[babakflame]

Dear Foamers

I am trying to simulate a bluff-body stabilized non-premixed flame. Previously, I have simulated this case with Smagorinsky and spallart-Allmaras sub-grid scales with no problem. I have taken Courant number in these simulations 0.36 and the case was successfully simulated.

Nevertheless, during my simulation with oneEqEddy sub-grid scale a strange behavior happens. After the flow reaches the outlet of the domain, an oscillation occurs in the courant number. I mean the courant number increases partially and the the time step collapses from around 1e-07 to 1e-014. Even, I have examined Courant numbers as low as 0.18 and this phenomenon happens again. I think 0.18 is a relatively low value for Courant number.

All files including the LESProperties and U and P are the same for three utilized sub-grid scales i.e. Smagorinsky, Spallart-Allmaras and oneEqEddy models. Nonetheless, this significant collapse of time step happens only in oneEqeddy sub-grid scale.
Here are the LESProperties, U and P files repectively. My case contains a Cylindrical grid which features a bluff-body seperating fuel and oxidizer streams.

 LESModel        oneEqEddy;

printCoeffs     on;

delta        vanDriest;


vanDriestCoeffs
{
    delta           cubeRootVol;
    cubeRootVolCoeffs
    {
        deltaCoeff      1;
    }

    smoothCoeffs
    {
        delta           cubeRootVol;
        cubeRootVolCoeffs
        {
            deltaCoeff      1;
        }

        maxDeltaRatio   1.1;
    }

    Aplus           26;
    Cdelta          0.158;
}

  
 FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0.995722";
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [1 -1 -2 0 0 0 0];

internalField   uniform 101325; 

boundaryField
{
    OUTLET
    {
        type            waveTransmissive;
        gamma           1.4;
        fieldInf        101325;
        lInf            0.025;
        value           uniform 101325; 
    }
    COFLOW
    {
        type            zeroGradient;
    }
    SIDE
    {
        type            fixedValue;
      value       uniform 101325;
    }
    FUEL
    {
        type            zeroGradient;
    }
    WALL
    {
        type            zeroGradient;
    }
}


// 

 FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    location    "0.995722";
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0.1 0); 

boundaryField
{
    OUTLET
    {
        type            zeroGradient;
    }
    COFLOW
    {
        type            fixedValue;
        value           uniform (0 40 0);
    }
    SIDE
    {
        type            zeroGradient;
    }
    FUEL
    {
        type            turbulentInlet;
        referenceField  nonuniform List<vector>
252
(
(-0.296506256 142.798641 0.146544894)
(-0.334651696 142.991259 -0.0378759468)

  ...
...
...

 (-1.8824955152    4.9390407   0.144344149)
(0.4145645725     -1.4054917  -0.694103849)      
);

    }
    WALL
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
}

Any hint is appreciated.

Best
Bobi