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Old   May 12, 2011, 03:16
Default question to courant criterion
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Hi,

does someone know how the courant criterion is used in OpenFoam?
I'm using the chtMultiRegionFoam (transient-version).
Does the solver fit the time step according to the criterion? Thus, the time step isn't constant during the simulation?

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Old   May 12, 2011, 08:08
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I have just recognized that it is possible to set the time step also to delta t = 0.1

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Old   May 16, 2011, 03:22
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Hi,

can I use relaxationFactors for a transient solver like chtMultiRegionFoam?
I have read here that this doesn't work. But I don't understand why?
There is also mentioned that a simpletransient-Solver can work with relaxationFactors. But what is the transientsimple-Solver? Is this solver still calculating a transient case?

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Dirk
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Old   May 16, 2011, 04:27
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Relaxation only applies to the SIMPLE algorithm, whereas most transient solvers in openFoam use PISO. A combination of both algorithms is called PIMPLE in openFoam.
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Old   May 16, 2011, 04:58
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Quote:
Originally Posted by akidess View Post
Relaxation only applies to the SIMPLE algorithm, whereas most transient solvers in openFoam use PISO. A combination of both algorithms is called PIMPLE in openFoam.
Hi,
thanks for your answer.
So can I set up the relaxationFactors in PIMPLE manually? Because you said PIMPLE is a combination of both algorithms.

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Old   May 16, 2011, 05:27
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Yes, you should be able to specify the relaxation parameters in all SIMPLE and PIMPLE based solvers.
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Old   May 16, 2011, 05:32
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Quote:
Originally Posted by akidess View Post
Yes, you should be able to specify the relaxation parameters in all SIMPLE and PIMPLE based solvers.
Hi,

do you know if this is simply done by typing the following into the fvSolution-file?
Code:
relaxationFactors
{
   U   0.7;
   p   0.8;
...
}
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