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pimpleDyMFoam high time step cont. errors simulating stirred tank 

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March 14, 2018, 10:51 
pimpleDyMFoam high time step cont. errors simulating stirred tank

#1 
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MichG
Join Date: Nov 2017
Posts: 6
Rep Power: 8 
Dear Foamers,
I want to simulate a stirred tank (rotorstatorsystem using a sliding mesh with a cyclicAMI BC). I use OpenFOAM 2.3.x and run the simulation in parallel on a cluster with 96 cores. For the simulation I use the kOmegaSST turbulence model. The checkMesh shows no errors and the quality of the mesh regarding orthogonality and skewness is okay. Code:
Mesh stats points: 1423216 internal points: 1254741 faces: 11352709 internal faces: 11015967 cells: 5242115 faces per cell: 4.26711 boundary patches: 12 point zones: 0 face zones: 1 cell zones: 3 Overall number of cells of each type: hexahedra: 0 prisms: 1400186 wedges: 0 pyramids: 30 tet wedges: 0 tetrahedra: 3841899 polyhedra: 0 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. *Number of regions: 2 The mesh has multiple regions which are not connected by any face. <<Writing region information to "0/cellToRegion" <<Writing region 0 with 4084840 cells to cellSet region0 <<Writing region 1 with 1157275 cells to cellSet region1 Checking patch topology for multiply connected surfaces... Patch Faces Points Surface topology heiss 84322 42161 ok (closed singly connected) kalt 84548 42274 ok (closed singly connected) rotor 80940 40481 ok (nonclosed singly connected) wand 70816 35545 ok (nonclosed singly connected) welle 3774 1912 ok (nonclosed singly connected) oben 4468 2385 ok (nonclosed singly connected) ami_stator_mantel 1237 687 ok (nonclosed singly connected) ami_stator_unten 801 436 ok (nonclosed singly connected) ami_stator_oben 988 588 ok (nonclosed singly connected) ami_rotor_oben 1661 924 ok (nonclosed singly connected) ami_rotor_mantel 1736 935 ok (nonclosed singly connected) ami_rotor_unten 1451 760 ok (nonclosed singly connected) Checking geometry... Overall domain bounding box (9.08279e18 0.61 0.61) (1.22 0.61 0.61) Mesh (nonempty, nonwedge) directions (1 1 1) Mesh (nonempty) directions (1 1 1) Boundary openness (9.98975e17 2.10661e15 5.01181e16) OK. Max cell openness = 5.07085e16 OK. Max aspect ratio = 9.82912 OK. Minimum face area = 3.50454e07. Maximum face area = 0.00173417. Face area magnitudes OK. Min volume = 1.18683e10. Max volume = 2.12797e05. Total volume = 1.37666. Cell volumes OK. Mesh nonorthogonality Max: 69.3312 average: 17.8113 Nonorthogonality check OK. Face pyramids OK. Max skewness = 2.63992 OK. Coupled point location match (average 0) OK. Mesh OK. I read many posts in the forum and therefore want to know:  time step continuity errors: are my BC, fvSolution and fvOptionsfile okay? I have read to "sqeeze" the pEquation and that these errors occur using wrong BCs  How to avoid those time step continuity errors? Does it have an effect?  Is my velocity BC for the rotor okay (movingWallVelocity) ?  Do i have to preserve the cyclicAMIpatches in the decomposePar?  What else can I do to get a stable simulation? Details are attached. Kind regards Michael 

