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What is the "dpdt" term?--chtMultiRegionFoam

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Old   June 26, 2013, 05:46
Default What is the "dpdt" term?--chtMultiRegionFoam
  #1
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Qing, Cao
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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?
2, what does that "rad.Sh(thermo)" means?

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

Regards,
Qing
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Old   June 26, 2013, 09:21
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Fumiya Nozaki
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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
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Old   June 26, 2013, 09:38
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Quote:
Originally Posted by fumiya View Post
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..

Best regards,
Qing
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Old   June 26, 2013, 10:39
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Fumiya Nozaki
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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
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Old   June 26, 2013, 11:08
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  #5
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Qing, Cao
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Quote:
Originally Posted by fumiya View Post
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,
have a nice day!

Regards,
Qing
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