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Old   March 31, 2014, 08:49
Default Question about testcase euler/oneram6
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Becky
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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.

Thanks for your help!
Becky
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File Type: zip output.zip (9.9 KB, 5 views)
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Old   April 3, 2014, 19:47
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David Manosalvas
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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
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Old   April 4, 2014, 10:53
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Becky
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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
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Old   April 6, 2014, 00:32
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David Manosalvas
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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
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Old   April 6, 2014, 07:29
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Becky
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David,

I understand how it works now.
Thanks for your replies they help me a lot! (:

Becky
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