# p_rgh initial residual no change with different settings

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 March 15, 2017, 05:18 p_rgh initial residual no change with different settings #1 Senior Member   Manu Chakkingal Join Date: Feb 2016 Location: Delft, Netherlands Posts: 129 Rep Power: 10 Hello All I am doing a conjugate heat transfer problem with 2 regions: 1. Air 2. plate The issue I face The initial pressure residual doesn't change Code: ```Region: air Courant Number mean: 0.025093108 max: 0.40052825 Region: plate Diffusion Number mean: 3.7111592e-07 max: 7.8177845e-07 deltaT = 0.0071130688 Time = 5.8941 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 0.0015977895, Final residual = 7.1757907e-08, No Iterations 2 max(T) [0 0 0 1 0 0 0] 307.07585 GAMG: Solving for p_rgh, Initial residual = 0.29225662, Final residual = 0.00014979926, No Iterations 5 time step continuity errors : sum local = 5.6147294e-07, global = -3.626898e-21 GAMG: Solving for p_rgh, Initial residual = 0.29228288, Final residual = 0.0001558772, No Iterations 5 time step continuity errors : sum local = 5.8412794e-07, global = 1.6563367e-21 GAMG: Solving for p_rgh, Initial residual = 0.29228292, Final residual = 0.0001561875, No Iterations 5 time step continuity errors : sum local = 5.8528492e-07, global = -1.0209638e-20 Solving for solid region plate DICPCG: Solving for T, Initial residual = 0.00033675569, Final residual = 1.8134589e-10, No Iterations 1 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77487 max(T) [0 0 0 1 0 0 0] 300.23137 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 0.00086688609, Final residual = 5.8887298e-08, No Iterations 2 max(T) [0 0 0 1 0 0 0] 307.07154 GAMG: Solving for p_rgh, Initial residual = 0.28837172, Final residual = 0.00025808741, No Iterations 5 time step continuity errors : sum local = 9.6388206e-07, global = -3.7600441e-21 GAMG: Solving for p_rgh, Initial residual = 0.28839029, Final residual = 0.00026193496, No Iterations 5 time step continuity errors : sum local = 9.7833528e-07, global = 2.6948758e-21 GAMG: Solving for p_rgh, Initial residual = 0.28839033, Final residual = 0.00026213134, No Iterations 5 time step continuity errors : sum local = 9.7907289e-07, global = -2.6309657e-21 Solving for solid region plate DICPCG: Solving for T, Initial residual = 7.843695e-07, Final residual = 7.843695e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.7751 max(T) [0 0 0 1 0 0 0] 300.23089 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 0.00047949062, Final residual = 3.5964391e-08, No Iterations 2 max(T) [0 0 0 1 0 0 0] 307.06885 GAMG: Solving for p_rgh, Initial residual = 0.28572757, Final residual = 0.0002516689, No Iterations 6 time step continuity errors : sum local = 9.4478046e-07, global = -6.5188299e-21 GAMG: Solving for p_rgh, Initial residual = 0.28574053, Final residual = 0.00025317592, No Iterations 6 time step continuity errors : sum local = 9.5044118e-07, global = 4.7719539e-21 GAMG: Solving for p_rgh, Initial residual = 0.28574058, Final residual = 0.00025325281, No Iterations 6 time step continuity errors : sum local = 9.5072952e-07, global = 3.728089e-22 Solving for solid region plate DICPCG: Solving for T, Initial residual = 1.2740441e-06, Final residual = 6.9627797e-13, No Iterations 1 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77523 max(T) [0 0 0 1 0 0 0] 300.23051 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 0.0002695116, Final residual = 2.4592606e-08, No Iterations 2 max(T) [0 0 0 1 0 0 0] 307.06714 GAMG: Solving for p_rgh, Initial residual = 0.2840107, Final residual = 0.00027359005, No Iterations 6 time step continuity errors : sum local = 1.0255247e-06, global = 1.0332132e-21 GAMG: Solving for p_rgh, Initial residual = 0.28401878, Final residual = 0.00027452449, No Iterations 6 time step continuity errors : sum local = 1.0290257e-06, global = 7.5413915e-21 GAMG: Solving for p_rgh, Initial residual = 0.28401879, Final residual = 0.00027457255, No Iterations 6 time step continuity errors : sum local = 1.0292054e-06, global = 1.4401075e-20 Solving for solid region plate DICPCG: Solving for T, Initial residual = 2.5904077e-07, Final residual = 2.5904077e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77529 max(T) [0 0 0 1 0 0 0] 300.23051 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 0.00014960406, Final residual = 6.311792e-07, No Iterations 1 max(T) [0 0 0 1 0 0 0] 307.06612 GAMG: Solving