# A question about the residuals

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 March 13, 2008, 12:06 Hi to all, I have a stupid qu #1 matteo_gautero Guest   Posts: n/a 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... Thanks in advance, Matteo.

 March 14, 2008, 03:54 i dont have any experience wit #2 New Member   Laurence Griffiths Join Date: Mar 2009 Location: Bristol, UK Posts: 18 Rep Power: 14 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

 March 14, 2008, 05:58 Hi Laurence, thanks for your #3 matteo_gautero Guest   Posts: n/a 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.

 March 14, 2008, 09:41 yes, using the final resid #4 New Member   Laurence Griffiths Join Date: Mar 2009 Location: Bristol, UK Posts: 18 Rep Power: 14 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.