Micro Scale Pore, icoFoam
 

Hi FOAMers,

I'm working with icoFoam, incompressible fluid (water) in a very tiny pores (diameter is about 2-10 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 = 6.91785e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.574148, Final residual = 9.70984e-06, No Iterations 26
DICPCG: Solving for Uz, Initial residual = 0.579967, Final residual = 8.64667e-06, 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 = -1.18248e-18, cumulative = -9.13022e-19
DICPCG: Solving for p, Initial residual = 0.713102, Final residual = 0.00340517, No Iterations 1001
time step continuity errors : sum local = 0.000346162, global = 5.90852e-20, cumulative = -8.53937e-19
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 = 7.07612e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.567511, Final residual = 9.88047e-06, No Iterations 26
DICPCG: Solving for Uz, Initial residual = 0.576988, Final residual = 8.42121e-06, 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 = -1.87682e-18, cumulative = -2.73076e-18
DICPCG: Solving for p, Initial residual = 0.711657, Final residual = 0.00392582, No Iterations 1001
time step continuity errors : sum local = 0.000839034, global = 2.6569e-19, cumulative = -2.46507e-18
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 = 7.24442e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.571475, Final residual = 6.69346e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.580093, Final residual = 8.40165e-06, 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 = -7.13966e-18, cumulative = -9.60473e-18
DICPCG: Solving for p, Initial residual = 0.712068, Final residual = 0.00362861, No Iterations 1001
time step continuity errors : sum local = 0.00168029, global = -2.94268e-19, cumulative = -9.89899e-18
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 = 7.2858e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.567273, Final residual = 6.75068e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.579016, Final residual = 8.25097e-06, 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 = 1.98959e-18, cumulative = -7.90941e-18
DICPCG: Solving for p, Initial residual = 0.710811, Final residual = 0.00470349, No Iterations 1001
time step continuity errors : sum local = 0.00469284, global = -2.94113e-18, cumulative = -1.08505e-17
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 = 7.49024e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.573837, Final residual = 6.84839e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.583038, Final residual = 8.35092e-06, 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 = -1.80299e-17, cumulative = -2.88804e-17
DICPCG: Solving for p, Initial residual = 0.711456, Final residual = 0.00311159, No Iterations 1001
time step continuity errors : sum local = 0.00690337, global = 6.73494e-19, cumulative = -2.82069e-17
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 = 7.42311e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.568091, Final residual = 6.94978e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.578544, Final residual = 8.29321e-06, 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 = -4.48831e-17, cumulative = -7.309e-17
DICPCG: Solving for p, Initial residual = 0.708487, Final residual = 0.00505239, No Iterations 1001
time step continuity errors : sum local = 0.0239581, global = 1.65593e-17, cumulative = -5.65307e-17
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 = 7.66668e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.576227, Final residual = 6.96544e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.58572, Final residual = 8.32394e-06, 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 = -1.36231e-16, cumulative = -1.92762e-16
DICPCG: Solving for p, Initial residual = 0.71164, Final residual = 0.00335635, No Iterations 1001
time step continuity errors : sum local = 0.0360795, global = -2.07856e-17, cumulative = -2.13548e-16
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 = 7.56456e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.569976, Final residual = 7.02741e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.580772, Final residual = 8.27355e-06, 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 = 2.93421e-16, cumulative = 7.98734e-17
DICPCG: Solving for p, Initial residual = 0.707404, Final residual = 0.00524665, No Iterations 1001
time step continuity errors : sum local = 0.12082, global = 2.5704e-17, cumulative = 1.05577e-16
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 = 7.7861e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.580135, Final residual = 7.03556e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.58724, Final residual = 8.29394e-06, 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 = 2.22438e-17, cumulative = 1.27821e-16
DICPCG: Solving for p, Initial residual = 0.710842, Final residual = 0.00367794, No Iterations 1001
time step continuity errors : sum local = 0.192344, global = 1.45524e-16, cumulative = 2.73345e-16
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 = 7.66645e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.571524, Final residual = 7.03783e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.581587, Final residual = 8.22364e-06, 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 = 1.12307e-16, cumulative = 3.85652e-16
DICPCG: Solving for p, Initial residual = 0.707011, Final residual = 0.00556059, No Iterations 1001
time step continuity errors : sum local = 0.62673, global = 8.22528e-17, cumulative = 4.67905e-16
