Hi,

I'm modeling liquid fuel evaporation and combustion. With UD the calculation runs and converges ok, but when I choose MARS for momentum and density calculation - it diverges after 325th iteration (before it converged after 1700somethingth iteration). The drops go completely crazy, filling all the volume of the vaporizer (before there was just one nice track line) and going in the opposite ditection they should, i.e. towards the injection point.

Can somebody explain this? PS I work on v3.150A.

Regards,

Julie

I'd say don't worry too much about the droplet tracks. They are just following the velocity field. You need to worry about why the velocity field is diverging. Have you tried reducing the under-relaxation factors for velocity and pressure? Quite often these need to be lower with MARS than with UD, say 0.5 and 0.15 respectively.

Hi Richard,

Yes, I've tried to lower the under-relaxation factors, but not so much (min to 0.4). Now I runned the case with UD for density and MARS for momentum and it seems to work well (at least it converged)even with under-relaxation factors of 0.6 for momentum.

Regards,

Julie