# PisoFoam case terminating

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 November 28, 2011, 16:14 PisoFoam case terminating #1 New Member   Andrew Wood Join Date: Oct 2011 Posts: 15 Rep Power: 14 Hi, I am very new to OpenFoam and CFD in general and my knowledge is pretty limited, but could do with some help! I have been running some fairly hefty cases with good results using SimpleFoam RAS K epsilon, and would like to run the same case using PisoFoam but there is something wrong. I run the case and it starts, runs about 6 iterations then stops... Create time Create mesh for time = 0 Reading field p Reading field U Reading/calculating face flux field phi Selecting incompressible transport model Newtonian Selecting turbulence model type RASModel Selecting RAS turbulence model kEpsilon Starting time loop Time = 1 Courant Number mean: 0 max: 22.3405 DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.0177764, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 0.080159, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 1, Final residual = 0.064155, No Iterations 2 DICPCG: Solving for p, Initial residual = 1, Final residual = 0.00988745, No It erations 16 time step continuity errors : sum local = 0.0238766, global = -7.05036e-006, cum ulative = -7.05036e-006 DICPCG: Solving for p, Initial residual = 0.0429108, Final residual = 8.08946e- 007, No Iterations 32 time step continuity errors : sum local = 1.92361e-005, global = -1.04776e-006, cumulative = -8.09813e-006 DILUPBiCG: Solving for epsilon, Initial residual = 0.0747366, Final residual = 0.00498244, No Iterations 7 bounding epsilon, min: -0.0552828 max: 3.18431 average: 1.50393 DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 0.0662276, No Iterations 4 ExecutionTime = 7.753 s ClockTime = 7 s Time = 2 Courant Number mean: 2.28129 max: 22.3405 DILUPBiCG: Solving for Ux, Initial residual = 0.683011, Final residual = 0.0254 887, No Iterations 4 DILUPBiCG: Solving for Uy, Initial residual = 0.666654, Final residual = 0.0397 083, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.541532, Final residual = 0.0400 149, No Iterations 4 DICPCG: Solving for p, Initial residual = 0.310939, Final residual = 0.00303243 , No Iterations 41 time step continuity errors : sum local = 0.0193994, global = -0.00070995, cumul ative = -0.000718048 DICPCG: Solving for p, Initial residual = 0.168895, Final residual = 8.11337e-0 07, No Iterations 82 time step continuity errors : sum local = 7.50547e-006, global = -1.25482e-007, cumulative = -0.000718174 DILUPBiCG: Solving for epsilon, Initial residual = 0.133022, Final residual = 0 .00903727, No Iterations 7 bounding epsilon, min: -4.12792 max: 24.4349 average: 1.36762 DILUPBiCG: Solving for k, Initial residual = 0.79566, Final residual = 0.060510 1, No Iterations 14 bounding k, min: -181.446 max: 752.263 average: 0.187323 ExecutionTime = 12.972 s ClockTime = 13 s Time = 3 Courant Number mean: 9.33323 max: 783.484 DILUPBiCG: Solving for Ux, Initial residual = 0.872314, Final residual = 0.0140 605, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.822447, Final residual = 0.0221 085, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.908123, Final residual = 0.0650 906, No Iterations 1 DICPCG: Solving for p, Initial residual = 0.655174, Final residual = 0.00654775 , No Iterations 74 time step continuity errors : sum local = 0.0175415, global = -0.000610279, cumu lative = -0.00132845 DICPCG: Solving for p, Initial residual = 0.661673, Final residual = 5.42804e-0 07, No Iterations 170 time step continuity errors : sum local = 5.70389e-006, global = -1.50213e-007, cumulative = -0.0013286 DILUPBiCG: Solving for epsilon, Initial residual = 0.977602, Final residual = 0 .0376696, No Iterations 2 bounding epsilon, min: -2.18559e+007 