# simpleFoamResidual

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 October 14, 2013, 06:17 simpleFoamResidual #1 Senior Member   M. Montero Join Date: Mar 2009 Location: Madrid Posts: 121 Rep Power: 9 Hi all, My question is related to the utility simpleFoamResidual implemented into OF1.6ext. According to the code, it analyze the momentum equation. The perfect situation, I think, would be that uResidual is equal "0". The attached convergence is OK but the maxium uResidual that I obtain is around 76 and the mean around 0.09. In other different mesh, the maximum uResidual obtained was around 2000. Could anyone tell me how much is a high value of uResidual? Is possible to have a physical meaning about the uResidual? If I have higher values than 0.05, for example, does it tell me that it is require to refine the mesh? I would appreciate any help. I would like to have a criteria to know if current mesh resolution is enough or not for my purposes without doing a mesh resolution analysis in detail. Thank you very much. Code: ``` Info<< " Calculating uResidual" << endl; volScalarField uResidual ( IOobject ( "uResidual", runTime.timeName(), mesh, IOobject::NO_READ ), mag ( fvc::div(phi, U) + fvc::div(turbulence->R()) + fvc::grad(p) ) );``` Code: ```Time = 3000 DILUPBiCG: Solving for Ux, Initial residual = 1.48121e-08, Final residual = 6.66887e-11, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 1.09835e-05, Final residual = 1.32954e-08, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 1.96974e-05, Final residual = 3.96294e-08, No Iterations 2 GAMG: Solving for p, Initial residual = 0.00085226, Final residual = 4.08688e-05, No Iterations 8 time step continuity errors : sum local = 2.32144e-10, global = -6.39797e-11, cumulative = 2.45607e-07 DILUPBiCG: Solving for epsilon, Initial residual = 2.62941e-07, Final residual = 2.54438e-10, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 9.73059e-07, Final residual = 3.07595e-10, No Iterations 2 ExecutionTime = 7790.51 s ClockTime = 7792 s```

 October 14, 2013, 06:26 #2 Senior Member     Anton Kidess Join Date: May 2009 Location: Delft, Netherlands Posts: 1,151 Rep Power: 20 I don't think this tool can replace a mesh sensitivity study. All it tells you is that a solution is converged, not that it is converged and accurate. __________________ *On twitter @akidTwit *Spend as much time formulating your questions as you expect people to spend on their answer. *Join the OpenFOAM stackexchange Q&A site: http://area51.stackexchange.com/prop...oHPxcPqde7HtA2

 October 14, 2013, 07:10 #3 Senior Member   M. Montero Join Date: Mar 2009 Location: Madrid Posts: 121 Rep Power: 9 I am trying to link Dr.Jasak Thesis about error estimation with my case and to know if it is needed to refine the mesh once convegence has been "obtained" (residuals). Chapter 5 is dedicated to the adaptative mesh refinement to reduce the numerical error up to the desired level. There should be a criteria ( I hope that) about when the error (uResidual) has been reduced enough to minimize the numerical error.

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