Global Courant Number of VOF
 

Hello,
I am using Fluent 6.3.26 to solve a VOF model about Air Pump, but I fall across a difficulty about how to set Variable Time Step Parameters only used in VOF model, thereinto the Global Courant Number I cann't confirm and I have not seen any article discussing its reasonable range, and I know the default is 2.
Now I want a larger Time Step Size which can assure convergence to consume fewer time, is it right that I change the default Global Courant Number 2 to 20 if 20 can also assure my model convergence.
I spent ten days to get a result with a computer of 4 CPU & 8G EMS memory & 32 bit WinXP, the Time Step Size I gave is 1e-5, but I feel it is too small and cost me too much time, I still have many types of Air Pump. How much time I will spend having them finished! My God!
Thanks for any reply!

No one answers me? No one knows how to confirm it?
I'm disappointed, very very disappointed..........