[Aadhavan]

Dear Experts,
I am using gambit for meshing, my geometry is passage of a fan, not tip clearance. The fan has 8 blades, but I am using one passage. Its has 4 periodic faces.

I have a serious problem in periodic BC, I have no clue how to solve this. I am looking for some one help, please help me to solve this problem.

(just for information, I am using OpenFoam)

I checked the Mesh in fluent the check mesh has failed.
The problem I noticed is as follows,

while reading the mesh:

olr
Skipping zone olr_shadow (not referenced by grid).
ilr
Skipping zone ilr_shadow (not referenced by grid).

while checking the Mesh:

WARNING: Periodic face 26703 in zone 6 is not pointing to the right shadow.
WARNING: Periodic face 26704 in zone 6 is not pointing to the right shadow.
WARNING: Periodic face 26705 in zone 6 is not pointing to the right shadow.
WARNING: Periodic face 26706 in zone 6 is not pointing to the right shadow.
WARNING: Periodic face 26707 in zone 6 is not pointing to the right shadow.
WARNING: Periodic face 26708 in zone 6 is not pointing to the right shadow.
WARNING: Periodic face 26709 in zone 6 is not pointing to the right shadow.
WARNING: Periodic face 26710 in zone 6 is not pointing to the right shadow.
Periodic zone 6: x-translation: min (m) = -5.505108e-01, max (m) = -2.299646e-01
y-translation: min (m) = 4.896301e-02, max (m) = 2.115150e-01
z-translation: min (m) = -1.287460e-05, max (m) = 4.715398e-04
Done.

WARNING: Mesh check failed.

I have attached the picture of the geometry, please have look.

please help me solve this problem,

Thanks in advance,

Aadhavan.

[-mAx-]

http://www.cfd-online.com/Forums/flu...ht-shadow.html

Any warning or error while exporting the mesh from Gambit, because faces which are matching with periodicity have to be linked.

The warnings you get are from Fluent. Maybe it is because you didn t set the periodicity in Fluent. I would try to import and set the case in OF.
Do the check mesh in OF:> checkMesh

[Aadhavan]

Hi mAx,
Thanks for the reply, I am using OF-2.0.1. in OF-2.0.1 check mesh not giving any complaint.

my colleague using OF-2.1.1, we did the check mesh in that.
I am getting the result as follows,

******
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 956202
faces: 2747240
internal faces: 2628760
cells: 896000
boundary patches: 12
point zones: 0
face zones: 1
cell zones: 2

Overall number of cells of each type:
hexahedra: 896000
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 0

Checking topology...
Boundary definition OK.
Cell to face addressing 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
inlet 1000 1066 ok (non-closed singly connected)
top0 5750 6006 ok (non-closed singly connected)
center0 5750 6006 ok (non-closed singly connected)
top1 400 442 ok (non-closed singly connected)
fan 1680 1802 ok (non-closed singly connected)
center1 16250 16926 ok (non-closed singly connected)
top2 16250 16926 ok (non-closed singly connected)
outlet 1000 1066 ok (non-closed singly connected)
ILR0 9200 9471 ok (non-closed singly connected)
ILR1 9200 9471 ok (non-closed singly connected)
OLR0 26000 26691 ok (non-closed singly connected)
OLR1 26000 26691 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-3.06977 -0.559055 0.177709) (7.58764 0.036331 0.771368)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-2.2403e-16 9.94107e-17 -1.10234e-15) OK.
Max cell openness = 3.09843e-16 OK.
Max aspect ratio = 3.28903 OK.
Minumum face area = 6.00795e-05. Maximum face area = 0.000328932. Face area magnitudes OK.
Min volume = 5.79624e-07. Max volume = 3.77792e-06. Total volume = 2.07671. Cell volumes OK.
Mesh non-orthogonality Max: 54.5448 average: 7.72232
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 1.06841 OK.
**Error in coupled point location: 26000 faces have their 0th vertex not opposite their coupled equivalent. Average mismatch 0.00876061.
<<Writing 26000 faces with incorrectly matched 0th vertex to set coupledFaces

Failed 1 mesh checks.

