CFD Online Discussion Forums - Mixture fraction and scalar dissipation rate based on filtered quantities?

Hello,

I would be grateful for some clarification and comments regarding the validity of using the Favre filtered quantities (species mass fractions, temperature) from LES for obtaining the mixture fraction and scalar dissipation rate in non-premixed combustion. Let say, I assume perfectly stirred reactor conditions inside a filter box in my computations and use the resolved scalars in solving the reaction rates. I want to display the mixture fraction and scalar dissipation rate distributions on contour plots. However, these quantities are not resolved or transported since I don't use any combustion model I simply want to use the formulas for mixture fraction and scalar dissipation rate.

Are such derived quantities meaningful?

I have some doubts because I feel I neglect the effect of subfilter scales in derivation of those quantities.

Would be kindly grateful for your opinions.

Regards