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December 28, 2011, 12:01 
High Courant Number @ icoFoam

#1 
New Member
Patrick Pazour
Join Date: Nov 2011
Posts: 9
Rep Power: 5 
Dear Foamers!
I designed a raw tetra mesh for a first view over the geometry. I wanted to test the flow with icoFoam. Unfortunately the courant number explodes after a few timesteps. Do you have any ideas how to get this work? Thanks a lot! checkMesh: Code:
Exec : checkMesh Date : Dec 29 2011 Time : 12:51:33 Host : ubuntu PID : 4305 Case : /home/ubuntu/OpenFOAM/ubuntu1.5dev/run/duese_3_tet_icofoam nProcs : 1 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create polyMesh for time = constant Time = constant Mesh stats points: 17575 faces: 173802 internal faces: 159746 cells: 83387 boundary patches: 4 point zones: 0 face zones: 0 cell zones: 0 Number of cells of each type: hexahedra: 0 prisms: 0 wedges: 0 pyramids: 0 tet wedges: 0 tetrahedra: 83387 polyhedra: 0 Checking topology... Boundary definition OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Number of regions: 1 (OK). Checking patch topology for multiply connected surfaces ... Patch Faces Points Surface topology ColdWall 3374 1772 ok (nonclosed singly connected) HotWall 10453 5279 ok (nonclosed singly connected) Inlet 93 60 ok (nonclosed singly connected) Outlet 136 89 ok (nonclosed singly connected) Checking geometry... This is a 3D mesh Overall domain bounding box (0.04 0.0199997 0.14) (0.02 0.0199993 0) Mesh (nonempty) directions (1 1 1) Mesh (nonempty, nonwedge) dimensions 3 Boundary openness (1.76704e19 2.54345e19 4.48772e20) Threshold = 1e06 OK. Max cell openness = 1.54305e16 OK. Max aspect ratio = 12.3272 OK. Minumum face area = 1.59421e07. Maximum face area = 5.57485e06. Face area magnitudes OK. Min volume = 4.23187e11. Max volume = 3.34644e09. Total volume = 8.00739e05. Cell volumes OK. Mesh nonorthogonality Max: 58.8765 average: 19.8095 Threshold = 70 Nonorthogonality check OK. Face pyramids OK. Max skewness = 0.813531 OK. Mesh OK. End Code:
FoamFile { version 2.0; format ascii; class dictionary; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { p PCG { preconditioner DIC; tolerance 1e06; relTol 0; }; U PBiCG { preconditioner DILU; tolerance 1e05; relTol 0; }; } PISO { nCorrectors 2; nNonOrthogonalCorrectors 1; pRefCell 0; pRefValue 0; } Code:
FoamFile { version 2.0; format ascii; class dictionary; object controlDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // application icoFoam; startFrom startTime; startTime 0; stopAt endTime; endTime 2; deltaT 0.02; writeControl timeStep; writeInterval 20; purgeWrite 0; writeFormat ascii; writePrecision 6; writeCompression uncompressed; timeFormat general; timePrecision 6; runTimeModifiable yes; adjustTimeStep no; Last edited by Artex85; December 29, 2011 at 09:38. Reason: update mesh and controlDict 

December 28, 2011, 12:09 

#2 
Senior Member
Join Date: Mar 2011
Posts: 174
Rep Power: 6 
What is the value of your Courant number? Have you tried a smaller time step?
You have turned off the adjustable time step by the way, maybe this could help if it was on. Could you post the log file? 

