Time for fluid replacement

Andreas

Hello,

I'm working on a VoF-model of a quickfilter for water treatment. Water is pumped upwards through a zylinder and flowing out over the edge of a funnel inside of that zylinder. The system is open to atmosphere.

What I'm interested in is the time it takes to replace the water in the system.

Could it work to use VoF and define a third phase (water-new) additionoal to air and water-old, as VoF is ment for non-interpenetrating phases?

Any suggestions?

Thanks, Andreas