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Pressure equation & icoFoam

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Old   June 19, 2013, 15:56
Default Pressure equation & icoFoam
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Sasan Ghomi
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Hi Foamers,

I have a question about pressure equation in icoFoam . we know pressure equation in icoFoam is as below : (according to Prof.jasak's thesis)
\triangledown .(\frac{1}{a_{p}}\triangledown p)=\triangledown .\frac{H(u)}{a_{p}}

In the source code we have :

Code:
 fvm::laplacian(rUA, p) == fvc::div(phi)
I don't understand how div(phi) ensures below term in the pressure equation !
\triangledown .\frac{H(u)}{a_{p}}
what is the relation between this term and divergence of flux (phi) ?

I appreciate any help from you,
Thanks and best regards,
Sasan.
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Old   June 20, 2013, 03:47
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Cyp
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Hi Sasam,

it is just a programing trick that has disappear in the latest OF version.

see meaning of HbyA for additional informations.

Best,
Cyp
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Old   June 20, 2013, 04:00
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Sasan Ghomi
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Hi Cyprien ,

Thanks for your reply But I didn't find my answer in meaning of HbyA .
I think the pressure term should drop for getting this relation.
Can you explain more ? about this trick ?

Thanks and best regards,
Sasan.
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Old   June 20, 2013, 04:06
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Cyp
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what I mean is that

\nabla .\frac{H(u)}{a_{p}}= \nabla . \phi

but in reality, in this equation \phidoes not represent the velocity field. \phi is overwritten just after the calculation of p to obtain the corrected velocity flux field.
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Old   June 20, 2013, 04:21
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Sasan Ghomi
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I got it , thank you very much.
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Old   July 16, 2013, 04:17
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Dongyue Li
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Quote:
Originally Posted by Cyp View Post
what I mean is that

\nabla .\frac{H(u)}{a_{p}}= \nabla . \phi

but in reality, in this equation \phidoes not represent the velocity field. \phi is overwritten just after the calculation of p to obtain the corrected velocity flux field.
Hi Cyp,

\nabla .\frac{H(u)}{a_{p}}= \nabla . \phi
Im confused about this, I think divergence of a scalar equals zero. Can you explain more?
Thanks
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