December 29, 2011, 09:50 

#3 
New Member
Patrick Pazour
Join Date: Nov 2011
Posts: 9
Rep Power: 5 
Hello anon_a!
Thanks for your quick reply, here is the log file: Code:
Exec : icoFoam Date : Dec 29 2011 Time : 13:36:10 Host : ubuntu PID : 5099 Case : /home/ubuntu/OpenFOAM/ubuntu1.5dev/run/duese_3_tet_icofoam nProcs : 1 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create mesh for time = 0 Reading transportProperties Reading field p Reading field U Reading/calculating face flux field phi Starting time loop Time = 0.02 Courant Number mean: 0 max: 0 velocity magnitude: 0 PBiCG: Solving for Ux, Initial residual = 0, Final residual = 0, No Iterations 0 PBiCG: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0 PBiCG: Solving for Uz, Initial residual = 1, Final residual = 7.92461e06, No Iterations 42 PCG: Solving for p, Initial residual = 1, Final residual = 8.51221e07, No Iterations 484 PCG: Solving for p, Initial residual = 0.102054, Final residual = 9.82929e07, No Iterations 459 time step continuity errors : sum local = 1.31195e07, global = 3.07613e10, cumulative = 3.07613e10 PCG: Solving for p, Initial residual = 0.054511, Final residual = 8.62196e07, No Iterations 472 PCG: Solving for p, Initial residual = 0.466713, Final residual = 8.97311e07, No Iterations 467 time step continuity errors : sum local = 2.20975e08, global = 1.92533e11, cumulative = 2.88359e10 ExecutionTime = 16.7 s ClockTime = 17 s Time = 0.04 Courant Number mean: 0.00506339 max: 3.82497 velocity magnitude: 0.0552267 PBiCG: Solving for Ux, Initial residual = 0.748645, Final residual = 8.16663e06, No Iterations 31 PBiCG: Solving for Uy, Initial residual = 0.771322, Final residual = 9.49122e06, No Iterations 34 PBiCG: Solving for Uz, Initial residual = 0.6344, Final residual = 8.92808e06, No Iterations 39 PCG: Solving for p, Initial residual = 0.602528, Final residual = 8.92601e07, No Iterations 488 PCG: Solving for p, Initial residual = 0.110327, Final residual = 8.24463e07, No Iterations 459 time step continuity errors : sum local = 5.43346e07, global = 8.05496e10, cumulative = 5.17137e10 PCG: Solving for p, Initial residual = 0.0449353, Final residual = 8.84106e07, No Iterations 470 PCG: Solving for p, Initial residual = 0.461692, Final residual = 8.98988e07, No Iterations 466 time step continuity errors : sum local = 1.19582e07, global = 1.29784e10, cumulative = 3.87353e10 ExecutionTime = 34.37 s ClockTime = 34 s Time = 0.06 Courant Number mean: 0.0263615 max: 13.485 velocity magnitude: 0.19658 PBiCG: Solving for Ux, Initial residual = 0.764436, Final residual = 9.74761e06, No Iterations 34 PBiCG: Solving for Uy, Initial residual = 0.778582, Final residual = 9.481e06, No Iterations 37 PBiCG: Solving for Uz, Initial residual = 0.645542, Final residual = 7.43444e06, No Iterations 40 PCG: Solving for p, Initial residual = 0.60749, Final residual = 8.64835e07, No Iterations 488 PCG: Solving for p, Initial residual = 0.129048, Final residual = 8.77098e07, No Iterations 457 time step continuity errors : sum local = 3.23187e06, global = 1.31075e09, cumulative = 9.234e10 PCG: Solving for p, Initial residual = 0.0464013, Final residual = 9.64245e07, No Iterations 468 PCG: Solving for p, Initial residual = 0.490751, Final residual = 9.75743e07, No Iterations 464 time step continuity errors : sum local = 8.02591e07, global = 2.05433e09, cumulative = 1.13093e09 ExecutionTime = 52.24 s ClockTime = 52 s Time = 0.08 Courant Number mean: 0.17455 max: 55.7621 velocity magnitude: 0.812884 PBiCG: Solving for Ux, Initial residual = 0.775338, Final residual = 9.18494e06, No Iterations 36 PBiCG: Solving for Uy, Initial residual = 0.780003, Final residual = 8.83473e06, No Iterations 38 PBiCG: Solving for Uz, Initial residual = 0.649195, Final residual = 7.62692e06, No Iterations 40 PCG: Solving for p, Initial residual = 0.661197, Final residual = 9.82732e07, No Iterations 479 PCG: Solving for p, Initial residual = 0.163826, Final residual = 9.35047e07, No Iterations 442 time step continuity errors : sum local = 2.31072e05, global = 1.43139e07, cumulative = 1.4427e07 PCG: Solving for p, Initial residual = 0.0544162, Final residual = 9.93518e07, No Iterations 465 PCG: Solving for p, Initial residual = 0.535228, Final residual = 9.42873e07, No Iterations 448 time step continuity errors : sum local = 6.10979e06, global = 3.08389e08, cumulative = 1.13431e07 ExecutionTime = 69.79 s ClockTime = 70 s Time = 0.1 Courant Number mean: 1.52184 max: 251.177 velocity magnitude: 3.66159 PBiCG: Solving for Ux, Initial