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Odd lagrangian particle behavior at small size

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Old   November 3, 2015, 11:59
Unhappy Odd lagrangian particle behavior at small size
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Paul Handy
Join Date: Sep 2014
Location: Idaho, USA
Posts: 21
Rep Power: 8
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I'm attempting to reproduce the results of Hoffman et al (http://onlinelibrary.wiley.com/doi/1...71109/abstract) in OpenFOAM (Data retrieved from "Gas Cyclones and Swirl Tubes" https://books.google.com/books?id=jq...page&q&f=false). It seemed to me that the best solver to use in this case was MPPICFoam, and that's how I set it up.

Here's my basic case setup:

constant/kinematicCloudProperties:

Code:
FoamFile
{
  version     2.0;
  format      ascii;
  class       dictionary;
  location    "constant";
  object      particleProperties;
}

solution
{
  active          true;
  coupled         true;
  transient       yes;
  cellValueSourceCorrection off;

  maxCo           1.0;

  interpolationSchemes
  {
    rho.air         cell;
    U.air           cellPoint;
    mu.air          cell;
  }

  averagingMethod dual;

  integrationSchemes
  {
    U               Euler;
  }

  sourceTerms
  {
    schemes
    {
      U           semiImplicit 1;
    }
  }
}

constantProperties
{
  rho0            2730;
  alphaMax        0.9;
}

subModels
{
  particleForces
  {
       ErgunWenYuDrag
       {
       alphac alpha.air;
       }
    gravity;
  }

  injectionModels
  {
    model1
    {
      type            patchInjection;
      massTotal       .1125;
      SOI             1;
      parcelBasisType mass;
      patchName       inlet;
      duration        1;
      parcelsPerSecond 3e4;
      U0              (0 0 -10 );
      flowRateProfile constant 1;
      sizeDistribution
      {
        type        general;
        generalDistribution
        {
          distribution
            (
             ( 0.30000e-6   0.11602)
             ( 0.89700e-6   0.10512)
             ( 1.49400e-6   0.09194)
             ( 2.09100e-6   0.08211)
             ( 2.68800e-6   0.08818)
             ( 3.28500e-6   0.07266)
             ( 3.88200e-6   0.04576)
             ( 4.47900e-6   0.03196)
             ( 5.07600e-6   0.02825)
             ( 5.67300e-6   0.02596)
             ( 6.27000e-6   0.02365)
             ( 6.86700e-6   0.02130)
             ( 7.46400e-6   0.01891)
             ( 8.06100e-6   0.01654)
             ( 8.65800e-6   0.01435)
             ( 9.25500e-6   0.01237)
             ( 9.85200e-6   0.01059)
             (10.44900e-6   0.00903)
             (11.04600e-6   0.00767)
             (11.64300e-6   0.00652)
             (12.24000e-6   0.00557)
             (12.83700e-6   0.00484)
             (13.43400e-6   0.00431)
             (14.03100e-6   0.00399)
             (14.62800e-6   0.00387)
             (15.22500e-6   0.00388)
             (15.82200e-6   0.00388)
             (16.41900e-6   0.00389)
             (17.01600e-6   0.00389)
             (17.61300e-6   0.00389)
             (18.21000e-6   0.00388)
             (18.80700e-6   0.00386)
             (19.40400e-6   0.00385)
             (20.00100e-6   0.00382)
             (20.59800e-6   0.00380)
             (21.19500e-6   0.00377)
             (21.79200e-6   0.00373)
             (22.38900e-6   0.00369)
             (22.98600e-6   0.00364)
             (23.58300e-6   0.00359)
             (24.18000e-6   0.00354)
             (24.77700e-6   0.00348)
             (25.37400e-6   0.00342)
             (25.97100e-6   0.00335)
             (26.56800e-6   0.00328)
             (27.16500e-6   0.00320)
             (27.76200e-6   0.00312)
             (28.35900e-6   0.00303)
             (28.95600e-6   0.00294)
             (29.55300e-6   0.00285)
             (30.15000e-6   0.00275)
             (30.74700e-6   0.00265)
             (31.34400e-6   0.00256)
             (31.94100e-6   0.00247)
             (32.53800e-6   0.00238)
             (33.13500e-6   0.00229)
             (33.73200e-6   0.00220)
             (34.32900e-6   0.00212)
             (34.92600e-6   0.00204)
             (35.52300e-6   0.00196)
             (36.12000e-6   0.00188)
             (36.71700e-6   0.00180)
             (37.31400e-6   0.00173)
             (37.91100e-6   0.00166)
             (38.50800e-6   0.00159)
             (39.10500e-6   0.00152)
             (39.70200e-6   0.00145)
             (40.29900e-6   0.00139)
             (40.89600e-6   0.00133)
             (41.49300e-6   0.00127)
             (42.09000e-6   0.00121)
             (42.68700e-6   0.00115)
             (43.28400e-6   0.00110)
             (43.88100e-6   0.00105)
             (44.47800e-6   0.00100)
             (45.07500e-6   0.00095)
             (45.67200e-6   0.00091)
             (46.26900e-6   0.00086)
             (46.86600e-6   0.00082)
             (47.46300e-6   0.00078)
             (48.06000e-6   0.00074)
             (48.65700e-6   0.00071)
             (49.25400e-6   0.00068)
             (49.85100e-6   0.00064)
             (50.44800e-6   0.00061)
             (51.04500e-6   0.00059)
             (51.64200e-6   0.00056)
             (52.23900e-6   0.00054)
             (52.83600e-6   0.00052)
             (53.43300e-6   0.00050)
             (54.03000e-6   0.00048)
             (54.62700e-6   0.00047)
             (55.22400e-6   0.00045)
             (55.82100e-6   0.00044)
             (56.41800e-6   0.00043)
             (57.01500e-6   0.00043)
             (57.61200e-6   0.00042)
             (58.20900e-6   0.00042)
             (58.80600e-6   0.00042)
             (59.40300e-6   0.00042)
             (60.00000e-6   0.00000)
             );
        }
      }
    }
  }

