CFD Online Discussion Forums - [snappyHexMesh] autoPatch for SnappyHexMesh

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autoPatch for SnappyHexMesh

Hello friends
How do we find autoPatch angle for snappyHexMesh
upto 0-90 angle it produces 319 patches
and above 90 it produces only 1 patches
it's very difficult add layer in further steps

snappyHexMesh for tee-junction

https://sites.google.com/site/snappy.../cylinder-case

Hello ,

I am doing mesh for T-Junction using snappyHexMesh using above tutorial for layer addition.
The autoPatch utility mentioned in this tutorial is not working properly for t-junction and number patches exceeds or lessen than required patches
what should be the problem???

Quick question: Which OpenFOAM version are you using?

OpenFOAM 2.3.1

even same problem for elbow..

but I can easily add layer for reducer and for annuals geometry

Quick answer: You can use regular expressions in "snappyHexMeshDict" for selecting the patch names. For example, this is shown here: https://github.com/OpenFOAM/OpenFOAM...xMeshDict#L219 - which you also have in your installation, whose path is indicated by the following command:

Code:

echo $FOAM_TUTORIALS/incompressible/simpleFoam/motorBike/system/snappyHexMeshDict

The example in this file is this:

Code:

    layers

    {

        "(lowerWall|motorBike).*"

        {

            nSurfaceLayers 1;

        }

    }

Which equates to:

Code:

    layers

    {

        "lowerWall.*"

        {

            nSurfaceLayers 1;

        }

         "motorBike.*"

        {

            nSurfaceLayers 1;

        }

    }

and the ".*" means that any character after that is also included. For more details about regular expressions, use an online search engine such as Google for the following sentence:

Code:

linux introduction to regular expressions

while using autoPatch utility, when I use angle 0-90 it generate around 319 patches
on the other hand when I use angle >90 it generate only 1 patches so it's becomming complecated for layer additon as well as giving boundary condition.

for T-junction the number of patches should be generate is equal to five

should I submite case and stl

Thanks and Regards

Harshawardhan

Quick answer: At least the STL file would come in handy to test and diagnose. It's possible that the STL file is not properly sorted or something like that... or maybe it's the numerical precision of the vertices...

What does surfaceCheck give you?

Code:

surfaceCheck filename.stl

Reading surface from "wall_1.stl" ...

Statistics:
Triangles : 86
Vertices : 84
Bounding Box : (-127 -12.7 -12.5999) (127 12.7 12.7)

Region Size
------ ----
solid 86

Surface has no illegal triangles.

Triangle quality (equilateral=1, collapsed=0):
0 .. 0.05 : 1
0.05 .. 0.1 : 0
0.1 .. 0.15 : 0
0.15 .. 0.2 : 0
0.2 .. 0.25 : 0
0.25 .. 0.3 : 0
0.3 .. 0.35 : 0
0.35 .. 0.4 : 0
0.4 .. 0.45 : 0
0.45 .. 0.5 : 0
0.5 .. 0.55 : 0
0.55 .. 0.6 : 0
0.6 .. 0.65 : 0
0.65 .. 0.7 : 0
0.7 .. 0.75 : 0
0.75 .. 0.8 : 0
0.8 .. 0.85 : 0
0.85 .. 0.9 : 0
0.9 .. 0.95 : 0
0.95 .. 1 : 0

min 2.05166e-05 for triangle 62
max 0.0428367 for triangle 27

Edges:
min 1.35491 for edge 113 points (-12.7 3.1106e-15 12.7)(-12.6279 1.35107 12.6279)
max 254.02 for edge 5 points (127 -7.46487 -10.2745)(-127 -9.78552 -8.09529)

Checking for points less than 1e-6 of bounding box ((254 25.4 25.2999) metre) apart.
Found 0 nearby points.

Surface is not closed since not all edges connected to two faces:
connected to one face : 84
connected to >2 faces : 0
Conflicting face labels:84
Dumping conflicting face labels to "problemFaces"
Paste this into the input for surfaceSubset

Number of unconnected parts : 1

Number of zones (connected area with consistent normal) : 1

End