[mqsim]

Hi, foamers,

I'd like your help to understand why SHM does not want to add layers in my case.

I think the reason is because I want a boundary layer thickness of 1.3e-5 m. I could manage to have a thicker boundary layer but it would not be worth it in my case since I want an accurate stagnation pressure and an accurate lift coefficient.

Shrinking and layer addition phase
----------------------------------
Using mesh parameters
{
maxNonOrtho 65;
maxBoundarySkewness 20;
maxInternalSkewness 4;
maxConcave 80;
minVol 1e-013;
minTetQuality 1e-015;
minArea -1;
minTwist 0.02;
minDeterminant 1e-005;
minFaceWeight 0.02;
minVolRatio 0.01;
minTriangleTwist -1;
nSmoothScale 4;
errorReduction 0.75;
}

Merging all faces of a cell
---------------------------
- which are on the same patch
- which make an angle < 180 degrees
(cos:-1)
- as long as the resulting face doesn't become concave by more than 90 degrees
(0=straight, 180=fully concave)
Merging 0 sets of faces.
No faces merged ...
Merging all points on surface that
- are used by only two boundary faces and
- make an angle with a cosine of more than -1.
No straight edges simplified and no points removed ...
Checking mesh manifoldness ...
Checking initial mesh ...
Checking faces in error :
non-orthogonality > 65 degrees : 0
faces with face pyramid volume < 1e-013 : 0
faces with face-decomposition tet quality < 1e-015 : 0
faces with concavity > 80 degrees : 0
faces with skewness > 4 (internal) or 20 (boundary) : 0
faces with interpolation weights (0..1) < 0.02 : 0
faces with volume ratio of neighbour cells < 0.01 : 0
faces with face twist < 0.02 : 0
faces on cells with determinant < 1e-005 : 0
Detected 0 illegal faces (concave, zero area or negative cell pyramid volume)
Adding in total 0 inter-processor patches to handle extrusion of non-manifold processor boundaries.
Handling points with inconsistent layer specification ...
Handling non-manifold points ...
Checking patch manifoldness ...
Outside of local patch is multiply connected across edges or points at 0 points.
Set displacement to zero for all 0 non-manifold points
Handling feature edges ...
patch faces layers avg thickness[m]
near-wall overall
----- ----- ------ --------- -------
motorBike 77024 3 1.3e-005 3.9e-005
Selecting externalDisplacementMeshMover displacementMedialAxis
displacementMedialAxis : Calculating distance to Medial Axis ...
displacementMedialAxis : Smoothing normals ...
Iteration 0 residual 0.0028854
displacementMedialAxis : Inserting points on patch frontAndBack if angle to nearest layer patch > 30 degrees.
displacementMedialAxis : Inserting points on patch inlet if angle to nearest layer patch > 30 degrees.
displacementMedialAxis : Inserting points on patch outlet if angle to nearest layer patch > 30 degrees.
displacementMedialAxis : Inserting points on patch lowerWall if angle to nearest layer patch > 30 degrees.
displacementMedialAxis : Inserting points on patch upperWall if angle to nearest layer patch > 30 degrees.
displacementMedialAxis : Smoothing normals in interior ...
Iteration 0 residual 0.00915374
Layer addition iteration 0
--------------------------
Determining displacement for added points according to pointNormal ...
Detected 0 points with point normal pointing through faces.
Reset displacement at 0 points to average of surrounding points.
displacementMedialAxis : Smoothing using Medial Axis ...
displacementMedialAxis : Reducing layer thickness at 0 nodes where thickness to medial axis distance is large
displacementMedialAxis : Removing isolated regions ...
displacementMedialAxis : Number of isolated points extrusion stopped : 0
displacementMedialAxis : Smoothing field ...
Iteration 0 residual 4.32263e-011
displacementMedialAxis : Moving mesh ...
displacementMedialAxis : Iteration 0
Moving mesh using displacement scaling : min:1 max:1
Checking faces in error :
non-orthogonality > 65 degrees : 0
faces with face pyramid volume < 1e-013 : 0
faces with face-decomposition tet quality < 1e-015 : 0
faces with concavity > 80 degrees : 0
faces with skewness > 4 (internal) or 20 (boundary) : 0
faces with interpolation weights (0..1) < 0.02 : 0
faces with volume ratio of neighbour cells < 0.01 : 0
faces with face twist < 0.02 : 0
faces on cells with determinant < 1e-005 : 0
displacementMedialAxis : Successfully moved mesh
displacementMedialAxis : Finished moving mesh ...
truncateDisplacement : Unextruded 0 faces due to non-consecutive vertices being extruded.
