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xiaof November 1, 2013 00:08

strange result for non-orthogonality mesh using icoFoam
 
2 Attachment(s)
hello everyone
I am simulating a duct flow with icoFoam. I use periodic boundary condition for inlet and outlet.The other boundary condition I set as no-slip.
I have attached the velocity profile here.You can find that there are some velocity jumps which I think affected by the mesh.

The followings are the fvschemes, fvsolution, and the result of the checkMesh.


Thank you in advance.
fvSchemes
Code:

ddtSchemes
{
    default        Euler;
}

gradSchemes
{
      default        cellMDLimited leastSquares 1;
  // grad(p)        Gauss linear;
}

divSchemes
{
    default        none;
    div(phi,U)      Gauss reconCentral cellLimited leastSquares 1.0;
    div(phi)      Gauss linearUpwindV cellMDLimited leastSquares 1.0;

}

laplacianSchemes
{
    default        Gauss linear corrected;
    laplacian(nu,U) Gauss linear corrected;
    laplacian((1|A(U)),p)  Gauss linear corrected;

    laplacian(DT,T)    Gauss linear corrected;
}

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

snGradSchemes
{
    default        corrected;
}

fluxRequired
{
    default        no;
    p;
}

fvSolution
Code:

solvers
{
    p
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance        1e-08;
        relTol          0;
    };
 

    U
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance        1e-08;
        relTol          0;
    };
 
}

PISO
{
    nCorrectors    3;
    nNonOrthogonalCorrectors 2;
    pRefCell        0;
    pRefValue      0;
}

checkMesh
Code:

Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:          48548
    faces:            119960
    internal faces:  94888
    cells:            35808
    boundary patches: 2
    point zones:      0
    face zones:      0
    cell zones:      0

Overall number of cells of each type:
    hexahedra:    35808
    prisms:        0
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:    0

Checking topology...
    Boundary definition OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
    Patch              Faces    Points  Surface topology                 
    INTERFACE          1200    1600    ok (non-closed singly connected) 
    inout              23872    24274    ok (non-closed singly connected) 

Checking geometry...
    This is a 3-D mesh
    Overall domain bounding box (-1 -1 -4.33680869e-19) (1 1 0.01999999955)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Mesh (non-empty, non-wedge) dimensions 3
    Boundary openness (6.5506050833e-20 -8.7921189539e-20 -1.6233662817e-19) Threshold = 1e-06 OK.
    Max cell openness = 2.1714371522e-16 OK.
    Max aspect ratio = 350.00000279 OK.
    Minumum face area = 9.999999e-08. Maximum face area = 0.0011896420623.  Face area magnitudes OK.
    Min volume = 6.6666658486e-10. Max volume = 7.9309469101e-06.  Total volume = 0.0799999982.  Cell volumes OK.
    Mesh non-orthogonality Max: 44.27477573 average: 9.93239561 Threshold = 70
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.57381680369 OK.

Mesh OK.

End


xiaof

nsf November 2, 2013 08:48

Hi xiof,

I don't have any indepth knowledge of the schemes you are using but I would try to switch to a second order time stepping scheme like backward or CrankNicolson.

Secondly are you sure that the velocity jump isn't an artifact of the warping? Is it still there if you make a a linear plot?

Best
Nicolas


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