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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.

## Preparation

Note

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.

## Approach

• In the simulation tree, navigate to Advanced Concepts and add a Momentum Source by clicking on the ‘+’ button (circled):
• Simscale currently supports only the Average velocity momentum source. This simulates a linear momentum defined by a velocity vector $$\vec{u} = [u_x u_y u_z]$$.

## Example

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

Last updated: December 30th, 2020

What's Next

part of: Advanced Concepts