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-   -   A question about the residuals (http://www.cfd-online.com/Forums/openfoam-solving/59033-question-about-residuals.html)

 matteo_gautero March 13, 2008 13:06

Hi to all, I have a stupid qu

Hi to all,
I have a stupid question about the residuals that are printed by OF during the simulation. When I used Fluent, there was a window where the residuals of the equation involved in the simulation were plotted. In OF there are two kind of residuals, "initial residual" and "final residual"... which of these is the equivalent residuals of Fluent plot?

Sorry for my stupid question, but I have this doubt...

Matteo.

 lgriffiths March 14, 2008 04:54

i dont have any experience wit

i dont have any experience with fluent, and quite new to foam too - but as i understood it the 'normal' residual is the one before the iteration.

the initial represents how your actual solution is progressing... if that makes sense - your 'final' residual is probably set to some criteria in fvSolutions file.

... i hope thats right

 matteo_gautero March 14, 2008 06:58

Hi Laurence, thanks for your

Hi Laurence,
thanks for your response. I asked this because my friend told me that the correspondent residual of Fluent in OF is the first ("initial residual") and I'm not sure of this.

Matteo.

 lgriffiths March 14, 2008 10:41

yes, using the final resid

yes,

using the final residual to check the convergence of your solution wouldnt really make sense - if you check the fvSolutions file, your final residual should be converging too (or less than) the tolerances defined for the respective matrix solvers (hence wont give the standard 'convergence' curves).

the initial residual, will be your residual between your time steps - so your friend is correct if this is what fluent is plotting.

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