Propeller

Device that transmits rotational power into linear thrust on a fluid

A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a type of propulsor with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which exerts linear thrust upon a working fluid such as water or air when rotated. Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a boat through water or an aircraft through air. The blades are shaped so that their rotational motion through the fluid causes a pressure difference between the two surfaces of the blade by Bernoulli's principle which exerts force on the fluid.

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