truncateDisplacement : Unextruded 0 faces due to stringed edges with inconsistent extrusion.
Setting up information for layer truncation ...
[5] processorPolyPatch::calcGeometry : Writing my 2754 faces to OBJ file "C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor5/procBoundary5to1_faces.obj"
[1] processorPolyPatch::calcGeometry : Writing my 2754 faces to OBJ file "C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor1/procBoundary1to5_faces.obj"
[6] processorPolyPatch::calcGeometry : Writing my 10713 faces to OBJ file "C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor6/procBoundary6to5_faces.obj"
[2] processorPolyPatch::calcGeometry : Writing my 10840 faces to OBJ file "C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor2/procBoundary2to1_faces.obj"
[0] processorPolyPatch::calcGeometry : Writing my 4897 faces to OBJ file "C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor0/procBoundary0to4_faces.obj"
[4] processorPolyPatch::calcGeometry : Writing my 4897 faces to OBJ file "C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor4/procBoundary4to0_faces.obj"
[1] processorPolyPatch::calcGeometry : Dumping cell centre lines between corresponding face centres to OBJ file"C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor1/procBoundary1to5_faceCentresConnections.obj"
[5] processorPolyPatch::calcGeometry : Dumping cell centre lines between corresponding face centres to OBJ file"C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor5/procBoundary5to1_faceCentresConnections.obj"
[0] processorPolyPatch::calcGeometry : Dumping cell centre lines between corresponding face centres to OBJ file"C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor0/procBoundary0to4_faceCentresConnections.obj"
[4] processorPolyPatch::calcGeometry : Dumping cell centre lines between corresponding face centres to OBJ file"C:/OpenFOAM/User-2.3.x/run/smooth_hangar/rho/processor4/procBoundary4to0_faceCentresConnections.obj"
[5]
[5]
[5] --> FOAM FATAL ERROR:
[5] face 2553 area does not match neighbour by 56.4532% -- possible face ordering problem.
patchrocBoundary5to1 my area:3.23586e-006 neighbour area:5.78102e-006 matching tolerance:1.54907e-006
Mesh face:1676775 vertices:4((-13.4243 -0.312502 23.4247) (-13.639 -0.312502 23.2988) (-13.639 -0.312502 23.2988) (-13.4243 -0.312502 23.4247))
If you are certain your matching is correct you can increase the 'matchTolerance' setting in the patch dictionary in the boundary file.
Rerun with processor debug flag set for more information.
[5]
[5] From function processorPolyPatch::calcGeometry()
[5] in file meshes/polyMesh/polyPatches/constraint/processor/processorPolyPatch.C at line 243.
[5]
FOAM parallel run exiting
[5]
job aborted:
[ranks] message
[0-4] terminated
[5] application aborted
aborting MPI_COMM_WORLD (comm=0x44000000), error 1, comm rank 5
[6-7] terminated
---- error analysis -----
[5] on DESKTOP-RITOP2J
snappyHexMesh aborted the job. abort code 1
---- error analysis -----

As you can see in my SHM log file, the layer addition crashes after the first iteration. I do not understand the error message.

My geometry is basically a half cylinder with two quarter of a sphere at each end so the surface is smooth. With a smooth surface I did not expect to have so much difficulties to create boundary layers...

Regards,

mqsim

[ozi]

Originally Posted by mqsim

Hi, foamers,

I'd like your help to understand why SHM does not want to add layers in my case.

I think the reason is because I want a boundary layer thickness of 1.3e-5 m. I could manage to have a thicker boundary layer but it would not be worth it in my case since I want an accurate stagnation pressure and an accurate lift coefficient.

As you can see in my SHM log file, the layer addition crashes after the first iteration. I do not understand the error message.

My geometry is basically a half cylinder with two quarter of a sphere at each end so the surface is smooth. With a smooth surface I did not expect to have so much difficulties to create boundary layers...

Regards,

mqsim

The post is too old but I currently have the same problem. Due to y+<=1 requirement of k-w SST I decrease the first layer thickness drastically. The outcome is nearly all the cell in the first layer can not meet the minDeterminant criteria and addLayers phase of the snappyHexMesh crashes due to that problem. Is there a solution for that.