[Ladnam]

I have this 2D mesh of a circular cylinder in Starccm+ that works well with drag coefficient about 1.2 using laminar model.

Then I convert the mesh using ccm26ToFoam.

In Paraview the mesh looks like all the hexahedra have been split in two tetrahedra, but checkMesh tells me than only a few hexahedra have been converted into polyhedra. (I read a thread that paraview does not display the mesh correctly).

Then I use an icoFoam model that I know gives me nice oscillating drag coefficient around 1.2 using a mesh from blockMeshDict. On the converted mesh the drag coefficient is oscillating around 2-4, and the vortex shedding is not regular as for the blockMesh (see images).

So the question is what is wrong with the converted mesh?

The converted mesh is finer than the blockMesh so that shouldn't be a problem. Could it be because of the "hanging" nodes?


The output from ccm26ToFoam is:

/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.x |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
Build : 1.7.x-4bbf33160caf
Exec : ccm26ToFoam 3_res_bare_cylinder_OF_mesh.ccm
Date : Sep 14 2011
Time : 12:22:36
Host : glenn-VirtualBox
PID : 4417
Case : /home/glenn/OpenFOAM/glenn-1.7.1/run/tutorials/star_test
nProcs : 1
SigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time
Reading state 'default' (Default state)
nPoints:71830
bounding box-0.25 -0.25 0.01) (1 0.25 1.01)
nInternalFaces:70855
Read kCCMIOBoundaryFaces entry with 172 faces.
Read kCCMIOBoundaryFaces entry with 26 faces.
Read kCCMIOBoundaryFaces entry with 70584 faces.
Read kCCMIOBoundaryFaces entry with 26 faces.
Read kCCMIOBoundaryFaces entry with 128 faces.
patchSizes:5(172 26 70584 26 128)
patchStarts:5(70855 71027 71053 141637 141663)
nFaces:141791
For region:0 did not find ProstarRegionNumber entry. Assuming 0
region:0 ProstarRegionNumber:0 foamPatchStart:70855 size:172
For region:1 did not find ProstarRegionNumber entry. Assuming 1
region:1 ProstarRegionNumber:1 foamPatchStart:71027 size:26
For region:2 did not find ProstarRegionNumber entry. Assuming 2
region:2 ProstarRegionNumber:2 foamPatchStart:71053 size:70584
For region:3 did not find ProstarRegionNumber entry. Assuming 3
region:3 ProstarRegionNumber:3 foamPatchStart:141637 size:26
For region:4 did not find ProstarRegionNumber entry. Assuming 4
region:4 ProstarRegionNumber:4 foamPatchStart:141663 size:128
nCells:35292
nFaces:141791
nPatches:5
nInternalFaces:70855
Celltype:1 name:fluid
For region:0did not find ProstarRegionNumber entry. Assuming 0
Read patch:0 name:walls foamPatchTypes:wall
For region:1did not find ProstarRegionNumber entry. Assuming 1
Read patch:1 nameutlet foamPatchTypes:wall
For region:2did not find ProstarRegionNumber entry. Assuming 2
Read patch:2 name:sides foamPatchTypes:wall
For region:3did not find ProstarRegionNumber entry. Assuming 3
Read patch:3 name:inlet_ foamPatchTypes:wall
For region:4did not find ProstarRegionNumber entry. Assuming 4
Read patch:4 name:lowerUpper foamPatchTypes:wall
foamPatchNames:
5
(
walls
outlet
sides
inlet_
lowerUpper
)
foamOwner : min:284465 max:319756
foamNeighbour : min:-1 max:319755
foamCellType : min:1 max:1
Patch:walls start at:70855 size:172 end at:71027
Patchutlet start at:71027 size:26 end at:71053
Patch:sides start at:71053 size:70584 end at:141637
Patch:inlet_ start at:141637 size:26 end at:141663
Patch:lowerUpper start at:141663 size:128 end at:141791
Writing mesh to "/home/glenn/OpenFOAM/glenn-1.7.1/run/tutorials/star_test/constant/region0"...
Writing cellIds as volScalarField to "/home/glenn/OpenFOAM/glenn-1.7.1/run/tutorials/star_test/8.500000e+00/cellId"...
End