residual = 0.785002, Final residual = 7.78131e06, No Iterations 37 PBiCG: Solving for Uy, Initial residual = 0.775493, Final residual = 7.00292e06, No Iterations 38 PBiCG: Solving for Uz, Initial residual = 0.653513, Final residual = 7.65689e06, No Iterations 39 PCG: Solving for p, Initial residual = 0.73722, Final residual = 8.38555e07, No Iterations 487 PCG: Solving for p, Initial residual = 0.210158, Final residual = 8.81948e07, No Iterations 458 time step continuity errors : sum local = 0.000179504, global = 6.47978e09, cumulative = 1.19911e07 PCG: Solving for p, Initial residual = 0.0671591, Final residual = 9.26519e07, No Iterations 469 PCG: Solving for p, Initial residual = 0.577796, Final residual = 8.43418e07, No Iterations 464 time step continuity errors : sum local = 5.39014e05, global = 3.38347e08, cumulative = 1.53746e07 ExecutionTime = 88.14 s ClockTime = 88 s Time = 0.12 Courant Number mean: 15.771 max: 1213.58 velocity magnitude: 17.2683 PBiCG: Solving for Ux, Initial residual = 0.791247, Final residual = 4.09263e06, No Iterations 47 PBiCG: Solving for Uy, Initial residual = 0.768959, Final residual = 1.95723e06, No Iterations 53 PBiCG: Solving for Uz, Initial residual = 0.660241, Final residual = 7.56799e06, No Iterations 53 PCG: Solving for p, Initial residual = 0.809628, Final residual = 8.35623e07, No Iterations 481 PCG: Solving for p, Initial residual = 0.270383, Final residual = 9.78329e07, No Iterations 459 time step continuity errors : sum local = 0.00202547, global = 2.30268e06, cumulative = 2.45642e06 PCG: Solving for p, Initial residual = 0.0840898, Final residual = 8.179e07, No Iterations 468 PCG: Solving for p, Initial residual = 0.611435, Final residual = 9.48164e07, No Iterations 464 time step continuity errors : sum local = 0.000754444, global = 2.30185e07, cumulative = 2.22624e06 ExecutionTime = 107.21 s ClockTime = 107 s Time = 0.14 Courant Number mean: 203.818 max: 6315.59 velocity magnitude: 144.106 PBiCG: Solving for Ux, Initial residual = 0.799529, Final residual = 7.23114e06, No Iterations 118 PBiCG: Solving for Uy, Initial residual = 0.768657, Final residual = 8.52382e06, No Iterations 119 PBiCG: Solving for Uz, Initial residual = 0.67574, Final residual = 6.44984e06, No Iterations 123 PCG: Solving for p, Initial residual = 0.644255, Final residual = 9.53304e07, No Iterations 501 PCG: Solving for p, Initial residual = 0.124882, Final residual = 8.26806e07, No Iterations 468 time step continuity errors : sum local = 0.0255069, global = 5.32141e06, cumulative = 3.09518e06 PCG: Solving for p, Initial residual = 0.0625569, Final residual = 9.64602e07, No Iterations 485 PCG: Solving for p, Initial residual = 0.476678, Final residual = 9.36606e07, No Iterations 483 time step continuity errors : sum local = 0.00664253, global = 2.03334e05, cumulative = 2.34285e05 ExecutionTime = 134.23 s ClockTime = 134 s Time = 0.16 Courant Number mean: 1224.81 max: 5.8799e+06 velocity magnitude: 95137.2 PBiCG: Solving for Ux, Initial residual = 0.995393, Final residual = 0.0200732, No Iterations 1000 PBiCG: Solving for Uy, Initial residual = 0.991433, Final residual = 0.307995, No Iterations 1000 PBiCG: Solving for Uz, Initial residual = 0.985122, Final residual = 0.0269352, No Iterations 1000 PCG: Solving for p, Initial residual = 0.929687, Final residual = 11.7345, No Iterations 1000 PCG: Solving for p, Initial residual = 0.794915, Final residual = 2.26295, No Iterations 1000 time step continuity errors : sum local = 3.50337e+06, global = 10532.6, cumulative = 10532.6 PCG: Solving for p, Initial residual = 0.969994, Final residual = 1.9792, No Iterations 1000 PCG: Solving for p, Initial residual = 0.680809, Final residual = 4.05222, No Iterations 1000 time step continuity errors : sum local = 1.599e+09, global = 1.22747e+07, cumulative = 1.22852e+07 ExecutionTime = 238.53 s ClockTime = 239 s Time = 0.18 Courant Number mean: 9.19732e+08 max: 1.85522e+12 velocity magnitude: 7.06915e+10 PBiCG: Solving for Ux, Initial residual = 0.999745, Final residual = 9.62717, No Iterations 1000 PBiCG: Solving for Uy, Initial residual = 0.999748, Final residual = 10.851, No Iterations 1000 PBiCG: Solving for Uz, Initial residual = 0.999861, Final residual = 2.88039, No Iterations 1000 PCG: Solving for p, Initial residual = 1, Final residual = 196.18, No Iterations 1000 PCG: Solving for p, Initial residual = 0.843622, Final residual = 5.02074, No Iterations 1000 time step continuity errors : sum local = 2.12167e+18, global = 4.6608e+09, cumulative = 