I have a problem using Fluent concerning determining mixing times (low Froude number problem). After running into serious problems I decided to do a simple test which also didn't go well..i.e.

tank (2d) with stratified flow (50-50%), on top the lighter and warm water-salt mixture and the bottom the heavy and the cold water-salt mixture. Setting the thermal conductivity to 1e-24 (so only turbulent mixing) the stratification should be stable and no mixing should occur (velocity patched zero).. however velocities in the order of 5 cm/s occur (no pattern) and the tank starts equaling out the temperature in about 1 hour where mixing times of over 100 hours with a mixer switched on were obtained in the experiments ...

Did anybody run into similar problems or has an idea where the poblem could be?

Thanks...

Ha die Rai,

Mooi pakket he? Heb je al een fijner grid geprobeerd? En loopt die wel op 2nd order?

Groetjes Bart