Boundary Conditions / Forces
First, the inlet must be defined using the Fluid Flow Conditions. In the Add drop down menu by Fluid Flow Conditions, select Inlet. Then, using the face selection tool, define an inlet at all 12 flat faces of the large volume, as shown below. Change Flow specification to Pressure, input the Gauge total pressure as 88744 [Pa] and 0 [C] as Total temperature.
Once the inlet is defined, the outlet is next. In the same Add menu, choose Outlet to define an outlet at the small, annular end of the duct. Change Regime to Supersonic.
Next, a Wall condition must be added to all surfaces that are not already defined. Wall can be found in the same Add menu as the previous conditions. AIM will automatically select every face that doesn't already have a constraint on it.