[natantyt]

Hi Guys

I have a viscous film (a mixture with water) in the middle of a rectangular channel. Hot air flows in the channel and water evaporates from the film. I'm using FLUENT VOF laminar tried Geo-Reconstruct, CICSAM and modified HRIC in explicit and compressive and HRIC in implicit (for Pressure setting tested both PRESTO and Body weight ), It is not stable for time steps higher than 1e-7 which is very low, despite low residuals I see wavy interface (water concentration profile in the film) and high velocity vortex at the interface (Picture). The inlet velocity is 0.2-0.3 m/s and Reynolds is around 1500. I used quad mesh and refined a couple of times. I had to try higher velocities (up to 1 m/s) for which the regime becomes turbulent. I tried k-e and k-w couldn't converge the case either and keep it stable even at low time steps.

I appreciate any advice, the transient simulation is for a few minute data so higher time steps should be achieved. Attached is the velocity profile.

Nathan