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

Strange gamma field on wedge case

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 27, 2008, 08:36
Default Hello World. I'm getting a
  #1
Senior Member
 
sega's Avatar
 
Sebastian Gatzka
Join Date: Mar 2009
Location: Frankfurt, Germany
Posts: 729
Rep Power: 11
sega is on a distinguished road
Hello World.

I'm getting a strange problem with one of my case. It's a wedge geometry and I have used a second symmetryPlane.

It's basically a well know setup to the readers of my "bubble in zero gravity" case.

It's a relaxing fluid volume after a pertubation. After quite some time there is an error occuring at the intersection of the symmetry Planes.

Have a look at the image:


I don't know why the gamma field is beginning to break up at this point.

Does anyone have an idea?

My case is here:
http://therealsega.th.funpic.de/openfoam/stwedge.tar.gz

Thanks so far!
Have a nice weekend.
__________________
Schrödingers wife: "What did you do to the cat? It's half dead!"
sega is offline   Reply With Quote

Old   October 10, 2008, 00:16
Default Hey People. I did a quick r
  #2
Senior Member
 
sega's Avatar
 
Sebastian Gatzka
Join Date: Mar 2009
Location: Frankfurt, Germany
Posts: 729
Rep Power: 11
sega is on a distinguished road
Hey People.

I did a quick review of the problems mentioned above. It looks like the unwanted gamma values are original generated at the symmetry Plane (the left boundary of the geometry).

Have a look at the two first timesteps t=0.1 and 0.2 seconds:




In the further progress of the simulation the yellow spots are moving to the lower left corner like in the image in my first post.

So, does anybody have a clue why this is happening?
I'm currently experiencing this problem on a mesh with 60x60 cells. A 30x30 and 120x120 cell simulation doesn't seem to generate this problem.
Why does it happen at this intermediate sized grid?

If someone wants to have a look at the case itself try this file:
http://therealsega.th.funpic.de/open...onWedge.tar.gz

Any help is appreciated.
Greetings from Hawaii ...
(btw: nice spot in the US)
Sebastian
__________________
Schrödingers wife: "What did you do to the cat? It's half dead!"
sega is offline   Reply With Quote

Old   October 11, 2008, 10:00
Default The patch of zero surface wher
  #3
New Member
 
nicasch
Join Date: Mar 2009
Posts: 23
Rep Power: 8
nicasch is on a distinguished road
The patch of zero surface where you have the axis of symmetry should be specified as empty (not symmetryPlane) in the blockMeshDict. For any fields in the 0 directory this boundary condition should be empty also.
nicasch is offline   Reply With Quote

Old   October 11, 2008, 16:25
Default Than what is the symmetryPlane
  #4
Senior Member
 
sega's Avatar
 
Sebastian Gatzka
Join Date: Mar 2009
Location: Frankfurt, Germany
Posts: 729
Rep Power: 11
sega is on a distinguished road
Than what is the symmetryPlane bc for?
I will try the empty bc later.

Thanks so far ...
__________________
Schrödingers wife: "What did you do to the cat? It's half dead!"
sega is offline   Reply With Quote

Old   October 12, 2008, 06:48
Default The plane of symmetry is used
  #5
New Member
 
nicasch
Join Date: Mar 2009
Posts: 23
Rep Power: 8
nicasch is on a distinguished road
The plane of symmetry is used when you have a mirror reflection of your domain through that plane.
For axi-symetric cases, OpenFOAM provides a special treatment of the axis through the empty BC. At the axis you actually have no faces (i.e. you have faces of zero surface), so an ordinary BC may not be applied.
nicasch is offline   Reply With Quote

Old   October 19, 2008, 11:45
Default Changing the bc from symmetryP
  #6
Senior Member
 
sega's Avatar
 
Sebastian Gatzka
Join Date: Mar 2009
Location: Frankfurt, Germany
Posts: 729
Rep Power: 11
sega is on a distinguished road
Changing the bc from symmetryPlane to empty made no difference in this case.

I'm trying a different approach to the problem.
Maybe a wedge case is not the right one.
__________________
Schrödingers wife: "What did you do to the cat? It's half dead!"
sega 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
Overriding Wedge Symmetry and Cyclic BC for a single field diegon OpenFOAM Running, Solving & CFD 1 December 2, 2014 01:45
Arcs in wedge case sega OpenFOAM Native Meshers: blockMesh 1 September 20, 2008 11:34
Gamma field on boundary patch tom OpenFOAM Post-Processing 0 March 23, 2008 07:56
Gamma field initialisation mer OpenFOAM Pre-Processing 0 March 1, 2008 09:12
Gamma field initialization Pei-Ying Hsieh (Hsieh) OpenFOAM Pre-Processing 10 November 10, 2005 11:44


All times are GMT -4. The time now is 03:34.