[Pat84]

Hello,

I have add the enthalpy equation in temperature form to simpleFoam. The Equation has now this form:

fvScalarMatrix TEqn
        (
          fvm::div(phi, T)
        - fvm::Sp(fvc::div(phi),T)
        - fvm::laplacian(turbulence->nut()/0.85, T)
        - fvm::laplacian(DT,T)
    ==
          1/cp*fvc::div(phi*fvc::interpolate(p))
        - 1/cp*p*fvc::div(phi)
        );
    
        TEqn.relax();
        TEqn.solve();

The terms fvm::Sp(fvc::div(phi),T) and 1/cp*p*fvc::div(phi) are there to take account of partial convergence in simpleFoam. The Value 0.85 represents the turbulent prandtl number and DT is equal to k/cp/rho since the whole equation is divided by rho*cp.

The equation is added to simpleFoam.c in after the pressure correction:

    while (runTime.loop())
    {
        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();

#       include "TEqn.H"

        runTime.write();

        Info<< "ExecutionTime = " << runTime.elapsedCpuTime() << " s"
            << "  ClockTime = " << runTime.elapsedClockTime() << " s"
            << nl << endl;

#       include "convergenceCheck.H"
    }

    Info<< "End\n" << endl;

    return 0;
}

The code works fine, but the results are not - as expected - in agreement with the results calculated by fluent, cfx with constant rho and rhoSimpleFoam.

The difference between the result of fluent and my code is shown by the picture below, where the upper is result is my code and the result below was calculated by fluend - the result of fluent is equal to cfx and rhoSimpleFoam.



Can someone tell me what´s wrong with my code? I´ve tested the temperature equation with and without the terms "1/cp*fvc::div(phi*fvc::interpolate(p)) - 1/cp*p*fvc::div(phi)" since this is an incompressible case, there is no big difference.

The div and grad schemes are 1st order upwind and least squares in all cases. The velocity field is in very close agreement with the other calculations.

Best regards,
Patrick

[Pat84]

No idea?
This is strange

btw. the temperature BC at the wall is zeroGradient

[SKLee]

Hi Patrick,

Have you solved your problem ? and you can share me your code adding temperature equation into simpleFoam ?

Lee

[ybapat]

Hello,

Can you just check if your energy equation is fully converged? What URF are you using for energy equation?

Regards,
-Yogesh

[SKLee]

Hi Yogesh,

URF = 0.15 ;

The energy equation seems not to be fully converged. Have you tried this for your cases ? What are you experiencing this problem ?

SKLee

[ybapat]

Hello,

I think you should try with much larger under-relaxation and make sure that energy equation is converged.

-Yogesh