Turbulence BCs for flow into vacuum chamber
 

Hey Foamers,

I'm simulating airflow into a vacuum chamber through a small diameter capillary (0.508 mm) from atmosphere using rhoCentralFoam. I've modeled the chamber, capillary and small control volume outside of the capillary. My flow becomes turbulent inside of the capillary (Re ~ 5000) and due to high pressure gradients and areas of low Re in my domain I've chosen the k-omega SST model.

I'm having trouble determining the proper boundary condition at the inlet (control volume outside of capillary.) Using the average calculated inlet velocity and length scale from this boundary I get very small values of k and omega (on the order of 1e-4 and 1 respectively.)

My calculated boundary conditions for the walls of the capillary and vacuum chamber are based on Menter's paper and summarized here: http://turbmodels.larc.nasa.gov/sst.html. The omega calculated omega values are extremely high on the order 1E9 and 1E11

If anyone has an suggestions on the topic I would greatly appreciate it.

Thanks in advance.

-Eric