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-   -   Pressure equation & icoFoam (https://www.cfd-online.com/Forums/openfoam-programming-development/119560-pressure-equation-icofoam.html)

sasanghomi June 19, 2013 15:56
Pressure equation & icoFoam
 
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.

Cyp June 20, 2013 03:47
Hi Sasam,

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

see http://www.cfd-online.com/Forums/ope...ning-hbya.html for additional informations.

Best,
Cyp

sasanghomi June 20, 2013 04:00
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.

Cyp June 20, 2013 04:06
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.

sasanghomi June 20, 2013 04:21
I got it , thank you very much.

sharonyue July 16, 2013 04:17
Quote:
Originally Posted by Cyp (Post 434980)
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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