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 = 7.90521e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.581466, Final residual = 7.06778e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.588583, Final residual = 8.27456e-06, 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 = 3.7251e-15, cumulative = 4.19301e-15
DICPCG: Solving for p, Initial residual = 0.710382, Final residual = 0.00466448, No Iterations 1001
time step continuity errors : sum local = 1.19823, global = 1.17052e-16, cumulative = 4.31006e-15
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 = 7.76904e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.576009, Final residual = 7.07257e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.584752, Final residual = 8.26019e-06, 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 = -9.23762e-16, cumulative = 3.3863e-15
DICPCG: Solving for p, Initial residual = 0.706756, Final residual = 0.00638689, No Iterations 1001
time step continuity errors : sum local = 3.55537, global = 1.39197e-16, cumulative = 3.52549e-15
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 = 8.04913e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.587058, Final residual = 7.13481e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.592451, Final residual = 8.33298e-06, 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 = 8.47836e-15, cumulative = 1.20039e-14
DICPCG: Solving for p, Initial residual = 0.709951, Final residual = 0.00588492, No Iterations 1001
time step continuity errors : sum local = 7.50459, global = -3.2648e-15, cumulative = 8.73906e-15
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 = 7.89289e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.580022, Final residual = 7.09539e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.587747, Final residual = 8.34433e-06, 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 = 6.51948e-14, cumulative = 7.39339e-14
DICPCG: Solving for p, Initial residual = 0.705882, Final residual = 0.00851879, No Iterations 1001
time step continuity errors : sum local = 23.6354, global = -7.08639e-16, cumulative = 7.32252e-14
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 = 8.15774e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.589421, Final residual = 7.1739e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.595603, Final residual = 8.43067e-06, 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 = 2.64221e-13, cumulative = 3.37447e-13
DICPCG: Solving for p, Initial residual = 0.70866, Final residual = 0.00759285, No Iterations 1001
time step continuity errors : sum local = 48.2584, global = -3.66974e-14, cumulative = 3.00749e-13
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 = 7.92147e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.582074, Final residual = 7.11416e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.590417, Final residual = 8.38927e-06, 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 = 2.10567e-13, cumulative = 5.11316e-13
DICPCG: Solving for p, Initial residual = 0.705608, Final residual = 0.00868781, No Iterations 1001
time step continuity errors : sum local = 119.384, global = -1.2958e-14, cumulative = 4.98358e-13
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 = 8.11783e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.59222, Final residual = 7.14387e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.598781, Final residual = 8.47531e-06, 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 = -1.05587e-12, cumulative = -5.57514e-13
DICPCG: Solving for p, Initial residual = 0.708802, Final residual = 0.00626718, No Iterations 1001
time step continuity errors : sum local = 196.182, global = 9.41478e-14, cumulative = -4.63367e-13
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 = 7.98765e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.583149, Final residual = 7.10919e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.59027, Final residual = 8.39816e-06, 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 = 8.3174e-13, cumulative = 3.68374e-13
DICPCG: Solving for p, Initial residual = 0.704891, Final residual = 0.00771748, No Iterations 1001
time step continuity errors : sum local = 518.214, global = -1.10143e-13, cumulative = 2.58231e-13
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 = 8.16306e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.58882, Final residual = 7.13879e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.593815, Final residual = 8.4357e-06, 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 = 1.13706e-12, cumulative = 1.39529e-12
DICPCG: Solving for p, Initial residual = 0.707044, Final residual = 0.00698948, No Iterations 1001
time step continuity errors : sum local = 1060.53, global = -2.30004e-13, cumulative = 1.16529e-12
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 = 8.0269e-06, No Iterations 26
DICPCG: Solving for Uy, Initial residual = 0.58522, Final residual = 7.16413e-06, No Iterations 27
DICPCG: Solving for Uz, Initial residual = 0.591963, Final residual = 8.47402e-06, 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 = -2.51385e-12, cumulative = -1.34856e-12
DICPCG: Solving for p, Initial residual = 0.705036, Final residual = 0.00970701, No Iterations 1001
time step continuity errors : sum local = 3184.13, global = 1.13382e-12, cumulative = -2.14735e-13
ExecutionTime = 1318.78 s ClockTime = 1325 s

Time = 36

/QUOTE]

time step continuity error
 

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

You should! The courant number should always stay below 1.