[ihu945]

Hello, guys.
I am a beginner of openfoam
I am trying some basic simulations, and I faced a weird situation now.

error3.jpg
error1.jpg
error2.jpg

These are all same result.
Reynolds number is hundred, and these are velocity field.
First one is from paraFoam -block, and others are just from paraFoam.
I really have no idea why the velocity looks like that.

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  3.0.1                                |
|   \\  /    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 0 0);

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform (1 0 0);
    }

    outlet
    {
        type            zeroGradient;
    }
    
    top
    {
    type        zeroGradient;
    }

    bottom
    {
    type        fixedValue;
    value        uniform (0 0 0);
    
    }
    
    cylinder
    {
    type        fixedValue;
    value        uniform (0 0 0);
    }
    
    sides
    {
        type            empty;
    }
}

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

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1;

vertices
(
    (-10 -1.5 0)                
    (-1.0607 -1.5 0)
    (1.0607 -1.5 0)    
    ( 10 -1.5 0)            
    (30 -1.5 0)    
    (-0.3536 -0.3536 0)        
    ( 0.3536 -0.3536 0)        
    (-0.3536  0.3536 0)        
    ( 0.3536  0.3536 0)
    (-1.0607 1.0607 0)
    (1.0607 1.0607 0)
    (-10 5 0)            
    ( 10 5 0)            
    (30 5 0)            
    
    (-10 -1.5 1)                
    (-1.0607 -1.5 1)
    (1.0607 -1.5 1)    
    ( 10 -1.5 1)            
    (30 -1.5 1)    
    (-0.3536 -0.3536 1)        
    ( 0.3536 -0.3536 1)        
    (-0.3536  0.3536 1)        
    ( 0.3536  0.3536 1)
    (-1.0607 1.0607 1)
    (1.0607 1.0607 1)
    (-10 5 1)            
    ( 10 5 1)            
    (30 5 1)    
    
);

blocks
(
    hex (0 1 9 11 14 15 23 25) (50 50 1) simpleGrading (1 1 1)
    hex (2 3 12 10 16 17 26 24) (50 50 1) simpleGrading (1 1 1)
    hex (10 12 11 9 24 26 25 23) (50 50 1) simpleGrading (1 1 1)
    hex (1 5 7 9 15 19 21 23) (50 50 1) simpleGrading (1 1 1)
    hex (5 1 2 6 19 15 16 20) (50 50 1) simpleGrading (1 1 1)
    hex (6 2 10 8 20 16 24 22) (50 50 1) simpleGrading (1 1 1)
    hex (9 7 8 10 23 21 22 24) (50 50 1) simpleGrading (1 1 1)
    hex (3 4 13 12 17 18 27 26) (50 50 1) simpleGrading (1 1 1)
);

edges
(
   arc 5 7 (-0.5 0 0)
   arc 19 21 (-0.5 0 1)
   arc 6 8 (0.5 0 0)
   arc 20 22 (0.5 0 1)
   arc 7 8 (0 0.5 0)
   arc 21 22 (0 0.5 1)
   arc 5 6 (0 -0.5 0)
   arc 19 20(0 -0.5 1)
   arc 9 10 (0 1.5 0)
   arc 23 24 (0 1.5 1)
);

boundary
(
    inlet
    {
        type wall;
        faces
        (
            (25 11 0 14)
        );
    }
    
    outlet
    {
        type wall;
        faces
        (
            (13 27 18 4)
        );
    }
    
    top
    {
        type wall;
        faces
        (
            (12 11 25 26)
        (13 12 26 27)
        );
    }
    
    bottom
    {
        type wall;
        faces
        (
            (0 1 15 14)
        (1 2 16 15)
        (2 3 17 16)
        (3 4 18 17)
        );
    }
    
    cylinder
    {
        type wall;
        faces
        (
            (7 8 22 21)
            (22 8 6 20)
        (6 5 19 20)
        (5 7 21 19)        
    );
    }
    
    sides
    {
        type empty;
        faces
        (
            (11 12 10 9)
        (0 11 9 1)
        (2 10 12 3)
        (9 10 8 7)
        (1 9 7 5)
        (1 5 6 2)
        (6 8 10 2)
        (12 13 4 3)
        
        (25 23 24 26)
        (14 15 23 25)
        (16 17 26 24)
        (23 21 22 24)
        (15 19 21 23)
        (15 16 20 19)
        (20 16 24 22)
        (26 17 18 27)

        );
    }
);

mergePatchPairs
(
);

And, these are my initial condition of velocity and blockmeshdict.

Please, help me.
Thank you.

[linnemann]

Hi

Your cells are approximately angled 20-30° to the general flow direction in those zones.
That is not good from a mathematical point of view.

So you can either try other fvScheme settings to find a better suited setup or you can change the mesh. The last method is most likely the best option to take.

I would make the mesh like so.