March 14, 2018, 10:58 

#2 
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MichG
Join Date: Nov 2017
Posts: 6
Rep Power: 8 
And of course the files.
From the log file: Code:
Create time Create mesh for time = 0 Selecting dynamicFvMesh solidBodyMotionFvMesh Selecting solidbody motion function rotatingMotion Applying solid body motion to cellZone region1 PIMPLE: max iterations = 50 field "(Ukomega)" : relTol 0, tolerance 0.0001 field p : relTol 0, tolerance 0.001 Reading field p Reading field U Reading/calculating face flux field phi AMI: Creating addressing and weights between 1237 source faces and 1736 target faces AMI: Patch source sum(weights) min/max/average = 0.999836, 1.00065, 1.00026 AMI: Patch target sum(weights) min/max/average = 0.999852, 1.00068, 1.00019 AMI: Creating addressing and weights between 801 source faces and 1451 target faces AMI: Patch source sum(weights) min/max/average = 0.986399, 1, 0.999513 AMI: Patch target sum(weights) min/max/average = 0.991773, 1, 0.999798 AMI: Creating addressing and weights between 988 source faces and 1661 target faces AMI: Patch source sum(weights) min/max/average = 0.986501, 1, 0.999611 AMI: Patch target sum(weights) min/max/average = 0.990178, 1, 0.999789 Selecting incompressible transport model Newtonian Selecting turbulence model type RASModel Selecting RAS turbulence model kOmegaSST kOmegaSSTCoeffs { alphaK1 0.85; alphaK2 1; alphaOmega1 0.5; alphaOmega2 0.856; gamma1 0.555556; gamma2 0.44; beta1 0.075; beta2 0.0828; betaStar 0.09; a1 0.31; b1 1; c1 10; F3 false; } Reading field C Reading transportProperties Reading/calculating face velocity Uf No finite volume options present Courant Number mean: 0 max: 0 Starting time loop forces forces: Not including porosity effects Courant Number mean: 0 max: 0 Time = 0.001 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 0.001 transformation: ((0 0 0) (0.999956 (0.00941986 0 0))) AMI: Creating addressing and weights between 1237 source faces and 1736 target faces AMI: Patch source sum(weights) min/max/average = 0.99983, 1.0007, 1.00025 AMI: Patch target sum(weights) min/max/average = 0.999836, 1.00074, 1.00018 AMI: Creating addressing and weights between 801 source faces and 1451 target faces AMI: Patch source sum(weights) min/max/average = 0.986731, 1, 0.999506 AMI: Patch target sum(weights) min/max/average = 0.990875, 1, 0.999794 AMI: Creating addressing and weights between 988 source faces and 1661 target faces AMI: Patch source sum(weights) min/max/average = 0.969973, 1, 0.999087 AMI: Patch target sum(weights) min/max/average = 0.970237, 1, 0.99948 PIMPLE: iteration 1 DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.0284447, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 0.0342313, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 1, Final residual = 0.0348894, No Iterations 1 GAMG: Solving for p, Initial residual = 1, Final residual = 0.00833246, No Iterations 8 GAMG: Solving for p, Initial residual = 0.836537, Final residual = 0.00428101, No Iterations 3 time step continuity errors : sum local = 1.05925e05, global = 1.84807e09, cumulative = 1.84807e09 DILUPBiCG: Solving for omega, Initial residual = 0.00491671, Final residual = 5.84322e05, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 0.00113274, No Iterations 1 DILUPBiCG: Solving for C, Initial residual = 0, Final residual = 0, No Iterations 0 PIMPLE: iteration 2 DILUPBiCG: Solving for Ux, Initial residual = 0.396998, Final residual = 0.0212716, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.435977, Final residual = 0.0202887, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.433552, Final residual = 0.0198901, No Iterations 1 GAMG: Solving for p, Initial residual = 0.295205, Final residual = 0.00246142, No Iterations 6 GAMG: Solving for p, Initial residual = 0.405041, Final residual = 0.00205782, No Iterations 3 time step continuity errors : sum local = 5.09199e06, global = 6.09731e09, cumulative = 7.94538e09 DILUPBiCG: Solving for omega, Initial residual = 0.00109439, Final residual = 6.77543e06, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.181064, Final residual = 0.000223387, No Iterations 1 DILUPBiCG: Solving for C, Initial residual = 0, Final residual = 0, No Iterations 0 PIMPLE: iteration 3 DILUPBiCG: Solving for Ux, Initial residual = 0.210643, Final residual = 0.0112387, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.227965, Final residual = 0.0106337, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.224639, Final residual = 0.0103029, No Iterations 1 GAMG: Solving for p, Initial residual = 0.273154, Final residual = 0.00173302, No Iterations 5 GAMG: Solving for p, Initial residual = 0.171607, Final residual = 0.000936492, No Iterations 3 time step