Bubble column liquid fraction

Sally

I'm simulating a bubble column. I know from correlations that the vapour fraction is about 0.50, but CFX is blowing all of the liquid out of the overflow leaving me with a vapour fraction of 0.95. I've tried changing the bubble size (4mm to 1 cm) and changed the drag models and the amount of lift, but no success. k-epsilon and FOU solution scheme. Does anybody have a magic bullet for getting the right liquid hold-up ?

Thanks, Sally.