# Unexpect icoFoam behavior

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 September 28, 2010, 14:02 Unexpected icoFoam behavior #1 Senior Member   Senthil Kabilan Join Date: Mar 2009 Posts: 113 Rep Power: 10 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 . . . 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 Last edited by skabilan; September 30, 2010 at 19:14.

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