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-   -   icoFoam diverges when simpleFoam converges (https://www.cfd-online.com/Forums/openfoam-solving/159190-icofoam-diverges-when-simplefoam-converges.html)

leizhao512 September 10, 2015 13:07

icoFoam diverges when simpleFoam converges
 
3 Attachment(s)
Hi, I am trying to simulate a laminar flow through a tube. Because it has complex geometry , I meshed it through ICEM and here iis the picture. https://drive.google.com/file/d/0BzN...ew?usp=sharing
The minimum mesh quality is 0.3 in ICEM and I also used checkMesh in openFoam, which said everything is OK.
Initially I used Fluent to simulate the flow on both steady state and transient state and I proved that the flow is steady. (the time step I used in Fluent is 10s)Then I used icoFoam to simulate this case, however, it got divergent quickly in the first 100 time steps. Then I tried simpleFoam to simulate it as steady state and it converged. What I did next is that I used the steady state solution ofsimpleFoam as the initial condition of icoFoam, and keep the same schemes and linear solvers. However, icoFoam got divergent real fast, even if I shrink the time step to 0.1s.

Can anybody help me with this? Thank you.

Quote:

Time = 3003

Courant Number mean: 1.44865 max: 40989.8
smoothSolver: Solving for Ux, Initial residual = 0.927528, Final residual = 8.93978e-06, No Iterations 156
smoothSolver: Solving for Uy, Initial residual = 0.933172, Final residual = 9.00634e-06, No Iterations 154
smoothSolver: Solving for Uz, Initial residual = 0.934392, Final residual = 9.09487e-06, No Iterations 164
GAMG: Solving for p, Initial residual = 0.269707, Final residual = 1.87423e-06, No Iterations 16
time step continuity errors : sum local = 5.44156e-06, global = 1.2902e-07, cumulative = 1.6054e-07
GAMG: Solving for p, Initial residual = 0.01606, Final residual = 1.1425e-07, No Iterations 15
time step continuity errors : sum local = 1.22906e-05, global = 1.24249e-07, cumulative = 2.84789e-07
ExecutionTime = 348.32 s ClockTime = 349 s

Time = 3003.1

Courant Number mean: 2.80059 max: 32857.3
smoothSolver: Solving for Ux, Initial residual = 0.938765, Final residual = 9.33157e-06, No Iterations 171
smoothSolver: Solving for Uy, Initial residual = 0.934481, Final residual = 9.3031e-06, No Iterations 270
smoothSolver: Solving for Uz, Initial residual = 0.935665, Final residual = 9.24883e-06, No Iterations 281
GAMG: Solving for p, Initial residual = 0.28984, Final residual = 2.32895e-06, No Iterations 15
time step continuity errors : sum local = 1.85582e-05, global = 4.94828e-08, cumulative = 3.34272e-07
GAMG: Solving for p, Initial residual = 0.0101664, Final residual = 8.05664e-08, No Iterations 14
time step continuity errors : sum local = 4.56476e-05, global = 1.87007e-07, cumulative = 5.21278e-07
ExecutionTime = 394.82 s ClockTime = 396 s

Time = 3003.2

Courant Number mean: 9.53619 max: 62332.5
smoothSolver: Solving for Ux, Initial residual = 0.884443, Final residual = 8.72835e-06, No Iterations 553
smoothSolver: Solving for Uy, Initial residual = 0.890166, Final residual = 8.89899e-06, No Iterations 528
smoothSolver: Solving for Uz, Initial residual = 0.889302, Final residual = 8.77769e-06, No Iterations 537
GAMG: Solving for p, Initial residual = 0.168963, Final residual = 1.59669e-06, No Iterations 15
time step continuity errors : sum local = 6.90831e-05, global = 7.5791e-07, cumulative = 1.27919e-06
GAMG: Solving for p, Initial residual = 0.00349722, Final residual = 2.23965e-08, No Iterations 14
time step continuity errors : sum local = 0.000157283, global = -1.18665e-06, cumulative = 9.25401e-08
ExecutionTime = 491.15 s ClockTime = 492 s

