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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.

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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