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July 13, 2009, 09:52 
Problems with simulating TurbFOAM

#1 
New Member
Barath Ezhilan
Join Date: Jun 2009
Posts: 20
Rep Power: 8 
Hi All,
I am trying to simulate swirling flow in the draft tube of the turbine using KOmegaSST turbulence model with TurbFOAM and I am having a problem with it. The simulations stops after a few time steps. I have a delta T 1e5 and I have also tried increasing the number of correctors and orthogonal correctors etc. The Mesh is fine, checkMesh says the Mesh is OK. I have also checked the boundary files The log file::: Time = 9.55556e05 Courant Number mean: 0.00131032 max: 7.52485 velocity magnitude: 260.087 PBiCG: Solving for Ux, Initial residual = 0.104884, Final residual = 0.00497614, No Iterations 2 PBiCG: Solving for Uy, Initial residual = 0.110647, Final residual = 0.00209042, No Iterations 2 PBiCG: Solving for Uz, Initial residual = 0.0109506, Final residual = 0.000402031, No Iterations 2 PCG: Solving for p, Initial residual = 0.905193, Final residual = 0.00849971, No Iterations 19 time step continuity errors : sum local = 3.95906e06, global = 2.96857e08, cumulative = 2.60243e07 PCG: Solving for p, Initial residual = 0.903698, Final residual = 0.0077981, No Iterations 21 time step continuity errors : sum local = 5.59011e06, global = 2.96251e08, cumulative = 2.89868e07 PBiCG: Solving for omega, Initial residual = 0.0521617, Final residual = 0.00171759, No Iterations 2 bounding omega, min: 3.10703e+06 max: 1.37457e+07 average: 6537.53 PBiCG: Solving for k, Initial residual = 0.0759318, Final residual = 0.00116278, No Iterations 2 bounding k, min: 0.228331 max: 4.29478 average: 0.0111114 ExecutionTime = 293.4 s ClockTime = 295 s Time = 0.000105556 Courant Number mean: 0.00177524 max: 16.8808 velocity magnitude: 532.235 PBiCG: Solving for Ux, Initial residual = 0.207847, Final residual = 0.0171767, No Iterations 2 PBiCG: Solving for Uy, Initial residual = 0.230103, Final residual = 0.0131825, No Iterations 2 PBiCG: Solving for Uz, Initial residual = 0.0368306, Final residual = 0.00168079, No Iterations 2 PCG: Solving for p, Initial residual = 0.905287, Final residual = 0.00834842, No Iterations 24 time step continuity errors : sum local = 7.86545e06, global = 3.42434e08, cumulative = 3.24111e07 PCG: Solving for p, Initial residual = 0.909423, Final residual = 0.00750422, No Iterations 24 time step continuity errors : sum local = 1.0548e05, global = 3.40615e08, cumulative = 3.58173e07 PBiCG: Solving for omega, Initial residual = 0.0586053, Final residual = 0.00481685, No Iterations 2 bounding omega, min: 1.3806e+07 max: 2.58179e+07 average: 13489.3 PBiCG: Solving for k, Initial residual = 0.0920886, Final residual = 0.00343743, No Iterations 2 bounding k, min: 1.52212 max: 6.6377 average: 0.0125395 ExecutionTime = 307.73 s ClockTime = 309 s Time = 0.000115556 Courant Number mean: 0.00234709 max: 21.606 velocity magnitude: 748.857 PBiCG: Solving for Ux, Initial residual = 0.344634, Final residual = 0.0099675, No Iterations 3 PBiCG: Solving for Uy, Initial residual = 0.329588, Final residual = 0.0101443, No Iterations 3 PBiCG: Solving for Uz, Initial residual = 0.0829345, Final residual = 0.00185229, No Iterations 3 PCG: Solving for p, Initial residual = 0.894228, Final residual = 0.0069595, No Iterations 77 time step continuity errors : sum local = 1.32459e05, global = 3.74457e08, cumulative = 3.95619e07 PCG: Solving for p, Initial residual = 0.941143, Final residual = 0.00818695, No Iterations 100 time step continuity errors : sum local = 4.97055e05, global = 3.5411e08, cumulative = 4.3103e07 PBiCG: Solving for omega, Initial residual = 1, Final residual = 0.0738547, No Iterations 76 bounding omega, min: 1.39421e+19 max: 2.83497e+19 average: 8.33634e+14 PBiCG: Solving for k, Initial residual = 0.929398, Final residual = 2.79674e11, No Iterations 1 bounding k, min: 1.05884 max: 9.29845 average: 0.00995458 ExecutionTime = 347.03 s ClockTime = 349 s Time = 0.000125556 Courant Number mean: 0.0842083 max: 107356 velocity magnitude: 6.87564e+06 PBiCG: Solving for Ux, Initial residual = 0.999926, Final residual = 5.05889, No Iterations 1000 PBiCG: Solving for Uy, Initial residual = 0.999817, Final residual = 15.8907, No Iterations 1000 PBiCG: Solving for Uz, Initial residual = 0.999843, Final residual = 6.45841, No Iterations 1000 PCG: Solving for p, Initial residual = 0.999999, Final residual = 0.415433, No Iterations 1000 time step continuity errors : sum local = 6410.55, global = 3.66894e08, cumulative = 4.67719e07 PCG: Solving for p, Initial residual = 0.996811, Final residual = 0.317644, No Iterations 1000 time step continuity errors : sum local = 1.70248e+06, global = 3.65351e08, cumulative = 5.04254e07 ~ The files in the system folder are given below ControlDict:::: application turbFoam; startFrom latestTime; startTime 0; stopAt endTime; endTime 0.3; deltaT 0.00005; writeControl timeStep; writeInterval 50; purgeWrite 0; writeFormat ascii; writePrecision 6; writeCompression compressed; timeFormat general; timePrecision 6; runTimeModifiable no; // libs ("libaddedIncompressibleRASModels.so"); libs ("libOpenFoamTurbo.so" ); Schemes File:: ddtSchemes { default Euler; } gradSchemes { default Gauss linear; grad(p) Gauss linear; grad(U) Gauss linear; } divSchemes { default none; div(phi,U) Gauss limitedLinearV 1; div(phi,k) Gauss limitedLinear 1; div(phi,epsilon) Gauss limitedLinear 1; div(phi,omega) Gauss limitedLinear 1; div(phi,R) Gauss limitedLinear 1; div(R) Gauss linear; div(phi,nuTilda) Gauss limitedLinear 1; div((nuEff*dev(grad(U).T()))) Gauss linear; } laplacianSchemes { default none; laplacian(nuEff,U) Gauss linear corrected; laplacian((1A(U)),p) Gauss linear corrected; laplacian(DkEff,k) Gauss linear corrected; laplacian(DepsilonEff,epsilon) Gauss linear corrected; laplacian(DomegaEff,omega) Gauss linear corrected; laplacian(DREff,R) Gauss linear corrected; laplacian(DnuTildaEff,nuTilda) Gauss linear corrected; } interpolationSchemes { default linear; interpolate(U) linear; } snGradSchemes { default corrected; } fluxRequired { default no; p; } Solution File:: solvers { p PCG { preconditioner DIC; tolerance 1e06; relTol 0.01; }; U PBiCG { preconditioner DILU; tolerance 1e05; relTol 0.1; }; k PBiCG { preconditioner DILU; tolerance 1e05; relTol 0.1; }; epsilon PBiCG { preconditioner DILU; tolerance 1e05; relTol 0.1; }; omega PBiCG { preconditioner DILU; tolerance 1e05; relTol 0.1; }; R PBiCG { preconditioner DILU; tolerance 1e05; relTol 0.1; }; nuTilda PBiCG { preconditioner DILU; tolerance 1e05; relTol 0.1; }; PISO { nCorrectors 4; nNonOrthogonalCorrectors 2; pRefCell 0; pRefValue 0; } Please do help me this regard as to what I can do to solve this problem??? 

