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Old   June 7, 2006, 14:31
Default residuals
Siddharth Khowala
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hi all, I am having a confusion as to whether the amount of residuals affects the solution.I am trying to calculate my velocity in a simple 2d channel (laminar,segregated solver) using residuals of 1e-4(for x,y and pressure ),but when i do it for residuals =1e-5 i see different velocity which i guess is obvious.hence i wanted to know as to what should be the reidual limits and how are they addressed in any problem.I tried to let the solution converge to less than 1e-5 so that at some point the solution remains the same but when left the residuals become even less than 1e-7 and goes on decreasing.Any help on this matter would be welcome

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Old   June 8, 2006, 03:41
Default Re: residuals
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there are 2 differents aspects to check for the residuals:

1) the CV criteria: basically, the lower the better, but...

2) the variations: if your residuals remain the same for a "long" time, the solution doesn't evolve anymore so your solution is CV, even if they haven't reached your criteria.

to be convinced by the CV, the best way is to monitor a relevant value, like the drag or lift on your geometry for external aero studies... and check it has reached a constant value before you stop the computations.

good luck
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