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Momentum Sources

Momentum sources can be used to simulate fans, ventilators, propellers, and other similar fluid acceleration devices without having to model the exact geometry and motion of the device. For instance, one may want to model an axial fan whose dimensions and output velocity are known. With this feature, it is possible to assign the velocity output to a cylinder with the same cross-section as the fan.



It is recommended to refine the mesh in the vicinity of the source (e.g. refinement region downstream of the source), in order to better capture the dynamics of the flow.


  • In the simulation tree, navigate to Advanced Concepts and add a Momentum Source by clicking on the ‘+’ button (circled):
setup of a momentum source in the simscale workbench
Figure 1: Accessing Momentum sources feature in the SimScale Workbench. The source can be a CAD part, a geometry primitive or a cell zone.
  • Simscale currently supports only the Average velocity momentum source. This simulates a linear momentum defined by a velocity vector \(\vec{u} = [u_x u_y u_z]\).


Consider an example application where a rectangular duct has a fan sitting in the middle whose flow needs to be simulated.

momentum source assignment using cartesian  box
Figure 2: Defining momentum source with cartesian box geometry primitive positioned inside rectangular duct domain
momentum source results in simscale onine post processor
Figure 3: Velocity distribution shown using controues after modeling a momentum source as shown in Figure 2
velocity and pressure contours for momentum source
Figure 4: Momentum source accelerates velocity through its volume (left) and Pressure being adapted to the velocity gradient respectively

Last updated: December 30th, 2020

What's Next

part of: Advanced Concepts