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

cyclicACMI boundary condition treatment

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 10, 2015, 13:08
Default cyclicACMI boundary condition treatment
  #1
New Member
 
Jim
Join Date: Feb 2014
Location: UK
Posts: 22
Rep Power: 12
jimteb is on a distinguished road
Hi All,

I was wondering if anyone could enlighten me on how the cyclicACMI boundary condition introduced in OpenFOAM 2.3.x works, more specifically:

-How are two boundary conditions handled on the same cell face? e.g. when there is partial overlap of a cell face (with say a wall BC) with another mesh region where fluxes are being interpolated to/from?

The reason I am interested in this is I am trying to use this BC for a compressible flow model with rhoPimpleDyMFoam. I am consistently getting oscillating pressure fluctuations at the region connecting the two non-conforming meshes, maybe suggesting some sort of conservation problem ...

Any comments would be much appreciated,

Thanks
jimteb is offline   Reply With Quote

Old   April 24, 2015, 16:15
Default
  #2
Retired Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,980
Blog Entries: 45
Rep Power: 128
wyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to all
Greetings James,

I know I wrote about this the other day here on the forum... ah, found it:
Quote:
Originally Posted by wyldckat View Post
I did some checking of how it works and wrote it here: http://www.openfoam.org/mantisbt/view.php?id=1450#c3770 - essentially there are actually 4 patches needed for each "cyclicACMI" pair or patches: 1 wall and 1 cyclic for each side.
Mmm... this doesn't answer your question. If I remember correctly, the problem with the current ACMI implementation is that it assumes/enforces that the wall part of the pairs must act as a convention wall boundary:
  • no-slip condition (flow speed always set to 0);
  • with zero gradient for pressure, as well as for all other fields.
This is why there are a few bug reports about not being able to define other boundary conditions for the wall part of the patch pairs.


What this effectively/probably results in is the situation where the ongoing fluid flow hits a wall when it wasn't expected, i.e. there is an unexpected backward step or forward step that occurs when the faces are only partially covered. Oh, and it should be using AMI interpolation for weighting the overlapped faces, hence using both wall and cyclicAMI for weighting the exchange between the two sides.



Beyond this, I'll have a look into your other post on this topic, since it might be easier to diagnose the problem that way: http://www.cfd-online.com/Forums/ope...interface.html


Best regards,
Bruno
wyldckat is offline   Reply With Quote

Reply

Tags
acmi, dynamic meshing

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
conjugate boundary condition Daniel_Khazaei OpenFOAM Programming & Development 0 December 31, 2013 13:11
Question about heat transfer coefficient setting for CFX Anna Tian CFX 1 June 16, 2013 06:28
Opening Boundary Condition andreachan Main CFD Forum 11 March 19, 2013 16:46
inlet velocity boundary condition murali CFX 5 August 3, 2012 08:56
Fluent Treatment of mixed boundary condition HELP Amr FLUENT 0 May 26, 2006 05:46


All times are GMT -4. The time now is 02:49.