CFD Online Discussion Forums - simpleFoam with energy equation

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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

Hi Sebastian,

have a look at buoyantSimpleFoam.

Regards, Markus.

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...

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?

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

Markus

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.

Please advice me.

Best regards,
Suranga.

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