In this step, we define the return. This is easy because we use a gage pressure to represent where the exhausts to the return ducts.
Left click on the return surface.
Click Edit from the Boundary Conditions context panel:
On the Type row, select Pressure.
Leave the Unit as Psi and the Pressure value = 0.
Click Apply.
What it should look like...
6. To verify that the boundary condition is correctly applied to the return, check the Design Study Bar and the colored stripe on the return surface:
On the Design Study bar, the Pressure condition should be listed with a value of 0 psi.
There should be a colored stripe on the return face that corresponds to the legend.