Boundary condition issue in 3D problem
 

Hi,

As it is shown in image I am trying to model a 3D impinging jet problem. i used the boolean - subtract (Subtract the inside of target box from the enclosure) but in fluent it adds the interior for target box in boundary conditions list. It also adds some other boundary conditions that I don't require. How can I define that in which area I want the fluent to solve the flow?
That tube is also my nozzle.