4.67308e+09 PCG: Solving for p, Initial residual = 0.922669, Final residual = 2.7607, No Iterations 1000 PCG: Solving for p, Initial residual = 0.873783, Final residual = 3.07253, No Iterations 1000 time step continuity errors : sum local = 3.67336e+20, global = 4.99835e+15, cumulative = 4.99835e+15 ExecutionTime = 341.26 s ClockTime = 341 s Time = 0.2 Courant Number mean: 2.28604e+20 max: 8.40228e+23 velocity magnitude: 3.89946e+22 PBiCG: Solving for Ux, Initial residual = 0.999885, Final residual = 6.49499, No Iterations 1000 PBiCG: Solving for Uy, Initial residual = 0.999815, Final residual = 3.9282, No Iterations 1000 PBiCG: Solving for Uz, Initial residual = 0.999772, Final residual = 2.70425, No Iterations 1000 PCG: Solving for p, Initial residual = 1, Final residual = 57.7895, No Iterations 1000 PCG: Solving for p, Initial residual = 0.771788, Final residual = 124.919, No Iterations 1000 time step continuity errors : sum local = 4.00756e+33, global = 5.1915e+25, cumulative = 5.1915e+25 PCG: Solving for p, Initial residual = 0.923169, Final residual = 4.28131, No Iterations 1000 PCG: Solving for p, Initial residual = 0.74075, Final residual = 392.082, No Iterations 1000 time step continuity errors : sum local = 1.39632e+38, global = 1.04069e+30, cumulative = 1.04064e+30 ExecutionTime = 446.61 s ClockTime = 447 s Time = 0.22 Courant Number mean: 6.86548e+37 max: 1.692e+42 velocity magnitude: 6.1894e+40 PBiCG: Solving for Ux, Initial residual = 0.999959, Final residual = 2.91466, No Iterations 1000 PBiCG: Solving for Uy, Initial residual = 0.999976, Final residual = 0.549805, No Iterations 1000 PBiCG: Solving for Uz, Initial residual = 0.99999, Final residual = 0.420483, No Iterations 1000 PCG: Solving for p, Initial residual = 1, Final residual = 248.252, No Iterations 1000 PCG: Solving for p, Initial residual = 0.0273632, Final residual = 0.0501284, No Iterations 1000 time step continuity errors : sum local = 1.22223e+60, global = 1.90958e+44, cumulative = 1.90958e+44 PCG: Solving for p, Initial residual = 0.132324, Final residual = 1.12506, No Iterations 1000 PCG: Solving for p, Initial residual = 0.0522075, Final residual = 0.24675, No Iterations 1000 time step continuity errors : sum local = 1.9022e+63, global = 1.83909e+50, cumulative = 1.83909e+50 ExecutionTime = 551.96 s ClockTime = 552 s Time = 0.24 Courant Number mean: 1.41686e+63 max: 2.14683e+67 velocity magnitude: 7.26454e+65 PBiCG: Solving for Ux, Initial residual = 0.999941, Final residual = 5.11203, No Iterations 1000 PBiCG: Solving for Uy, Initial residual = 0.99994, Final residual = 0.204469, No Iterations 1000 PBiCG: Solving for Uz, Initial residual = 0.999928, Final residual = 1.03388, No Iterations 1000 PCG: Solving for p, Initial residual = 1, Final residual = 3.266, No Iterations 1000 PCG: Solving for p, Initial residual = 1.9343e11, Final residual = 1.9343e11, No Iterations 0 time step continuity errors : sum local = 1.47482e+88, global = 3.62724e+71, cumulative = 3.62724e+71 PCG: Solving for p, Initial residual = 3.87133e11, Final residual = 3.87133e11, No Iterations 0 PCG: Solving for p, Initial residual = 3.87133e11, Final residual = 3.87133e11, No Iterations 0 time step continuity errors : sum local = 2.95171e+88, global = 2.1468e+72, cumulative = 2.50952e+72 ExecutionTime = 633.62 s ClockTime = 634 s Time = 0.26 Courant Number mean: 8.67119e+87 max: 2.38864e+92 velocity magnitude: 8.00775e+90 PBiCG: Solving for Ux, Initial residual = 0.999973, Final residual = 0.645976, No Iterations 1000 PBiCG: Solving for Uy, Initial residual = 0.99999, Final residual = 0.272165, No Iterations 1000 PBiCG: Solving for Uz, Initial residual = 0.999979, Final residual = 0.313018, No Iterations 1000 PCG: Solving for p, Initial residual = 1, Final residual = 11.673, No Iterations 1000 PCG: Solving for p, Initial residual = 2.40327e11, Final residual = 2.40327e11, No Iterations 0 time step continuity errors : sum local = 1.46936e+101, global = 1.28168e+98, cumulative = 1.28168e+98 PCG: Solving for p, Initial residual = 7.36934e11, Final residual = 7.36934e11, No Iterations 0 PCG: Solving for p, Initial residual = 7.36934e11, Final residual = 7.36934e11, No Iterations 0 time step continuity errors : sum local = 4.5056e+101, global = 1.7056e+98, cumulative = 2.98729e+98 ExecutionTime = 718.06 s ClockTime = 718 s Time = 0.28 Courant Number mean: 1.45564e+101 max: 9.1374e+104 velocity magnitude: 3.16353e+103 Floating point exception (core dumped) Last edited by Artex85; January 3, 2012 at 09:56. 

