About "DO radiation model" for flame

Harry Qiu

Hi,Mr or Mrs:

I am modeling a laminar-premixed-gaseos-combustion problem.

I have two questions:

(1)There are two DO(Discrete-Ordinate) radiation models(Gry-Discrete-Ordinate and Nongray -Discrete-Ordinate). Which one is applicable(suitable) for flue gas(flame)radiation?

(2)I have tried only to model radiation between the walls, which means radiation of the flue gas is not taken into consideration(disable it in DEFINE--> boudary conditions-->fluid zone-->not selecting radiation check-box). But the residual of the DO equation was always zero when the computer started iterating. It seems that the DO equation is not being calculated, Can you tell me why?

looking forward to your answer. Thank you a lot!! Sincerely yours,Harry.