Thank you for your reply. I've read the manual and I know how to set up the fan boundary condition. Everything normally functions when I run single simulations and I manually check the direction before starting the solver. The issue starts when I try to run a batch of design point simulations, where the mesh is updated each time. Let me try to clarify:
My issue is with controlling the zone average direction that the solver calculates automatically when reading in the mesh. For the same mesh topology/layout, it will sometimes calculate a zone average direction of opposite sign. This is normally easily solved by checking the reverse direction box, but because I'm using design point operations, I cannot control this parameter for each design point separately. Furthermore, there is no way to check the calculated direction without opening Fluent physically.
What I am trying to do is to either specify the zone direction myself or set up my geometry in such a way that the zone average direction is predictably calculated, such that I always know which direction the pressure jump will be applied to in every design point. Currently, it is inverting seemingly at random and I only find out about that after the simulation fo the design point has been completed. Being able to view the zone average direction from workbench (e.g. as an output parameter) would be an acceptable workaround, but I have not been able to figure out a way to do this.
I hope this makes my issue more clear. Thanks again!