How does "Momentum Source" work?

I am trying to figure out what “momentum source” actually does.
I have read these two pages:

but none of them provide any formulae that would help figure out how the input “mean velocity” is represented in the Navier Stokes equations.

Let’s say I assign a “momentum source” to a box and provide a desired mean velocity.
I assume that the “momentum source” feature then computes a mass-specific force F required to achieve that the velocity averaged in the box equals the user-input mean velocity.
I assume that this mass-specific force is imposed at every location inside this box, F thus being constant in space within the box.

What I actually need is a means of assigning a mass- or volume-specific force that is than added to the right-hand side of the Navier-Stokes equations.
This does not seem to be implemented though.

Is this correct?

Hi @bastian!

I can check that and see if there is just a simple change in the velocity terms. More information will follow!



Hi, any updates on this? Also wondering how the momentum source actually works…

All transport equations (momentum, energy, species) have a source term into them. When the equations are discretized, the source term will represent a direct momentum source within the cell. When you add a momentum source, you need to select the cells or regions, which will get the specific source when the discretization occurs. This can be solved either explicitly or implicitly.

In the image below, the source terms are represented as S,phi (in the general form), or Sx,Sy,Sz for the specific form.

I hope this helps,

J.A. Gutiérrez.

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