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-   -   energy equation in rhoCentralFoam (http://www.cfd-online.com/Forums/openfoam/80897-energy-equation-rhocentralfoam.html)

nakul October 10, 2010 15:07

energy equation in rhoCentralFoam
 
Hi,
I have a few questions on the formulation of energy equation in rhoCentralFoam. In the source code, the energy equation looks like this:

00176 solve
00177 (
00178 fvm::ddt(rhoE)
00179 + fvc::div(phiEp)
00180 - fvc::div(sigmaDotU)
00181 );
00182
00183 e = rhoE/rho - 0.5*magSqr(U);
00184 e.correctBoundaryConditions();
00185 thermo.correct();
00186 rhoE.boundaryField() =
00187 rho.boundaryField()*
00188 (
00189 e.boundaryField() + 0.5*magSqr(U.boundaryField())
00190 );
00191
00192 if (!inviscid)
00193 {
00194 volScalarField k("k", thermo.Cp()*mu/Pr);
00195 solve
00196 (
00197 fvm::ddt(rho, e) - fvc::ddt(rho, e)
00198 - fvm::laplacian(thermo.alpha(), e)
00199 + fvc::laplacian(thermo.alpha(), e)
00200 - fvc::laplacian(k, T)
00201 );
00202 thermo.correct();
00203 rhoE = rho*(e + 0.5*magSqr(U));
00204 }

1. Why is the viscous term "sigmaDotU" included in the inviscid equation?
2. I think I understand the heat conduction in line 200. What kind of conduction of internal energy is in lines 198-199 ?
3. What is the use of the repeated use of fvm and fvc discretisation of the same expressions in lines 197-199? Why is it not applied to the heat conduction in line 200?
4. Where is the pressure term Dp/Dt?

I'd be glad if anybody could help me in understanding this issue.


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