| taban |
September 6, 2015 03:41 |
simulation radiation and convection
3 Attachment(s)
Dear foamers,
I really need your help to solve my problems in running openFoam 2.2.1. I am trying to solve a convection and radiation case, so far with little success:confused:. The case is a 2D room (4m*8m) with 2 inlet and 2 outlet for air flow. There are 2 heaters at uniform temperature (850 K) on the ceiling ,the geometry is attached (geometry.png)
For this, I use the bouyantBoussinesqPimpleFoam solver, fvDOM radiation model and RNGkEpsilon for turbulence model. This case is steady state. I am running unsteady solver for a longer physical time until it reaches steady state.
Some boundary conditions are defined as follows ...
T:
Code:
internalField uniform 263;
boundaryField
{
heater
{
type fixedValue;
value uniform 850;
}
inletL
{
type fixedValue;
value uniform 263;
}
inletR
{
type fixedValue;
value uniform 263;
}
outletL
{
type inletOutlet;
value uniform 263;
inletValue uniform 263;
}
outletR
{
type inletOutlet;
value uniform 263;
inletValue uniform 263;
}
sidewalls
{
type fixedValue;
value uniform 263;
}
".*"
{
type groovyBC;
variables "gradT=Qr/0.02334;";// air conductivity= 0.02334
fractionExpression "0";
gradientExpression "gradT";
value uniform 263;
}
}
}
U:
Code:
internalField uniform (0 0 0);
boundaryField
{
inletL
{
type fixedValue;
value uniform (0.213 0 0);
}
inletR
{
type fixedValue;
value uniform (-0.213 0 0);
}
outletL
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
inletValue uniform (0 0 0);
}
outletR
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
inletValue uniform (0 0 0);
}
".*"
{
type fixedValue;
value uniform (0 0 0);
}
}
IDefault
Code:
internalField uniform 0;
boundaryField
{
"heater"
{
type greyDiffusiveRadiation;
T T;
emissivityMode lookup;
emissivity uniform 0.9;
value uniform 0;
}
".*"
{
type greyDiffusiveRadiation;
T T;
emissivityMode lookup;
emissivity uniform 0.5;
value uniform 0;
}
}
controlDict
Code:
application buoyantBoussinesqPimpleFoam;
startFrom latestTime;
startTime 0;
stopAt endTime;
endTime 50;
deltaT 0.001;
writeControl timeStep;
writeInterval 1000;
purgeWrite 0;
writeFormat ascii;
writePrecision 9;
writeCompression compressed;
timeFormat general;
timePrecision 6;
runTimeModifiable true;
adjustTimeStep yes;
maxCo 0.1;
functions
{
probes
{
type probes;
functionObjectLibs ("libsampling.so");
enabled true;
outputControl outputTime; //timeStep;
outputInterval 1;
fields
(
T
U
);
probeLocations
(
(2 0.0 0.0)
(4 0 0.0)
(6 0 0.0)
);
}
}
libs ( "libOpenFOAM.so" "libgroovyBC.so" ) ;
fvSchemes:
Code:
ddtSchemes
{
default Euler;
}
gradSchemes
{
default Gauss linear;
}
divSchemes
{
default none;
div(phi,U) Gauss upwind;
div(phi,T) Gauss upwind;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R) Gauss upwind;
div(R) Gauss linear;
div((nuEff*dev(T(grad(U))))) Gauss linear;
div(Ji,Ii_h) Gauss linearUpwind grad(Ii_h);//ezafe shod
}
laplacianSchemes
{
default none;
laplacian(nuEff,U) Gauss linear uncorrected;
laplacian(Dp,p_rgh) Gauss linear uncorrected;
laplacian(alphaEff,T) Gauss linear uncorrected;
laplacian(DkEff,k) Gauss linear uncorrected;
laplacian(DepsilonEff,epsilon) Gauss linear uncorrected;
laplacian(DREff,R) Gauss linear uncorrected;
}
interpolationSchemes
{
default linear;
}
snGradSchemes
{
default uncorrected;
}
fluxRequired
{
default no;
p_rgh;
}
fvSolution
Code:
solvers
{
p_rgh
{
solver GAMG;
tolerance 1e-4;
relTol 0;
smoother symGaussSeidel;
cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
maxIter 1;
nPreSweeps 0;
nPostSweeps 1;
}
p_rghFinal
{
$p_rgh;
relTol 0;
}
"(U|T|k|epsilon|R)"
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-4;//6
relTol 0.1;
}
"(U|T|k|epsilon|R)Final"
{
$U;
relTol 0;
}
Ii
{
solver GAMG;
tolerance 1e-4;
relTol 0;
smoother symGaussSeidel;
cacheAgglomeration true;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;
maxIter 1;
nPreSweeps 0;
nPostSweeps 1;
}
}
PIMPLE
{
momentumPredictor no;
nOuterCorrectors 1;
nCorrectors 2;
nNonOrthogonalCorrectors 0;
pRefCell 0;
pRefValue 0;
}
relaxationFactors
{
fields
{
}
equations
{
"(U|T|k|epsilon|R)" 1;
"(U|T|k|epsilon|R)Final" 1;
}
}
radiation properties:
Code:
radiation on;
radiationModel fvDOM;
fvDOMCoeffs
{
nPhi 80; // azimuthal angles in PI/2 on X-Y.(from Y to X)
nTheta 2; // polar angles in PI (from Z to X-Y plane)
convergence 0.001; // convergence criteria for radiation iteration
maxIter 2; // maximum number of iterations
cacheDiv true; // cache the div of the RTE equation.
// NOTE: Caching div is "only" accurate if the upwind scheme is used in
// div(Ji,Ii_h)
}
// Number of flow iterations per radiation iteration
solverFreq 20;//5
absorptionEmissionModel constantAbsorptionEmission;
constantAbsorptionEmissionCoeffs
{
absorptivity absorptivity [ 0 -1 0 0 0 0 0 ] 0;
emissivity emissivity [ 0 -1 0 0 0 0 0 ] 0;
E E [ 1 -1 -3 0 0 0 0 ] 0;
}
scatterModel none;
The correct solution isn't available but temperature contour and speed contour obviously shows that solution is incorrect (both images are attached). It would be nice if anyone can help me :)
1) I want the floor and cieling of the room define as adiabatic boundary so i use groovy bc as you see above in T code. Is it correct?
2) if i choose maxcorunt number > 0.1 in controlDict the solver crash after some timesteps. what is the problem?
3) Maybe i choose an improper scheme or other parameters in controldict , fvSolution or ..., please check them and tell me What might be the mistake? If it is required more information in details feel free to ask.
thanks in advance
Best regards:) |