continuity errors : sum local = 1.92538e06, global = 1.07954e08, cumulative = 1.87408e08 DILUPBiCG: Solving for omega, Initial residual = 0.000340442, Final residual = 3.48788e06, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.0710379, Final residual = 0.000123145, No Iterations 1 DILUPBiCG: Solving for C, Initial residual = 0, Final residual = 0, No Iterations 0 PIMPLE: iteration 4 DILUPBiCG: Solving for Ux, Initial residual = 0.115488, Final residual = 0.00618736, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.123694, Final residual = 0.00589422, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.121163, Final residual = 0.00567863, No Iterations 1 GAMG: Solving for p, Initial residual = 0.286487, Final residual = 0.00150616, No Iterations 6 GAMG: Solving for p, Initial residual = 0.378669, Final residual = 0.00273378, No Iterations 3 time step continuity errors : sum local = 4.71711e06, global = 1.17942e08, cumulative = 3.0535e08 DILUPBiCG: Solving for omega, Initial residual = 0.000122516, Final residual = 1.70868e06, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.0369097, Final residual = 7.32202e05, No Iterations 1 DILUPBiCG: Solving for C, Initial residual = 0, Final residual = 0, No Iterations 0 PIMPLE: iteration 5 DILUPBiCG: Solving for Ux, Initial residual = 0.0555343, Final residual = 0.00294634, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.0567241, Final residual = 0.00274847, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.0550717, Final residual = 0.00262941, No Iterations 1 GAMG: Solving for p, Initial residual = 0.271987, Final residual = 0.00193688, No Iterations 6 GAMG: Solving for p, Initial residual = 0.534424, Final residual = 0.00355508, No Iterations 3 time step continuity errors : sum local = 5.48211e06, global = 1.134e08, cumulative = 4.1875e08 DILUPBiCG: Solving for omega, Initial residual = 5.57167e05, Final residual = 1.42868e06, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.0217183, Final residual = 4.68592e05, No Iterations 1 DILUPBiCG: Solving for C, Initial residual = 0, Final residual = 0, No Iterations 0 PIMPLE: iteration 6 DILUPBiCG: Solving for Ux, Initial residual = 0.0192802, Final residual = 0.000938646, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.021321, Final residual = 0.00107651, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.0208575, Final residual = 0.00105196, No Iterations 1 GAMG: Solving for p, Initial residual = 0.241582, Final residual = 0.00190977, No Iterations 6 GAMG: Solving for p, Initial residual = 0.559528, Final residual = 0.00354837, No Iterations 3 time step continuity errors : sum local = 4.4691e06, global = 9.18418e09, cumulative = 5.10592e08 DILUPBiCG: Solving for omega, Initial residual = 3.08845e05, Final residual = 2.04467e06, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.0128353, Final residual = 3.08331e05, No Iterations 1 DILUPBiCG: Solving for C, Initial residual = 0, Final residual = 0, No Iterations 0 PIMPLE: iteration 7 DILUPBiCG: Solving for Ux, Initial residual = 0.0228589, Final residual = 0.00122298, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.0312112, Final residual = 0.00163726, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.0313295, Final residual = 0.00161643, No Iterations 1 GAMG: Solving for p, Initial residual = 0.217324, Final residual = 0.00159824, No Iterations 6 GAMG: Solving for p, Initial residual = 0.470618, Final residual = 0.0026836, No Iterations 3 time step continuity errors : sum local = 2.48011e06, global = 6.14519e09, cumulative = 5.72044e08 DILUPBiCG: Solving for omega, Initial residual = 2.01208e05, Final residual = 1.30397e06, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.00791098, Final residual = 2.33801e05, No Iterations 1 DILUPBiCG: Solving for C, Initial residual = 0, Final residual = 0, No Iterations 0 PIMPLE: iteration 8 DILUPBiCG: Solving for Ux, Initial residual = 0.0358105, Final residual = 0.0021287, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.0448533, Final residual = 0.00235797, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.0450134, Final residual = 0.00232139, No Iterations 1 GAMG: Solving for p, Initial residual = 0.227131, Final residual = 0.00190435, No Iterations 5 GAMG: Solving for p, Initial residual = 0.248351, Final residual = 0.00159494, No Iterations 3 time step continuity errors : sum local = 1.24288e06, global = 3.51663e09, cumulative = 6.0721e08 DILUPBiCG: Solving for omega, Initial residual = 1.4326e05, Final residual = 4.90266e07, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.00558223, Final residual = 2.04897e05, No Iterations 1 DILUPBiCG: Solving for C, Initial residual = 0, Final residual = 0, No Iterations 0 PIMPLE: iteration 9 