July 14, 2009, 02:13 

#2 
Member
Mandar
Join Date: Mar 2009
Posts: 39
Rep Power: 8 
Hi Barath
The epsilon and omega are getting out of bounds, Use the 'limited settings' for laplacian of omega and epsilon, say, laplacian(DepsilonEff,epsilon) Gauss linear limited 0.3; laplacian(DomegaEff,omega) Gauss linear limited 0.3; also, possibly see if BC value's of epsilon and omega can be made more realistic. 

July 14, 2009, 04:34 

#3 
Senior Member

Hello,
Try to decrease your deltaT, your max Courant number is very high (it should be <1). Also, run your case first with upwind on div convection terms, and change your relTol to 0 for all variables in fvSolution. Regards, Jose Santos 

July 14, 2009, 06:51 
Limited settings not working

#4  
New Member
Barath Ezhilan
Join Date: Jun 2009
Posts: 20
Rep Power: 8 
Hi Menter,
I have tried applying the limited settings, but it still doesnt seem to work. Please tell what else can be done. Quote:


July 14, 2009, 06:55 
Hi!!!

#5 
New Member
Barath Ezhilan
Join Date: Jun 2009
Posts: 20
Rep Power: 8 
Hi Jose Santos,
I have chosen a time step 5E5 and the initial courant number is quite low only (of the order of 1E3). My FvSolution doesnot have any relTol, (I am using the settings provided in the cavity folder of TURBfoam tutorials) Will that be in any way the reason for the problem? 

July 15, 2009, 05:05 

#6 
Senior Member

Does it still diverge with those settings? The settings you showed on your first post were different.
Jose Santos 

July 15, 2009, 05:35 

#7 
New Member
Barath Ezhilan
Join Date: Jun 2009
Posts: 20
Rep Power: 8 
Hi santos,
Which settings are you referring to ?? My first post also shows the deltaT settings to be 5E5 (deltaT 0.00005), and the courant number of the first few time steps was also 1E3 . 

July 15, 2009, 05:45 

#8 
Senior Member

Your mean Co was 1e3, but your max Co = 7. Moreover, the fvSolution you showed has relTol 0.01 and 0.1 for most variables.
Jose Santos 

