The fan object is used in fluid simulations. It generates a fluid environment and produces a flow with the following controls:

Turbulence: Amount of turbulence in the flow. If turbulence is zero, the flow has the same constant direction everywhere.

Radius: The radius of the fan object. Radial falloff below uses the radius.

Radial falloff: This setting defines how the flow reduces away from the fan axis.

Axis falloff: Defines how rapidly the flow decreases in the direction of the fan axis. The falloff is symmetric in front of and behind the fan.

[Note] Note
The actual flow speed and other fluid properties can be defined from the Physics tab of the property window.