[sooraj546]

i am working on a steady state methane-combustion problem solved using 1.Energy eq, 2. k-epsilon 3.species transport ( Eddy Dissipation Model) 4. radiation- Discrete ordinate model. The model works fine and the entire system temperature wrt to iteration became constant after 16000 iteration as shown in figure 1 which symbolizes convergence. My geometry is too complicated......as shown below as meshed geometry...........so i dnt think i will ever be able to reduce my residuals beyond 10e-3 as the problem is too complicated.

Now the interesting thing, i changed my fuel to some other with different methane composition, the temperature is not converging as before, infact cyclic repeating temperature vs iteration profile is being obtained what should i do regarding this. I have attached the figure of temperature vs iteration as well as its corresponding residual pic as well.

How can i rectify this problem and being a steady state problem at least temp need to be stabilized?

will refining the mesh further solve this problem