March 15, 2018, 02:11 
Files

#3 
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MichG
Join Date: Nov 2017
Posts: 6
Rep Power: 8 
The Dict Files


March 15, 2018, 03:50 

#4 
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Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 744
Rep Power: 15 
Your log ist for time=0.001 where everything is or at least seems ok. It would be helpful to have a log snippet from later times, where the simulation gets slow.
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Uwe Pilz  Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) 

March 15, 2018, 05:35 
log file end

#5 
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Moa Miche
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I attached the end of the log file with the last time step which was ok.


March 15, 2018, 06:05 

#6 
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Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
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From your log
Code:
forces forces output: sum of forces: pressure : (1.45681e+12 6.68787e+10 4.42744e+10) viscous : (2.2505e+07 1.02148e+08 5.4285e+08) porous : (0 0 0) sum of moments: pressure : (1.34002e+08 2.0655e+10 2.72405e+10) viscous : (1.2777e+07 2.25572e+08 4.14318e+07) porous : (0 0 0) Courant Number mean: 12685.4 max: 1.20778e+06 The Courant number is HUGE. That means your time step is magnitudes to high. All i all I assume your case has general problems and is set up in a non physical manner. I recommend to write results at every time step and look what happens and at which boundary it starts to arise. I possible, use Courant number control instead of a fixed time step.
__________________
Uwe Pilz  Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) 

March 15, 2018, 06:18 

#7 
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MichG
Join Date: Nov 2017
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In all the time steps before the simulation is diverging the Courant number is almost constant and quite okay
Code:
Time = 0.179 Courant Number mean: 0.040338 max: 26.9502 I tried it also with a smaller timestep (Co_max ~ 10), i thought this is no problem because im using the solver in Pimplemode. 

March 15, 2018, 09:10 

#8 
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Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
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I don't recommend even a max Co of this size (27). Keep it lower than 1, if you have problems, even lower.
If large gradients arise during your simulation, and your max Co ist this large, it is easy to explain how your simulation crashes.
__________________
Uwe Pilz  Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) 

March 16, 2018, 03:41 
Adaption of schemes

#9 
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MichG
Join Date: Nov 2017
Posts: 6
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I adapted the divSchemes and now the simulation is running without problems. Due to my mesh (max nonOrhogonality ~ 70°) the linear scheme maybe caused the crash.
Code:
divSchemes { default none; div(phi,U) Gauss upwind; div(phi,C) Gauss upwind; div(phi,K) Gauss linear; div(meshPhi,p) Gauss linear; div(phi,k) Gauss upwind; div(phi,omega) Gauss upwind; div((nuEff*dev(T(grad(U))))) Gauss linear; } Code:
div(phi,K) Gauss upwind; div(meshPhi,p) Gauss upwind; 

Tags 
diverging, pimpledymfoam, stirred tank reactor, time step cont. error 
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