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-   -   diverge in low courant number (https://www.cfd-online.com/Forums/openfoam-solving/116004-diverge-low-courant-number.html)

immortality April 10, 2013 20:59

diverge in low courant number
 
i have set a filling process of a tube.i have set totalPressure and totalTemperature in inlet and tube is closed at other end and flow is compressible.
A shoch should occur that occures but has low resolution and other issue is that this sowewhat simple problem diverges at low courants like .1 with printstack error.but in higher cfl's like .6 doesn't occure an error but continuity residuals goes far away zero in minus direction when the shocks hits to wall and residuals after that return back to zero again.
What may be the cause of this strange behaviour?

immortality April 11, 2013 09:41

my BC's are
p:
Code:

left
    {
        type totalPressure;
            p0 uniform 932190;
            gamma 1.4;
            rho rho;
            //psi none;
            U U;
            phi phi;
            value uniform 303975;
    }

T:
Code:

left
    {
        type totalTemperature;
        T0 uniform 1248;
        gamma 1.4;
     
    }

U:
Code:

left
    {
      type pressureDirectedInletOutletVelocity;
      inletDirection uniform (1 0 0);
      value uniform (300 0 0);
    }

controlDict:
Code:

application    rhoPimpleFoam;

startFrom      latestTime;

startTime      0;

stopAt          endTime;

endTime        0.020708089;

deltaT          5.6e-9;

writeControl    adjustableRunTime;

writeInterval  .000001;

purgeWrite      0;

writeFormat    binary;

writePrecision  10;

writeCompression on;

timeFormat      general;

timePrecision  6;

runTimeModifiable true;

adjustTimeStep  yes;

maxCo          0.6;

maxDeltaT      .0001;

libs ( "libOpenFOAM.so" "libgroovyBC.so" ) ;

and schemes:
Code:

ddtSchemes
{
    default        backward;
}

gradSchemes
{
    default        Gauss linear;
    grad(p)        Gauss linear;
    grad(U)        cellLimited leastSquares 1.0;
}

divSchemes
{
    default        none;
    div(phi,U)      Gauss upwind;
    div(phid,p)    Gauss upwind;
    div(phi,K)      Gauss upwind;
    div(phi,h)      Gauss upwind;
    div(phi,k)      Gauss upwind;
    div(phi,epsilon) Gauss upwind;
    div(phi,R)      Gauss upwind;
    div(phi,omega)  Gauss upwind;
    div((rho*R))    Gauss linear;
    div(R)          Gauss linear;
    div(U)          Gauss linear;
    div((muEff*dev2(T(grad(U))))) Gauss linear;
    div(tauMC)  Gauss linear;
}

laplacianSchemes
{
    default        Gauss linear corrected;//limited .5
    /*laplacian(muEff,U) Gauss linear corrected;
    laplacian(mut,U) Gauss linear corrected;
    laplacian(DkEff,k) Gauss linear corrected;
    laplacian(DepsilonEff,epsilon) Gauss linear corrected;
    laplacian(DREff,R) Gauss linear corrected;
    laplacian(DomegaEff,omega) Gauss linear corrected;
    laplacian((rho*(1|A(U))),p) Gauss linear corrected;
    laplacian(alphaEff,h) Gauss linear corrected;
    laplacian(k,T)  Gauss linear corrected; 
    laplacian(alpha,e) Gauss linear corrected;
    laplacian(alphaEff,e)  Gauss linear corrected;*/
}

interpolationSchemes
{
    default        linear;
}

snGradSchemes
{
    default      corrected;//limited .5
}

fluxRequired
{
    default        no;
    p              ;
}



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