[Sungki]

Hello Foamers,
I am a newbie at openFoam.
Now I am struggling with heat transfer problem of a simple box with heat sources using buoyantSimpleFoam. I used P1 radiation model at first but I changed it to fvDOM model because I thought fvDOM is more proper with this small box.
Let me say about system first.

Geometry is a box(600X400X400mm) with 4 heat sources on a ceiling surface. there is air inside the simple box(Look at attached geometry).
ceiling, floor : insulated
fixedWalls(sidewalls): 473K(initial T)
4 heat sources on ceiling(circular shape): constant 1273K
air: 473K(initial T)
outer Temerature: 293K

There is no chemical reaction inside the box.
At first, I expect there is major radiation with convection and conduction due to the large temperature difference and that the temperature of fixedWalls and air needed to be changed with iterations. Unfortunately, my expectation looks wrong.

(Q1) There is big temperature difference between air(473K) inside this small box and heat sources(1273K) on ceiling surface. why did the temperature of air change slightly?
After several iterations, the temperature of air did not look on watching temperature profile after 9400 iterations.
constant folder file is 26M. If there is anyone who want this, I will send it to him.

(Q2) I set fixedWalls as varying temperature bc with 0/T folder as follows.

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.3.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 0 0 1 0 0 0];

internalField uniform 473; // air Temperature 200 C

boundaryField
{
floor
{
type zeroGradient; // floor surface insulated
}

ceiling
{
type zeroGradient; // ceiling surface insulated
}

fixedWalls
{
type externalWallHeatFluxTemperature;
kappa fluidThermo;
kappaName default;
Qr Qr;
h uniform 3; //heat transfer coefficient (W/Km2)
thicknessLayer 0.003; //thickness(m)
Ta 293; // ambient Temperature
value uniform 473; // inintial Temperature
}

circle
{
type fixedValue;
value uniform 1273; //heat source 1,000 C
}
}

// ************************************************** *********************** //

Is there anyone who give me some advice for this Temperature bc?

system/fvsolution
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.3.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
p_rgh
{
solver PCG;
preconditioner DIC;
tolerance 1e-06;
relTol 0.01;
}

Ii
{
solver GAMG;
tolerance 1e-4;
relTol 0;
smoother symGaussSeidel;
cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
maxIter 5;
nPreSweeps 0;
nPostSweeps 1;
}

"(U|h|k|epsilon)"
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}
}

SIMPLE
{
nNonOrthogonalCorrectors 4;
pRefCell 0;
pRefValue 0;

residualControl
{
p_rgh 1e-3;
U 1e-4;
h 1e-4;
G 1e-4;

// possibly check turbulence fields
"(k|epsilon|omega)" 1e-4;
"ILambda.*" 1e-4;
}
}

relaxationFactors
{
fields
{
rho 0.2;
p_rgh 0.7;
}
equations
{
U 0.2;
h 0.2;
k 0.5;
epsilon 0.5;
"ILambda.*" 0.7;
}
}


// ************************************************** *********************** //
For this file, I adjusted residual control, relaxation factor of rho and nNonOrthogonalCorrectors.

I appreciate your reading and attention and Thank you in advance.

Have a nice day!!