Gas-Liquid flow in bubble column need help to understand why water is leaving out???
 

Hi,
I am working on CFD of bubble columns.I have a issue I am encountering in it .As I run the simulation i find that there is water leaving out from the column.Even with a patch of air above the liquid I encounter the same .Why is that so...My iterations are going on (continuity fluctuation between 10^-3 to 10^-4) but they are not converging.Any one can plz help me understand whats going wrong?
I specified the outlet as pressure outlet.(i even tried putting the Back flow air volume fraction as 1) but no good results yet..

Thank you in advance.