Reading the configuration file of the multiple perpendicular flaps tutorial, I get the impression that there are two fluid participants, Fluid1 and Fluid2 (which is not the case, the only fluid participant is Fluid):

We have as a guideline:

Mesh names start with the participant/domain name, e.g. Fluid-Mesh.

The guideline seems to be followed, even if the example does not apply here.

I suggest that we name the branches Fluid-Solid1-Mesh-Centers (and similarly for the rest), as this makes it clear what the mesh is used for.