# no convergence with simplefoam

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 March 28, 2012, 00:15 no convergence with simplefoam #1 Member   张德胜 Join Date: Oct 2011 Posts: 71 Rep Power: 7 Everyone,i use simplefoam with standard k-epsilon model to calculate the wind farm.when i type the command "simpleFoam",i get the following information:Create mesh for time = 0 Reading field p Reading field U --> FOAM Warning : From function Field::Field(const word& keyword, const dictionary&, const label) in file /opt/openfoam210/src/OpenFOAM/lnInclude/Field.C at line 262 Reading "/root/OpenFOAM/root-2.1.0/run/tutorials/incompressible/simpleFoam/wf39/0/U::boundaryField::inlet" from line 37 to line 16 expected keyword 'uniform' or 'nonuniform', assuming deprecated Field format from Foam version 2.0. Reading/calculating face flux field phi Selecting incompressible transport model Newtonian Selecting RAS turbulence model kEpsilon kEpsilonCoeffs { Cmu 0.028; C1 1.5; C2 1.92; C3 -0.33; sigmak 1; sigmaEps 2.51; Prt 1; } No field sources present SIMPLE: convergence criteria field p tolerance 0.001 field U tolerance 0.001 field "(k|epsilon)" tolerance 0.001 Starting time loop Time = 1 smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 0.00644545010997, No Iterations 3 smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 0.00464444535134, No Iterations 4 smoothSolver: Solving for Uz, Initial residual = 1, Final residual = 0.00708579374941, No Iterations 5 GAMG: Solving for p, Initial residual = 1, Final residual = 0.00735995074387, No Iterations 5 GAMG: Solving for p, Initial residual = 0.000167838426709, Final residual = 1.56259657312e-06, No Iterations 6 GAMG: Solving for p, Initial residual = 2.2891470536e-05, Final residual = 1.89675102907e-07, No Iterations 4 GAMG: Solving for p, Initial residual = 4.86359414644e-06, Final residual = 4.25624108873e-08, No Iterations 4 time step continuity errors : sum local = 3.77016513754e-08, global = -7.42217873687e-09, cumulative = -7.42217873687e-09 smoothSolver: Solving for epsilon, Initial residual = 1, Final residual = 0.00132760727343, No Iterations 2 smoothSolver: Solving for k, Initial residual = 1, Final residual = 0.00285899835651, No Iterations 2 bounding k, min: 0 max: 50.8029155486 average: 1.44150802022 ExecutionTime = 126.62 s ClockTime = 141 s Time = 2 smoothSolver: Solving for Ux, Initial residual = 0.446656785658, Final residual = 0.00197538615297, No Iterations 2 smoothSolver: Solving for Uy, Initial residual = 0.143272919974, Final residual = 0.000770220501008, No Iterations 3 smoothSolver: Solving for Uz, Initial residual = 0.159528815298, Final residual = 0.00142906124564, No Iterations 2 GAMG: Solving for p, Initial residual = 0.374485256388, Final residual = 0.00336921418749, No Iterations 6 GAMG: Solving for p, Initial residual = 0.00020659453246, Final residual = 1.28186320376e-06, No Iterations 7 GAMG: Solving for p, Initial residual = 5.21634568919e-05, Final residual = 4.89086468001e-07, No Iterations 4 GAMG: Solving for p, Initial residual = 1.85185182451e-05, Final residual = 7.29808804296e-08, No Iterations 5 time step continuity errors : sum local = 5.23267147276e-08, global = -9.14582863274e-09, cumulative = -1.65680073696e-08 #0 Foam::error:rintStack(Foam::Ostream&) in "/opt/openfoam210/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #1 Foam::sigFpe::sigHandler(int) in "/opt/openfoam210/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #2 Uninterpreted: #3 Foam::divide(Foam::Field&, Foam::UList const&, Foam::UList const&) in "/opt/openfoam210/platforms/linuxGccDPOpt/lib/libOpenFOAM.so" #4 void Foam::divide(Foam::GeometricField&, Foam::GeometricField const&, Foam::GeometricField const&) in "/opt/openfoam210/platforms/linuxGccDPOpt/lib/libincompressibleRASModels.so" #5 Foam::tmp > Foam:perator/(Foam::tmp > const&, Foam::GeometricField const&) in "/opt/openfoam210/platforms/linuxGccDPOpt/lib/libincompressibleRASModels.so" #6 Foam::incompressible::RASModels::kEpsilon::correct () in "/opt/openfoam210/platforms/linuxGccDPOpt/lib/libincompressibleRASModels.so" #7 at /opt/openfoam210/applications/solvers/incompressible/simpleFoam/simpleFoam.C:66 #8 __libc_start_main in "/lib/tls/i686/cmov/libc.so.6" #9 in "/opt/openfoam210/platforms/linuxGccDPOpt/bin/simpleFoam" 浮点数例外 who can give me some advice?Thanks every reply.

 March 28, 2012, 00:40 #2 Member   张德胜 Join Date: Oct 2011 Posts: 71 Rep Power: 7 my fvsolution is: /*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.0 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { p { solver GAMG; tolerance 1e-7; relTol 0.01; smoother GaussSeidel; nPreSweeps 0; nPostSweeps 2; cacheAgglomeration on; agglomerator faceAreaPair; nCellsInCoarsestLevel 10; mergeLevels 1; } U { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.1; nSweeps 1; } k { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.1; nSweeps 1; } epsilon { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.1; nSweeps 1; } } SIMPLE { nNonOrthogonalCorrectors 3; residualControl { p 1e-3; U 1e-3; "(k|epsilon)" 1e-3; } } relaxationFactors { fields { p 0.2; } equations { U 0.7; k 0.7; epsilon 0.7; } } cache { grad(U); } // ************************************************** *********************** // my fvschemes is: /*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.0 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default steadyState; } gradSchemes { default Gauss linear; grad(p) Gauss linear; grad(U) Gauss linear; } divSchemes { default none; div(phi,U) Gauss upwind grad(U); div((nuEff*dev(T(grad(U))))) Gauss linear; div(phi,epsilon) Gauss upwind; div(phi,k) Gauss upwind; } laplacianSchemes { default Gauss linear limited 0.333; } interpolationSchemes { default linear; } snGradSchemes { default limited 0.333; } fluxRequired { default no; p; } // ************************************************** *********************** //

 March 28, 2012, 05:22 #3 Senior Member   lore Join Date: Mar 2010 Location: Italy Posts: 464 Rep Power: 10 Don't know if it may cause the issue, but, as the error says, you're missing the word "uniform" in your U conditions. I would start by correcting that.