End

I agree this error, while exporting the .msh file to OF, I have noticed the error as follows,
I have posted the error in the other thread, (the information is here)

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Dimension of grid: 3
Number of points: 3261384
PointGroup: 1 start: 0 end: 3261383. Reading points...done.
Number of faces: 9496429
FaceGroup: 3 start: 0 end: 26039. Reading mixed faces...done.
FaceGroup: 4 start: 26040 end: 52079. Reading mixed faces...done.
--> FOAM Warning : Found unknown block of type: "18"
on line 3313480
FaceGroup: 5 start: 52080 end: 113583. Reading mixed faces...done.
FaceGroup: 6 start: 113584 end: 175087. Reading mixed faces...done.
--> FOAM Warning : Found unknown block of type: "18"
on line 3462534
FaceGroup: 7 start: 175088 end: 177257. Reading mixed faces...done.
FaceGroup: 8 start: 177258 end: 211977. Reading mixed faces...done.
FaceGroup: 9 start: 211978 end: 212852. Reading mixed faces...done.
FaceGroup: 10 start: 212853 end: 227552. Reading mixed faces...done.
FaceGroup: 11 start: 227553 end: 262272. Reading mixed faces...done.
FaceGroup: 12 start: 262273 end: 266247. Reading mixed faces...done.
FaceGroup: 13 start: 266248 end: 280947. Reading mixed faces...done.
FaceGroup: 14 start: 280948 end: 283117. Reading mixed faces...done.
FaceGroup: 16 start: 283118 end: 9496428. Reading mixed faces...done.
Number of cells: 3118290
CellGroup: 2 start: 0 end: 3118289 type: 1
Zone: 2 name: fluid type: fluid. Reading zone data...done.
Zone: 3 name: ILR_shadow type: shadow. Reading zone data...done.
Zone: 4 name: ILR type: periodic. Reading zone data...done.
Zone: 5 name: OLR_shadow type: shadow. Reading zone data...done.
Zone: 6 name: OLR type: periodic. Reading zone data...done.
Zone: 7 name: outlet type: pressure-outlet. Reading zone data...done.
Zone: 8 name: top2 type: wall. Reading zone data...done.
Zone: 9 name: top1 type: wall. Reading zone data...done.
Zone: 10 name: top0 type: wall. Reading zone data...done.
Zone: 11 name: center1 type: wall. Reading zone data...done.
Zone: 12 name: fan type: wall. Reading zone data...done.
Zone: 13 name: center0 type: wall. Reading zone data...done.
Zone: 14 name: inlet type: velocity-inlet. Reading zone data...done.
Zone: 16 name: default-interior type: interior. Reading zone data...done.

FINISHED LEXING

Creating patch 0 for zone: 3 name: ILR_shadow type: shadow
Adding polyPatch for unknown Fluent type shadow
Creating patch 1 for zone: 4 name: ILR type: periodic
Adding polyPatch for unknown Fluent type periodic
Creating patch 2 for zone: 5 name: OLR_shadow type: shadow
Adding polyPatch for unknown Fluent type shadow
Creating patch 3 for zone: 6 name: OLR type: periodic
Adding polyPatch for unknown Fluent type periodic
Creating patch 4 for zone: 7 name: outlet type: pressure-outlet
Creating patch 5 for zone: 8 name: top2 type: wall
Creating patch 6 for zone: 9 name: top1 type: wall
Creating patch 7 for zone: 10 name: top0 type: wall
Creating patch 8 for zone: 11 name: center1 type: wall
Creating patch 9 for zone: 12 name: fan type: wall
Creating patch 10 for zone: 13 name: center0 type: wall
Creating patch 11 for zone: 14 name: inlet type: velocity-inlet
Creating cellZone 0 name: fluid type: fluid
Creating faceZone 0 name: default-interior type: interior
faceZone from Fluent indices: 283118 to: 9496428 type: interior
patch 0 from Fluent indices: 0 to: 26039 type: shadow
patch 1 from Fluent indices: 26040 to: 52079 type: periodic
patch 2 from Fluent indices: 52080 to: 113583 type: shadow
patch 3 from Fluent indices: 113584 to: 175087 type: periodic
patch 4 from Fluent indices: 175088 to: 177257 type: pressure-outlet
patch 5 from Fluent indices: 177258 to: 211977 type: wall
patch 6 from Fluent indices: 211978 to: 212852 type: wall
patch 7 from Fluent indices: 212853 to: 227552 type: wall
patch 8 from Fluent indices: 227553 to: 262272 type: wall
patch 9 from Fluent indices: 262273 to: 266247 type: wall
patch 10 from Fluent indices: 266248 to: 280947 type: wall
patch 11 from Fluent indices: 280948 to: 283117 type: velocity-inlet

Writing mesh to "/home/cerecam/OpenFOAM/OpenFOAM-2.0.1/tutorials/incompressible/MRFSimpleFoam/meshCheck/constant/region0"

End

2) while executing the createPatch, I am facing the strange error as follows,
Create time

Reading createPatchDict.

