Courant Number in unsteady problems...
 

Hi everyone
I am simulating an unsteady two-phase problem using VOF. Up to my setting (mesh size, time step and velocity) the actual Courant Number should be around 0.2 and I also leaved the default of 0.25 for it, but when I apply the wall adhesion and surface tension between two phases in the interaction menu, the Courant Number goes up dramatically to over than 400 during iterating!
Note that without considering the wall adhesion and surface tension there is no error in iterations and it goes with the Courant Number that I predicted. (of course with wrong results)
I really dont understand any relation between Courant Number and phase interaction settings... Could anyone help?
Thanks...