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March 31, 2014, 08:49
#1
New Member

Becky
Join Date: Mar 2014
Posts: 6
Rep Power: 5
Hi,

I try to run the testcase euler/oneram6 given by the website.
I don't really understand why it terminated at iteration 100.

The convergence criteria it used is RESIDUAL.
According to Tutorial, it means that the simulation will terminate once the density residual reaches a value that is RESIDUAL_REDUCTION orders of magnitude smaller than its value at iteration STARTCONV_ITER

However, the simulation stopped exactly at STARTCONV_ITER (100).
The density residual didn't reach RESIDUAL_MINVAL either.

I am quite confused with it.....

The attachment is the configuration file I used and the information printed on screen when I ran the simulation.

Becky
Attached Files
 output.zip (9.9 KB, 5 views)

 April 3, 2014, 19:47 #2 New Member   David Manosalvas Join Date: Feb 2014 Posts: 24 Rep Power: 5 Becky, The reason why your simulation is stopping is because the stopping criteria is either the reduction of 5 orders of magnitude or the residual reaching a -6 order. In your case the -6 order is reached before the 5 orders of magnitude reduction. % Residual reduction (order of magnitude with respect to the initial value) RESIDUAL_REDUCTION= 5 % % Min value of the residual (log10 of the residual) RESIDUAL_MINVAL= -6 David

 April 4, 2014, 10:53 #3 New Member   Becky Join Date: Mar 2014 Posts: 6 Rep Power: 5 David, Thanks for your reply! After decreasing the RESIDUAL_MINVAL value to a smaller one, the testcase finally follow the convergence criteria (stop at the reduction of 5 orders of magnitude). However, when I increase the RESIDUAL_MINVAL value which is equal to or bigger than -6, the testcase always stopped at iter100 and the residual value was around -8, which is obviously smaller than -6. I just don't understand why it didin't stop immediately after reaching the RESIDUAL_MINVAL. :S Becky

 April 6, 2014, 00:32 #4 New Member   David Manosalvas Join Date: Feb 2014 Posts: 24 Rep Power: 5 Becky, This is because you are telling the code to start checking the convergence criteria at iteration 100 : % Start convergence criteria at iteration number STARTCONV_ITER= 100 If you want to check it much sooner, and stop as soon as it hits the criteria, try reducing the value in STARTCONV_ITER (the option shown above) to 10. Hope this helps, David

 April 6, 2014, 07:29 #5 New Member   Becky Join Date: Mar 2014 Posts: 6 Rep Power: 5 David, I understand how it works now. Thanks for your replies they help me a lot! (: Becky

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