CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Sliding interface- ACMI

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

Like Tree10Likes

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 15, 2017, 18:23
Default
  #41
Senior Member
 
khedar
Join Date: Oct 2016
Posts: 111
Rep Power: 9
khedar is on a distinguished road
Because in the real geometry my inlet and outlet sections are not rectangular channels but they are somewhat elliptical...

i.e. In the first picture (which is a test case before simulating the real one) the inlet and outlet sections are rectangle which is a simplification of the real one.

http://www.pic-upload.de/view-32496605/case1.png.html

Inlet and Outlet sections for the real one are like shown in the second link.

http://www.pic-upload.de/view-324966...ction.png.html

This allows me two mesh the three parts separately without any dependence on the other. The reason is I would need an O-grid mesh for the circular inlet and outlet section to get a quality mesh, whereas for the main channel i would like to use normal mesh.
khedar is offline   Reply With Quote

Old   January 15, 2017, 18:30
Default
  #42
Super Moderator
 
Tobi's Avatar
 
Tobias Holzmann
Join Date: Oct 2010
Location: Tussenhausen
Posts: 2,708
Blog Entries: 6
Rep Power: 51
Tobi has a spectacular aura aboutTobi has a spectacular aura aboutTobi has a spectacular aura about
Send a message via ICQ to Tobi Send a message via Skype™ to Tobi
Ah okay, got the point. However, I do not agree with your statement, that you would get not a good mesh if you mesh everything together. But that is up to you and your meshing procedure. However, your question does finally not fit into this thread.
__________________
Keep foaming,
Tobias Holzmann
Tobi is offline   Reply With Quote

Old   January 15, 2017, 19:46
Default
  #43
Senior Member
 
khedar
Join Date: Oct 2016
Posts: 111
Rep Power: 9
khedar is on a distinguished road
Why not. Is it not possible to use ACMI for non-sliding problems when the mesh has non-overlapping patches?
khedar is offline   Reply With Quote

Old   January 16, 2017, 01:24
Default
  #44
Senior Member
 
Arjun
Join Date: Mar 2009
Location: Nurenberg, Germany
Posts: 1,273
Rep Power: 34
arjun will become famous soon enougharjun will become famous soon enough
Quote:
Originally Posted by khedar View Post
Why not. Is it not possible to use ACMI for non-sliding problems when the mesh has non-overlapping patches?

rotate the mesh little bit arbitrarily and check if it runs now.

Sometimes the neighbour search fails if the patch is flat along one of the coordinate. Once the interface is calculated it seems like simple enough problem to run.

If the intersection took place properly then the problems could come up due to skew. At the interface the skew of newly generated cells could be extremely bad. So start the calculation with first order schemes and more non orthoginal correctors. Then later upon convergence change the options to higher order terms.

Hope it helps.
arjun is offline   Reply With Quote

Old   January 21, 2017, 20:30
Default
  #45
Senior Member
 
khedar
Join Date: Oct 2016
Posts: 111
Rep Power: 9
khedar is on a distinguished road
thanks arjun, The problem might have been with ACMI patch. I found the ACMI implementation of 4.x to be the most recent and I tested with that version. The simulation ran for 10-12 iterations before blowing up. But at least it was running. Second change what I did was the Velocity internal field initialised to 0 instead of inlet velocity earlier. This did the trick and the simulation ran flawlessly. Also I ran the simulation for first few iterations using PCG solver for p_rgh equation and then switched to GAMG for better stability. Now everything is running perfectly.

There might also be a problem with mergeMeshes/createBaffles, since after i run these in 2.3 i was getting open boundaries but in 4.x it was okay. So basically i have switched to 4.x now.
khedar is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wind turbine simulation Saturn CFX 58 July 3, 2020 02:13
Question about heat transfer coefficient setting for CFX Anna Tian CFX 1 June 16, 2013 07:28
An error has occurred in cfx5solve: volo87 CFX 5 June 14, 2013 18:44
Error finding variable "THERMX" sunilpatil CFX 8 April 26, 2013 08:00
RPM in Wind Turbine Pankaj CFX 9 November 23, 2009 05:05


All times are GMT -4. The time now is 18:10.