Create polyMesh for time = 0

Adding new patch ILR0 as patch 12 from
{
type cyclic;
neighbourPatch ILR1;
transform rotational;
rotationAxis ( 1 0 0 );
rotationCentre ( 0 0 0 );
matchTolerance 0.001;
}

Adding new patch ILR1 as patch 13 from
{
type cyclic;
neighbourPatch ILR0;
transform rotational;
rotationAxis ( 1 0 0 );
rotationCentre ( 0 0 0 );
matchTolerance 0.001;
}

Adding new patch OLR0 as patch 14 from
{
type cyclic;
neighbourPatch OLR1;
transform rotational;
rotationAxis ( 1 0 0 );
rotationCentre ( 0 0 0 );
matchTolerance 0.001;
}

Adding new patch OLR1 as patch 15 from
{
type cyclic;
neighbourPatch OLR0;
transform rotational;
rotationAxis ( 1 0 0 );
rotationCentre ( 0 0 0 );
matchTolerance 0.001;
}


Moving faces from patch ILR_shadow to patch 12
Moving faces from patch ILR to patch 13
Moving faces from patch OLR_shadow to patch 14
Moving faces from patch OLR to patch 15

Doing topology modification to order faces.

Cannot find point in pts1 matching point 32 coord-0.0736604 0.0160827 0.550332) in pts0 when using tolerance 5.23475e-06
Searching started from:1195 in pts1
Compared coord-0.115922 0.0165229 0.542977) with difference to point 0.0428991
Compared coord-0.0736604 0.0160827 0.550327) with difference to point 5.27824e-06
Cannot find point in pts1 matching point 94 coord-0.0806652 0.0160937 0.550398) in pts0 when using tolerance 5.23717e-06
Searching started from:1205 in pts1
Compared coord-0.345983 0.0237373 0.435209) with difference to point 0.289345
Compared coord-0.0806652 0.0160936 0.550393) with difference to point 5.27625e-06
Cannot find point in pts1 matching point 156 coord-0.0876774 0.0161047 0.550465) in pts0 when using tolerance 5.23967e-06

--> FOAM FATAL ERROR:
face 0 area does not match neighbour by 0.118326% -- possible face ordering problem.
patch:OLR0 my area:4.88022e-05 neighbour area:4.886e-05 matching tolerance:0.001
Mesh face:9373421 fc0.0913107 -0.258775 0.180536)
Neighbour fc0.0908193 -0.0562288 0.310645)
If you are certain your matching is correct you can increase the 'matchTolerance' setting in the patch dictionary in the boundary file.
Rerun with cyclic debug flag set for more information.

From function cyclicPolyPatch::calcTransforms()
in file meshes/polyMesh/polyPatches/constraint/cyclic/cyclicPolyPatch.C at line 220.

FOAM exiting


I am able to create patches by increasing the matchTolerance 0.01

but the checkMesh failed.
CheckMesh error message:

**Error in coupled point location: 26000 faces have their 0th vertex not opposite their coupled equivalent. Average mismatch 0.00876061.
<<Writing 26000 faces with incorrectly matched 0th vertex to set coupledFaces

please help me

Thanks in advance,
Aadhavan

[-mAx-]

I am also not experienced with periodicity in OF, but try to unset periodics bc in gambit, and reimport in OF.
Then checkMesh. (just to be sure that your problem, is just on periodicity and not a general mesh issue)

[Aadhavan]

Hi mAx,
thanks for your suggestion, I followed your suggestion.
instead of periodic BC I have given wall BC. while converting to OF there is no error, I feel it is fine.

but with periodic BC, while executing fluent3DMeshToFoam step itself I am getting the error as follows:

Create time

Dimension of grid: 3
Number of points: 2610741
PointGroup: 1 start: 0 end: 2610740. Reading points...done.
Number of faces: 7649900
FaceGroup: 3 start: 0 end: 13999. Reading mixed faces...done.
FaceGroup: 4 start: 14000 end: 27999. Reading mixed faces...done.
--> FOAM Warning : Found unknown block of type: "18"
on line 2638757
FaceGroup: 5 start: 28000 end: 60899. Reading mixed faces...done.
FaceGroup: 6 start: 60900 end: 93799. Reading mixed faces...done.
--> FOAM Warning : Found unknown block of type: "18"
on line 2718563
FaceGroup: 7 start: 93800 end: 97299. Reading mixed faces...done.

It seems the problem is in the periodic BC, can you please give me some idea how to solve this error.

Thanks,
Aadhavan

[-mAx-]

As I said I don't have any experience with cyclic BC in OF
Maybe you should move your thread to OF-forum

[macchio]

Greetings good people of cfd!
I had the same problem with perioidic conditions while simulating 2-d flow of water in kaplan turbine. I had three periodic conditions which all worked well in gambit but periodic BC 1 had this exact error in mesh check in fluent. I went back to gambit to check it, and the only thing that differentiated periodic BC 1 from other two was the fact that the two straight edges comprising it POINTED IN DIFFERENT DIRECTIONS. I've deleted the face mesh, changed the direction of one of the edges,remade the linking, remade the mesh, remade the conditions, loaded to fluent and everything worked like a charm.

Hope this helps... cheers!