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-   -   Definitions for Initial and Final Residuals (http://www.cfd-online.com/Forums/openfoam/78240-definitions-initial-final-residuals.html)

 will_avoid_comm_solvers July 15, 2010 18:09

Definitions for Initial and Final Residuals

Dear FOAMers

I am trying to learn the importance of initial and final residuals.

Is there any place where I can get their definitions?
I am learning to use simpleFoam to solve simple problems like internal flow over through a pipe with sudden expansion. For low Re (~300) both the initial and final residuals drop to 1e-6. But when I triple the Re (~1000), the initial residual stay at ~0.002 range while the final residual drops to 1e-7.

Irrespective of the problem, If I want to say the solution is converged, how low should the initial residuals go?

Thanks

 marcbest July 16, 2010 03:55

hi patrick,

the initial residuals are the important ones, by default the residuals must be lower than 10^-5 that the simulation is converged. The final residuals are the residuals in the current step after n-iterations -> No Iterations n
with pyFoamPlotWatcher you can visualise the initial residuals. http://openfoamwiki.net/index.php/Contrib_PyFoam

regards

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