Scalar Dissipation in Flamelet Equations

tar

Hello folks,

could someone plz explain to me, how fluent is modeling the scalar dissipation rate, when creating the flamelet libraries. I am quite confused. When telling fluent, that it should create a flamlet with a scalar dissipation rate of about 10 s^-1, does it solve the flamelet equations with a constant scalar dissipation rate of 10? But why is there the equation to model the scalar dissipation rate along the mixture fraction space? I don't understand this.

If someone could explain this to me, I would be extremely grateful.

Thx, Tar.