July 15, 2009, 05:51 

#9 
New Member
Barath Ezhilan
Join Date: Jun 2009
Posts: 20
Rep Power: 8 

July 15, 2009, 18:29 

#10 
New Member
Barath Ezhilan
Join Date: Jun 2009
Posts: 20
Rep Power: 8 
Hi Santos,
I changed the relTol settings to 0 and simulated. The problem still exists (as you see below, in the log file)!!!! any suggestions?? Time = 5e05 Courant Number mean: 0.000358108 max: 0.243795 velocity magnitude: 3.22114 PBiCG: Solving for Ux, Initial residual = 1, Final residual = 1.81664e06, No Iterations 2 PBiCG: Solving for Uy, Initial residual = 1, Final residual = 1.82548e06, No Iterations 2 PBiCG: Solving for Uz, Initial residual = 1, Final residual = 5.26316e06, No Iterations 3 PCG: Solving for p, Initial residual = 1, Final residual = 9.93795e07, No Iterations 439 PCG: Solving for p, Initial residual = 0.0190973, Final residual = 9.01639e07, No Iterations 359 PCG: Solving for p, Initial residual = 0.00380892, Final residual = 9.84682e07, No Iterations 353 time step continuity errors : sum local = 2.62486e08, global = 8.42758e11, cumulative = 8.42758e11 PCG: Solving for p, Initial residual = 0.00477481, Final residual = 9.89681e07, No Iterations 360 PCG: Solving for p, Initial residual = 0.00557558, Final residual = 9.75184e07, No Iterations 353 PCG: Solving for p, Initial residual = 0.00209781, Final residual = 9.6199e07, No Iterations 346 time step continuity errors : sum local = 2.32097e08, global = 6.46285e12, cumulative = 7.78129e11 PCG: Solving for p, Initial residual = 0.00252374, Final residual = 9.31564e07, No Iterations 346 PCG: Solving for p, Initial residual = 0.00159287, Final residual = 9.71556e07, No Iterations 342 PCG: Solving for p, Initial residual = 0.00109841, Final residual = 9.93416e07, No Iterations 338 time step continuity errors : sum local = 2.37934e08, global = 1.25654e10, cumulative = 4.78414e11 PCG: Solving for p, Initial residual = 0.00147234, Final residual = 9.52147e07, No Iterations 341 PCG: Solving for p, Initial residual = 0.00126403, Final residual = 8.98022e07, No Iterations 338 PCG: Solving for p, Initial residual = 0.00100686, Final residual = 9.89063e07, No Iterations 333 time step continuity errors : sum local = 2.36568e08, global = 1.71118e10, cumulative = 2.1896e10 PBiCG: Solving for omega, Initial residual = 0.0079402, Final residual = 4.81707e06, No Iterations 2 bounding omega, min: 39.8115 max: 12127.3 average: 105.149 PBiCG: Solving for k, Initial residual = 1, Final residual = 2.89074e06, No Iterations 5 ExecutionTime = 606.88 s ClockTime = 614 s Time = 0.0001 Courant Number mean: 0.00502222 max: 0.918015 velocity magnitude: 5.37594 PBiCG: Solving for Ux, Initial residual = 0.335416, Final residual = 2.71144e07, No Iterations 3 PBiCG: Solving for Uy, Initial residual = 0.335463, Final residual = 2.6876e07, No Iterations 3 PBiCG: Solving for Uz, Initial residual = 0.863441, Final residual = 5.86173e06, No Iterations 2 PCG: Solving for p, Initial residual = 0.00982878, Final residual = 8.78105e07, No Iterations 372 PCG: Solving for p, Initial residual = 0.20334, Final residual = 9.20665e07, No Iterations 384 PCG: Solving for p, Initial residual = 0.0678486, Final residual = 9.55188e07, No Iterations 380 time step continuity errors : sum local = 2.04639e09, global = 3.35027e13, cumulative = 2.19295e10 PCG: Solving for p, Initial residual = 0.0850855, Final residual = 9.56664e07, No Iterations 379 PCG: Solving for p, Initial residual = 0.38827, Final residual = 9.73532e07, No Iterations 390 PCG: Solving for p, Initial residual = 0.316163, Final residual = 9.23616e07, No Iterations 386 time step continuity errors : sum local = 4.21096e10, global = 2.25754e13, cumulative = 2.1952e10 PCG: Solving for p, Initial residual = 0.424259, Final residual = 