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-   -   ways to create cellZones and faceZones (http://www.cfd-online.com/Forums/openfoam-meshing/105268-ways-create-cellzones-facezones.html)

kalyangoparaju July 26, 2012 10:36

ways to create cellZones and faceZones
 
5 Attachment(s)
Friends,

I've been playing around a lot with the creation of cellZones and faceZones and here is what I have to report !

Till now I have found 3 ways to do it. ( I am sure there are more)

1. To use setSet utility and cellZonesSet and faceZoneSet commands.
This works amazingly well and creates the zones. A small problem can arrise if you are trying to set zones for an internal flow case and at the center of your geometry you have level 0 cells. These cells are not properly broken down and hence your zone is not exactly what you think it is. The work around for this is to just have a higher resolution where there are level 0 cells.

Attachment 14782

2. Using snappyHexMesh to create the zones.
Even this method does a very good job but somehow, atleast for my geometry, I see stitched kinda break where the cellZones starts and ends and where there is a faceZone. I have a strong feeling this might be because of the stl quality but I am quite sure that it is pretty decent.

Here are the pics.

Attachment 14778

Attachment 14779

The break in the second picture is where I have a faceZone.



3. This is something which I stumbled upon unintentionally ( i am so glad I did) - Using setSet utility but for blockMesh.
In method-1, the setSet command is used for the latest time step created by snappyHexMesh or for the mesh imported from other places but if you want to mesh in snappy and you want to create zones and don't want to see the problems which you saw in method-1 or method-2, the best way to do this is to actually create the cell and faceZones for the blockMesh. I accidentally did this when I forgot to use the -latestTime tag for method-1. This seems to be the best I saw. It doesn't have the breaks from method-2 nor does it have the extra cells from method-1

Here are the pics.

Attachment 14780

Attachment 14781




I just wanted to share this info with all of you and see if you have any suggestions.

There are 2 things which perplex me in the meshes which I uploaded. The geometry just infront of the cylindrical section has a lot of polyhedral cells. It is a very very simple geometry ( diverging section) and I am really surprised that snappy is not able to put hex cells there. Also, the featureEdge setting is put to 160 so that it captures all the curves ( as a matter of fact it does) but unfortunately, the circles aren't really round ! I have the nFeatureSnapIter at 10. Is there anything else I can do to improve this?

Sorry for the long post. Hope this info helps :-)

Kalyan

hfs November 12, 2012 15:22

Thank you for sharing your experience

Could you please let me know how can I execute setSet to get the faceZone without using snappyHexMesh?

I have an STL file and want to create the faceZone according to it .. how can I do it?

I don't know what to choose between all of those:

Code:

boundaryToFace
boxToCell
boxToFace
boxToPoint
cellToCell
cellToFace
cellToPoint
cylinderAnnulusToCell
cylinderToCell
faceToCell
faceToFace
faceToPoint
faceZoneToCell
faceZoneToFaceZone
fieldToCell
labelToCell
labelToFace
labelToPoint
nbrToCell
nearestToCell
nearestToPoint
normalToFace
patchToFace
pointToCell
pointToFace
pointToPoint
regionToCell
rotatedBoxToCell
setToCellZone
setToFaceZone
setToPointZone
setsToFaceZone
shapeToCell
sphereToCell
surfaceToCell
surfaceToPoint
zoneToCell
zoneToFace
zoneToPoint

I mean there is no STL to Face !

Appreciate your help

hfs November 12, 2012 19:11

Ok I found out how to create cellSets from surface:
cellZoneSet cZone new surfaceToCell ".../constant/triSurface/Umb.stl" ((0 0 20)) false false false 0.3 -100000

Then faceSet from cellSet:
faceZoneSet fZone_all new cellToFace cZone all

Then faceZone out of faceSet:
faceZoneSet FFF new setToFaceZone fZone_all

So now when I ran Snappy those faces did not snap!
Can you please explain what did you do?

CFDUser_ April 26, 2014 17:05

Quote:

Originally Posted by kalyangoparaju (Post 373726)
Friends,

I've been playing around a lot with the creation of cellZones and faceZones and here is what I have to report !

Till now I have found 3 ways to do it. ( I am sure there are more)

1. To use setSet utility and cellZonesSet and faceZoneSet commands.
This works amazingly well and creates the zones. A small problem can arrise if you are trying to set zones for an internal flow case and at the center of your geometry you have level 0 cells. These cells are not properly broken down and hence your zone is not exactly what you think it is. The work around for this is to just have a higher resolution where there are level 0 cells.

Attachment 14782

2. Using snappyHexMesh to create the zones.
Even this method does a very good job but somehow, atleast for my geometry, I see stitched kinda break where the cellZones starts and ends and where there is a faceZone. I have a strong feeling this might be because of the stl quality but I am quite sure that it is pretty decent.

Here are the pics.

Attachment 14778

Attachment 14779

The break in the second picture is where I have a faceZone.



3. This is something which I stumbled upon unintentionally ( i am so glad I did) - Using setSet utility but for blockMesh.
In method-1, the setSet command is used for the latest time step created by snappyHexMesh or for the mesh imported from other places but if you want to mesh in snappy and you want to create zones and don't want to see the problems which you saw in method-1 or method-2, the best way to do this is to actually create the cell and faceZones for the blockMesh. I accidentally did this when I forgot to use the -latestTime tag for method-1. This seems to be the best I saw. It doesn't have the breaks from method-2 nor does it have the extra cells from method-1

Here are the pics.

Attachment 14780

Attachment 14781




I just wanted to share this info with all of you and see if you have any suggestions.

There are 2 things which perplex me in the meshes which I uploaded. The geometry just infront of the cylindrical section has a lot of polyhedral cells. It is a very very simple geometry ( diverging section) and I am really surprised that snappy is not able to put hex cells there. Also, the featureEdge setting is put to 160 so that it captures all the curves ( as a matter of fact it does) but unfortunately, the circles aren't really round ! I have the nFeatureSnapIter at 10. Is there anything else I can do to improve this?

Sorry for the long post. Hope this info helps :-)

Kalyan

Hi Kalyan,

Glad that you have done something extremely well. I would like to borrow method to create faceSets for simple blockMesh. Lets say i have similar geometry like you (cylinder of length L). I wanted to create faceSets at 10 different locations along the length.

Can you please help me?

Regards,
CFDUser_

Artur May 7, 2014 16:04

Hi

Try using searchableCylinder ahen running topoSet (or setSet). by using different end point locations you can then select various parts of the mssh cylinder you're interested in. Mjch like you would slice a salami :)

Peace

A

CFDUser_ May 7, 2014 16:10

now i kno how to use them :)
thankyou :)

Regards,
CFDUser_


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