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-   -   What is the "dpdt" term?--chtMultiRegionFoam (http://www.cfd-online.com/Forums/openfoam/119851-what-dpdt-term-chtmultiregionfoam.html)

Q.Cao June 26, 2013 05:46

What is the "dpdt" term?--chtMultiRegionFoam
 
Hi Foamers!

in the energy equation of the solver chtMultiRegionFoam, there is some code like following:

fvScalarMatrix hEqn
(
fvm::ddt(rho, h)
+ fvm::div(phi, h)
- fvm::laplacian(turb.alphaEff(), h)
==
dpdt
- (fvc::ddt(rho, K) + fvc::div(phi, K))
+ rad.Sh(thermo)
);

my questions are:
1, what does that "dpdt" means? :confused:
2, what does that "rad.Sh(thermo)" means?

thank you guys, i am a really newbie in OpenFOAM..

Regards,
Qing

fumiya June 26, 2013 09:21

Hi,

1. You might want to look at the bottom of this page:
http://www.openfoam.org/version2.2.0/thermophysical.php

2. This is the source term from the radiation.

Hope that helps,
Fumiya

Q.Cao June 26, 2013 09:38

Quote:

Originally Posted by fumiya (Post 436096)
Hi,

1. You might want to look at the bottom of this page:
http://www.openfoam.org/version2.2.0/thermophysical.php

2. This is the source term from the radiation.

Hope that helps,
Fumiya

Thanks Fumiya,

for point 1, i read that part but i still dont unterstand the mathematical formula of the dpdt.. Is dpdt the "pressure-work term" and what it looks like? Or the dpdt is just a selector?

for point 2, what is the mathematical formula of that source term? Does the "Sh" mean Sherwood number?

So anyway, if someone can show me the complett mathematical equation of that energy equation code, that will be very nice..:p

Best regards,
Qing

fumiya June 26, 2013 10:39

Hi,

1. In the pEqn.H(https://github.com/OpenFOAM/OpenFOAM...m/fluid/pEqn.H)
Code:

// Update pressure time derivative if needed
if (thermo.dpdt())
{
    dpdt = fvc::ddt(p);
}

2. In the radiationModel.C(https://github.com/OpenFOAM/OpenFOAM...diationModel.C)
Code:

Foam::tmp<Foam::fvScalarMatrix> Foam::radiation::radiationModel::Sh
(
    fluidThermo& thermo
) const
{
    volScalarField& he = thermo.he();
    const volScalarField Cpv(thermo.Cpv());
    const volScalarField T3(pow3(T_));

    return
    (
        Ru()
      - fvm::Sp(4.0*Rp()*T3/Cpv, he)
      - Rp()*T3*(T_ - 4.0*he/Cpv)
    );
}

I think this document(http://www.tfd.chalmers.se/~hani/kur...Foam_final.pdf) is a good reference.

Hope that helps,
Fumiya

Q.Cao June 26, 2013 11:08

Quote:

Originally Posted by fumiya (Post 436124)
Hi,

1. In the pEqn.H(https://github.com/OpenFOAM/OpenFOAM...m/fluid/pEqn.H)
Code:

// Update pressure time derivative if needed
if (thermo.dpdt())
{
    dpdt = fvc::ddt(p);
}

2. In the radiationModel.C(https://github.com/OpenFOAM/OpenFOAM...diationModel.C)
Code:

Foam::tmp<Foam::fvScalarMatrix> Foam::radiation::radiationModel::Sh
(
    fluidThermo& thermo
) const
{
    volScalarField& he = thermo.he();
    const volScalarField Cpv(thermo.Cpv());
    const volScalarField T3(pow3(T_));

    return
    (
        Ru()
      - fvm::Sp(4.0*Rp()*T3/Cpv, he)
      - Rp()*T3*(T_ - 4.0*he/Cpv)
    );
}

I think this document(http://www.tfd.chalmers.se/~hani/kur...Foam_final.pdf) is a good reference.

Hope that helps,
Fumiya

Thank you Fumiya!

that s a wonderful answer, :D
have a nice day!

Regards,
Qing


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