max: 8.2803e+006 average: 6981.89 DILUPBiCG: Solving for k, Initial residual = 1.27945e-007, Final residual = 1.2 7945e-007, No Iterations 0 ExecutionTime = 19.17 s ClockTime = 19 s Time = 4 Courant Number mean: 71.8097 max: 4.08253e+006 DILUPBiCG: Solving for Ux, Initial residual = 0.931317, Final residual = 0.0607 204, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.822577, Final residual = 0.0342 344, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.910466, Final residual = 0.0371 86, No Iterations 2 DICPCG: Solving for p, Initial residual = 0.998214, Final residual = 0.00879498 , No Iterations 71 time step continuity errors : sum local = 10.4873, global = 4.33564, cumulative = 4.33431 DICPCG: Solving for p, Initial residual = 0.0379911, Final residual = 9.28994e- 007, No Iterations 135 time step continuity errors : sum local = 1862.64, global = 494.993, cumulative = 499.327 DILUPBiCG: Solving for epsilon, Initial residual = 0.999319, Final residual = 6 .48079, No Iterations 1001 bounding epsilon, min: -8.20939e+015 max: 6.91709e+015 average: -1.10719e+012 DILUPBiCG: Solving for k, Initial residual = 0.0116847, Final residual = 0.0758 928, No Iterations 1001 bounding k, min: -1.30958e+015 max: 1.33593e+015 average: 9.7251e+010 ExecutionTime = 110.045 s ClockTime = 110 s Time = 5 Courant Number mean: 7.30475e+008 max: 1.14002e+014 DILUPBiCG: Solving for Ux, Initial residual = 0.850483, Final residual = 0.0704 834, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.807872, Final residual = 0.0769 487, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.927567, Final residual = 0.0562 261, No Iterations 1 DICPCG: Solving for p, Initial residual = 0.999788, Final residual = 94280.9, N o Iterations 1001 time step continuity errors : sum local = 2.01679e+016, global = -2.17307e+014, cumulative = -2.17307e+014 DICPCG: Solving for p, Initial residual = 1.69848e-005, Final residual = 0.0002 58383, No Iterations 1001 time step continuity errors : sum local = 1.07146e+034, global = 1.19886e+032, c umulative = 1.19886e+032 DILUPBiCG: Solving for epsilon, Initial residual = 1, Final residual = 8.74346e +014, No Iterations 1001 bounding epsilon, min: -8.96533e+067 max: 1.50189e+067 average: -6.53566e+062 DILUPBiCG: Solving for k, Initial residual = 1.08791e-010, Final residual = 1.0 8791e-010, No Iterations 0 ExecutionTime = 192.418 s ClockTime = 192 s Time = 6 Courant Number mean: 1.61566e+034 max: 3.84916e+039 C:\piso> I looked at a couple of other threads that might have a similar problem, and noticed one about the courant number going crazy, which seems to be the same here. the above test was on a simple cube case and should have no meshing issues as far as I can tell. If anyone has any ideas what might be the problem I would really appreciate some help. Thanks very much in advance, Andrew

 November 28, 2011, 16:48 #2 New Member   Andrew Wood Join Date: Oct 2011 Posts: 15 Rep Power: 14 Ahh, I have just tried the same case with no object (it was a cube) and it runs fine, so guess there must be a problem with the mesh. Still, I am confused why a case that works with simplefoam would not work with Piso? Any ideas? Sorry to be so vague! Andrew

 November 29, 2011, 03:02 #3 Senior Member     Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,377 Rep Power: 29 To me it looks like your timestep is way too big. With PISO, you need smaller timesteps than with SIMPLE. Keep the maximum Courant number under 1 (i.e. reduce the time step from 1 to 0.01), and things should work better. Solo Sails likes this.

 November 29, 2011, 07:04 #4 New Member   Andrew Wood Join Date: Oct 2011 Posts: 15 Rep Power: 14 As simple as that! Thank you so much, you have just sorted a small problem for most, a massive problem for me! Thanks again. Andrew