# What is the "dpdt" term?--chtMultiRegionFoam

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 June 26, 2013, 05:46 What is the "dpdt" term?--chtMultiRegionFoam #1 New Member   Qing, Cao Join Date: Nov 2012 Posts: 6 Rep Power: 5 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

 June 26, 2013, 09:21 #2 Senior Member   Fumiya Nozaki Join Date: Jun 2010 Location: Yokohama, Japan Posts: 194 Rep Power: 9 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

June 26, 2013, 09:38
#3
New Member

Qing, Cao
Join Date: Nov 2012
Posts: 6
Rep Power: 5
Quote:
 Originally Posted by fumiya 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

 June 26, 2013, 10:39 #4 Senior Member   Fumiya Nozaki Join Date: Jun 2010 Location: Yokohama, Japan Posts: 194 Rep Power: 9 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::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 elham usefi likes this.

June 26, 2013, 11:08
#5
New Member

Qing, Cao
Join Date: Nov 2012
Posts: 6
Rep Power: 5
Quote:
 Originally Posted by fumiya 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::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!

have a nice day!

Regards,
Qing

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