Rob
Ansys Employee

The walls associated with the interface zones are to account for pairs that don't fully overlap. They aren't visible, and are generally left alone. Interior zones represent the surface between connected cell zone but are also created to contain all of the facets of the cells within a fluid (or solid) zone, again, the latter are left alone. 

In your model, none of the parts are connected, and unless you're moving these you may want to look at multibody parts to get a conformal mesh. You'll then have no interface pairs.