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Errors at boundaries between hex blocks

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Old   February 6, 2014, 17:11
Question Errors at boundaries between hex blocks
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So I've got this simulation of a cube on a plate in a flow that I've managed to get running up to this point, but when I look at the velocity contours I can see that there is something happening between the boundaries between the blocks. Does anyone have any idea whats going on here?

I'm using freestream boundaries on the inlet, outlet, top, and sides with a k-e turbulence model in simpleFoam.

I've tried to match the cell sizes at the boundaries but, it didn't seem to help at all. link to screen shot of contours


Here is my blockMeshDict:

(the hex block that's commented out would make up the cube itself)
Quote:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters .01;

vertices
(

(0 0 0) //0
(2 0 0) //1
(2 10 0) //2
(0 10 0) //3
(0 0 1) //4
(2 0 1) //5
(2 10 1) //6
(0 10 1) //7

(3 0 0) //8
(3 10 0) //9
(3 0 1) //10
(3 10 1) //11
(5 0 0) //12
(5 10 0) //13
(5 0 1) //14
(5 10 1) //15

(0 0 4) //16
(5 0 4) //17
(5 10 4) //18
(3 10 4) //19
(2 10 4) //20
(0 10 4) //21

(2 11 0) //22
(0 11 0) //23
(2 11 1) //24
(0 11 1) //25
(3 11 0) //26
(3 11 1) //27
(5 11 0) //28
(5 11 1) //29
(5 11 4) //30
(3 11 4) //31
(2 11 4) //32
(0 11 4) //33

(2 20 0) //34
(0 20 0) //35
(2 20 1) //36
(0 20 1) //37
(3 20 0) //38
(3 20 1) //39
(5 20 0) //40
(5 20 1) //41
(5 20 4) //42
(0 20 4) //43
);

blocks
(

hex (0 1 2 3 4 5 6 7) (10 20 20) simpleGrading (1 1 2) //0
hex (1 8 9 2 5 10 11 6) (10 20 20) simpleGrading (1 1 2) //1
hex (8 12 13 9 10 14 15 11) (10 20 20) simpleGrading (1 1 2) //2
hex (4 14 15 7 16 17 18 21) (30 20 20) simpleGrading (1 1 .5) //3

hex (3 2 22 23 7 6 24 25) (10 2 20) simpleGrading (1 1 2) //4
//hex (2 9 26 22 6 11 27 24) (10 2 20) simpleGrading (1 1 2) //5
hex (9 13 28 26 11 15 29 27) (10 2 20) simpleGrading (1 1 2) //6
hex (7 6 24 25 21 20 32 33) (10 2 20) simpleGrading (1 1 .5) //7
hex (6 11 27 24 20 19 31 32) (10 2 20) simpleGrading (1 1 .5) //8
hex (11 15 29 27 19 18 30 31) (10 2 20) simpleGrading (1 1 .5) //9

hex (23 22 34 35 25 24 36 37) (10 20 20) simpleGrading (1 1 2) //10
hex (22 26 38 34 24 27 39 36) (10 20 20) simpleGrading (1 1 2) //11
hex (26 28 40 38 27 29 41 39) (10 20 20) simpleGrading (1 1 2) //12
hex (25 29 41 37 33 30 42 43) (30 20 20) simpleGrading (1 1 .5) //13
);

edges
(
);

boundary
(
inlet
{
type patch;
faces
(
(1 5 4 0)
(1 8 10 5)
(8 12 14 10)
(4 14 17 16)
);
}
outlet
{
type patch;
faces
(
(35 37 36 34)
(34 36 39 38)
(38 39 41 40)
(37 43 42 41)
);
}
leftWall
{
type patch;
faces
(
(0 4 7 3)
(4 16 21 7)
(3 7 25 23)
(7 21 33 25)
(23 25 37 35)
(25 33 43 37)
);
}
rightWall
{
type patch;
faces
(
(13 15 14 12)
(15 18 17 14)
(28 29 15 13)
(29 30 18 15)
(40 41 29 28)
(41 42 30 29)
);
}
lowerWall
{
type wall;
faces
(
(0 3 2 1)
(1 2 9 8)
(8 9 13 12)
(3 23 22 2)
//(2 22 26 9)
(9 26 28 13)
(23 35 34 22)
(22 34 38 26)
(26 38 40 28)
);
}
upperWall
{
type patch;
faces
(
(17 18 21 16)
(20 32 33 21)
(19 31 32 20)
(18 30 31 19)
(30 42 43 33)
);
}
blockWall
{
type wall;
faces
(
(9 11 6 2)
(22 24 27 26)
(26 27 11 9)
(2 6 24 22)
(6 11 27 24)
);
}
);

mergePatchPairs
(
);


// ************************************************** *********************** //


and my U file.

Quote:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform (0 10 0);

boundaryField
{
inlet
{
type freestream;
freestreamValue uniform (0 10 0);
}
outlet
{
type freestream;
freestreamValue uniform (0 10 0);
}
leftWall
{
type freestream;
freestreamValue uniform (0 0 0);
}
rightWall
{
type freestream;
freestreamValue uniform (0 0 0);
}
lowerWall
{
type fixedValue;
value uniform (0 0 0);
}
upperWall
{
type freestream;
freestreamValue uniform (0 0 0);
}
blockWall
{
type fixedValue;
value uniform (0 0 0);
}

}

// ************************************************** *********************** //
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Old   February 10, 2014, 13:14
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One of the issues is that you have some faces that get lumped into defaultFaces and cause you some issues. I would use another tool to make your mesh so its harder to make mistakes like this.
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Old   February 19, 2014, 20:08
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Quote:
Originally Posted by reynoldsStress View Post
One of the issues is that you have some faces that get lumped into defaultFaces and cause you some issues. I would use another tool to make your mesh so its harder to make mistakes like this.
I started over with a new simulation. Now I do not have this problem with default faces but the original problem still remains.

If you're interested I started a new thread with more information.

simpleFoam 2D plate flow with obstacle errors between hex blocks
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