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October 29, 2013, 04:30 
Micro Scale Pore, icoFoam

#1 
Member
Reza
Join Date: Feb 2012
Posts: 67
Rep Power: 6 
Hi FOAMers,
I'm working with icoFoam, incompressible fluid (water) in a very tiny pores (diameter is about 210 micrometers). I tried many boundary conditions such as: inlet: pressure: zeroGradient, velocity: fixedValue outlet: pressure: fixedValue, velocity: fixedValue or: inlet: pressure: fixedValue, velocity: pressureInletVelocity outlet: pressure: fixedValue, velocity: fixedValue As simulation starts, Courant number start to increase and maybe after 30 time step, it reaches to 10+4, and velocity and pressure values reach 10+10. I thought it could be because of high boundary condition in fixedValues but decrease in the B.C. just postpones the 30 time step to maybe 50 time step. Now I'm confusing with the data and how I can converge the simulation and your comments can help me a lot. Thanks To add more information, the log file is as follow: (from 16) [QUOTE]Time = 16 Courant Number mean: 0.153578 max: 20.706 DICPCG: Solving for Ux, Initial residual = 0.586454, Final residual = 6.91785e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.574148, Final residual = 9.70984e06, No Iterations 26 DICPCG: Solving for Uz, Initial residual = 0.579967, Final residual = 8.64667e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.915668, Final residual = 0.00341124, No Iterations 1001 time step continuity errors : sum local = 0.000298567, global = 1.18248e18, cumulative = 9.13022e19 DICPCG: Solving for p, Initial residual = 0.713102, Final residual = 0.00340517, No Iterations 1001 time step continuity errors : sum local = 0.000346162, global = 5.90852e20, cumulative = 8.53937e19 ExecutionTime = 553.09 s ClockTime = 554 s Time = 17 Courant Number mean: 0.327887 max: 45.4381 DICPCG: Solving for Ux, Initial residual = 0.578642, Final residual = 7.07612e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.567511, Final residual = 9.88047e06, No Iterations 26 DICPCG: Solving for Uz, Initial residual = 0.576988, Final residual = 8.42121e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.914977, Final residual = 0.00390539, No Iterations 1001 time step continuity errors : sum local = 0.000717964, global = 1.87682e18, cumulative = 2.73076e18 DICPCG: Solving for p, Initial residual = 0.711657, Final residual = 0.00392582, No Iterations 1001 time step continuity errors : sum local = 0.000839034, global = 2.6569e19, cumulative = 2.46507e18 ExecutionTime = 594.15 s ClockTime = 595 s Time = 18 Courant Number mean: 0.707737 max: 99.7878 DICPCG: Solving for Ux, Initial residual = 0.576575, Final residual = 7.24442e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.571475, Final residual = 6.69346e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.580093, Final residual = 8.40165e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.915265, Final residual = 0.00503088, No Iterations 1001 time step continuity errors : sum local = 0.00198916, global = 7.13966e18, cumulative = 9.60473e18 DICPCG: Solving for p, Initial residual = 0.712068, Final residual = 0.00362861, No Iterations 1001 time step continuity errors : sum local = 0.00168029, global = 2.94268e19, cumulative = 9.89899e18 ExecutionTime = 633.22 s ClockTime = 635 s Time = 19 Courant Number mean: 1.54739 max: 219.104 DICPCG: Solving for Ux, Initial residual = 0.571621, Final residual = 7.2858e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.567273, Final residual = 6.75068e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.579016, Final residual = 8.25097e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.914407, Final residual = 0.00501194, No Iterations 1001 time step continuity errors : sum local = 0.00427993, global = 1.98959e18, cumulative = 7.90941e18 DICPCG: Solving for p, Initial residual = 0.710811, Final residual = 0.00470349, No Iterations 1001 time step continuity errors : sum local = 0.00469284, global = 2.94113e18, cumulative = 1.08505e17 ExecutionTime = 674.02 s ClockTime = 676 s Time = 20 Courant Number mean: 3.38704 max: 482.002 DICPCG: Solving for Ux, Initial residual = 