 March 28, 2012, 05:48 #4 Member   张德胜 Join Date: Oct 2011 Posts: 71 Rep Power: 7 Thanks for your reply.I think it is just a warning and it should not the reason for my problem.Because i can calculate well in the other case with the warning.

 March 28, 2012, 06:44 #5 Member   Join Date: Nov 2009 Posts: 34 Rep Power: 8 Hi, if you are sure that your BCs are okay for U (you can check in paraview) I would try to stabilize the first iterations by using a cellLimited grad schemes and setting the relaxation factors for k and eps to 05. or 0.4 Best regards Stawrogin

 March 28, 2012, 07:03 #6 Member   张德胜 Join Date: Oct 2011 Posts: 71 Rep Power: 7 Thanks for your reply.I will ues your advice some seconds later.I hope it will works.Thanks again.

 March 28, 2012, 07:05 #7 Member   张德胜 Join Date: Oct 2011 Posts: 71 Rep Power: 7 which solver for p,u,k,epsilon should i choose?

 March 28, 2012, 07:19 #8 Member   张德胜 Join Date: Oct 2011 Posts: 71 Rep Power: 7 when i use cellLimited,there gives me the following error:--> FOAM FATAL IO ERROR: Grad scheme not specified Valid grad schemes are : 8 ( Gauss cellLimited cellMDLimited extendedLeastSquares faceLimited faceMDLimited fourth leastSquares ) file: /root/OpenFOAM/root-2.1.0/run/tutorials/incompressible/simpleFoam/wf40/system/fvSchemes::gradSchemes::grad(U) at line 26. From function gradScheme::New(const fvMesh& mesh, Istream& schemeData) in file /home/opencfd/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/gradScheme.C at line 54. FOAM exiting

 March 28, 2012, 09:01 #9 Member   Join Date: Nov 2009 Posts: 34 Rep Power: 8 Hi I would try: gradSchemes { default cellLimited Gauss linear 1; } Stawrogin

 March 28, 2012, 11:06 #11 Member   Kalyan Join Date: Oct 2011 Location: Columbus, Ohio Posts: 53 Blog Entries: 1 Rep Power: 7 Hi, When you used cellLimited Gauss linear 1; what do you mean it failed. Did it fail to even start or did it fail to converge like before? And also, is there a reason for using limited scheme for sngrad and laplacian terms? Kalyan

 March 28, 2012, 20:19 #12 Member   张德胜 Join Date: Oct 2011 Posts: 71 Rep Power: 7 it fail to converge like before.i make some changes,and it convergence.But i do not know the output is right or not.when i solve my problem,i will share my experience.

 March 29, 2012, 21:42 #13 Member   张德胜 Join Date: Oct 2011 Posts: 71 Rep Power: 7 The following is my case files:https://dl-web.dropbox.com/u/69253136/system/fvSchemes https://dl-web.dropbox.com/u/69253136/system/fvSolution https://dl-web.dropbox.com/u/69253136/0/epsilon https://dl-web.dropbox.com/u/69253136/0/k https://dl-web.dropbox.com/u/69253136/0/nut https://dl-web.dropbox.com/u/69253136/0/p https://dl-web.dropbox.com/u/69253136/0/U The problems I am now facing with are as following:first,when it calculate to the time=353,it occure noconvergence;second,I sample same points's value of velocity,i am sure they are wrong.I only change the files of fvsolution and fvschemes.please give me some advice to correct them.

 May 22, 2012, 08:28 #14 Senior Member     Tobias Holzmann Join Date: Oct 2010 Location: Leoben (Austria) Posts: 1,519 Blog Entries: 6 Rep Power: 26 Hi, your breakup is coused by the turbulence model! Code: ```bounding k, min: 0 max: 50.8029155486 average: 1.44150802022 ExecutionTime = 126.62 s ClockTime = 141 s``` bounding is not very "good" it can appear in the simulation but should stabilize while running your case. But you have a problem with your model: Code: `#6 Foam::incompressible::RASModels::kEpsilon::correct () in "/opt/openfoam210/platforms/linuxGccDPOpt/lib/libincompressibleRASModels.so"` Well maybe you`ve wrong BC or completely unrealistic values for k? I would have a look at that be for trying to change the schemes! I think you `ve got a BC-problem. If you are not sure, save your first time step and have a look at the results. There you should see where your peaks are (k, espilon, p, U ...) - maybe there is a mesh problem at all? I would give you the advice to correct the "uniform" error. Well maybe its not a problem but you should set the files for OF correct. Tobi PS: Solver for k, eps.... PBiCG -- have a look at the tutorials pitzDaily

 May 22, 2012, 08:34 #15 Senior Member     Niels Nielsen Join Date: Mar 2009 Location: NJ - Denmark Posts: 472 Rep Power: 16 please give the same info as in How to give enough info to get help It will help atg likes this. __________________ Linnemann PS. I do not do personal support, so please post in the forums.

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