Momentum source is a feature that accelerates fluids with respect to the assigned Cartesian axis and magnitude. It can be used to simulate fans, ventilators, propellers, and other similar fluid acceleration devices.
This feature can be found under Advanced Concepts.
All you need to do is to define a simple volumetric zone (a model that imitates the region of source), and assign velocity value with respect to the axis.
Momentum sources can be used in every analysis type, except Compressible and Multiphase.
Velocity distribution after using momentum source