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-   -   UEqn.relax() (http://www.cfd-online.com/Forums/openfoam/95141-ueqn-relax.html)

mugi December 7, 2011 10:35

UEqn.relax()
 
In the PIMPLE algorithm the momentum equation is defined and afterwards used by UEqun.relax(). As far as I could figure out this means that an underrelaxation is applied, but what does this relax do exactly or where is it defined in the code?

Thanks for any help!
Maike.

giack June 20, 2013 06:11

Hi,
Do you find the answer at your question? I have the same question. Moreover in my fvSolution file I don't specify any under relaxation factor..
Thanks

santiagomarquezd July 3, 2013 00:14

http://foam.sourceforge.net/docs/cpp/a04763_source.html, line 524

immortality July 3, 2013 02:41

it isn't clear how the relaxation is applied even in the code.
Where alpha is defined?
Can we set it and whats alpha at all?
How relaxation is applied?

Bernhard July 3, 2013 02:51

See line 658 of the same file, the relax() member function without argument is defined. Then, the parameter are read from a file, as here http://foam.sourceforge.net/docs/cpp...ce.html#l00313

Note that on the docs, you can search for member functions that you want to find (I used it on "equationRelaxationFactor")

giack July 3, 2013 06:17

So if I don't specify any relaxation factor in fvSolution file the relaxation is not applied to equation,it's right?

immortality July 3, 2013 09:39

its not obvious enough to find out how automatically this relaxation is implemented yet,how can avoid relaxation?

cfdonline2mohsen July 3, 2013 14:06

Thanks Santiago & Bernhard
If you don't specify any under relaxation factor then the default is zero
Code:

00099        eqnRelaxDefault_ =
00100        eqnRelaxDict_.lookupOrDefault<scalar>("default", 0.0);



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