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pressure unit ? boundary condition

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Old   October 28, 2009, 05:52
Default pressure unit ? boundary condition
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Jiang
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Dear Foamers,

I am confused about pressure unit.
in SI unit ,should use Pascals, that's kg/(m*s2).
and so [1 -1 -2 0 0 0 0].

why openfoam use like this in many tutorials:

dimensions [0 2 -2 0 0 0 0];
internalField uniform 0;

for pressure boundary conditions ,we should use real pressure?
for example: 101325 Pa.

Thank you.
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Old   October 28, 2009, 06:43
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OpenFOAM uses the rho-normalized pressure p*=p/rho
[p*] = {kg/(m.s**2)} /(kg/m**3) = m**2/s**2 = [0 2 -2 0 0 0 0]
in your BC you just have to divide your real pressure with your density
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Old   October 28, 2009, 08:14
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Quote:
Originally Posted by -mAx- View Post
OpenFOAM uses the rho-normalized pressure p*=p/rho
[p*] = {kg/(m.s**2)} /(kg/m**3) = m**2/s**2 = [0 2 -2 0 0 0 0]
in your BC you just have to divide your real pressure with your density
Thank you very much, mAx
I understand.
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Old   December 29, 2013, 19:21
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Quote:
Originally Posted by -mAx- View Post
OpenFOAM uses the rho-normalized pressure p*=p/rho
[p*] = {kg/(m.s**2)} /(kg/m**3) = m**2/s**2 = [0 2 -2 0 0 0 0]
in your BC you just have to divide your real pressure with your density
How about other unit like velocity

Any normalization applied to those units

Thanks
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Old   January 2, 2014, 05:43
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Hi Ke Wu,

Nope. Rest of the variables are generally not normalized by the density. As far as I know only p and p_rgh.

If you want to double check, you can always see dimensions for every variable and check if it is the right unit or not.

Regards,

Antimony
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