# Divergence after high number of iterations

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 November 14, 2013, 06:22 Divergence after high number of iterations #1 New Member   erik gustafsson Join Date: Oct 2013 Posts: 19 Rep Power: 6 Hello I got a really frustrating problem. I have established a procedure for simulating conjugated heat transfer between fluid and solid with chtMultiRegionSimpleFoam. My models have always worked but now when i have a really fine model everything crash after around 600 iterations. Until this the solution converge good and the all residuals are less than 0.001. Is there anyone who knows how to solve this problem?

 November 14, 2013, 06:55 #2 Senior Member     Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,280 Rep Power: 23 __________________ *On twitter @akidTwit *Spend as much time formulating your questions as you expect people to spend on their answer.

 November 14, 2013, 08:08 #3 New Member   erik gustafsson Join Date: Oct 2013 Posts: 19 Rep Power: 6 My mesh seems ok when i runned the checkMesh. Since i run it on our cluster i dont get t Code: ```Time = 585 Solving for fluid region fluid DILUPBiCG: Solving for Ux, Initial residual = 0.0002279771, Final residual = 7.889007e-06, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.0003652472, Final residual = 9.324946e-06, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.001360254, Final residual = 3.218115e-05, No Iterations 1 GAMG: Solving for h, Initial residual = 0.0004399999, Final residual = 9.285599e-07, No Iterations 2 Min/max T:337.9997 341.8999 GAMG: Solving for p_rgh, Initial residual = 0.002022551, Final residual = 1.222316e-05, No Iterations 5 GAMG: Solving for p_rgh, Initial residual = 0.0005562866, Final residual = 5.387977e-06, No Iterations 3 time step continuity errors : sum local = 0.0563915, global = -8.993817e-05, cumulative = -62.71551 Min/max rho:1054 1054 DILUPBiCG: Solving for epsilon, Initial residual = 0.0849624, Final residual = 0.0002585619, No Iterations 1 bounding epsilon, min: -26.73187 max: 15466.52 average: 2.532161 DILUPBiCG: Solving for k, Initial residual = 0.00134489, Final residual = 1.96022e-05, No Iterations 1 Solving for solid region solid DICPCG: Solving for h, Initial residual = 0.0003222915, Final residual = 9.867308e-06, No Iterations 2 DICPCG: Solving for h, Initial residual = 0.0003249724, Final residual = 1.023341e-05, No Iterations 2 Min/max T:min(T) [0 0 0 1 0 0 0] 338 max(T) [0 0 0 1 0 0 0] 346.6688 ExecutionTime = 3132.69 s ClockTime = 3139 s Time = 586 Solving for fluid region fluid DILUPBiCG: Solving for Ux, Initial residual = 0.01086879, Final residual = 4.23718e-09, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.1005754, Final residual = 1.090088e-08, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.176239, Final residual = 1.885607e-08, No Iterations 1 GAMG: Solving for h, Initial residual = 0.1106389, Final residual = 0.001035424, No Iterations 1 Min/max T:337.9997 341.9038 GAMG: Solving for p_rgh, Initial residual = 0.002115051, Final residual = 2.05201e-05, No Iterations 5 GAMG: Solving for p_rgh, Initial residual = 0.9963446, Final residual = 0.004556654, No Iterations 8 time step continuity errors : sum local = 13971.99, global = -10.3378, cumulative = -73.05331 Min/max rho:1054 1054 DILUPBiCG: Solving for epsilon, Initial residual = 0.3303189, Final residual = 0.01969804, No Iterations 1 bounding epsilon, min: -22.85394 max: 36519.9 average: 2.713533 DILUPBiCG: Solving for k, Initial residual = 0.9996548, Final residual = 0.008013062, No Iterations 1 Solving for solid region solid DICPCG: Solving for h, Initial residual = 0.0003217334, Final residual = 9.850451e-06, No Iterations 2 DICPCG: Solving for h, Initial residual = 0.0003244086, Final residual = 1.021595e-05, No Iterations 2 Min/max T:min(T) [0 0 0 1 0 0 0] 338 max(T) [0 0 0 1 0 0 0] 346.6729 ExecutionTime = 3138.66 s ClockTime = 3145 s Time = 587 Solving for fluid region fluid DILUPBiCG: Solving for Ux, Initial residual = 0.2542555, Final residual = 0.003127732, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.229307, Final residual = 0.001091918, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.3299211, Final residual = 0.001057152, No Iterations 1 GAMG: Solving for