air into box filled with water, outflow for water at bottom
 

Hello forum members,
my name is Peter from Germany. I need to model the following situation and I wanted to ask you politely if my assumptions are correct:

A box (l/w/h 500mm/300mm/300mm) made of aluminium is filled with water. At the bottom of the box there is an outflow that is initially closed. At the top of the box is an air pressure inlet that is limited to 200 kPa (mass flow rate is approx. 0.008 kg/s) and is also initally closed.

I want to model the two phase behavior, more precisely the outpressing of the water by air, after inlet and outflow are opened simultanely.

What I did so far is:
(1) Since the box is symmetric in width direction I use a 2D-model.
(2) pressure based, transient solver, gravity enabled
(3) multiphase - VOF, Implicit, Implicit Body Force, 2 eulerian phases
(4) viscous model: i tried laminar and k-epsilon realizable
(5) i defined two materials, water and air
(6) phase 1: air, phase 2: water. interaction by surface tension coefficient 73.5 dyn/cm
(7) operating conditions: operating pressure 101325 pascal, gravity enabled, right spot of reference pressure location (= no water)
(8) inlet as massflow inlet, flow direction normal to water surface, no initial gauge pressure. mass flow rate (phase 1, air): 0.008 kg/s, mass flow rate (phase 2, air): 0 kg/s
(9) outlet aus pressure outlet. gauge pressure: 0 pascal, backflow normal to boundary. phase 2 backflow volume fracion: 1
(10) initialized the solution by massflow inlet and patched the water filled area accordingly

My problem is that the simulation results to not correspond to what I have measured by pressure and massflow sensor. Since I'm relatively new to this area of simulation I want to ask how you would model such a problem and if I did something wrong so far!

Thank you very much
Peter