CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Swirling Flow through nozzle and diffuser, NonlinearKEShih model

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 10, 2014, 04:04
Default Swirling Flow through nozzle and diffuser, NonlinearKEShih model
  #1
Member
 
Join Date: May 2014
Posts: 40
Rep Power: 12
Phil_ is on a distinguished road
Hi all,

Iím working on an incompressible swirling flow through a nozzle and diffuser (Re=30.000) using simpleFoam and OF 2.3.0.

For swirling flows I read itís best to use at least a non-linear k-epsilon turbulence model. Therefore I tried using the NonlinearKEShih model, but Iím running into problems with bounding epsilon and large continuity errors.

Usually the mesh is responsible for such behavior, so I tried simulating with different meshes (I attached one example with 300.000 hex cells). CheckMesh says:


Code:
Checking geometry...
    Overall domain bounding box (-0.01 -0.01 0) (0.01 0.01 0.08)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Boundary openness (2.2471e-16 3.30698e-16 9.79651e-16) OK.
    Max cell openness = 3.20034e-16 OK.
    Max aspect ratio = 7.45964 OK.
    Minimum face area = 1.015e-08. Maximum face area = 7.58503e-07.  Face area magnitudes OK.
    Min volume = 4.07554e-12. Max volume = 2.01323e-10.  Total volume = 1.07521e-05.  Cell volumes OK.
    Mesh non-orthogonality Max: 27.1515 average: 7.1929
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.883193 OK.
    Coupled point location match (average 0) OK.

Mesh OK.


Boundary Conditions:
For the velocity inlet I use the profile1DfixedValue to define the axial and tangential components (http://openfoamwiki.net/index.php/Si...le1DfixedValue), fixedValue 0 at the walls, and zeroGradient at the outlet.

For pressure I use zeroGradient at the inlet and walls, and fixedValue 0 at the outlet.

For k and epsilon I estimated inlet values (k fixedValue 0.0035, epsilon fixedValue 0.0183). At the walls I usually used kqRWallFunction and epsilonWallFunction but checkPatchFieldTypes forced me to use a zeroGradient-condition. Does anyone know how the wall functions work in the Shih-model? The mesh has to be a High-Re-Mesh with y+>30, am I right? Also zeroGradient at the outlet for k and epsilon.

I experimented with different fvSolution and fvScheme adjustments. Here are the current ones:

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

ddtSchemes
{
    default steadyState;
}

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

divSchemes
{
    default         none;
    div(phi,U)      bounded Gauss linearUpwind Gauss;
    div(phi,k)      bounded Gauss upwind;
    div(phi,epsilon) bounded Gauss upwind;
    div(phi,R)      Gauss upwind;
    div(R)          Gauss linear;
    div(phi,nuTilda) Gauss upwind;
    div((nuEff*dev(T(grad(U))))) Gauss linear;
    div(nonlinearStress) Gauss linear;
}

laplacianSchemes
{
    default         none;
    laplacian(nuEff,U) Gauss linear corrected;
    laplacian((1|A(U)),p) Gauss linear corrected;
    laplacian(DkEff,k) Gauss linear corrected;
    laplacian(DepsilonEff,epsilon) Gauss linear corrected;
    laplacian(DREff,R) Gauss linear corrected;
    laplacian(DnuTildaEff,nuTilda) Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
    interpolate(U)  linear;
}

snGradSchemes
{
    default         corrected;
}

fluxRequired
{
    default         no;
    p;
}






Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
  solvers
{
    p
    {
        solver           GAMG;
        tolerance        1e-5;
        relTol           0.01;
        smoother         GaussSeidel;
        nPreSweeps       0;
        nPostSweeps      2;
        cacheAgglomeration on;
        agglomerator     faceAreaPair;
        nCellsInCoarsestLevel 450;
        mergeLevels      1;
    }
 
      "(U|k|epsilon|R|nuTilda)"
    {
        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-8;
        relTol          0.0;
    }
}


SIMPLE
{
    nNonOrthogonalCorrectors 0;
    pRefCell                 0;
    pRefValue                0;
}

relaxationFactors
{
    p               0.3; 
    U               0.7; 
    k               0.5; 
    epsilon         0.5; 
    R               0.7;
    nuTilda         0.7;
}
Any suggestions?

Thanks & regards,

Philip
Attached Images
File Type: jpg mesh_ges.jpg (46.7 KB, 10 views)
Phil_ is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[How to obtain supersonic flow inside a supersonic wind tunnel ?] yx213 Siemens 1 September 17, 2014 13:52
Supersonic Inlet for a Compressible Flow in a Nozzle Daco FLUENT 8 November 8, 2012 03:34
Different flow patterns in CFX and Fluent avi@lpsc CFX 6 April 17, 2012 01:22
Different flow patterns in CFX and Fluent avi@lpsc FLUENT 4 April 8, 2012 06:12
Actuator disk model audrich FLUENT 0 September 21, 2009 07:06


All times are GMT -4. The time now is 00:04.