Hello,
You do not need to include a point mass for the internal tank. The mass of the fluid is accounted for automatically by the Aqwa solver.
The internal tank surfaces should be physical geometry, with their surface normals pointing into the internal tank fluid. This usually means that you need to apply a Surface Flip (in DesignModeler) or Reverse Normals (in SpaceClaim) to get the surface orientation right.
I'm sorry that I can't help with the user-defined force coding, I'm limited to the amount of support that I can provide on this forum - I can only point you to the example which is included in the Ansys installation, under e.g. C:\Program Files\ANSYS Inc\v232\aqwa\utils\ExternalForceCalculation. Hopefully someone else (not an Ansys employee!) will be able to assist you with that.
Mike
You are navigating away from the AIS Discovery experience