Hello,
The fan curve configuration looks unexpected to me. Usually, the custom fan boundary condition is defined to the inlet OR to the outlet (but not both). For instance, let’s say that we have a custom fan BC for the inlet.
For the outlet, I would normally expect either a pressure outlet boundary condition, or a natural convection inlet/outlet if you want the flow to figure itself out. It’s also possible to define a velocity outlet if you are interested in a particular flow rate.
This article should contain more details: How do I Model a Fan Curve in SimScale? | Knowledge Base