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-   -   Strange gamma field on wedge case (http://www.cfd-online.com/Forums/openfoam-solving/58453-strange-gamma-field-wedge-case.html)

sega September 27, 2008 08:36

Hello World. I'm getting a
 
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:
http://www.cfd-online.com/OpenFOAM_D...ges/1/9345.png

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.

sega October 10, 2008 00:16

Hey People. I did a quick r
 
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:

http://www.cfd-online.com/OpenFOAM_D...ges/1/9519.png
http://www.cfd-online.com/OpenFOAM_D...ges/1/9520.png

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

nicasch October 11, 2008 10:00

The patch of zero surface wher
 
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.

sega October 11, 2008 16:25

Than what is the symmetryPlane
 
Than what is the symmetryPlane bc for?
I will try the empty bc later.

Thanks so far ...

nicasch October 12, 2008 06:48

The plane of symmetry is used
 
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.

sega October 19, 2008 11:45

Changing the bc from symmetryP
 
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.


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