[eric.m.tridas]

Hey Foamers,

I'm attempting to model the airflow through a capillary into a vacuum system. The pump flow rate is 33 cubic meters per hour (which corresponds to an average velocity of 18.67 m/s through a KF-25 flange). The capillary is 65 mm long and 0.5 mm in diameter. I am trying to calculate the pressure in the vacuum chamber based on this pumping rate, therefore I do not want to impose any pressure boundary conditions on the vacuum side of the capillary. The inlet conditions are atmospheric.

The problem is that the simulation doesn't do anything when started. I believe the problem lies in my inlet boundary conditions. My BCs are as follows:

p:
inlet - fixedValue, value 101325
outlet - zeroGradient

U:
inlet - inletOutlet, inletValue uniform (0 0 0), value uniform (0 0 0)
outlet - fixedValue, value uniform (0 -18.674 0)

I've attached an image of my geometry for reference. The pump (outlet) boundary is on the middle of the face starting at (0.075, -0.05). If anyone is working on something similar or has encountered problems of this type your help would be greatly appreciated. Also, I can post my case if anyone is interested. Thanks in advance.

-Eric