[fabfi]

Dear all,

I got trouble with a transient multiphase case (continueous domains). It includes

- air (top)
- cold water (middle) separated through a narrow gap from
- hot water (bottom)

air and water are different domains with a free surface in between.

The hot water should mix up with the cold water and then heat up the air (there is also CHT around, but not interesting for the specific problem). Buoyancy is activated.

With a closed volume everything is working fine but I do not want to cool down the hot water (represents a big domain where temperature change is negligible). Thus, I defined an opening at the bottom. The opening relative pressure is zero and the temperature is equal to the hot water temperature. Now, hot water flows back in and temperature stays constant.

BUT the interface between air and cold water domain moves down, means the water level decreases. Of course, gravity does his job. Is there any trick to avoid this or can anyone recommend another workaround?