I have simulated engine combustion and the heat from combustion is in variable QSOR (in the info file). Now, I am also icluding radiation modeling and that seems to change QSOR also ? I though that QSOR is strictly the heat from combustion but it seems that something else is also added to it when radiation is included ? Does anybody know how does radiation affect the computation of QSOR ?

It depends on your definition of QSOR, but if your'e using the subroutine from Adapco - this calculates the heat release a-posteriori, rather than the chemical heat of combustion, and includes radiation or any other heat source.

I use my own coding for the combustion model (reacfn.f, an Eddy Break Up-type of a model). I also use the static, thermal enthalpy option. I wonder if it is somehow possible to extract the radiation part of the source term out from the QSOR ?

I did not quite understand where you define what QSOR is - is it in posdat.f? Anyway, if you calculate ther reaction rate in reacfn.f, why not just use the value you calculate there for the chemical rate?

I do not define QSOR anywhere. STAR does that. And the problem with taking the heat out from the reacfn.f routine is that it is iterated, i.e. called many times during a time step. But indeed, maybe I can use posdat.f to extract the heat of combustion out (?) Let's see...

Why don't you extract the heat release just in the first iteration in every time step? reacfn.f receives the iteration number - use the ITER variable.

Right, I could do that. (In principle, however, the first iteration result could still change quite a lot during the iteration process.) I will think about it.

another suggestion - define a "COMMON" variable in reacfn.f that would update after each iteration, and read it in the beginning of the next time step. good luck.