Understanding icoFoam.C

Pascal_doran · July 8, 2010, 19:34

Hi all,

After looking at this web page : http://openfoamwiki.net/index.php/IcoFoam
I still had one question :

I assume that:

Code:

        fvVectorMatrix UEqn
        (
            fvm::ddt(U)
          + fvm::div(phi, U)
          - fvm::laplacian(nu, U)
        );

is equivalent to :

Code:

         fvVectorMatrix UEqn = fvm::ddt(U) + fvm::div(phi, U) - fvm::laplacian(nu, U)

Am I right ?

If yes, what does the following code mean? :

Code:

fvScalarMatrix pEqn
                (
                    fvm::laplacian(rUA, p) == fvc::div(phi)
                );

I know it define the pressure equation 'pEqn'. How Is pEqn obtained? Is it possible to write a similar equation as the one obtained for UEqn (UEqn = ...)?

Thank you,

Pascal

bioexplore · July 9, 2010, 04:05

i have also the same question about the pressure equation.
Can anybody explain how this equation is derived?

marupio · July 9, 2010, 12:24

Look at Hrvoje Jasak's PhD thesis. The link is at the top of the wiki page you posted:

http://openfoamwiki.net/index.php/IcoFoam

He uses the same annotation there as OpenFOAM. The pressure equation is derived in section 3.8.1 starting on page 145.

Pascal_doran · July 9, 2010, 12:47

Thank you!

So it iterate over 'p' and when the equality is reached p become pEqn as describe in equation 3.141 in Jasak's thesis.

Am I right?

Pascal

July 8, 2010, 19:34	Understanding icoFoam.C	#1
Pascal_doran Member Pascal Join Date: Jun 2009 Location: Montreal Posts: 65 Rep Power: 17	Hi all, After looking at this web page : http://openfoamwiki.net/index.php/IcoFoam I still had one question : I assume that: Code: fvVectorMatrix UEqn ( fvm::ddt(U) + fvm::div(phi, U) - fvm::laplacian(nu, U) ); is equivalent to : Code: fvVectorMatrix UEqn = fvm::ddt(U) + fvm::div(phi, U) - fvm::laplacian(nu, U) Am I right ? If yes, what does the following code mean? : Code: fvScalarMatrix pEqn ( fvm::laplacian(rUA, p) == fvc::div(phi) ); I know it define the pressure equation 'pEqn'. How Is pEqn obtained? Is it possible to write a similar equation as the one obtained for UEqn (UEqn = ...)? Thank you, Pascal

July 9, 2010, 04:05	how derive the pressure equation	#2
bioexplore Member Jianye Xia Join Date: Mar 2009 Posts: 32 Rep Power: 18	i have also the same question about the pressure equation. Can anybody explain how this equation is derived?

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July 9, 2010, 12:24		#3
marupio Senior Member David Gaden Join Date: Apr 2009 Location: Winnipeg, Canada Posts: 437 Rep Power: 22	Look at Hrvoje Jasak's PhD thesis. The link is at the top of the wiki page you posted: http://openfoamwiki.net/index.php/IcoFoam He uses the same annotation there as OpenFOAM. The pressure equation is derived in section 3.8.1 starting on page 145.

July 9, 2010, 12:47		#4
Pascal_doran Member Pascal Join Date: Jun 2009 Location: Montreal Posts: 65 Rep Power: 17	Thank you! So it iterate over 'p' and when the equality is reached p become pEqn as describe in equation 3.141 in Jasak's thesis. Am I right? Pascal