for p_rgh, Initial residual = 0.28286788, Final residual = 0.00019960496, No Iterations 7 time step continuity errors : sum local = 7.4439393e-07, global = -5.7732121e-21 GAMG: Solving for p_rgh, Initial residual = 0.28287327, Final residual = 0.00020010332, No Iterations 7 time step continuity errors : sum local = 7.4626443e-07, global = -2.5670556e-21 GAMG: Solving for p_rgh, Initial residual = 0.28287328, Final residual = 0.00020013241, No Iterations 7 time step continuity errors : sum local = 7.4637356e-07, global = 5.006291e-21 Solving for solid region plate DICPCG: Solving for T, Initial residual = 4.0860369e-07, Final residual = 4.0860369e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77533 max(T) [0 0 0 1 0 0 0] 300.2305 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 8.915537e-05, Final residual = 7.1263867e-07, No Iterations 1 max(T) [0 0 0 1 0 0 0] 307.06574 GAMG: Solving for p_rgh, Initial residual = 0.2821784, Final residual = 0.00020594294, No Iterations 7 time step continuity errors : sum local = 7.6754809e-07, global = 1.5231907e-21 GAMG: Solving for p_rgh, Initial residual = 0.28218178, Final residual = 0.0002062782, No Iterations 7 time step continuity errors : sum local = 7.6880604e-07, global = 3.6428755e-21 GAMG: Solving for p_rgh, Initial residual = 0.28218178, Final residual = 0.00020629814, No Iterations 7 time step continuity errors : sum local = 7.6888083e-07, global = 1.3793929e-20 Solving for solid region plate DICPCG: Solving for T, Initial residual = 4.5828655e-07, Final residual = 4.5828655e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77536 max(T) [0 0 0 1 0 0 0] 300.2306 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 4.7827065e-05, Final residual = 2.2985107e-07, No Iterations 1 max(T) [0 0 0 1 0 0 0] 307.06551 GAMG: Solving for p_rgh, Initial residual = 0.28171533, Final residual = 0.00020993592, No Iterations 7 time step continuity errors : sum local = 7.8213501e-07, global = -9.3521776e-21 GAMG: Solving for p_rgh, Initial residual = 0.2817176, Final residual = 0.00021015795, No Iterations 7 time step continuity errors : sum local = 7.8296837e-07, global = -4.0582912e-21 GAMG: Solving for p_rgh, Initial residual = 0.28171761, Final residual = 0.00021017166, No Iterations 7 time step continuity errors : sum local = 7.830198e-07, global = 3.5363587e-21 Solving for solid region plate DICPCG: Solving for T, Initial residual = 4.9787724e-07, Final residual = 4.9787724e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77538 max(T) [0 0 0 1 0 0 0] 300.23065 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 2.6090939e-05, Final residual = 1.1814457e-07, No Iterations 1 max(T) [0 0 0 1 0 0 0] 307.06537 GAMG: Solving for p_rgh, Initial residual = 0.28140271, Final residual = 0.00021239068, No Iterations 7 time step continuity errors : sum local = 7.9111348e-07, global = -2.417932e-21 GAMG: Solving for p_rgh, Initial residual = 0.28140414, Final residual = 0.00021253976, No Iterations 7 time step continuity errors : sum local = 7.9167325e-07, global = 1.5657974e-21 GAMG: Solving for p_rgh, Initial residual = 0.28140414, Final residual = 0.00021254929, No Iterations 7 time step continuity errors : sum local = 7.9170899e-07, global = 1.101384e-20 Solving for solid region plate DICPCG: Solving for T, Initial residual = 5.222418e-07, Final residual = 5.222418e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77539 max(T) [0 0 0 1 0 0 0] 300.23068 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 1.4511823e-05, Final residual = 6.5523126e-08, No Iterations 1 max(T) [0 0 0 1 0 0 0] 307.06528 GAMG: Solving for p_rgh, Initial residual = 0.28119291, Final residual = 0.00021391702, No Iterations 7 time step continuity errors : sum local = 7.9670066e-07, global = -9.3841326e-21 GAMG: Solving for p_rgh, Initial residual = 0.28119381, Final residual = 0.00021401911, No Iterations 7 time step continuity errors : sum local = 7.9708407e-07, global = -1.1716851e-22 GAMG: Solving for p_rgh, Initial residual = 0.28119381, Final residual = 0.00021402582, No Iterations 7 time step continuity errors : sum local = 7.9710924e-07, global = -5.677347e-21 Solving for solid region plate DICPCG: Solving for T, Initial residual = 5.3730343e-07, Final residual = 5.3730343e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77539 max(T) [0 0 0 1 0 0 0] 300.23069 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 1.8336375e-05, Final residual = 