0.575768, Final residual = 7.49024e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.573837, Final residual = 6.84839e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.583038, Final residual = 8.35092e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.915017, Final residual = 0.00402223, No Iterations 1001 time step continuity errors : sum local = 0.00757513, global = 1.80299e17, cumulative = 2.88804e17 DICPCG: Solving for p, Initial residual = 0.711456, Final residual = 0.00311159, No Iterations 1001 time step continuity errors : sum local = 0.00690337, global = 6.73494e19, cumulative = 2.82069e17 ExecutionTime = 713.38 s ClockTime = 715 s Time = 21 Courant Number mean: 7.45941 max: 1058.67 DICPCG: Solving for Ux, Initial residual = 0.564429, Final residual = 7.42311e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.568091, Final residual = 6.94978e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.578544, Final residual = 8.29321e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.913466, Final residual = 0.00547878, No Iterations 1001 time step continuity errors : sum local = 0.0222682, global = 4.48831e17, cumulative = 7.309e17 DICPCG: Solving for p, Initial residual = 0.708487, Final residual = 0.00505239, No Iterations 1001 time step continuity errors : sum local = 0.0239581, global = 1.65593e17, cumulative = 5.65307e17 ExecutionTime = 754.78 s ClockTime = 757 s Time = 22 Courant Number mean: 16.3605 max: 2333.46 DICPCG: Solving for Ux, Initial residual = 0.575591, Final residual = 7.66668e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.576227, Final residual = 6.96544e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.58572, Final residual = 8.32394e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.915282, Final residual = 0.00447722, No Iterations 1001 time step continuity errors : sum local = 0.0406606, global = 1.36231e16, cumulative = 1.92762e16 DICPCG: Solving for p, Initial residual = 0.71164, Final residual = 0.00335635, No Iterations 1001 time step continuity errors : sum local = 0.0360795, global = 2.07856e17, cumulative = 2.13548e16 ExecutionTime = 794.76 s ClockTime = 797 s Time = 23 Courant Number mean: 36.4055 max: 5133.06 DICPCG: Solving for Ux, Initial residual = 0.563589, Final residual = 7.56456e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.569976, Final residual = 7.02741e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.580772, Final residual = 8.27355e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.912983, Final residual = 0.00583355, No Iterations 1001 time step continuity errors : sum local = 0.11506, global = 2.93421e16, cumulative = 7.98734e17 DICPCG: Solving for p, Initial residual = 0.707404, Final residual = 0.00524665, No Iterations 1001 time step continuity errors : sum local = 0.12082, global = 2.5704e17, cumulative = 1.05577e16 ExecutionTime = 834.12 s ClockTime = 836 s Time = 24 Courant Number mean: 79.7652 max: 11332.9 DICPCG: Solving for Ux, Initial residual = 0.574767, Final residual = 7.7861e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.580135, Final residual = 7.03556e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.58724, Final residual = 8.29394e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.915, Final residual = 0.00465197, No Iterations 1001 time step continuity errors : sum local = 0.205391, global = 2.22438e17, cumulative = 1.27821e16 DICPCG: Solving for p, Initial residual = 0.710842, Final residual = 0.00367794, No Iterations 1001 time step continuity errors : sum local = 0.192344, global = 1.45524e16, cumulative = 2.73345e16 ExecutionTime = 872.17 s ClockTime = 874 s Time = 25 Courant Number mean: 177.756 max: 24947.8 DICPCG: Solving for Ux, Initial residual = 0.563286, Final residual = 7.66645e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.571524, Final residual = 7.03783e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.581587, Final residual = 8.22364e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.912806, Final residual = 0.00614089, No Iterations 1001 time step continuity errors : sum local = 0.591813, global = 1.12307e16, cumulative = 3.85652e16 DICPCG: Solving for