance of many mechanical devices has been widely used when it is not clear. But before people fully understand its physical laws and complete theoretical analysis, it is difficult for these devices to achieve their best performance.

The propeller blade of a ship refers to the blade that can rotate in the water, which is a part of the device that converts the rotating power of the engine into the propulsion force. There can be two or more blades connected with the hub. The rear side of the blades is a helical surface or similar to the helical surface.