3.3775715e-07, No Iterations 1 max(T) [0 0 0 1 0 0 0] 307.06515 GAMG: Solving for p_rgh, Initial residual = 0.03702251, Final residual = 3.052687e-05, No Iterations 11 time step continuity errors : sum local = 3.3549545e-07, global = 1.0332132e-21 GAMG: Solving for p_rgh, Initial residual = 0.036786632, Final residual = 2.849982e-05, No Iterations 11 time step continuity errors : sum local = 3.1319121e-07, global = -4.0582912e-21 GAMG: Solving for p_rgh, Initial residual = 0.036785243, Final residual = 9.9930364e-08, No Iterations 31 time step continuity errors : sum local = 1.0904319e-09, global = 6.4053853e-21 Solving for solid region plate DICPCG: Solving for T, Initial residual = 5.5942857e-07, Final residual = 5.5942857e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.7754 max(T) [0 0 0 1 0 0 0] 300.2307 ExecutionTime = 9340.47 s ClockTime = 9355 s Region: air Courant Number mean: 0.025087667 max: 0.40051174 Region: plate Diffusion Number mean: 3.7061104e-07 max: 7.8071489e-07 deltaT = 0.0071039405 Time = 5.9012``` What is observed 1. There are 10 outercorrectors (though number of pimple iteration not displayed) and 3 ncorrectors in each loop. 2. No change in p_rgh initial residual found till the last outer loop 3.Sudden jump of p_rgh initial residual from [/b] 0.28[/b] to 0.03 (see code snippet) Code: ``` Solving for solid region plate DICPCG: Solving for T, Initial residual = 5.222418e-07, Final residual = 5.222418e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77539 max(T) [0 0 0 1 0 0 0] 300.23068 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 1.4511823e-05, Final residual = 6.5523126e-08, No Iterations 1 max(T) [0 0 0 1 0 0 0] 307.06528 GAMG: Solving for p_rgh, Initial residual = 0.28119291, Final residual = 0.00021391702, No Iterations 7 time step continuity errors : sum local = 7.9670066e-07, global = -9.3841326e-21 GAMG: Solving for p_rgh, Initial residual = 0.28119381, Final residual = 0.00021401911, No Iterations 7 time step continuity errors : sum local = 7.9708407e-07, global = -1.1716851e-22 GAMG: Solving for p_rgh, Initial residual = 0.28119381, Final residual = 0.00021402582, No Iterations 7 time step continuity errors : sum local = 7.9710924e-07, global = -5.677347e-21 Solving for solid region plate DICPCG: Solving for T, Initial residual = 5.3730343e-07, Final residual = 5.3730343e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77539 max(T) [0 0 0 1 0 0 0] 300.23069).``` I am not able to find why its happening ( Its observed in all time steps) 4. The prgh_initial value never changes in 1 outer iteration (see the specific region below) Code: ```Solving for solid region plate DICPCG: Solving for T, Initial residual = 5.222418e-07, Final residual = 5.222418e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77539 max(T) [0 0 0 1 0 0 0] 300.23068 Solving for fluid region air DILUPBiCG: Solving for T, Initial residual = 1.4511823e-05, Final residual = 6.5523126e-08, No Iterations 1 max(T) [0 0 0 1 0 0 0] 307.06528 GAMG: Solving for p_rgh, Initial residual = 0.28119291, Final residual = 0.00021391702, No Iterations 7 time step continuity errors : sum local = 7.9670066e-07, global = -9.3841326e-21 GAMG: Solving for p_rgh, Initial residual = 0.28119381, Final residual = 0.00021401911, No Iterations 7 time step continuity errors : sum local = 7.9708407e-07, global = -1.1716851e-22 GAMG: Solving for p_rgh, Initial residual = 0.28119381, Final residual = 0.00021402582, No Iterations 7 time step continuity errors : sum local = 7.9710924e-07, global = -5.677347e-21 Solving for solid region plate DICPCG: Solving for T, Initial residual = 5.3730343e-07, Final residual = 5.3730343e-07, No Iterations 0 Min/max T:min(T) [0 0 0 1 0 0 0] 299.77539 max(T) [0 0 0 1 0 0 0] 300.23069``` What did I try 1. Changing outercorrector and inner corrector numbers (no change observed) Code: ```/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.4.0 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { p_rgh { solver GAMG; tolerance 1e-7; relTol 1e-3; smoother GaussSeidel; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } p_rghFinal { \$p_rgh; tolerance 1e-7; relTol 0; } "(U|T|k|epsilon|R)" { solver PBiCG; preconditioner DILU; tolerance 1e-6; relTol 0.0001; } "(U|T|k|epsilon|R)Final" { \$U; relTol 0; } } PIMPLE { momentumPredictor no; nOuterCorrectors 10;//tried 20 aswell no change nCorrectors 3; nNonOrthogonalCorrectors 0; pRefPoint (0.5 0.01 0); pRefValue 0; } relaxationFactors { fields { p_rgh 0.2; } equations { U 0.3; T 0.5; "(k|epsilon|R)" 0.7; "(U|T|k|epsilon|R)Final" 1; } } // ************************************************************************* //``` 2. Tried changing solver for p_rgh to PCG Code: ```solvers { p_rgh { solver PCG; preconditioner DIC; tolerance 1e-8; relTol 1e-3; } p_rghFinal { \$p_rgh; relTol 0; }``` 3. Tried changing fvSchemes from linear to upwind fvsolution 1 Code: ```/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 1.7.1 | | \\ / A nd | Web: www.OpenFOAM.