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Biomass Combustion CFD error

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Old   August 8, 2017, 06:02
Question Biomass Combustion CFD error
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Mankaran Dhiman
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Hello
I am trying to run a cfd simulation for combustion of a biomass fuel in a furnace but when I try to solve the simulation, i get the following error in the beginning:
Code:
--> FOAM FATAL IO ERROR: 
wrong token type - expected Scalar, found on line 0 the word 'nan'

file: /home/mankaran90/simflow/qqqq/qqqq/system/data.solverPerformance.p at line 0.

--> FOAM Warning : 
    From function Foam::Istream& Foam::operator>>(Foam::Istream&, Foam::doubleScalar&)
    in file lnInclude/Scalar.C at line 93.

FOAM exiting
Please help! It is important.

Mankaran
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Old   August 8, 2017, 06:29
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By the way, i am simulating with three inlets.
Two for air, and one for fuel.
I imported a combustion mechanism and selected diffusion as combustion model
RANS k-E as turbulence model
with following boundary conditions:
Walls of the combustor:
pressure: zero gradient velocity: fixed value of 0 0 0, turbulence standard wall function

Air inlet:
pressure: zero gradient velocity fixed value of 0 3 0, turbulence fixed value

fuel inlet:
pressure: zero gradient velocity fixed value of 0 -3 0, turbulence fixed value
outlet:
pressure: fixed value velocity inlet outlet with 5 0 0, turbulence inlet outlet


Is there anything wrong with my BCs?
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Old   August 8, 2017, 07:14
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I don't understand your outlet conditions can you repeat them.

Your simulation diverged, probably due to a problem in setup with BC.
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Old   August 8, 2017, 07:36
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Outlet BC:
Pressure: fixed value (100000Pa)
velocity: inlet-outlet (with 5 0 0 in x y and z directions)
Turbulence:
k: inlet-outlet and E: inlet-outlet
For air inlet and fuel inlet patches, I am using velocity inlet BC.
I dont know how to setup BCs properly. I am a beginner in CFD and i cant find any tutorials which tell you how to set up BC for combustion using reacting foam solver
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Old   August 8, 2017, 08:18
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Pressure looks OK on Outlet.

But Velocity seems suspicious.
For the inletOutlet BC you need to define two things:

value (???)
and
inletValue (???)

What have you specified there precisely?
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Old   August 8, 2017, 08:25
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It only asks for the inlet value (m/sec) of velocity for the outlet patch. For other patches and wall it asks for value only, not the inlet value.
For wall value is 0
For air-inlet value is 0,3,0
For fuel-inlet value is 0,-3,0 and
for outlet, inlet-value is 5,0,0 in m/sec
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Old   August 8, 2017, 08:36
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Quote:
Originally Posted by mankaran90 View Post
It only asks for the inlet value (m/sec) of velocity for the outlet patch. For other patches and wall it asks for value only, not the inlet value.
For wall value is 0
For air-inlet value is 0,3,0
For fuel-inlet value is 0,-3,0 and
for outlet, inlet-value is 5,0,0 in m/sec

Try zeroGradient for velocity outlet and see if it runs. It should run or else it's a different problem.

For the inletOutlet BC. You need this:

{
type inletOutlet;
inletValue uniform (? ? ?);
value uniform (? ? ?);
}

Or else it's not setup correctly. Also try to understand what you impose there on outlet. If you impose a pressure BC and a velocity your problem is overconstraint and the solver does'nt know what to do resp. has a very hard time performing what you ask him to perform. Also please in future and in general post way more information on a) what you want to do (sketch, BCs) b) what your setup looks exactly (post full files for p, U etc) c) what your mesh, solver settings etc. are. Else it is really hard to understand and help and nobody can try to answer..

Also a tip, firstly try running without turbulence model than if it runs use a trubulence model.
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Old   August 9, 2017, 02:37
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Thanks!!! i'll keep that in mind!! Actually I am using an openfoam gui simflow and I think there is some difference between setting up the case using a notepad and that using a gui in terms of parameters to input.

Could you please suggest me some study material on how to set up BCs...
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Old   August 9, 2017, 03:11
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I tried to perform with a simple geometry but got the same error. It passed the checkmesh without any errors. I have used the following setup in my case:
Pressure ("Part1" in the boundaryField is the walls patch)
Code:
FoamFile
{
    version             2.0;
    format              binary;
    arch                "LSB;label=32;scalar=64";
    class               volScalarField;
    location            "0";
    object              p;
}


