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You don't need to include the metal bit unless you really want to see the temperature. Have a look at Fluent's wall boundary options to see what's possible. 

Looking at the mesh & contour. The "jet" is diffusing down the coarse mesh in the middle of the expansion. In CFD we mesh to both the geometry and the flow: we need to capture the domain shape, but also resolve the flow gradients. In this case you've refined the wall but not the core where the flow is getting interesting. Remesh with a pure poly mesh and have a look at Bodies of Influence: it'll be covered in the Learning modules on here or from Help in Fluent Meshing.