[silencebreak]

Hey there,

I got an issue with setting a better outlet boundary condition in an interFoam simulation.

The case:
I got an reservoir with water at free surface conditions and air (so two phases). I got an outlet/inlet at the bottom of the reservoir from where water could get in and out. The top of the reservoir is with an atmosphere patch where air could get in but no water out.

The issue is as followed:
I don't get any problems for the case that water is flooding in the reservoir.
But the problem is my case where the water is flooding out. When I set (in my opinion) the right boundary conditions the simulation is really slow, like 12 seconds of simulations with 12 hours and 60 cores running.
So I want to simplify it and just let water out at the outlet. So i tried just to set the outlet patch in alpha.water to fixedValue with value 1. It's running a lot faster but max (alpha.water) is rising really slowly so the case is running for some hours but after around 70 simulation seconds the time steps decrease massively and stops.

my outlet BC are for
U: inletOutlet
p_rgh: fixedValue
alpha.water: works with inletOutlet but is really slow
alpha.water: fails after some hours of calculating with fixedValue

Does anyone have any experience how to set the boundary condition for my outlet at alpha.water to let just water out or speed my calculation up and not using fixedValue?

Cheers,
Oli