mixture fraction at outlet
 

Hi everybody,

I am modelling a flow field, which includes the mixture of H2, O2 and N2. I know the mixture fractions at my two inlets, but not at my two outlets. The manual says, that the mixture fractions of an outlet have to be set just for the case of a reverse flow during the calculations. Unfortunatly, I had to model one outlet as "velocity inlet" with negative velocity. Therefore I always have got a reverse flow there. I did my first calculations by setting the mixture fractions and their variances to nought. The results seem to be good (they differ about 10% from the results I got using air in my calculations). My question is : What are the default setting to tell Fluent, that I don't know the fractions at the outlets? Is it OK to do it like I did?

Mark

PS: Happy Easter!