p, Initial residual = 0.707011, Final residual = 0.00556059, No Iterations 1001 time step continuity errors : sum local = 0.62673, global = 8.22528e17, cumulative = 4.67905e16 ExecutionTime = 912.49 s ClockTime = 915 s Time = 26 Courant Number mean: 390.775 max: 55080.8 DICPCG: Solving for Ux, Initial residual = 0.575144, Final residual = 7.90521e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.581466, Final residual = 7.06778e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.588583, Final residual = 8.27456e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.914581, Final residual = 0.0057074, No Iterations 1001 time step continuity errors : sum local = 1.23604, global = 3.7251e15, cumulative = 4.19301e15 DICPCG: Solving for p, Initial residual = 0.710382, Final residual = 0.00466448, No Iterations 1001 time step continuity errors : sum local = 1.19823, global = 1.17052e16, cumulative = 4.31006e15 ExecutionTime = 951.71 s ClockTime = 954 s Time = 27 Courant Number mean: 870.556 max: 121252 DICPCG: Solving for Ux, Initial residual = 0.565781, Final residual = 7.76904e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.576009, Final residual = 7.07257e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.584752, Final residual = 8.26019e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.912841, Final residual = 0.00737126, No Iterations 1001 time step continuity errors : sum local = 3.50482, global = 9.23762e16, cumulative = 3.3863e15 DICPCG: Solving for p, Initial residual = 0.706756, Final residual = 0.00638689, No Iterations 1001 time step continuity errors : sum local = 3.55537, global = 1.39197e16, cumulative = 3.52549e15 ExecutionTime = 997.25 s ClockTime = 1000 s Time = 28 Courant Number mean: 1917.05 max: 268059 DICPCG: Solving for Ux, Initial residual = 0.578745, Final residual = 8.04913e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.587058, Final residual = 7.13481e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.592451, Final residual = 8.33298e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.914639, Final residual = 0.00718143, No Iterations 1001 time step continuity errors : sum local = 7.70859, global = 8.47836e15, cumulative = 1.20039e14 DICPCG: Solving for p, Initial residual = 0.709951, Final residual = 0.00588492, No Iterations 1001 time step continuity errors : sum local = 7.50459, global = 3.2648e15, cumulative = 8.73906e15 ExecutionTime = 1043.17 s ClockTime = 1046 s Time = 29 Courant Number mean: 4281.41 max: 590512 DICPCG: Solving for Ux, Initial residual = 0.56918, Final residual = 7.89289e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.580022, Final residual = 7.09539e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.587747, Final residual = 8.34433e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.912823, Final residual = 0.00934463, No Iterations 1001 time step continuity errors : sum local = 22.132, global = 6.51948e14, cumulative = 7.39339e14 DICPCG: Solving for p, Initial residual = 0.705882, Final residual = 0.00851879, No Iterations 1001 time step continuity errors : sum local = 23.6354, global = 7.08639e16, cumulative = 7.32252e14 ExecutionTime = 1082.95 s ClockTime = 1086 s Time = 30 Courant Number mean: 9421.37 max: 1.3039e+06 DICPCG: Solving for Ux, Initial residual = 0.580493, Final residual = 8.15774e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.589421, Final residual = 7.1739e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.595603, Final residual = 8.43067e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.915033, Final residual = 0.00989074, No Iterations 1001 time step continuity errors : sum local = 52.94, global = 2.64221e13, cumulative = 3.37447e13 DICPCG: Solving for p, Initial residual = 0.70866, Final residual = 0.00759285, No Iterations 1001 time step continuity errors : sum local = 48.2584, global = 3.66974e14, cumulative = 3.00749e13 ExecutionTime = 1123.09 s ClockTime = 1126 s Time = 31 Courant Number mean: 21008.3 max: 2.86799e+06 DICPCG: Solving for Ux, Initial residual = 0.570359, Final residual = 7.92147e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.582074, Final residual = 