PisoFoam case terminating
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 = 7.05036e006, cum ulative = 7.05036e006 DICPCG: Solving for p, Initial residual = 0.0429108, Final residual = 8.08946e 007, No Iterations 32 time step continuity errors : sum local = 1.92361e005, global = 1.04776e006, cumulative = 8.09813e006 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 = 8.11337e0 07, No Iterations 82 time step continuity errors : sum local = 7.50547e006, global = 1.25482e007, 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 = 5.42804e0 07, No Iterations 170 time step continuity errors : sum local = 5.70389e006, global = 1.50213e007, 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 = 1.27945e007, Final residual = 1.2 7945e007, 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 = 1.69848e005, 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 = 1.08791e010, Final residual = 1.0 8791e010, 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 
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 
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.

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 
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