Hello friends.Please help!

My issue is not very dificult I bilieve but I have some truble solving it out. So: I have a simple model.A pipe with an object witch does not tuches the pipe wall.I want to model a pressure inlet and a velocity outlet.My results are concentrate on the flow around the part and after the cavitation. My problem is that fluent does not ''see'' the object and solves only the pipe.I have seen some options sutch ''merge volumes'' ''fuse volumes'' but I dont know what to do.

Thanks from now / Best regards from Greece!

How did you created the mesh? In Gambit? Make sure that you subtract the inner geometry from the surrounding pipe so that fluent recognizes this as a wall inside.