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problem with convergence in methane combustion using EDM model?

- September 13, 2019 at 2:10 pm
  
  sooraj546
  Subscriber
  
  i am working on a methane-combustion problem solved using EDM model. The model works fine and the entire system temperature wrt to iteration became constant after 16000 iteration as shown below
  
  But as 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. temperature vs iteration plots are shown below.
  
  upto 42000 iteration as shown above all looks fine seems like temperature is going to converge but after 42000 temperature goes to zero then again starts the same process i have checked the process to 1 lac iteration ......it reduced to zero again at around 68000 again its repeating continuous cyclic process
  
  Kindly someone can suggest me some remedies for this .................... going for more refined mesh an option for this ?
  
  any help will be highly appreciated.
- September 13, 2019 at 2:43 pm
  
  DrAmine
  Ansys Employee
  
  You need to provide some more information about your case: models used and boundary conditions. First diagnose: case not converging. What do residual and flux report tell you?
- September 13, 2019 at 5:49 pm
  
  sooraj546
  Subscriber
  
  i am using1.Energy eq, 2. k-epsilon 3.species transport ( Eddy Dissipation Model) 4. radiation- Discrete ordinate model.
  
  these are the models used ..........my geometry is too complicated......as shown below...........so i dnt think i will ever be able to reduce my residuals beyond 10e-3 as the problem is too complicated
  
  the temperature variation vs iteration and its corresponding residuals are shown below
- September 14, 2019 at 2:24 pm
  
  sooraj546
  Subscriber
  
  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
  
  this is the color picture of the figure posted before
- September 15, 2019 at 2:52 pm
  
  Raef.Kobeissi
  Subscriber
  
  We need more information about your case. Not enough info from what you’ve given to even guess why the temp is erratic at the end.

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