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-   -   why fixedValue pressure makes neighbor cells incorrect values (http://www.cfd-online.com/Forums/openfoam-solving/120080-why-fixedvalue-pressure-makes-neighbor-cells-incorrect-values.html)

immortality June 30, 2013 04:04

why fixedValue pressure makes neighbor cells incorrect values
 
it seems fixedValue isn't stable.when i set a fixed pressure on outlet the neighbor cells become very higher in pressur.it seems this BC isn't so stable.have had other users same experiences?how to overcome the issue?

ngj June 30, 2013 04:40

Good morning Ehsan,

Please, again, do read this thread:

http://www.cfd-online.com/Forums/ope...-get-help.html

The way you approach asking questions is not at all up to standard, and the only way of answering your question would be to guess.

Kind regards

Niels

immortality June 30, 2013 04:57

2 Attachment(s)
Hi dear Niels
I wrote that text by cellphone and wanted to add an image to it.thanks that you remembered me!
could you view these images?
the pressures of neighbors have been increased a lot.its a simple case like a forward step.
its a simple box that 1/4 height of its right wall is open(outlet).it has filled by a pressure of 1800000pa and BC is 800000pa.
in the case the whole of right wall is opened didn't such problem occur.
thanks so much.

immortality June 30, 2013 05:20

1 Attachment(s)
I set BC to 1550000 pa and it repeats.I don't know its a physical issue or numerical because of fixedValue BC is somewhat unstable.
I have attached more pressure on outlet BC.

immortality June 30, 2013 05:41

1 Attachment(s)
I set fixedMean and its the result again.
a jump in pressure in neighbor cells occurs.does it tell that pressure on boundary is low still?
is it true?
Code:

opening
    {
       
        type fixedMean;
        meanValue 1550000;
        value uniform 1550000;
    }

has had anyone such experiences?

immortality June 30, 2013 05:55

1 Attachment(s)
and for compare and to be complete its a case that all the right wall is open.
as you view no jump in neighbouring of patch cells is observing.
any idea?

immortality July 1, 2013 11:41

2 Attachment(s)
I add cases.


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