# how to check convergence??

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 November 19, 2010, 11:23 how to check convergence?? #1 Member   Sandeep Join Date: Jul 2010 Posts: 47 Rep Power: 6 Hello all, I am new to openFoam and started learning it with the available tutorials. I am able to run the case but I am not sure how to check if the residuals are converging. Where do I check them?? and where do I specify the the convergence criteria?? Any help woud be appreciated!! Thanks a ton!! Sandeep

 November 19, 2010, 12:10 #2 Member   Join Date: Dec 2009 Posts: 36 Rep Power: 7 Hello Sandeep! Take a look at system/fvSolution and check the screen output. Alternatively you can save the screen output in a log file. Regards fritz

 November 19, 2010, 12:15 #3 Member   Sandeep Join Date: Jul 2010 Posts: 47 Rep Power: 6 Hi fritz, I am sorry I did not understand what u meant to check the screen output. fvSolutions file has just solvers and PISO dictionaries in it.

November 19, 2010, 13:58
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Join Date: Dec 2009
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How are you running your case?
Normaly, you see something like below on your screen and in the log-file, too.
Quote:
 Time = 0.495 Courant Number mean: 0.116925 max: 0.852134 DILUPBiCG: Solving for Ux, Initial residual = 1.99665e-07, Final residual = 1.99665e-07, No Iterations 0 DILUPBiCG: Solving for Uy, Initial residual = 4.36311e-07, Final residual = 4.36311e-07, No Iterations 0 DICPCG: Solving for p, Initial residual = 1.0746e-06, Final residual = 3.53797e-07, No Iterations 1 time step continuity errors : sum local = 5.37651e-09, global = -2.9125e-19, cumulative = 8.07944e-18 DICPCG: Solving for p, Initial residual = 6.81574e-07, Final residual = 6.81574e-07, No Iterations 0 time step continuity errors : sum local = 8.06059e-09, global = 9.28097e-19, cumulative = 9.00754e-18 ExecutionTime = 0.16 s ClockTime = 0 s Time = 0.5 Courant Number mean: 0.116925 max: 0.852134 DILUPBiCG: Solving for Ux, Initial residual = 1.89493e-07, Final residual = 1.89493e-07, No Iterations 0 DILUPBiCG: Solving for Uy, Initial residual = 4.14522e-07, Final residual = 4.14522e-07, No Iterations 0 DICPCG: Solving for p, Initial residual = 1.06665e-06, Final residual = 3.39604e-07, No Iterations 1 time step continuity errors : sum local = 5.25344e-09, global = -9.50761e-19, cumulative = 8.05678e-18 DICPCG: Solving for p, Initial residual = 5.36118e-07, Final residual = 5.36118e-07, No Iterations 0 time step continuity errors : sum local = 6.86432e-09, global = 4.62063e-19, cumulative = 8.51884e-18 ExecutionTime = 0.16 s ClockTime = 0 s

 November 19, 2010, 19:50 #5 Member   Robin Gilbert Join Date: Jan 2010 Posts: 66 Rep Power: 7 Tutorial of how to plot residuals ! try that link. it shows how to plot residuals. or u can see the screen output while running the simulation. it shows the initial and final residual at each time step. generally as far as i know if the initial residuals are going down, it means solution is converging. Somebody please correct me if i am wrong.

 November 21, 2010, 10:20 yes! #6 Member   Mohammad.R.Shetab Join Date: Jul 2010 Posts: 49 Rep Power: 6 you are correct!! but I think thats not enough!! you should monitor some characteristics of your case in some points.( you can try sampleDict for this). To plot residuals you can try pyFoam. It works properly.

 November 22, 2010, 03:41 #7 Senior Member   Elvis Join Date: Mar 2009 Location: Sindelfingen, Germany Posts: 577 Blog Entries: 5 Rep Power: 13

 December 21, 2010, 09:07 #8 New Member     Gregor Seljak Join Date: Oct 2010 Posts: 21 Rep Power: 6 Hello! You can also use the foamLog script. http://www.openfoam.com/docs/user/mo...hp#dx35-201001

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