9.47635e07, No Iterations 386 PCG: Solving for p, Initial residual = 0.474849, Final residual = 9.68887e07, No Iterations 382 PCG: Solving for p, Initial residual = 0.512805, Final residual = 9.25307e07, No Iterations 381 time step continuity errors : sum local = 4.93901e10, global = 4.74778e13, cumulative = 2.19046e10 PCG: Solving for p, Initial residual = 0.618267, Final residual = 9.08134e07, No Iterations 380 PCG: Solving for p, Initial residual = 0.645274, Final residual = 9.47856e07, No Iterations 379 PCG: Solving for p, Initial residual = 0.684602, Final residual = 9.86349e07, No Iterations 378 time step continuity errors : sum local = 8.37812e10, global = 4.68039e13, cumulative = 2.18578e10 PBiCG: Solving for omega, Initial residual = 0.415049, Final residual = 8.50722e06, No Iterations 8 bounding omega, min: 2.38491e+06 max: 3.60791e+07 average: 6236.52 PBiCG: Solving for k, Initial residual = 0.65272, Final residual = 1.54235e06, No Iterations 4 bounding k, min: 0.00274926 max: 0.127536 average: 0.0102244 ExecutionTime = 1240.58 s ClockTime = 1253 s Time = 0.00015 Courant Number mean: 0.00524007 max: 5.76168 velocity magnitude: 44.0043 PBiCG: Solving for Ux, Initial residual = 0.0672304, Final residual = 9.43873e06, No Iterations 6 PBiCG: Solving for Uy, Initial residual = 0.0670888, Final residual = 1.98847e06, No Iterations 7 PBiCG: Solving for Uz, Initial residual = 0.00481512, Final residual = 7.2339e06, No Iterations 4 PCG: Solving for p, Initial residual = 0.824352, Final residual = 9.17862e07, No Iterations 389 PCG: Solving for p, Initial residual = 0.698699, Final residual = 9.93409e07, No Iterations 384 PCG: Solving for p, Initial residual = 0.727276, Final residual = 9.97471e07, No Iterations 387 time step continuity errors : sum local = 1.60855e09, global = 1.68868e12, cumulative = 2.16889e10 PCG: Solving for p, Initial residual = 0.876338, Final residual = 9.49251e07, No Iterations 389 PCG: Solving for p, Initial residual = 0.84503, Final residual = 9.53187e07, No Iterations 391 PCG: Solving for p, Initial residual = 0.879094, Final residual = 8.97079e07, No Iterations 392 time step continuity errors : sum local = 2.47347e09, global = 1.6306e12, cumulative = 2.15258e10 PCG: Solving for p, Initial residual = 0.95115, Final residual = 9.62471e07, No Iterations 391 PCG: Solving for p, Initial residual = 0.87138, Final residual = 9.16364e07, No Iterations 392 PCG: Solving for p, Initial residual = 0.887653, Final residual = 9.34473e07, No Iterations 392 time step continuity errors : sum local = 4.73105e09, global = 2.88022e12, cumulative = 2.18139e10 PCG: Solving for p, Initial residual = 0.962629, Final residual = 9.87552e07, No Iterations 390 PCG: Solving for p, Initial residual = 0.883919, Final residual = 9.9326e07, No Iterations 392 PCG: Solving for p, Initial residual = 0.905319, Final residual = 9.56255e07, No Iterations 393 time step continuity errors : sum local = 8.67916e09, global = 2.17652e12, cumulative = 2.15962e10 PBiCG: Solving for omega, Initial residual = 0.557895, Final residual = 8.90059e06, No Iterations 30 bounding omega, min: 1.9486e+07 max: 5.4919e+08 average: 159539 PBiCG: Solving for k, Initial residual = 0.607767, Final residual = 6.63983e06, No Iterations 5 bounding k, min: 0.254928 max: 1.0788 average: 0.0112812 ExecutionTime = 1902.14 s ClockTime = 1924 s Time = 0.0002 Courant Number mean: 0.0120517 max: 243.737 velocity magnitude: 1747.7 PBiCG: Solving for Ux, Initial residual = 0.760947, Final residual = 8.84033e06, No Iterations 39 PBiCG: Solving for Uy, Initial residual = 0.774137, Final residual = 3.97576e06, No Iterations 38 PBiCG: Solving for Uz, Initial residual = 0.506527, Final residual = 9.29213e06, No Iterations 33 PCG: Solving for p, Initial residual = 