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SiCaRiUs June 30, 2012 09:11

Strange temperatur flow in buoyantBoussinesqSimpleFoam with viscous heating
 
Hi all,

i need your help, please.

I have added viscous heating to buoyantBoussinesqSimpleFoam. Everythink works fine, but now i have a strange heat flow in my testcase.

I have a modell, similar to the driven cavity case, but with the upper and the lower wall running against each other. Both moving walls have fixed temperatur value of 300K. just to get a steady state solution. The internal field is also at 300K.

here is what i get from my solver, slice through the cavity and a plot over line from top to bottom:

http://sicarius.serverteil.de/testcase.jpg


Here is my code for my TEqn.H:

Code:

{
    kappat = turbulence->nut()/Prt;
    kappat.correctBoundaryConditions();

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

    fvScalarMatrix TEqn
    (
        fvm::div(phi, T)
      - fvm::Sp(fvc::div(phi), T)
      - fvm::laplacian(kappaEff, T)
      - ((U & fvc::grad(p)) / Cp)
      - (((turbulence->nuEff() / Cp) * (fvc::grad(U) + fvc::grad(U)().T())) && fvc::grad(U))
    );

    TEqn.relax();
    TEqn.solve();

    rhok = 1.0 - beta*(T - TRef);
}

Why is there a bend in temperatur. I would have expected a parabola between top and bottom.

I hope you can help me. thanks a lot!

Greetings

Sebastian

nimasam June 30, 2012 12:15

you add a "viscous heating" term, so it maybe not unphysical at all, because your mechanical energy turn into heat by that term
as "grad U" is higher near moving wall then the heat is higher there


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