So I have a "kinda" spherical but symmetric pressure vessel.

Inside this pressure vessel there is water.

I have a series of (lets call them) soda straws blowing air through the water.

And then an exhaust a the top of the tank.

I am trying capture what configuration of "soda straws" creates the lowest pressure drop. I am not looking to do multi-phase flow.

My problem/question stems from the fact that for the life of me, I cannot figure out how to model the water level in this vessel as it has an air-gap at the top.

I've tried using a cap and fluid subdomain and have tried putting a solid in that would be the water volume and disable that solid.

Neither approach worked.

Thoughts?

Help?

Thanks in advance.