designing an air intake under gambit
 

I tried to design an air-intake under gambit to study the creation of a vortex into it. I tried to recreate the experimental condition by designing the box which contains the intake. The problem is i don t not hopw to deal with my intake inside this volume, because what I am really interested in is the flow inside the intake. I tryed to substract the intake from the volume and did not succeed.I got the flow around and not inside the intake. Even if I define the volume just as the tickness of the intake, i still got problems. So please help me