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How to remove this openFoam error

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Old   December 12, 2017, 02:13
Default How to remove this openFoam error
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Taoyuan
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I have run the case using openFoam, but showing scalar error
Capture.PNG
please see this attachment
Please give me your suggestions to rectify this error
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Old   December 12, 2017, 05:52
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Alexey Matveichev
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Hi,

Look at Courant number, your simulation is diverging (and with the information, you have posted it is almost impossible to tell the reason).
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Old   December 14, 2017, 14:13
Default Quick advice
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Dominik Pltl
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Quote:
Originally Posted by alexeym View Post
Hi,

Look at Courant number, your simulation is diverging (and with the information, you have posted it is almost impossible to tell the reason).
Alexey's right.

Without deeper knowledge, here's some quick advice (1 or 2 or 3):
  1. Insert
    Code:
    runTimeModifiable yes;
    adjustTimeStep  yes;
    
    maxCo           0.2;
    in your controlDict
    (or choose something different <1)
  2. Decrease your deltaT by multiple orders of magnitude
  3. (if a similar case exists) map the internal field onto your case before starting your computation (check the tutorial "incompressible/icoFoam/cavity" for more infos)
Cheers,
Yeru
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Old   December 14, 2017, 18:23
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The useful OpenFoam advice has already been given in the previous two posts. I just wanted to add some more info and an explanation about the error itself.

What seems to be happening, as also stated previously, is that the simulated values explode, due to what seems to be a large time step of 0.005s. This causes the Courant number to be way too large.

The two first points of advice Yeru gives basically do the following:
  1. The code keeps the Courant number below the given value by adjusting the time step automatically. If a time step is too large and Courant number increases, it will automatically be lowered.
  2. Point two basically decreases the Courant number statically by choosing a small time step yourself, which will then be used throughout the whole simulation
Commonly values exploding in a simulation end up throwing a floating point exception, because of illegal mathematical operations like division by zero. The reason you end up with an IO (input/output) error is that in your last time step the calculated pressure ends up being nan (also known as NaN). NaN stands for "Not a Number". Here is the wikipedia page explaining further. The nan word is not interpreted as a scalar by the input stream, and thus the error results.

Last edited by pi__sec; December 14, 2017 at 18:25. Reason: Use of correct word
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Old   December 14, 2017, 23:24
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Thank you so much
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