CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Meshing & Mesh Conversion

ways to create cellZones and faceZones

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree2Likes
  • 2 Post By kalyangoparaju

Reply
 
LinkBack Thread Tools Display Modes
Old   July 26, 2012, 10:36
Default ways to create cellZones and faceZones
  #1
Member
 
Kalyan
Join Date: Oct 2011
Location: Columbus, Ohio
Posts: 53
Blog Entries: 1
Rep Power: 6
kalyangoparaju is on a distinguished road
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.

setSet_substrate.PNG

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.

snappy_zones.PNG

snappy_substrate.PNG

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.

constant_zones.PNG

constant_substrate.PNG




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 and jiaojiao like this.
kalyangoparaju is offline   Reply With Quote

Old   November 12, 2012, 15:22
Default
  #2
hfs
Member
 
Join Date: Jul 2012
Posts: 60
Rep Power: 5
hfs is on a distinguished road
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 is offline   Reply With Quote

Old   November 12, 2012, 19:11
Default
  #3
hfs
Member
 
Join Date: Jul 2012
Posts: 60
Rep Power: 5
hfs is on a distinguished road
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?
hfs is offline   Reply With Quote

Old   April 26, 2014, 17:05
Default
  #4
Member
 
CFDUser
Join Date: Mar 2014
Posts: 55
Rep Power: 4
CFDUser_ is on a distinguished road
Quote:
Originally Posted by kalyangoparaju View Post
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_
CFDUser_ is offline   Reply With Quote

Old   May 7, 2014, 16:04
Default
  #5
Senior Member
 
Artur's Avatar
 
Artur
Join Date: May 2013
Location: Southampton, UK
Posts: 233
Rep Power: 6
Artur is on a distinguished road
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
Artur is offline   Reply With Quote

Old   May 7, 2014, 16:10
Default
  #6
Member
 
CFDUser
Join Date: Mar 2014
Posts: 55
Rep Power: 4
CFDUser_ is on a distinguished road
now i kno how to use them
thankyou

Regards,
CFDUser_
CFDUser_ is offline   Reply With Quote

Reply

Tags
cell zone, face zone, feature edge handling, snappy hex mesh

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 05:00.