Negative pressure!
 

I am trying to model a horizontal cylindrical device with one inlet and 2 outlets (gas, liquid). The inlet fluids are air (continuous) and water (dispersed).The total pressure is 4 bar. The boundary conditions regarding pressure are 1)gas outlet- static pressure= 0 Pa 2)liquid outlet-static pressure= 12000 Pa 3) inlet pressure is governed by flowrates of air and water

Initially i had problems with backflow. Some of the guys here adviced me to extend geometry, many thanks to them, it works!

I have extended the geometry of the outlets in order to avoid backflow or re-circulation and I used the static pressure at the liquid outlet as 5000 Pa. to enable some hold up. Now , I dont get any backflow , but I still get negative pressure as in my previous cases. In CFX-post it seems like there is no interaction between water and air. It seems like only water is forced and not air, this is not true! Please advice.

Thanks, Neel