[ehecboy]

Hi,


I am simulating a 3 Phase flow (air, steam, water) in Fluent with the Eulerian-Model. I am considering phase-changes as well with the Lee-model. The flow region consids of solid und fluid domains. Hot steam is entering a chamber and condenses on the cold walls. Over the time, the walls are heated up.

Since there are 2 gases (steam and air), I wrote an udf which calculates the saturation temperature in dependence of the pressure and the volume fraction of the steam.

My problem is the mesh resolution near the walls. With a corse mesh the steam hits quite fast the solid walls directly. With a fine mesh the air stays quite long between the walls and the steam as a kind of cushion. This leads too a lower saturation temperature, because the volume fraction of the steam is lower near the walls.

Validation data has shown that the measured wall temperatures are in very good accordance with the simulation of a coarse mesh, but the condensed water is not at the right spots (wall adhesion does not work good).


With a fine mesh the temperatures rise too slow but the condensed water is at the right spots.

Has anyone any idea how I could solve this issue??

Attached you can see the fluid region near a wall. With the coarse mesh one can see a higher volume fraction of steam near the walls