  dispersionModel none;

  patchInteractionModel localInteraction;

  localInteractionCoeffs
  {
    patches
      (
       walls
       {
       type rebound;
       e    0.97;
       mu   0.09;
       }
       inlet
       {
       type rebound;
       e    0.97;
       mu   0.09;
       }
       outlet
       {
       type escape;
       }
       particleOutlet
       {
       type escape;
       }
       );
  }

  heatTransferModel none;

  surfaceFilmModel none;

  packingModel none; //was implicit;

  dampingModel none;

  isotropyModel stochastic;

  stochasticCollisionModel none;

  stochasticCoeffs
  {
    timeScaleModel
    {
      type isotropic;
      alphaPacked 0.6;
      e 0.9;
    }
  }

  radiation off;
}


cloudFunctions
{}
constant/turbulenceProperties.air

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "constant";
    object      turbulenceProperties.air;
}

simulationType  LES;

LES
{
    LESModel kEqn;

    turbulence      on;
    printCoeffs     on;

    delta           cubeRootVol;

    cubeRootVolCoeffs
    {
    }
}
constant/transportProperties:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "constant";
    object      transportProperties;
}

contiuousPhaseName air;

rho.air         1.2;

transportModel  Newtonian;
nu              1.568e-05;
constant/g

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       uniformDimensionedVectorField;
    location    "constant";
    object      g;
}

dimensions      [0 1 -2 0 0 0 0];
value           ( 0 -9.81 0 );
0/k.air:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      k.air;
}

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

internalField       uniform 1;

boundaryField
{
    inlet
    {
        type               fixedValue;
        value              $internalField;
    }

    outlet
    {
        type               inletOutlet;
        phi                phi.air;
        inletValue         $internalField;
        value              $internalField;
    }

    ".*"
    {
        type               kqRWallFunction;
        value              $internalField;
    }
}
0/nut.air

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      nut.air;
}

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

internalField       uniform 0;

boundaryField
{
    inlet
    {
        type               calculated;
        value              $internalField;
    }

    outlet
    {
        type               calculated;
        value              $internalField;
    }

    ".*"
    {
        type               nutkWallFunction;
        value              $internalField;
    }
}
0/p:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      p;
}

