Dam break simulation water level decreases over time
 

Hi guys,
After doing the dam break tutorial exercise I was looking at the animation of water level inside the tank. What I see is that the water level decreases overtime. Why is this? After the dam break experiment I tried simulating a settling tank with liquids of different densities. In the settling tank simulation everything looks good my problem is that after 30 seconds (simulation time) the liquid level of the lowest chamber starts to decrease to the point where there is none left. after that the same thing happens to the less dense liquid. I have added a little video for you to see what is happening (in both, the tutorial and in my 2d model. By the way I have used a very similar setup to the dam break tutorial. Maybe it has something to do that the upper walls are set as outlet pressure? If so what other conditions should I use if it is an open to atmosphere settling tank?

dam break tutorial
https://www.youtube.com/watch?v=i3Vg...ature=youtu.be

My simulation
https://www.youtube.com/watch?v=WIgJ...ature=youtu.be

best regards
AD

backflow created when going from pressure outlet to a wall boundary condition
 

I tried changing the boundary conditions at the top of the tank from outlet pressure to wall boundary condition. With these changes my boundary conditions are 1 velocity inlet and 3 pressure outlets. When I do that there is backflow in the material pressure outlets causing air to flow from it. Now there are air pockets at the outlets which is not an expected result. What should I do know?