[xiaof]

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

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

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

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]

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