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

internalField   uniform 0;

boundaryField
{
    inlet
    {
        type fixedFluxPressure;
        phi phi.air;
        value $internalField;
    }

    outlet
    {
        type fixedValue;
        phi phi.air;
        value uniform 0;
    }
    ".*"
    {
        type fixedFluxPressure;
        phi phi.air;
        value $internalField;
    }
}
0/U.air:

Code:
FoamFile
{
    version     2.0;
    format      binary;
    class       volVectorField;
    location    "0";
    object      U.air;
}

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

internalField   uniform (0 0 0);

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform (0 0 -10 );
    }

    outlet
    {
        type            pressureInletOutletVelocity;
        phi             phi.air;
        inletValue      uniform (0 0 0);
        value           uniform (0 0 0);
    }

    ".*"
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
}
system/controlDict:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}

application     MPPICFoam;

startFrom       latestTime;

startTime       0;

stopAt          endTime;

endTime         7;

deltaT          2e-4;

writeControl    runTime;

writeInterval   0.1;

purgeWrite      0;

writeFormat     binary;

writePrecision  6;

writeCompression yes;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;
system/fvSchemes:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSchemes;
}

ddtSchemes
{
    default Euler;
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    default         none;
    div(alphaPhic,U.air) Gauss linearUpwindV unlimited;
    div(((alpha.air*nuEff.air)*dev2(T(grad(U.air))))) Gauss linear;
    div(phiGByA,kinematicCloud:alpha) Gauss linear;
    div(alphaPhic,epsilon.air) Gauss limitedLinear 1;
    div(alphaPhic,k.air) Gauss limitedLinear 1;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

fluxRequired
{
    default         no;
    p;
    kinematicCloud:alpha;
}
system/fvSolution:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvSolution;
}


solvers
{
    p
    {
        solver          GAMG;
        tolerance       1e-06;
        relTol          0.01;
        smoother        GaussSeidel;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator    faceAreaPair;
        mergeLevels     1;
    }

    pFinal
    {
        solver          GAMG;
        tolerance       1e-06;
        relTol          0;
        smoother        GaussSeidel;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator    faceAreaPair;
        mergeLevels     1;
    }

    "(U|k|epsilon|omega).air"
    {
        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-05;
        relTol          0.1;
    }

    "(U|k|epsilon|omega).airFinal"
    {
        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-05;
        relTol          0.1;
    }

    kinematicCloud:alpha
    {
        solver          GAMG;
        tolerance       1e-06;
        relTol          0.1;
        smoother        GaussSeidel;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator    faceAreaPair;
        mergeLevels     1;
    }
}

PIMPLE
{
    nOuterCorrectors 1;
    nCorrectors     2;
    momentumPredictor yes;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue       0;
}

relaxationFactors
{
}
With particle sizes as I have them (.3um - 60um), I have extremely odd behavior when they enter the cyclone barrel. Instead of flowing in a circle around the cyclone, they are bunching at one end, and disrupt the air flow.
cyclone-particles.png

This shows the particles just moments after they first enter the cyclone. Note that they are flowing around both ends of the finder.

cyclone-particles-age.png

Moments later (colored for age), you can see that the particles are just filling the side with the inlet, not coming down much with gravity.

I can't explain why this is happening, but certain changes to the kinematic properties will stop it:
  • increase particle size
  • increase particle density
  • remove ErgunWenYuDrag.alphac from particleForces
Now, when I change size or density, my case no longer matches the setup in Hoffman et al. When I remove the ErgunWenYuDrag, no particles flow through the top - they all exit through the bottom; this doesn't match the results they found for fractional efficiency.


What am I missing here? Am I using the wrong solver for this case?
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Old   November 5, 2015, 16:54
Default
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Paul Handy
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Edit: I thougth that I had done this already, but I set coupling to false, and kept the drag parameter; the number of particles escaping through the top did not seem to quite match Hoffman's case, but it was greater than nothing, and the vortex kept. I suppose that the coupling means that particles can interact with ( and interrupt) the air flow. I was hoping that this would work for me, but I much prefer to have something that somewhat resembles reality.

Last edited by phandy; November 6, 2015 at 11:49.
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Old   November 11, 2017, 19:07
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By the way, do you know when to use packing, damping and isotropy models? whether to set them all for a case or any combinations of them?
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