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-   -   simpleFoam with energy equation (http://www.cfd-online.com/Forums/openfoam-programming-development/69148-simplefoam-energy-equation.html)

 sega October 13, 2009 12:49

simpleFoam with energy equation

Hello world.

I'm dealing with a case in which Navier-Stokes and energy equation can be solved one after the other.

I have little experience in manipulating solvers, but I think it's possible to alter the simpleFoam solver for such a case.

So where do I put the energy equation?

As I want to compute temperature after successfully converged Navier-Stokes-Equation I have thought about opening another time-loop and solving the energy equation there.

Something like this:
Code:

```  Info<< "\nStarting time loop\n" << endl;     for (runTime++; !runTime.end(); runTime++)     {         Info<< "Time = " << runTime.timeName() << nl << endl; #      include "readSIMPLEControls.H" #      include "initConvergenceCheck.H"         p.storePrevIter();         // Pressure-velocity SIMPLE corrector         { #          include "UEqn.H" #          include "pEqn.H"         }         turbulence->correct();         runTime.write();         Info<< "ExecutionTime = " << runTime.elapsedCpuTime() << " s"             << "  ClockTime = " << runTime.elapsedClockTime() << " s"             << nl << endl; #      include "convergenceCheck.H"     } #include 'TEqn.H'     Info<< "End\n" << endl;     return(0);```
TEqn.H will contain the energy equation. So much for the basics of this problem.

Thanks for your ideas. See you.
Sebastian

 markusrehm October 14, 2009 02:57

Hi Sebastian,

have a look at buoyantSimpleFoam.

Regards, Markus.

 sega October 19, 2009 14:04

Quote:
 Originally Posted by markusrehm (Post 232530) Hi Sebastian, have a look at buoyantSimpleFoam. Regards, Markus.
I did and it looks to me that the enthalpy equation is solved inside the brackets with U and p.

So I will put the energy equation inside it too?

Code:

```    { #          include "UEqn.H" #          include "pEqn.H" #          include "TEqn.H"         }```
Just to make sure...

 sega November 20, 2009 15:21

It took some time before I got back to this construction site:

Do you think buoyantSimpleFoam for itself (without chaning anything) will be the right choice for a simple convective heat transfer problem?

 markusrehm November 23, 2009 03:31

It worked well for me. But you can take out the buoyancy term as well.

Markus

 sdharmar January 25, 2013 16:05

TEqn.H

Hi Markus and Sebastian,

Why can't we put the TEqn.H out side the SIMPLE loop. I think we need to calculate temperature field after we got corrected velocity field. Is my idea right or wrong? And since simpleFoam calculates turbulent flows I put my Teqn.H as,

{

volScalarField kappaEff
(
"kappaEff",
turbulence->nu()/Pr + turbulence->nut()/Prt
);

fvScalarMatrix TEqn
(
//fvm::ddt(T)
fvm::div(phi, T)
- fvm::laplacian(kappaEff, T)
);

TEqn.relax();

TEqn.solve();

//rhok = 1.0 - beta*(T - TRef);
}

Please correct me if I am wrong. My temperature value fluctuates a lot whenever I used it out side the SIMPLE loop. But in pisoFoam I put it in outside the PISO loop and worked really good.

Best regards,
Suranga.

 Hisham January 26, 2013 07:42

Hi Suranga

I think the (rather old) discussion here was about the time loop not the Simple/pimple loop. Naturally one needs to keep the algorithm for the Navier-Stokes equations intact. You can add whatever equation outside the algorithm to let it resole the pressure-velocity coupling in peace. Of course all equations should be inside the time loop unless you need to solve an equation once.

Hisham

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