Time = 3003.3

Courant Number mean: 32.9325 max: 112992
smoothSolver: Solving for Ux, Initial residual = 0.881954, Final residual = 0.000100022, No Iterations 1000
smoothSolver: Solving for Uy, Initial residual = 0.887072, Final residual = 6.31404e-05, No Iterations 1000
smoothSolver: Solving for Uz, Initial residual = 0.880495, Final residual = 5.62691e-05, No Iterations 1000
GAMG: Solving for p, Initial residual = 0.142865, Final residual = 1.09615e-06, No Iterations 16
time step continuity errors : sum local = 0.000410075, global = -1.36218e-05, cumulative = -1.35293e-05
GAMG: Solving for p, Initial residual = 0.0017875, Final residual = 1.2698e-08, No Iterations 14
time step continuity errors : sum local = 0.00169306, global = 3.15075e-05, cumulative = 1.79783e-05
ExecutionTime = 664.65 s ClockTime = 666 s

kmooney September 11, 2015 11:00

What does the log look like for the 1st time step when you switch over to icoFoam?

leizhao512 September 11, 2015 16:02

Hi, the first several time steps look good.
Quote:

Starting time loop

Time = 3000.1

Courant Number mean: 0.00738877 max: 0.0862275
smoothSolver: Solving for Ux, Initial residual = 0.00324103, Final residual = 2.63846e-08, No Iterations 9
smoothSolver: Solving for Uy, Initial residual = 0.00789705, Final residual = 4.03015e-08, No Iterations 9
smoothSolver: Solving for Uz, Initial residual = 0.00320836, Final residual = 2.14152e-08, No Iterations 9
GAMG: Solving for p, Initial residual = 0.070141, Final residual = 5.60209e-07, No Iterations 10
time step continuity errors : sum local = 2.15494e-10, global = -1.53143e-11, cumulative = -1.53143e-11
GAMG: Solving for p, Initial residual = 0.0153475, Final residual = 9.4429e-08, No Iterations 11
time step continuity errors : sum local = 3.71145e-11, global = -5.76447e-13, cumulative = -1.58908e-11
ExecutionTime = 11.71 s ClockTime = 12 s

Time = 3000.2

Courant Number mean: 0.00738913 max: 0.0864764
smoothSolver: Solving for Ux, Initial residual = 0.00170492, Final residual = 9.83593e-09, No Iterations 10
smoothSolver: Solving for Uy, Initial residual = 0.00378203, Final residual = 2.15611e-08, No Iterations 9
smoothSolver: Solving for Uz, Initial residual = 0.00168689, Final residual = 9.26553e-09, No Iterations 10
GAMG: Solving for p, Initial residual = 0.0099275, Final residual = 8.10822e-08, No Iterations 11
time step continuity errors : sum local = 3.10713e-11, global = 3.67855e-13, cumulative = -1.55229e-11
GAMG: Solving for p, Initial residual = 0.00412922, Final residual = 2.07003e-08, No Iterations 12
time step continuity errors : sum local = 7.8214e-12, global = -7.48175e-14, cumulative = -1.55977e-11
ExecutionTime = 17.79 s ClockTime = 18 s

Time = 3000.3

Courant Number mean: 0.00738964 max: 0.0864449
smoothSolver: Solving for Ux, Initial residual = 0.00107745, Final residual = 1.03887e-08, No Iterations 9
smoothSolver: Solving for Uy, Initial residual = 0.00234194, Final residual = 2.07876e-08, No Iterations 8
smoothSolver: Solving for Uz, Initial residual = 0.00106498, Final residual = 8.43493e-09, No Iterations 9
GAMG: Solving for p, Initial residual = 0.00393705, Final residual = 1.47149e-08, No Iterations 12
time step continuity errors : sum local = 5.57695e-12, global = 2.41142e-13, cumulative = -1.53566e-11
GAMG: Solving for p, Initial residual = 0.00189037, Final residual = 1.2206e-08, No Iterations 12
time step continuity errors : sum local = 4.58154e-12, global = -3.13938e-14, cumulative = -1.5388e-11
ExecutionTime = 23.91 s ClockTime = 24 s

Time = 3000.4

Courant Number mean: 0.00739024 max: 0.0863294
smoothSolver: Solving for Ux, Initial residual = 0.000761046, Final residual = 5.61323e-09, No Iterations 10
smoothSolver: Solving for Uy, Initial residual = 0.00163139, Final residual = 8.66173e-09, No Iterations 9
smoothSolver: Solving for Uz, Initial residual = 0.000752019, Final residual = 4.95143e-09, No Iterations 10
GAMG: Solving for p, Initial residual = 0.00234193, Final residual = 1.17277e-08, No Iterations 12
time step continuity errors : sum local = 4.42116e-12, global = 6.41842e-14, cumulative = -1.53238e-11
GAMG: Solving for p, Initial residual = 0.00122008, Final residual = 1.10738e-08, No Iterations 12
time step continuity errors : sum local = 4.14382e-12, global = -3.28673e-14, cumulative = -1.53567e-11
ExecutionTime = 30.18 s ClockTime = 31 s


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