Converge Problem

Jen

I am using FLUENT to model spray in a big tank, the spray gun has several outlet, the one in the center is for water and the others are for air. I set these openings as velocity_inlet, and the outlet of tank is set to be pressure_outlet. I tried some ways, but it does not converge especially the residule of volume fraction of water( the water speed is 1.9m/s, and the air is 20m/s).

What's more, when I calculate, the warning message "reversed flow in 94 faces on pressure_outlet" appear. Does this means there is something wrong with my codes?

This is really a big headache to me, I really wish some one could help me or give me some suggestion, Thanks so much!!!