Checkmesh gives me this:
/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.x |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
Build : 1.7.x-4bbf33160caf
Exec : checkMesh
Date : Sep 14 2011
Time : 12:26:41
Host : glenn-VirtualBox
PID : 4427
Case : /home/glenn/OpenFOAM/glenn-1.7.1/run/tutorials/star_test
nProcs : 1
SigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time
Create polyMesh for time = 0
Time = 0
Mesh stats
points: 71830
internal points: 0
faces: 141791
internal faces: 70855
cells: 35292
boundary patches: 5
point zones: 0
face zones: 0
cell zones: 0
Overall number of cells of each type:
hexahedra: 34298
prisms: 64
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 930
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
walls 172 344 ok (non-closed singly connected)
outlet 26 54 ok (non-closed singly connected)
sides 70584 71830 ok (non-closed singly connected)
inlet 26 54 ok (non-closed singly connected)
lowerUpper 128 260 ok (non-closed singly connected)
Checking geometry...
Overall domain bounding box (-0.25 -0.25 0.01) (1 0.25 1.01)
Mesh (non-empty, non-wedge) directions (1 1 0)
Mesh (non-empty) directions (1 1 0)
All edges aligned with or perpendicular to non-empty directions.
Boundary openness (0 0 -5.87683e-20) OK.
Max cell openness = 1.35525e-16 OK.
Max aspect ratio = 28.5643 OK.
Minumum face area = 7.14757e-10. Maximum face area = 0.02. Face area magnitudes OK.
Min volume = 7.14757e-10. Max volume = 0.000400001. Total volume = 0.624294. Cell volumes OK.
Mesh non-orthogonality Max: 25.5315 average: 3.08919
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.333342 OK.
Mesh OK.
End



Here is the model.

controlDict:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.6 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application icoFoam;

startFrom latestTime;

startTime 0;

stopAt endTime;

endTime 20.0;

deltaT 2e-04;

writeControl adjustableRunTime;

writeInterval 1.0e-1;

purgeWrite 0;

writeFormat binary;

writePrecision 6;

writeCompression uncompressed;

timeFormat scientific;

timePrecision 6;

runTimeModifiable yes;

adjustTimeStep yes;

maxCo 0.5;

maxDeltaT 2.0e-3;

functions
{
probes
{
type probes;
functionObjectLibs ("libsampling.so");
enabled true;
outputControl timeStep;
outputInterval 1;
probeLocations
(
( 0.05 0.0 0.002 )
( 0.05 0.01 0.002 )
( 0.05 0.01 0.002 )
( 0.05 0.01 0.002 )
( 0.05 0.01 0.002 )
( 0.05 0.01 0.002 )
( 0.05 0.01 0.002 )
);

fields
(
p
);
}

forces
{
type forceCoeffs;
functionObjectLibs ( "libforces.so" );
outputControl timeStep;
outputInterval 1;
patches
(
walls
);
directForceDensity no;

pName p;
UName U;
rhoName rhoInf;
//log true;
rhoInf 994.5;
CofR ( 0 0 0 );
liftDir ( 0 1 0 );
dragDir ( 1 0 0 );
pitchAxis ( 0 0 1 );
magUInf 0.54;
lRef 0.04;
Aref 0.0157;
Aref1 0.004;
rhoRef 994.5;
}

fieldAverage1
{
type fieldAverage;
functionObjectLibs ("libfieldFunctionObjects.so");
enabled true;
outputControl outputTime;
fields
(
U
{
mean on;
prime2Mean on;
base time;
}

p
{
mean on;
prime2Mean on;
base time;
}
);
}
}


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

fvSceme:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.1 |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
ddtSchemes
{
default Euler;
}
gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
}
divSchemes
{
default none;
div(phi,U) Gauss limitedLinearV 1;
}
laplacianSchemes
{
default none;
laplacian(nu,U) Gauss linear corrected;
laplacian((1|A(U)),p) Gauss linear corrected;
}
interpolationSchemes
{
default linear;
interpolate(HbyA) linear;
}
snGradSchemes
{
default corrected;
}
fluxRequired
{
default no;
p ;
}

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

fvSolution:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.1 |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
solvers
{
p
{
solver PCG;
preconditioner DIC;
tolerance 1e-06;
relTol 0;
}
U
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0;
}
}
PISO
{
nCorrectors 2;
nNonOrthogonalCorrectors 4;
}

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

0/p:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.6 |
| \\ / A nd | Web: http://www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 2 -2 0 0 0 0];
internalField uniform 0;
boundaryField
{
inlet
{
type zeroGradient;
}
outlet
{
type fixedValue;
value uniform 0;
}
walls
{
type zeroGradient;
}
sides
{
type empty;
}
lowerUpper
{
type zeroGradient;
}
}
// ************************************************** *********************** //

0/U:


/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.6 |
| \\ / A nd | Web: http://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 (0.54 0 0);

boundaryField
{
inlet
{
type turbulentInlet;
referenceField uniform (0.54 0 0);
fluctuationScale (0.0 0.02 0.0);
value uniform (0.54 0 0);
}

inlet2
{
type fixedValue;
value uniform (0.54 0 0);
}

outlet
{
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);
}

walls
{
type fixedValue;
value uniform ( 0 0 0 );
}

sides
{
type empty;
}

lowerUpper
{
type slip;
}
}

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

turbulenceProperties:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.1 |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "constant";
object turbulenceProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
simulationType laminar;
// ************************************************** *********************** //