Unexpected icoFoam behavior
 

Hi All,

I am running a simple transient simulation using icoFoam; a pressure sine wave is prescribed at the inlet and the outlets are maintained at zero pressure. I am using variable time stepping algorithm with icoFoam. When I decrease the max Co limit from 0.5 to 0.2, I expect to see smaller delta T, but instead the delta T increases ultimately. Also, I am printing the average of the velocity components for the entire domain and see a blip once I decrease the Courant number. I have attached the output below.

Thanks in advance!
Senthil

Output:

Courant Number mean: 1.21379e-06 max: 0.5
deltaT = 3.0098e-07
Time = 0.182844

DILUPBiCG: Solving for Ux, Initial residual = 0.00173741, Final residual = 3.0566e-05, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 0.00121752, Final residual = 1.86997e-05, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.000650118, Final residual = 1.10411e-05, No Iterations 2
GAMG: Solving for p, Initial residual = 0.88763, Final residual = 0.0360369, No Iterations 2
time step continuity errors : sum local = 2.56772e-09, global = 2.54499e-13, cumulative = 8.80811e-10
GAMG: Solving for p, Initial residual = 0.882408, Final residual = 0.0358249, No Iterations 2
time step continuity errors : sum local = 2.56772e-09, global = -2.14226e-13, cumulative = 8.80597e-10

Average =(3.27006e-05 -7.01872e-05 -0.000136211)

ExecutionTime = 313863 s ClockTime = 313854 s

Courant Number mean: 1.21379e-06 max: 0.5
deltaT = 3.0098e-07
regIOobject::readIfModified() :
Reading object controlDict from file "/home/skabilan/workdir/openfoam/rat/25vox/trans/25vox_justtets/processor0/../system/controlDict"
Time = 0.182845

DILUPBiCG: Solving for Ux, Initial residual = 0.00173749, Final residual = 3.0566e-05, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 0.00121753, Final residual = 1.86997e-05, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.000650147, Final residual = 1.10411e-05, No Iterations 2
GAMG: Solving for p, Initial residual = 0.887633, Final residual = 0.0360369, No Iterations 2
time step continuity errors : sum local = 2.56772e-09, global = 2.13693e-13, cumulative = 8.80811e-10
GAMG: Solving for p, Initial residual = 0.882408, Final residual = 0.0358247, No Iterations 2
time step continuity errors : sum local = 2.56772e-09, global = -2.5474e-13, cumulative = 8.80556e-10

Average =(3.27006e-05 -7.01873e-05 -0.000136211)

ExecutionTime = 313864 s ClockTime = 313855 s

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Courant Number mean: 1.38864e-06 max: 0.200001
deltaT = 3.76131e-07
Time = 0.182864

DILUPBiCG: Solving for Ux, Initial residual = 0.000680175, Final residual = 1.17225e-05, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 0.000463945, Final residual = 7.47435e-06, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.000249574, Final residual = 4.1326e-06, No Iterations 2
GAMG: Solving for p, Initial residual = 0.797617, Final residual = 0.0307625, No Iterations 2
time step continuity errors : sum local = 1.09018e-09, global = 1.5995e-12, cumulative = 8.43192e-10
GAMG: Solving for p, Initial residual = 0.806811, Final residual = 0.0311036, No Iterations 2
time step continuity errors : sum local = 1.08972e-09, global = 1.33763e-12, cumulative = 8.4453e-10

Average =(2.36528e-05 -3.52415e-05 -0.000112656)

ExecutionTime = 313884 s ClockTime = 313875 s