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

internalField    uniform 100000.0;

boundaryField
{
    Part1
    {
        type    zeroGradient;
    }
    Part1_air_inet
    {
        type    zeroGradient;
    }
    Part1_fuel_inlet
    {
        type    zeroGradient;
    }
    Part1_outlet
    {
        type    zeroGradient;
    }
}
Temperature:
Code:
{
    version             2.0;
    format              binary;
    arch                "LSB;label=32;scalar=64";
    class               volScalarField;
    location            "0";
    object              T;
}


dimensions    [0 0 0 1 0 0 0];

internalField    uniform 300.0;

boundaryField
{
    Part1
    {
        type    zeroGradient;
    }
    Part1_air_inet
    {
        type    totalTemperature;
        T0    uniform 300.0;
        phi    phi;
        gamma    1.4;
    }
    Part1_fuel_inlet
    {
        type    totalTemperature;
        T0    uniform 300.0;
        phi    phi;
        gamma    1.4;
    }
    Part1_outlet
    {
        type    zeroGradient;
    }
}
Velocity:
Code:
FoamFile
{
    version             2.0;
    format              binary;
    arch                "LSB;label=32;scalar=64";
    class               volVectorField;
    location            "0";
    object              U;
}


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

internalField    uniform (0.0 0.0 0.0);

boundaryField
{
    Part1
    {
        type    noSlip;
    }
    Part1_air_inet
    {
        type    fixedValue;
        value    uniform (-1.0 0.0 0.0);
    }
    Part1_fuel_inlet
    {
        type    fixedValue;
        value    uniform (0.0 0.0 3.0);
    }
    Part1_outlet
    {
        type    zeroGradient;
    }
}
Fuel:
Code:
FoamFile
{
    version             2.0;
    format              binary;
    arch                "LSB;label=32;scalar=64";
    class               volScalarField;
    location            "0";
    object              C7H16;
}


dimensions    [0 0 0 0 0 0 0];

internalField    uniform 0.0;

boundaryField
{
    Part1
    {
        type    zeroGradient;
    }
    Part1_air_inet
    {
        type    inletOutlet;
        inletValue    uniform 0.0;
    }
    Part1_fuel_inlet
    {
        type    inletOutlet;
        inletValue    uniform 1;
    }
    Part1_outlet
    {
        type    zeroGradient;
    }
}
Oxygen: (nitrogen is 0.77)
Code:
FoamFile
{
    version             2.0;
    format              binary;
    arch                "LSB;label=32;scalar=64";
    class               volScalarField;
    location            "0";
    object              O2;
}


dimensions    [0 0 0 0 0 0 0];

internalField    uniform 0.23;

boundaryField
{
    Part1
    {
        type    zeroGradient;
    }
    Part1_air_inet
    {
        type    inletOutlet;
        inletValue    uniform 0.23;
    }
    Part1_fuel_inlet
    {
        type    inletOutlet;
        inletValue    uniform 0.0;
    }
    Part1_outlet
    {
        type    zeroGradient;
    }
}
k
Code:
FoamFile
{
    version             2.0;
    format              binary;
    arch                "LSB;label=32;scalar=64";
    class               volScalarField;
    location            "0";
    object              k;
}


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

internalField    uniform 1.0;

boundaryField
{
    Part1
    {
        type    kqRWallFunction;
        value    uniform 1.0;
    }
    Part1_air_inet
    {
        type    turbulentIntensityKineticEnergyInlet;
        value    uniform 1.0;
        intensity    0.05;
        phi    phi;
    }
    Part1_fuel_inlet
    {
        type    turbulentIntensityKineticEnergyInlet;
        value    uniform 1.0;
        intensity    0.05;
        phi    phi;
    }
    Part1_outlet
    {
        type    inletOutlet;
        inletValue    uniform 1.0;
        phi    phi;
    }
}
Code:
FoamFile
{
    version             2.0;
    format              binary;
    arch                "LSB;label=32;scalar=64";
    class               volScalarField;
    location            "0";
    object              epsilon;
}


dimensions    [0 2 -3 0 0 0 0];

internalField    uniform 1.0;

boundaryField
{
    Part1
    {
        type    epsilonWallFunction;
        value    uniform 1.0;
    }
    Part1_air_inet
    {
        type    turbulentMixingLengthDissipationRateInlet;
        value    uniform 1.0;
        phi    phi;
        mixingLength    0.001;
    }
    Part1_fuel_inlet
    {
        type    turbulentMixingLengthDissipationRateInlet;
        value    uniform 1.0;
        phi    phi;
        mixingLength    0.001;
    }
    Part1_outlet
    {
        type    inletOutlet;
        inletValue    uniform 1.0;
        phi    phi;
    }
}
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Old   August 9, 2017, 03:14
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fvschemes
Code:
FoamFile
{
    version    2.0;
    class    dictionary;
    format    ascii;
    location    "system";
    object    fvSchemes;
}
ddtSchemes
{
    default    Euler;
}
gradSchemes
{
    default    Gauss linear;
}
divSchemes
{
    default    Gauss upwind;
    div(phid,p)    Gauss upwind;
    div(phi,Yi_h)    Gauss upwind;
    div(phi,U)    Gauss upwind;
    div(phi,K)    Gauss linear;
    div(phi,epsilon)    Gauss upwind;
    div(phi,alphat)    Gauss upwind;
    div(phi,k)    Gauss upwind;
    div(U)    Gauss linear;
    div((muEff*dev2(T(grad(U)))))    Gauss linear;
    div(R)    Gauss linear;
    div(((rho*nuEff)*dev2(T(grad(U)))))    Gauss linear;
}
laplacianSchemes
{
    default    Gauss linear corrected;
}
interpolationSchemes
{
    default    linear;
}
snGradSchemes
{
    default    corrected;
}
fluxRequired
{
    default    no;
    p    ;
}
wallDist
{
    method    meshWave;
    nRequired    true;
}

