[jebin]

Hi,


I am fairly new to OpenFoam using version 6. I am trying to solve the heat transfer between a heatsink with heat source at the bottom and air traveling through the pipe in which only the heat sink is exposed.


I am using chtMultiRegionFoam solver. Split the mesh into two regions and created cellzones.
I gave the thermophysical properties to both heatsink and air and also defined the boundary conditions and the contact boundary as compressible::turbulentTemperatureCoupledBaffleMix ed.


Using RAS model for turbulence properties of air.
Initial temperature of air is 300k and that of heat sink is 273K but I am getting very low values of about -206k




I used fvschemes and fvsoultion from tutorial/heatTransfer/chtMultiRegionFoam/multiregionheater for both separately.


When I try to solve it, its showing "Negative initial temperature T0: -206.172"
and is exiting at 2.5 s while solving the solid


The error message is:

Solving for fluid region waterCellSet
DILUPBiCGStab:  Solving for Ux, Initial residual = 0.0201238, Final residual = 0.000422419, No Iterations 1
DILUPBiCGStab:  Solving for Uy, Initial residual = 0.0189649, Final residual = 0.000425249, No Iterations 1
DILUPBiCGStab:  Solving for Uz, Initial residual = 0.00718987, Final residual = 0.000186804, No Iterations 1
DILUPBiCGStab:  Solving for h, Initial residual = 0.00431549, Final residual = 0.000122464, No Iterations 1
Min/max T:-206.151 339.013
GAMG:  Solving for p_rgh, Initial residual = 0.0455872, Final residual = 0.000385342, No Iterations 2
time step continuity errors : sum local = 0.000534267, global = 8.44534e-05, cumulative = 8.44534e-05
Min/max rho:1.25 1.25
DILUPBiCGStab:  Solving for epsilon, Initial residual = 0.00599105, Final residual = 8.33063e-05, No Iterations 1
DILUPBiCGStab:  Solving for k, Initial residual = 0.0191864, Final residual = 0.000366755, No Iterations 1

Solving for solid region heaterCellSet
DICPCG:  Solving for h, Initial residual = 0.738924, Final residual = 7.06039e-07, No Iterations 32


--> FOAM FATAL ERROR: 
Negative initial temperature T0: -206.172

    From function Foam::scalar Foam::species::thermo<Thermo, Type>::T(Foam::scalar, Foam::scalar, Foam::scalar, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar) const) const [with Thermo = Foam::hConstThermo<Foam::rhoConst<Foam::specie> >; Type = Foam::sensibleEnthalpy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hConstThermo<Foam::rhoConst<Foam::specie> >, Foam::sensibleEnthalpy>]
    in file /home/ubuntu/OpenFOAM/OpenFOAM-6/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 54.

FOAM aborting

#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::error::abort() at ??:?
#2  Foam::heSolidThermo<Foam::solidThermo, Foam::pureMixture<Foam::constIsoSolidTransport<Foam::species::thermo<Foam::hConstThermo<Foam::rhoConst<Foam::specie> >, Foam::sensibleEnthalpy> > > >::calculate() at ??:?
#3  Foam::heSolidThermo<Foam::solidThermo, Foam::pureMixture<Foam::constIsoSolidTransport<Foam::species::thermo<Foam::hConstThermo<Foam::rhoConst<Foam::specie> >, Foam::sensibleEnthalpy> > > >::correct() at ??:?
#4  ? in "/opt/openfoam6/platforms/linux64GccDPInt32Opt/bin/chtMultiRegionFoam"
#5  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#6  ? in "/opt/openfoam6/platforms/linux64GccDPInt32Opt/bin/chtMultiRegionFoam"
Aborted (core dumped)

I suspect it might be some error with defining air as I am getting negative values in the result.
The Temp conditions I gave for air is given:

dimensions      [ 0 0 0 1 0 0 0 ];

internalField   uniform 300;

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform 300;
    }
    outlet
    {
        type            inletOutlet;
        value           uniform 300;
        inletValue      uniform 300;
    }
    wall-domain
    {
        type            zeroGradient;
    }
    default_wall
    {
        type            compressible::turbulentTemperatureCoupledBaffleMixed;
        value           $internalField;
        Tnbr            T;
        kappaMethod     fluidThermo;
    }
}

and that for solid is :

dimensions      [ 0 0 0 1 0 0 0 ];

internalField   uniform 273;

boundaryField
{
    base
    {
        type            fixedValue;
        value           uniform 273;
        inletValue      uniform 273;
    }
    sinkbody
    {
        type            zeroGradient;
    }
    wall-domain
    {
        type            zeroGradient;
    }
    default_wall
    {
        type            compressible::turbulentTemperatureCoupledBaffleMixed;
        value           uniform 273;
        Tnbr            T;
        kappaMethod     solidThermo ;
    }
}

the fvScheme for air is:

ddtSchemes
{
    default        steadyState;
}

gradSchemes
{
    default         Gauss linear;
    grad(U)         cellLimited Gauss linear 1;
}

divSchemes
{
    default         none;
    div(phi,U)      bounded Gauss upwind;
    div(phi,h)      bounded Gauss upwind;
    div(phi,e)      bounded Gauss upwind;
    div(phi,K)      bounded Gauss upwind;
    div(phi,k)      bounded Gauss upwind;
    div(phi,epsilon) bounded Gauss upwind;
    div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear limited corrected 0.33;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         limited corrected 0.33;
}

The fvScheme for solid is:

ddtSchemes
{
    default Euler;
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    default         none;
}

laplacianSchemes
{
    default             none;
    laplacian(alpha,h)  Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

Can somebody please explain to me what I have done wrong