[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