7.11416e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.590417, Final residual = 8.38927e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.91296, Final residual = 0.00906945, No Iterations 1001 time step continuity errors : sum local = 106.611, global = 2.10567e13, cumulative = 5.11316e13 DICPCG: Solving for p, Initial residual = 0.705608, Final residual = 0.00868781, No Iterations 1001 time step continuity errors : sum local = 119.384, global = 1.2958e14, cumulative = 4.98358e13 ExecutionTime = 1160.86 s ClockTime = 1164 s Time = 32 Courant Number mean: 46098.2 max: 6.32056e+06 DICPCG: Solving for Ux, Initial residual = 0.581733, Final residual = 8.11783e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.59222, Final residual = 7.14387e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.598781, Final residual = 8.47531e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.915125, Final residual = 0.00708628, No Iterations 1001 time step continuity errors : sum local = 186.854, global = 1.05587e12, cumulative = 5.57514e13 DICPCG: Solving for p, Initial residual = 0.708802, Final residual = 0.00626718, No Iterations 1001 time step continuity errors : sum local = 196.182, global = 9.41478e14, cumulative = 4.63367e13 ExecutionTime = 1202.01 s ClockTime = 1205 s Time = 33 Courant Number mean: 103020 max: 1.39021e+07 DICPCG: Solving for Ux, Initial residual = 0.571668, Final residual = 7.98765e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.583149, Final residual = 7.10919e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.59027, Final residual = 8.39816e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.912472, Final residual = 0.00808608, No Iterations 1001 time step continuity errors : sum local = 464.499, global = 8.3174e13, cumulative = 3.68374e13 DICPCG: Solving for p, Initial residual = 0.704891, Final residual = 0.00771748, No Iterations 1001 time step continuity errors : sum local = 518.214, global = 1.10143e13, cumulative = 2.58231e13 ExecutionTime = 1241.57 s ClockTime = 1245 s Time = 34 Courant Number mean: 225213 max: 3.06589e+07 DICPCG: Solving for Ux, Initial residual = 0.579956, Final residual = 8.16306e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.58882, Final residual = 7.13879e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.593815, Final residual = 8.4357e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.914487, Final residual = 0.00899155, No Iterations 1001 time step continuity errors : sum local = 1149.99, global = 1.13706e12, cumulative = 1.39529e12 DICPCG: Solving for p, Initial residual = 0.707044, Final residual = 0.00698948, No Iterations 1001 time step continuity errors : sum local = 1060.53, global = 2.30004e13, cumulative = 1.16529e12 ExecutionTime = 1279.49 s ClockTime = 1285 s Time = 35 Courant Number mean: 498495 max: 6.73873e+07 DICPCG: Solving for Ux, Initial residual = 0.571961, Final residual = 8.0269e06, No Iterations 26 DICPCG: Solving for Uy, Initial residual = 0.58522, Final residual = 7.16413e06, No Iterations 27 DICPCG: Solving for Uz, Initial residual = 0.591963, Final residual = 8.47402e06, No Iterations 26 DICPCG: Solving for p, Initial residual = 0.912914, Final residual = 0.0104296, No Iterations 1001 time step continuity errors : sum local = 2924.92, global = 2.51385e12, cumulative = 1.34856e12 DICPCG: Solving for p, Initial residual = 0.705036, Final residual = 0.00970701, No Iterations 1001 time step continuity errors : sum local = 3184.13, global = 1.13382e12, cumulative = 2.14735e13 ExecutionTime = 1318.78 s ClockTime = 1325 s Time = 36 /QUOTE] Last edited by gooya_kabir; October 29, 2013 at 10:52. 

October 30, 2013, 07:21 
time step continuity error

#2 
Member
Reza
Join Date: Feb 2012
Posts: 67
Rep Power: 6 
again Hi
as you see the above description, in solving pressure there is a time step continuity error, could be the problem this? should I decrease the time step? I do not think it affect in icoFoam? thanks 

November 2, 2013, 14:58 

#3 
Member
Robert
Join Date: Aug 2012
Location: Berlin
Posts: 74
Rep Power: 6 
You should! The courant number should always stay below 1.


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