h, Initial residual = 0.9999995, Final residual = 0.001948424, No Iterations 3 Min/max T:-1.192378e+07 3671610 GAMG: Solving for p_rgh, Initial residual = 0.9833382, Final residual = 0.004657309, No Iterations 20 GAMG: Solving for p_rgh, Initial residual = 0.5844197, Final residual = 0.003799768, No Iterations 4 time step continuity errors : sum local = 89309.59, global = -30.79077, cumulative = -103.8441 Min/max rho:1054 1054 DILUPBiCG: Solving for epsilon, Initial residual = 0.9930006, Final residual = 0.0390609, No Iterations 2 bounding epsilon, min: -25.73662 max: 6.531648e+09 average: 41468.83 DILUPBiCG: Solving for k, Initial residual = 0.999766, Final residual = 0.01822295, No Iterations 2 Solving for solid region solid DICPCG: Solving for h, Initial residual = 0.01450694, Final residual = 0.0007850409, No Iterations 2 DICPCG: Solving for h, Initial residual = 0.01102243, Final residual = 0.0005736408, No Iterations 2 Min/max T:min(T) [0 0 0 1 0 0 0] -669.9338 max(T) [0 0 0 1 0 0 0] 13726.58 ExecutionTime = 3146.34 s ClockTime = 3152 s Time = 588 Solving for fluid region fluid DILUPBiCG: Solving for Ux, Initial residual = 0.2112948, Final residual = 0.001279738, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.1900647, Final residual = 0.001276108, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.2537446, Final residual = 0.0007415269, No Iterations 1 GAMG: Solving for h, Initial residual = 0.6227222, Final residual = 0.0004394558, No Iterations 2 [15] [15] --> FOAM FATAL ERROR: [15] Maximum number of iterations exceeded [15] [15] From function thermo::T(scalar f, scalar T0, scalar (thermo::*F)(const scalar) const, scalar (thermo::*dFdT)(const scalar) const, scalar (thermo::*limit)(const scalar) const) const [15] in file /disk/sw/OpenFOAM/OpenFOAM-2.2.2/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 76. [15]``` After this step i got the error message Maximal number of iterations exceeded. My fv solution is Code: ```FoamFile { version 2.0; format ascii; class dictionary; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { rho { solver PCG preconditioner DIC; tolerance 1e-7; relTol 0; } p { solver PCG; preconditioner DIC; tolerance 1e-06; relTol 0.01; } U { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } p_rgh { solver GAMG; tolerance 1e-7; relTol 0.01; smoother GaussSeidel; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; maxIter 100; } h { solver GAMG; tolerance 1e-7; relTol 0.01; smoother GaussSeidel; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; maxIter 100; } k { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } epsilon { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } R { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } "(k|epsilon)" { solver PBiCG; preconditioner DILU; tolerance 1e-7; relTol 0.1; } } SIMPLE { momentumPredictor on; nNonOrthogonalCorrectors 0; pRefCell 0; pRefValue 100000; rhoMin rhoMin [1 -3 0 0 0] 1054; rhoMax rhoMax [1 -3 0 0 0] 1054; } relaxationFactors { fields { rho 1; p_rgh 0.7; } equations { U 0.3; h 0.7; nuTilda 0.7; k 0.7; epsilon 0.7; omega 0.7; "ILambda.*" 0.7; } } // ************************************************************************* //``` My fvSchemes Code: ```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) bounded Gauss upwind; div(phi,K) bounded Gauss upwind; div(phi,h) bounded Gauss upwind; div(phi,k) bounded Gauss upwind; div(phi,K) bounded Gauss upwind; div(phi,epsilon) bounded Gauss upwind; div(phi,R) bounded Gauss upwind; div(R) Gauss linear; div((muEff*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default none; laplacian(muEff,U) Gauss linear corrected; laplacian(Dp,p_rgh) Gauss linear corrected; laplacian(alphaEff,h) Gauss linear corrected; laplacian(DkEff,k) Gauss linear corrected; laplacian(DepsilonEff,epsilon) Gauss linear corrected; laplacian(DREff,R) Gauss linear corrected; } interpolationSchemes { default linear; interpolate(U) linear; } snGradSchemes { default corrected; } fluxRequired { default yes; p_rgh; T; }``` But i cant really figure out what is my problem since i runned the simulations before and then it's always converged. The only difference now is that my grid is finer and i switched properties from water to water/glycol

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