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default Euler; // steadyState; // } gradSchemes { default Gauss linear; } divSchemes { default none; div(phi,U) Gauss linear ; div(phi,h) Gauss linear limited 0.333; div(phi,k) Gauss linear limited 0.333; div(phi,T) Gauss linear limited 0.333; div(phi,epsilon) Gauss linear limited 0.333; div(phi,R) Gauss linear; div(R) Gauss linear; div((muEff*dev2(grad(U).T()))) Gauss linear; div(U,p) Gauss upwind; div((nuEff*dev(grad(U).T()))) Gauss linear; div((nuEff*dev(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear uncorrected; laplacian(muEff,U) Gauss linear limited 0.333; laplacian((rho*(1|A(U))),p_rgh) Gauss linear limited 0.333; laplacian((1|A(U)),p) Gauss linear corrected; laplacian(alphaEff,h) Gauss linear limited 0.333; laplacian(DkEff,k) Gauss linear limited 0.333; laplacian(DepsilonEff,epsilon) Gauss linear limited 0.333; laplacian(DREff,R) Gauss linear limited 0.333; laplacian(nuEff,U) Gauss linear corrected; laplacian(nu,U) Gauss linear corrected; laplacian(kappaEff,T) Gauss linear limited 0.333; } interpolationSchemes { default linear; } snGradSchemes { default limited 0.333; } fluxRequired { default no; p_rgh; } // ************************************************************************* //``` fvsolution 2 Code: ```/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 1.7.1 | | \\ / A nd | Web: www.OpenFOAM.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default Euler; } gradSchemes { default Gauss linear; } divSchemes { default none; div(phi,U) Gauss upwind; div(phi,T) Gauss upwind; div(phi,k) Gauss upwind; div(phi,epsilon) Gauss upwind; div(phi,R) Gauss upwind; div(R) Gauss linear; div((nuEff*dev(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear uncorrected; } interpolationSchemes { default linear; } snGradSchemes { default uncorrected; } fluxRequired { default no; p_rgh; } // ************************************************************************* //``` 5 also tried changing northogonal correctors as per the suggestion in a post by Hjasak up to 4. In all these cases I find no difference in the initial p_rgh residual. The values follow the same trend as above. It would be great if some suggestions could be provided on how to approach it. __________________ Regards Manu

 June 26, 2018, 15:40 #2 Member   Join Date: Jul 2010 Posts: 52 Rep Power: 15 Hi Manu, Did you find a solution? I am having exactly the same problem that you described and I have not been able to find a solution. I found this post that talks about the same issue, but no solution yet: How to use PIMPLE properly? Cheers, Mary

June 26, 2018, 15:43
#3
Senior Member

Manu Chakkingal
Join Date: Feb 2016
Location: Delft, Netherlands
Posts: 129
Rep Power: 10
Quote:
 Originally Posted by MaryBau Hi Manu, Did you find a solution? I am having exactly the same problem that you described and I have not been able to find a solution. I found this post that talks about the same issue, but no solution yet: How to use PIMPLE properly? Cheers, Mary
I use piso now with Gamg..in most cases it serves the purpose.
__________________
Regards
Manu

 June 26, 2018, 15:53 #4 Member   Join Date: Jul 2010 Posts: 52 Rep Power: 15 mmm.... I have been using GAMG, but I still have that problem. This is what I normally use: Code: ```"(p|p_rgh)" { solver GAMG; tolerance 1e-6; relTol 0.01; smoother DICGaussSeidel; minIter 1; maxIter 100; nPreSweeps 1; nPostSweeps 3; nFinestSweeps 3; scaleCorrection true; directSolveCoarsest false; cacheAgglomeration on; nCellsInCoarsestLevel 50; agglomerator faceAreaPair; mergeLevels 1; }``` I have tried modifying some of those values, but 1) I have to admit that I do not understand what all those parameters do, 2) I have not seen a difference in the simulation output. What parameters do you use for GAMG? Thanks for your help! cleitontrindade likes this.

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