December 29, 2011, 20:57 

#4 
Senior Member
Tarak
Join Date: Aug 2010
Location: State College, PA
Posts: 105
Rep Power: 6 
Hii,
Please check the quality of your mesh using the checkMesh utility, and judge whether the relevant parameters (e.g aspect ratio) look good or not. Thanks, Tarak 

December 30, 2011, 04:35 

#5 
Senior Member
Vincent RIVOLA
Join Date: Mar 2009
Location: France
Posts: 277
Rep Power: 9 
you can also run your computation by specifying a maximum courant number of 1 or 2, instead of specifying the time step.
This way, the time step will be adapted directly to avoid courant number being higher than the value you specify. At least, as long as possible. 

December 30, 2011, 04:37 

#6 
Senior Member
Tarak
Join Date: Aug 2010
Location: State College, PA
Posts: 105
Rep Power: 6 
You can also try the following link. It shows how to use an adjustable time step depending on the Courant No.
http://www.idurun.com/?p=371 

December 30, 2011, 04:59 

#7 
New Member
Patrick Pazour
Join Date: Nov 2011
Posts: 9
Rep Power: 5 
Dear Foamers!
After the problems with the tet mesh, i designed a simple pipe with hexas to check the openfoam mesh files which are created out of pointwise. checkMesh is just Fine, courent number with icoFoam is ... yea going up. If i change the ncorrectors to zero the courant number is stable. I tried to modify the icoFoam solver to be adjustable for the timesteps, dont get it worked. Last edited by Artex85; January 3, 2012 at 09:26. Reason: Killed dead link 

January 3, 2012, 04:26 

#8 
Senior Member
Join Date: Mar 2011
Posts: 174
Rep Power: 6 
Could you check your link? I don't have access to the file


January 3, 2012, 04:36 

#9 
New Member
Hossein
Join Date: Aug 2011
Posts: 2
Rep Power: 0 
Hi
i write a loop in my UDF by C_FACE_loop. its worked in 3D but in 2D in fluent show this error "noninteger subscript expression: unsigned char" whats that mean? please help me to solve this thanks 

January 3, 2012, 09:06 
Done

#10 
New Member
Patrick Pazour
Join Date: Nov 2011
Posts: 9
Rep Power: 5 
Dear Foamers!
The hex pipe is working, problem was the small cell size in combination with a too large timestep. The tet pipe is still pending, I think there is a problem with the mesh. The helix is done. All downloadable here > Pipe meshes with pointwise Working hex pipe Crashing tet pipe helix mesh with pointwise Last edited by Artex85; January 5, 2012 at 04:52. Reason: update helix case 

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