[cfd1609496]

Hi Foamers,
the solution was all fun and games until stop running after 1020s because the courant number blows up.

Below is my geometry, right arrow shows heatedWall(315celsius), left arrow shows wall (300celsius). Top and bottom big box are 'atmosphere' i trying to simulate, i may not catch the correct b.c. yet tho:https://drive.google.com/open?id=1G4...53g986ClGk3f2g


fvSchemes:

ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    default         none;

    div(phi,U)      Gauss linearUpwind grad(U);
    div(phi,T)      Gauss limitedLinear 1;

    turbulence      Gauss limitedLinear 1;
    div(phi,k)      $turbulence;
    div(phi,epsilon) $turbulence;

    div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

fvSolution:

solvers
{
    p_rgh
    {
        solver          GAMG;
        smoother        DIC;
        tolerance       1e-8;
        relTol          0.01;
    }

    p_rghFinal
    {
        $p_rgh;
        relTol          0;
    }

    "(U|T|k|epsilon)"
    {
        solver          PBiCGStab;
        preconditioner  DILU;
        tolerance       1e-8;
        relTol          0.01;
    }

    "(U|T|k|epsilon)Final"
    {
        $T;
        relTol          0;
    }

}


PIMPLE
{
    momentumPredictor no;
    nNonOrthogonalCorrectors 0;
    nCorrectors       2;
    pRefCell          0;
    pRefValue         0;
}

relaxationFactors
{
    equations
    {
        ".*"   1.0;
    }
}

from time 0 to 540 it was fine, should be acceptable convection look like this below...but start from somewhere 600+ the result seems weird and until last 1020s whole domain shows full velocity....???

time 540s:
https://drive.google.com/open?id=1ad...u5DYM4xcj-XPzh

time 640s:
https://drive.google.com/open?id=1-e...E1f9Dpi9Yyfr3T

time 960s:
https://drive.google.com/open?id=1Bf...Mzh1iaLDHPQIf6

time 1020s:
https://drive.google.com/open?id=1n9...50kGgpv8NjOQVf

would be so kind of you to help gives some idea to me


Many thanks,
Cham

[obiscolly50]

Are you using fixed or adjustable timestep?

[cfd1609496]

Originally Posted by obiscolly50

Are you using fixed or adjustable timestep?

should be fixed right?

application     buoyantBoussinesqPimpleFoam;

startFrom       latestTime;

startTime       0;

stopAt          endTime;

endTime         2000;

deltaT          0.005;

writeControl    runTime;

writeInterval   20;

purgeWrite      0;

writeFormat     binary;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;


runTimeModifiable true;

functions
{
    #includeFunc residuals
    #includeFunc streamlines
}

[obiscolly50]

Not necessarily. You can try using an adjustable time step and set the maximum courant number (maxCo) to 1. Check some of the openfoam tutorials on how to do this.

[cfd1609496]

Originally Posted by obiscolly50

Not necessarily. You can try using an adjustable time step and set the maximum courant number (maxCo) to 1. Check some of the openfoam tutorials on how to do this.

Thank you Obi! I will try it out first and see how

[cfd1609496]

Originally Posted by obiscolly50

Not necessarily. You can try using an adjustable time step and set the maximum courant number (maxCo) to 1. Check some of the openfoam tutorials on how to do this.

Hi Obi,
i tried with adjustable timestep with max Co number= 1 and even with max Co number= 3...the solver stop somewhere around 60s and 40s. This means theres something wrong with the fvSchemes and fvSolutions, or maybe the /0 files?