CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > ANSYS Meshing & Geometry

Meshing a cylindrical volume

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 18, 2010, 16:19
Default Meshing a cylindrical volume
  #1
Member
 
pranab_jha's Avatar
 
Pranab N Jha
Join Date: Nov 2009
Location: Houston, TX
Posts: 83
Rep Power: 7
pranab_jha is on a distinguished road
Hi
I want to mesh a 3d pipe. How can I do that?

What I tried was: I meshed one face (275 cells) and tried to sweep that face along the axis of the pipe to form the volume. But the mesh density is v high. Gambit takes a default value of 1 in the axial direction. How can I control the axial density of the mesh?

I am new to Gambit. Please help.

Geometry:
Dia: 50 mm
Length: 12.7 m
Approx nodes reqd: 38000.
pranab_jha is offline   Reply With Quote

Old   March 19, 2010, 00:03
Default
  #2
Member
 
pranab_jha's Avatar
 
Pranab N Jha
Join Date: Nov 2009
Location: Houston, TX
Posts: 83
Rep Power: 7
pranab_jha is on a distinguished road
Or.. I should put the question like this...
How can I mesh a 3d pipe in Gambit using hex elements?
pranab_jha is offline   Reply With Quote

Old   March 19, 2010, 01:55
Default
  #3
Super Moderator
 
-mAx-'s Avatar
 
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 2,992
Rep Power: 30
-mAx- will become famous soon enough
Build first the geometry.
Then deal with the mesh.
Once your pipe is build, mesh one cap with quad-pave, and then mesh the volume with the desired element size.
__________________
In memory of my friend Hervé: CFD engineer & freerider
-mAx- is offline   Reply With Quote

Old   March 19, 2010, 02:56
Default
  #4
Member
 
pranab_jha's Avatar
 
Pranab N Jha
Join Date: Nov 2009
Location: Houston, TX
Posts: 83
Rep Power: 7
pranab_jha is on a distinguished road
I did mesh one cap with quad-pave. What option do I choose to control the element size. Is 'cooper' the best option and do I specify the interval count/size appropriately in the axial direction?
pranab_jha is offline   Reply With Quote

Old   March 19, 2010, 03:54
Default
  #5
Super Moderator
 
-mAx-'s Avatar
 
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 2,992
Rep Power: 30
-mAx- will become famous soon enough
Yes Cooper is the best option (if your volume enables it).
If the cap is meshed, (and you are using Cooper), then the surface mesh for caps are fixed. The "mesh-freedom's degree" remaining is the axial one, so giving the element size for the volume mesh, will be the element size for the axial direction.

Else you can mesh one edge in axial direction, and it will govern the volume mesh densiy (you can try to give a very fine element size for the volume mesh, but as the axial edge is already meshed, this volume element size will be ignored, since you don't enable the delete lowe mesh option)
__________________
In memory of my friend Hervé: CFD engineer & freerider
-mAx- is offline   Reply With Quote

Old   March 20, 2010, 11:00
Default
  #6
Member
 
pranab_jha's Avatar
 
Pranab N Jha
Join Date: Nov 2009
Location: Houston, TX
Posts: 83
Rep Power: 7
pranab_jha is on a distinguished road
Thanks Max... that was really helpful
pranab_jha is offline   Reply With Quote

Old   March 22, 2010, 18:13
Default
  #7
Member
 
pranab_jha's Avatar
 
Pranab N Jha
Join Date: Nov 2009
Location: Houston, TX
Posts: 83
Rep Power: 7
pranab_jha is on a distinguished road
Hi,

I have another problem now. I want to split the inlet of my mesh into two equal parts-upper and lower for two different fluid inlets. How can I do that?

I created a semi-circular face first and then swept it to make myself a "semi-cylinder". Then I mirrored it to get myself two semi-cylindrical geometries with mesh. But the problem is that the two new faces generated due to this (interface between the two semi-cylinders) is taken as a wall when I export the mesh to fluent. I only want two inlets and one outlet to allow mixing of the fluids.