0.78, Final residual = 8.87942e07, No Iterations 615 PCG: Solving for p, Initial residual = 0.547448, Final residual = 7.41311e07, No Iterations 601 PCG: Solving for p, Initial residual = 0.455372, Final residual = 6.3829e07, No Iterations 620 time step continuity errors : sum local = 7.9754e09, global = 6.46518e11, cumulative = 2.80614e10 PCG: Solving for p, Initial residual = 0.832319, Final residual = 8.24641e07, No Iterations 601 PCG: Solving for p, Initial residual = 0.487072, Final residual = 7.58123e07, No Iterations 619 PCG: Solving for p, Initial residual = 0.354087, Final residual = 8.01443e07, No Iterations 604 time step continuity errors : sum local = 4.46259e08, global = 6.1831e11, cumulative = 2.18783e10 PCG: Solving for p, Initial residual = 0.978763, Final residual = 6.43371e07, No Iterations 616 PCG: Solving for p, Initial residual = 0.487253, Final residual = 9.60152e07, No Iterations 602 PCG: Solving for p, Initial residual = 0.33208, Final residual = 3.72602e07, No Iterations 596 time step continuity errors : sum local = 6.06844e07, global = 4.93755e09, cumulative = 5.15634e09 PCG: Solving for p, Initial residual = 0.983923, Final residual = 9.73328e07, No Iterations 606 PCG: Solving for p, Initial residual = 0.48976, Final residual = 7.46673e07, No Iterations 591 PCG: Solving for p, Initial residual = 0.291791, Final residual = 6.55602e07, No Iterations 587 time step continuity errors : sum local = 4.414e05, global = 7.197e07, cumulative = 7.24857e07 PBiCG: Solving for omega, Initial residual = 0.999997, Final residual = 3.08064e+07, No Iterations 1000 bounding omega, min: 7.25689e+24 max: 5.46641e+24 average: 1.03469e+20 PBiCG: Solving for k, Initial residual = 0.81231, Final residual = 3.54624e11, No Iterations 1 bounding k, min: 53823.1 max: 106.182 average: 6.48604 ExecutionTime = 3236.79 s ClockTime = 3276 s Time = 0.00025 Courant Number mean: 25.0656 max: 2.5079e+07 velocity magnitude: 2.38043e+08 PBiCG: Solving for Ux, Initial residual = 0.999999, Final residual = 0.999999, No Iterations 1000 PBiCG: Solving for Uy, Initial residual = 0.999999, Final residual = 0.999999, No Iterations 1000 PBiCG: Solving for Uz, Initial residual = 0.999999, Final residual = 1.16832, No Iterations 1000 PCG: Solving for p, Initial residual = 0.999999, Final residual = 0.119066, No Iterations 1000 PCG: Solving for p, Initial residual = 0.0904133, Final residual = 3.89395, No Iterations 1000 PCG: Solving for p, Initial residual = 0.796989, Final residual = 2.27701, No Iterations 1000 time step continuity errors : sum local = 3.30829e+08, global = 1.40983e06, cumulative = 2.13468e06 PCG: Solving for p, Initial residual = 0.999459, Final residual = 4.68481, No Iterations 1000 PCG: Solving for p, Initial residual = 0.870245, Final residual = 1.35971, No Iterations 1000 PCG: Solving for p, Initial residual = 0.848326, Final residual = 6.07145, No Iterations 1000 time step continuity errors : sum local = 6.48284e+13, global = 0.0104131, cumulative = 0.0104153 PCG: Solving for p, Initial residual = 0.999416, Final residual = 1.60614, No Iterations 1000 PCG: Solving for p, Initial residual = 0.831019, Final residual = 1.93253, No Iterations 1000 PCG: Solving for p, Initial residual = 0.833148, Final residual = 2.24912, No Iterations 1000 time step continuity errors : sum local = 2.18907e+18, global = 93.1258, cumulative = 93.1154 PCG: Solving for p, Initial residual = 0.999613, Final residual = 6.6956, No Iterations 1000 PCG: Solving for p, Initial residual = 0.880524, Final residual = 37.3175, No Iterations 1000 PCG: Solving for p, Initial residual = 0.880441, Final residual = 3.30312, No Iterations 1000 time step continuity errors : sum local = 1.23502e+25, global = 5.00345e+08, cumulative = 5.00345e+08 

