Help with slug flow simulation.

Kes

Dear all, i was previously trying to model droplet formation with a slug flow pattern in a T-junction and it was working fine. When i increase the flow rate of the oil phase (i'm creating water in oil emulsion), the droplets decrease in size which is expected. However the droplets are sticking to the walls and are not located at the centre of the tube even when it is smaller than the diameter of the tube. Thus i think this is due to me turning on the Wall Adhesion option under Define->Phases->Interaction. I turned it off and now i couldn't get back the flow pattern that i wanted. The solutions take very long to converge when i am using the time step recommended by the Fluent system, around 30-40 iterations per time step and the flow pattern that results is somewhat like the slug flow disintegrating into small bubbles. Reversed flow is also observed during iterations. Therefore i would like to ask if anybody could guide me the right way?