Thanks,
Pranab
pranab_jha is offline   Reply With Quote

Old   March 23, 2010, 01:46
Default
  #8
Super Moderator
 
-mAx-'s Avatar
 
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 2,992
Rep Power: 30
-mAx- will become famous soon enough
your "interfaces" seem to be not connected.
You can connect them in gambit (Surface/Connect)
__________________
In memory of my friend Hervé: CFD engineer & freerider
-mAx- is offline   Reply With Quote

Old   March 23, 2010, 06:07
Default Similar Problem
  #9
New Member
 
Jon
Join Date: Mar 2010
Posts: 10
Rep Power: 7
Sidewinder is on a distinguished road
post removed!

Last edited by Sidewinder; March 29, 2010 at 08:00.
Sidewinder is offline   Reply With Quote

Old   March 23, 2010, 15:58
Default
  #10
Member
 
pranab_jha's Avatar
 
Pranab N Jha
Join Date: Nov 2009
Location: Houston, TX
Posts: 83
Rep Power: 7
pranab_jha is on a distinguished road
I did get my geometry and mesh right (finally). But I used very basic method to do that.
-I created two semi-circular faces (like a circle) at both ends of the pipe.
-I made faces out of the pair of upper and lower circles.
-I joined the two faces to make the pipe volume. Then I specified the inlet conditions for the two fluids at the two inlet faces.
But I would like to know how I can mirror a half cylinder to form two cylinders (described in my earlier post) and neglect the interface as I do not need it. I will give Max's suggestion a try and see.
pranab_jha is offline   Reply With Quote

Old   March 24, 2010, 01:55
Default
  #11
Super Moderator
 
-mAx-'s Avatar
 
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 2,992
Rep Power: 30
-mAx- will become famous soon enough
you can copy your volume, enables reflect option and give the right direction's vector. Also enable copy mesh unlinked option. Depending on your coordinate system, you may have to aligne your reflected volume for "glueing" it with the original one.
Then connect the interfaces each other.
Watch out sometimes, the connect operation delete the volume mesh, and you will have to remesh it
__________________
In memory of my friend Hervé: CFD engineer & freerider
-mAx- is offline   Reply With Quote

Old   March 24, 2010, 06:56
Default
  #12
New Member
 
Jon
Join Date: Mar 2010
Posts: 10
Rep Power: 7
Sidewinder is on a distinguished road
post removed!

Last edited by Sidewinder; March 29, 2010 at 08:01.
Sidewinder is offline   Reply With Quote

Old   March 24, 2010, 07:10
Default
  #13
Super Moderator
 
-mAx-'s Avatar
 
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 2,992
Rep Power: 30
-mAx- will become famous soon enough
post a picture, or mail me your geometry
__________________
In memory of my friend Hervé: CFD engineer & freerider
-mAx- is offline   Reply With Quote

Old   March 24, 2010, 09:17
Default
  #14
New Member
 
Jon
Join Date: Mar 2010
Posts: 10
Rep Power: 7
Sidewinder is on a distinguished road
post removed!
Attached Images
File Type: jpg mesh_2.JPG (80.5 KB, 27 views)

Last edited by Sidewinder; March 29, 2010 at 08:00.
Sidewinder is offline   Reply With Quote

Reply

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
'Tetrahedral meshing has failed for volume...' Murat FLUENT 5 February 19, 2011 05:22
BlockMesh FOAM warning gaottino OpenFOAM Native Meshers: blockMesh 7 July 19, 2010 14:11
On the damBreak4phaseFine cases paean OpenFOAM Running, Solving & CFD 0 November 14, 2008 22:14
fluent add additional zones for the mesh file SSL FLUENT 2 January 26, 2008 12:55
Axisymmetrical mesh Rasmus Gjesing (Gjesing) OpenFOAM Native Meshers: blockMesh 10 April 2, 2007 14:00


All times are GMT -4. The time now is 11:22.