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

[ICEM] Blocking strategy for two hemispheres connected by a pipe(negative volume)

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

Like Tree2Likes
  • 2 Post By Far

Reply
 
LinkBack Thread Tools Display Modes
Old   May 27, 2014, 12:30
Default Blocking strategy for two hemispheres connected by a pipe(negative volume)
  #1
New Member
 
Join Date: Jan 2014
Posts: 19
Rep Power: 4
Polarbear is on a distinguished road
Hi all,
I have a problem that I've been banging my head against the wall for the whole day.
I have a hemisphere that is connected to a cylinder which in turn is connected to a second hemisphere. I want to do a structured mesh and approach the problem like this.

1. I start with making a block and split it up into three blocks.
2. I make an O-grid split and remove the other blocks from the cylinders.
3. I make a second O-grid split since I want boundary layers in the cylinder.
4. I then associate faces with surfaces and edges with curves
5. I snap the vertices into place and start working on the distribution of nodes. I can also use Edit edge-automatic linear to achieve a blocking that follows the surface.
6. I look at the 2x2x2 determinants, loads of them are negative and this becomes a problem when I load it into an unstrucutred mesh and check for errors, I get tons of errors(regarding negative volume).

Anyone having any ideas?
Attached Images
File Type: jpg 1.jpg (22.0 KB, 37 views)
File Type: jpg 2.jpg (22.8 KB, 28 views)
File Type: jpg 3.jpg (28.1 KB, 31 views)
File Type: jpg 4.jpg (28.1 KB, 27 views)
File Type: jpg 5.jpg (45.0 KB, 26 views)
Polarbear is offline   Reply With Quote

Old   May 27, 2014, 12:32
Default
  #2
New Member
 
Join Date: Jan 2014
Posts: 19
Rep Power: 4
Polarbear is on a distinguished road
More pics and files
Attached Images
File Type: jpg 6.jpg (21.9 KB, 28 views)
File Type: jpg 7.jpg (35.4 KB, 33 views)
Attached Files
File Type: zip ICEMCFD.zip (94.2 KB, 9 views)
Polarbear is offline   Reply With Quote

Old   May 27, 2014, 15:28
Default
  #3
kad
Senior Member
 
Join Date: Feb 2013
Location: Germany
Posts: 173
Rep Power: 14
kad will become famous soon enoughkad will become famous soon enough
Your blocking strategy is not correct. Do not select the faces on the round side of the hemispheres. Check the tutorial cube in a hemisphere. It comes with ICEM. Blocking strategy should be easy to derive from this.
kad is offline   Reply With Quote

Old   May 29, 2014, 02:26
Default
  #4
New Member
 
Join Date: Jan 2014
Posts: 19
Rep Power: 4
Polarbear is on a distinguished road
Thanks kad! I devised a new blocking strategy by using the tutorial, that is to make box-cylinder-box block mesh. And then connect it to two hemispheres with a hole in them(as shown in the sphere cube ICEM tutorial) using a interface.

Rep to you!

Cheers
Polarbear is offline   Reply With Quote

Old   August 21, 2014, 09:02
Default
  #5
Far
Super Moderator
 
Sijal
Join Date: Mar 2009
Location: Islamabad
Posts: 4,285
Blog Entries: 6
Rep Power: 43
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
it is almost two month old thread, but i feel it is good idea to post solution to this problem. Steps are:

1. Create one block with name "fluid" and also create three materials points "fluid" in both hemispheres and connecting pipe.

2. Split block flat sides of both hemispheres. And delete center block (corresponding to center pipe) permanently. When blocks are deleted permanently, edges on either sides are no more parallel and therefore you can specify different no of nodes on both sides.

Associate edges to curves and snap vertices to the surfaces of both hemisphere.

3. Apply sphere-cube strategy, but select face(s) on flat side for both blocks. Adjust ogrid using either move vertices or rescale o-block command.

4. Now make four splits for the pipe connecting both sides. You need to apply split operation on both sides as geometry is no parallel and hence split will not propagate to other side.

5. Now create block for the pipe using "block from vertices" and select eight vertices on both ends of pipe in particular order. See help for this command.

5. Now create ogrid around centre block passing from both HS (hemisphere) and pipe.

6. Again use O-grid command and again select same blocks and this time create ogrid inside by unchecking option "around". Adjust ogrid edges on the surfaces of HS

7. Adjust pre edge mesh parameters and see the premesh. If satisfied with mesh quality and no of nodes on each edge convert this mesh to unstructured mesh and set boundary conditions, solver and output mesh.

8. Import mesh in fluent and check the mesh quality there as well. Min orthogonal quality should be atleast 0.1 (0.01 is minimum requirement through)

Attached Files
File Type: zip twospheres_pipe.zip (62.4 KB, 9 views)
kad and Polarbear like this.
Far is offline   Reply With Quote

Old   August 21, 2014, 15:57
Default
  #6
New Member
 
Join Date: Jan 2014
Posts: 19
Rep Power: 4
Polarbear is on a distinguished road
Thanks far for the extensive answer! I'm finished with this problem but it's always good to learn something new. It was way above me block meshing skills at the time!

Cheers, thank you both(kad) for taking your time to help people and spread knowledge!
Polarbear is offline   Reply With Quote

Old   August 22, 2014, 08:10
Default
  #7
Far
Super Moderator
 
Sijal
Join Date: Mar 2009
Location: Islamabad
Posts: 4,285
Blog Entries: 6
Rep Power: 43
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
just a side question: Was this problem related to multiphase simulation?
Far is offline   Reply With Quote

Old   August 23, 2014, 07:38
Default
  #8
New Member
 
Join Date: Jan 2014
Posts: 19
Rep Power: 4
Polarbear is on a distinguished road
Nope. Single phase compressible flow
Polarbear 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
Import netgen mesh to OpenFOAM hsieh Open Source Meshers: Gmsh, Netgen, CGNS, ... 32 September 13, 2011 05:50
BlockMesh FOAM warning gaottino OpenFOAM Native Meshers: blockMesh 7 July 19, 2010 14:11
CheckMeshbs errors ivanyao OpenFOAM Running, Solving & CFD 2 March 11, 2009 03:34
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 06:36.