[mattmirsad]

Dear FOAMers,

I am trying to solve a simple internal flow case in a pipe with rhoSimpleFoam where an external heat flux is specified using "externalWallHeatFluxTemperature" as shown in the code below:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 0 0 1 0 0 0];

internalField   uniform 300;

boundaryField
{
    Inlet
    {
        type            fixedValue;
        value           $internalField;
    }

    outlet
    {
        type            inletOutlet;
        value           $internalField;
        inletValue      $internalField;
    }

    sides
    {

        type            externalWallHeatFluxTemperature;
		mode            coefficient;
        Ta              constant 700.0;
        h               constant 1000.0;
        thicknessLayers (0.001 0.002);
        kappaLayers     (1 2.5);
        kappaMethod     fluidThermo;
        value           $internalField;

    }
}

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

The solver runs smoothly without any problem and the results are reasonable. But if I only change the "sides" boundary condition to uniform heat flux (as shown below), the solver stops in the first iteration without any error message!

PHP Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 0 0 1 0 0 0];

internalField   uniform 300;

boundaryField
{
    Inlet
    {
        type            fixedValue;
        value           $internalField;
    }

    outlet
    {
        type            inletOutlet;
        value           $internalField;
        inletValue      $internalField;
    }

    sides
    {
        type            externalWallHeatFluxTemperature;
        mode            flux;
        q               uniform 111; // W/m^2
        value           $internalField;
        kappaMethod     fluidThermo;
        kappa           none;
        Qr              none;
    }
}

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


In a nutshell, mode "coefficient" works perfectly but mode "flux" cause the solver to crash without any error message. Here is how the solver stops:

PHP Code:

Time = 1

GAMG:  Solving for Ux, Initial residual = 1, Final residual = 0.0495507, No Iterations 2
GAMG:  Solving for Uy, Initial residual = 1, Final residual = 0.0551383, No Iterations 2
GAMG:  Solving for Uz, Initial residual = 1, Final residual = 0.0278211, No Iterations 1 


Could you please share your thoughts on the possible root causes for this?

Cheers,
Matt

[Roman1]

One of the possible reason is unbalance between heat flux from gas media to solid wall and fixed heat flux that you have written as boundary condition. For example, cell size, temperature, gas speed can not provide desired 111 w/sq.m from gas phase to solid. So heat flux from gas becomes unequal to heat flux from surface into solid, continuity becomes broken, program stops.

[mattmirsad]

Originally Posted by Roman1

One of the possible reason is unbalance between heat flux from gas media to solid wall and fixed heat flux that you have written as boundary condition. For example, cell size, temperature, gas speed can not provide desired 111 w/sq.m from gas phase to solid. So heat flux from gas becomes unequal to heat flux from surface into solid, continuity becomes broken, program stops.

Thanks for your response.

I just did some more tests with this case:
For the case described above, I am using "OpenFOAM-v2012-windows10".
if I transfer it to a LINUX system I get more information when it crashes:

PHP Code:

/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2012                                  |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 79e353b8-20201222 OPENFOAM=2012
Arch   : "LSB;label=32;scalar=64"
Exec   : rhoSimpleFoam
Date   : Apr 13 2021
Time   : 13:24:16
Host   : xxxxxxxxxxxxxxxxxxxx
PID    : 2462
I/O    : uncollated
Case   : /home/matt/OpenFOAM_ESI/rhoSF/squareBend_To_Pipe
nProcs : 1
trapFpe: Floating point exception trapping enabled (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 5, maxFileModificationPolls 20)
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 0


SIMPLE: convergence criteria
    field p tolerance 0.001
    field U tolerance 0.0001
    field e tolerance 0.001
    field "(k|epsilon)" tolerance 0.001

Reading thermophysical properties

Selecting thermodynamics package
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       sutherland;
    thermo          hConst;
    equationOfState perfectGas;
    specie          specie;
    energy          sensibleInternalEnergy;
}

Reading field U

Reading/calculating face flux field phi

pressureControl
    pMax 220000
    pMin 11000

Creating turbulence model

Selecting turbulence model type RAS
Selecting RAS turbulence model kEpsilon
RAS
{
    RASModel        kEpsilon;
    turbulence      on;
    printCoeffs     on;
    Cmu             0.09;
    C1              1.44;
    C2              1.92;
    C3              0;
    sigmak          1;
    sigmaEps        1.3;
}

No MRF models present

No finite volume options present

Starting time loop

wallHeatFlux wallHeatFlux1:
    processing wall patches:
        sides

Time = 1

GAMG:  Solving for Ux, Initial residual = 1, Final residual = 0.0495507, No Iterations 2
GAMG:  Solving for Uy, Initial residual = 1, Final residual = 0.0551383, No Iterations 2
GAMG:  Solving for Uz, Initial residual = 1, Final residual = 0.0278211, No Iterations 1
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in /lib/x86_64-linux-gnu/libpthread.so.0
#3  Foam::heThermo<Foam::rhoThermo, Foam::pureMixture<Foam::sutherlandTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::he(Foam::Field<double> const&, Foam::Field<double> const&, int) const at ??:?
#4  Foam::mixedEnergyFvPatchScalarField::updateCoeffs() at ??:?
#5  Foam::fvMatrix<double>::fvMatrix(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&, Foam::dimensionSet const&) in /usr/lib/openfoam/openfoam2012/platforms/linux64GccDPInt32Opt/bin/rhoSimpleFoam
#6  Foam::tmp<Foam::fvMatrix<double> > Foam::fv::optionList::operator()<double>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>&, Foam::word const&) in /usr/lib/openfoam/openfoam2012/platforms/linux64GccDPInt32Opt/bin/rhoSimpleFoam
#7  ? in /usr/lib/openfoam/openfoam2012/platforms/linux64GccDPInt32Opt/bin/rhoSimpleFoam
#8  __libc_start_main in /lib/x86_64-linux-gnu/libc.so.6
#9  ? in /usr/lib/openfoam/openfoam2012/platforms/linux64GccDPInt32Opt/bin/rhoSimpleFoam
Floating point exception (core dumped) 


The interesting point is that if I use openFOAM foundation on a LINUX system this problems runs smoothly without any problem!

Any more thoughts on this are appreciated.

Cheers,
Matt