July 15, 2009, 18:32 

#11  
New Member
Barath Ezhilan
Join Date: Jun 2009
Posts: 20
Rep Power: 8 
And I dont think there is much of a problem with the initial settings also. Because i tested the same case with transient Simple Foam and it runs properly. What could be the reason for this discrepancy with respect to TURBFOAM???
Quote:


July 15, 2009, 21:08 

#12 
Member
Mandar
Join Date: Mar 2009
Posts: 39
Rep Power: 8 
Hi Barath
Is this still happening if you initialize the turbfoam with your simpleFoam results? The simplefoam is a steadystate solver, the transient thing isn't possible with it. Your pressure iterations are taking long time to converge. Try using GAMG solver for Pressure, and the suggestions by Jose for limiting ur courant number. 

July 16, 2009, 05:46 

#13  
New Member
Barath Ezhilan
Join Date: Jun 2009
Posts: 20
Rep Power: 8 
Hi Mandar,
I was referring to the solver transientSimpleFoam, anyways I will change the solver to GAMG and check Quote:


July 16, 2009, 05:55 

#14 
Senior Member

I agree with Mandar, maybe what you are missing is an adequate field initialization. If you dont want to use simpleFoam for that, potentialFoam is also a good option.
Anyway, you could use an even lower deltaT in the first iterations just to make sure your Co stabilizes. Then you can increase your deltaT to a better value. Regards, Jose Santos 

Tags 
courant number increasing, turbfoam 
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