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Old   November 25, 2012, 05:28
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Dongyue Li
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Hi Foamers:



I see the internalField of p and p_rhg is uniform 0 in many cases, and I change "0" to any value such as "5000","10000", the result is the same. you can try it in damBreak case.the different value of internalfield p has totally no compact to the result. I dont know why. I would be appreciated if you can give me some hints.
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Old   November 25, 2012, 11:57
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Florian
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This is true for incompressible solvers. Changing the pressure has no effect on the result but a pressure higher by the some amount everywhere.

From http://www.cfd-online.com/Wiki/Incompressible_flow
Quote:
A consequence of incompressible flow is that there is no equation of state for pressure, unlike in compressible flow. Since there is no separate equation for pressure, it must be obtained from the continuity and momentum equations. The main role of pressure is to satisfy the zero divergence condition of the velocity field. Note that pressure is only determined up to a constant.
Additionally OpenFOAM does not use physical pressure in this case but p_OF = p/rho (afaik for reasons of machine precision).

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Florian
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Old   November 25, 2012, 20:06
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Quote:
Originally Posted by Horus View Post
This is true for incompressible solvers. Changing the pressure has no effect on the result but a pressure higher by the some amount everywhere.

The main role of pressure is to satisfy the zero divergence condition of the velocity field. Note that pressure is only determined up to a constant.
Thanks Florian, but regarding to damBreak case, I set the internalField of p_rgh is "5000" instead of "0", the result dont show a raise of p as a whole. neither of p_rgh.

In that wikki, it surely makes sense, but I think , does this problem be ralated to the PISO or SIMPLE algorithm?
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Old   November 26, 2012, 03:16
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Originally Posted by namld094nh View Post
c?m on vi th├┤ng tin b? ├*ch........................
um.....thats Mars language? jk...
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