fvsolutions
Code:
FoamFile
{
    version    2.0;
    class    dictionary;
    format    ascii;
    location    "system";
    object    fvSolution;
}
solvers
{
    U
    {
        relTol    0.1;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    h
    {
        relTol    0.1;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    epsilon
    {
        relTol    0.1;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    p
    {
        smoother    GaussSeidel;
        relTol    0.01;
        cacheAgglomeration    true;
        nFinestSweeps    2;
        maxIter    100;
        nPreSweeps    0;
        nPostSweeps    1;
        agglomerator    faceAreaPair;
        nCellsInCoarsestLevel    10;
        tolerance    1.0E-6;
        mergeLevels    1;
        solver    GAMG;
    }
    Yi
    {
        relTol    0.1;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    rho
    {
        relTol    0.1;
        preconditioner    DIC;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PCG;
    }
    k
    {
        relTol    0.1;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    UFinal
    {
        relTol    1.0E-4;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    hFinal
    {
        relTol    1.0E-4;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    epsilonFinal
    {
        relTol    1.0E-4;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    pFinal
    {
        smoother    GaussSeidel;
        relTol    1.0E-4;
        cacheAgglomeration    true;
        nFinestSweeps    2;
        maxIter    100;
        nPreSweeps    0;
        nPostSweeps    1;
        agglomerator    faceAreaPair;
        nCellsInCoarsestLevel    10;
        tolerance    1.0E-6;
        mergeLevels    1;
        solver    GAMG;
    }
    YiFinal
    {
        relTol    1.0E-4;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    rhoFinal
    {
        relTol    1.0E-4;
        preconditioner    DIC;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PCG;
    }
    kFinal
    {
        relTol    1.0E-4;
        preconditioner    DILU;
        tolerance    1.0E-6;
        maxIter    100;
        solver    PBiCGStab;
    }
    Phi
    {
        solver    GAMG;
        smoother    GaussSeidel;
        nPreSweeps    0;
        nPostSweeps    1;
        nFinestSweeps    1;
        nCellsInCoarsestLevel    10;
        mergeLevels    2;
        agglomerator    faceAreaPair;
        cacheAgglomeration    true;
        tolerance    1.0E-8;
        relTol    0.01;
        maxIter    100;
    }
}
PIMPLE
{
    nNonOrthogonalCorrectors    1;
    nCorrectors    1;
    nOuterCorrectors    1;
    momentumPredictor    true;
    pRefCell    0;
    pRefValue    100000.0;
    residualControl
    {
        p
        {
            tolerance    1.0E-4;
            relTol    0.0;
        }
        Yi
        {
            tolerance    1.0E-4;
            relTol    0.0;
        }
        epsilon
        {
            tolerance    1.0E-4;
            relTol    0.0;
        }
        U
        {
            tolerance    1.0E-4;
            relTol    0.0;
        }
        h
        {
            tolerance    1.0E-4;
            relTol    0.0;
        }
        rho
        {
            tolerance    1.0E-4;
            relTol    0.0;
        }
        k
        {
            tolerance    1.0E-4;
            relTol    0.0;
        }
    }
}
relaxationFactors
{
    p    1.0;
    Yi    1.0;
    epsilon    1.0;
    U    1.0;
    h    1.0;
    rho    1.0;
    k    1.0;
}
potentialFlow
{
    nNonOrthogonalCorrectors    10;
    PhiRefCell    0;
    PhiRefValue    100000.0;
}
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Old   August 9, 2017, 03:54
Question
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Mankaran Dhiman
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Please find the required files attached (0, constant, chemkin and system). I havent attached the polymesh files in the system folder as their size exceeds the max limit
Attached Files
File Type: zip Reacting foam.zip (28.4 KB, 4 views)
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Old   August 11, 2017, 09:17
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Hello Mankaran,
I am not sure if this may help, but have you tried using fixedValue instead of inletOutlet for the species? you can find references in the tutorials. Moreover, I think you may have future problems with the mass balance (that is, divergence in temperatures from the Janaf tables) because how you set the internal field and inlets for oxygen (non-inert species) the same. But I am only a novice so I am not sure if this will be the case.
Regards,
David
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Old   August 16, 2017, 07:51
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Mankaran Dhiman
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Thanks David

I randomly tried to decrease the time-step. I got a divergence with an error at 0.001 but the simulation ran fine when I decreased the time step to 0.0001. But it took like 8 hrs for simulating 10 seconds of the combustion
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