# Check the convergence of the transient run--> HOW ??!!

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 February 13, 2012, 02:10 Check the convergence of the transient run--> HOW ??!! #1 Senior Member   mohammad Join Date: Dec 2010 Location: Seoul, South korea Posts: 210 Rep Power: 7 Dear all, I am solving a 3D transient airfoil( with a synthetic jet) with DES turbulence model. I want to know answers for the following questions: 1- How can i know the convergence level due to "coefficient loop"? In an other word, how can i know if the number of "inner loops" per iteraion is enough or not? 2-The "synthetic jet" problem is a secondary flow added to the main flow. This injected flow is " a Sinusoidal" flow. Thus, the value of lift on the blade is varying from timestep to timestep. Thus I want to know how can I understand the convergence for my case. what paramaeters should I use to realize whether my results are converged or not?? Regards, `

February 13, 2012, 06:04
#3
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Join Date: Dec 2010
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Quote:
 Originally Posted by monkey1 1)) I asked the same question to a guy from the cfx support and the answer was: "Usually your case should converge within 10 Iterations. 2)) You should try to figure out which value would have to become constant during your calculation and then monitor it to see if further computation is needed or the stationary solution reached... 3)) If you don't manage to get convergence in 10 iterations then you could try and increase the number of iteration loops (to 20 or more) and see how many are needed to reach convergence. .

Hi monkey1, thanks for you thorough answer.

In the above quote:
1-By Saying " 10" , you mean 10 inner iterations, don't you?
2- For my case as I have told , the results would have to be kind of "sinusoidal" responses. So, it i am thinking be cause all the values will be changed from time to time, which values can I compare.???
3- AND THIS QUESTION PLEASE......think that i run my model with coefficient loops=15 ( inner loops) . My question is HOW CAN I MONITOR THE RESULTS of inner loops, to see whether the results are converged within any single timestep( outer iteration) or not. Actually as I can monitor the results of different time steps, I also want to monitor the results of inner loops in any iteration. If they are not converged I can increase the inner loops from 15 to a higher number.

Thanks a lot.

February 13, 2012, 06:16
#4
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Lance
Join Date: Mar 2009
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Quote:
 Originally Posted by mohammad My question is HOW CAN I MONITOR THE RESULTS of inner loops, to see whether the results are converged within any single timestep( outer iteration) or not.
Output control/Monitor/ and check "Monitor Coefficient Loop Convergence".
Then you will see how your monitor points converge within each time step.

 February 13, 2012, 06:17 #5 Senior Member   mohammad Join Date: Dec 2010 Location: Seoul, South korea Posts: 210 Rep Power: 7 Thank you Lance

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