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

Mesh Updating

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

Like Tree1Likes
  • 1 Post By gimli79

Reply
 
LinkBack Thread Tools Display Modes
Old   July 2, 2010, 02:27
Default Mesh Updating
  #1
New Member
 
Andreas Beck
Join Date: Apr 2010
Posts: 5
Rep Power: 7
gimli79 is on a distinguished road
Hi Foamers,

I am working on a FSI topic and have now some kind of problems.
In this case I have to update the mesh after every iteration, but I do not know how I should manage this. Is there any possibility to do that (maybe some fields), without changing the solvers, cause I am not allowed to do that.

Thanks a lot

Andy
hectorstar likes this.
gimli79 is offline   Reply With Quote

Old   July 2, 2010, 08:12
Default
  #2
Senior Member
 
Sandeep Menon
Join Date: Mar 2009
Location: Amherst, MA
Posts: 386
Rep Power: 15
deepsterblue will become famous soon enough
Update your mesh with either a moving-mesh and/or re-meshing approach.
__________________
Sandeep Menon
University of Massachusetts Amherst
https://github.com/smenon
deepsterblue is offline   Reply With Quote

Old   July 2, 2010, 08:38
Default
  #3
New Member
 
Lasse
Join Date: Jun 2010
Posts: 5
Rep Power: 7
lars. is on a distinguished road
Hi Sandeep, I work on an FSI problem, where the mesh deformation approach always fails after very few iterations, because several cells collapse or become inverted.

I tried to remesh with netgen whenever the mesh quality drops, which happens every 2-5 iterations. This is horribly slow. Do you know any tools that perform fast selective remeshing only in the severely deformed regions? The goal must be that the remeshing is not orders of magnitude slower than the equation solvers.

Lasse
lars. is offline   Reply With Quote

Old   July 2, 2010, 08:41
Default
  #4
Senior Member
 
Sandeep Menon
Join Date: Mar 2009
Location: Amherst, MA
Posts: 386
Rep Power: 15
deepsterblue will become famous soon enough
Every 2-5 iterations? Seems to be quite unusual to get mesh problems that quickly. Are you using a mesh-motion solver?
__________________
Sandeep Menon
University of Massachusetts Amherst
https://github.com/smenon
deepsterblue is offline   Reply With Quote

Old   July 2, 2010, 09:14
Default
  #5
New Member
 
Lasse
Join Date: Jun 2010
Posts: 5
Rep Power: 7
lars. is on a distinguished road
Yes, I used the laplaceFaceDecomposition solver with quadratic diffusivity. Of course I also tried a number of different settings. The question is not whether my case is usual or unusual. I am not talking about a small deformation of elastic parts. I am talking about obstacles moving freely in a fluid domain. We have tried the MRF and GGI methods, but they are both not optimal. Please refrain from discussing these points because this is a different topic.

The question is what tools are available for an efficient remeshing approach as you suggested it. Do you have experience with this approach?

Lasse
lars. is offline   Reply With Quote

Old   July 2, 2010, 09:27
Default
  #6
Senior Member
 
Sandeep Menon
Join Date: Mar 2009
Location: Amherst, MA
Posts: 386
Rep Power: 15
deepsterblue will become famous soon enough
Yup - quite a bit, in fact. I suspect that you want something similar to this:

http://www.ecs.umass.edu/~smenon/Mov...stonMotion.avi

I have the re-meshing algorithms nailed down pretty well, but I'm currently working on accurate field remapping at the moment. So until I have that sorted out, I'm afraid this won't be available for general use. Do keep a lookout for a release on OF-1.5-dev or 1.6-dev.
__________________
Sandeep Menon
University of Massachusetts Amherst
https://github.com/smenon
deepsterblue is offline   Reply With Quote

Old   July 2, 2010, 10:26
Default
  #7
New Member
 
Lasse
Join Date: Jun 2010
Posts: 5
Rep Power: 7
lars. is on a distinguished road
Nice.

As you are working in this field you have probably come across some relevant publications about dynamic remeshing. I am sure quite a few people here would be grateful if you share some links about the algorithms or even better about implementations that could be used until you are ready to contribute your work to OF1.x-dev.

Lasse
lars. is offline   Reply With Quote

Old   July 2, 2010, 11:06
Default
  #8
Senior Member
 
Sandeep Menon
Join Date: Mar 2009
Location: Amherst, MA
Posts: 386
Rep Power: 15
deepsterblue will become famous soon enough
The only other mesh-topology modification algorithms in place (that I'm aware of) are Hrv's layering / hex-refinement stuff. While this has been sufficient for a lot of cases, it isn't well suited for general mesh topologies.

My approach has been to use Shewchuk's edge-removal algorithm (can't remember the reference), with refinement features on tri-prism / tet-meshes. I can tell you that it's not easy to implement, given the complexity of the project, but it's been done.

You could temporarily hook-up your solvers to netgen, have it re-mesh, perform a mesh-to-mesh interpolation of fields, and re-start your solution. This is a global re-meshing approach that nobody is fond of, for obvious reasons. But unfortunately, that's the only solution I have for you at the moment.
__________________
Sandeep Menon
University of Massachusetts Amherst
https://github.com/smenon
deepsterblue is offline   Reply With Quote

Old   July 8, 2010, 06:09
Default
  #9
New Member
 
Andreas Beck
Join Date: Apr 2010
Posts: 5
Rep Power: 7
gimli79 is on a distinguished road
Thanks for help,
I am a beginner with openfoam, so I am happy about any kind of help.
But I have to move the single points which corresponds to the deformed structure of the transient CSD computation. How can I do that, without changing the code? The reason is that I am not allowed to compile.
I tried several dictionaries, but with them I can just move complete boundaries.
So, which dictionaries or maybe solvers should I use for that case.

The next problem is, that I have to update the mesh every timestep but I have absolutly no idea how I should achieve that. So, should I define a file for movement of all timesteps at the start in 0 directory.Or can I update the mesh every timestep. But here I dont know how to stop and restart the computation.

Thanks for your suggestions

Best regards
Andy

Last edited by gimli79; July 8, 2010 at 10:19.
gimli79 is offline   Reply With Quote

Old   August 17, 2010, 10:39
Default laplaceFaceDecomposition in OpenFOAM 1.6.x for FSI
  #10
Senior Member
 
Albrecht vBoetticher
Join Date: Aug 2010
Location: Zürich, Swizerland
Posts: 183
Rep Power: 7
vonboett is on a distinguished road
Dear deepsterblue,

I simulate VOF-based freeface mudflows with herrschel-bulkley rheology and LES-turbulence modeling in OpenFOAM 1.6.x, and now I have to connect that to my landslide barrier code that catches the mud with steel nets. Since I have some implementations regarding the turbulence subgridscale modeling from the LTTE-Rostock, I really want to avoid changing to OpenFOAM 1.5.dev, but it seems not trivial to get laplaceFaceDecomposition solver implemented in OpenFOAM 1.6. Do you know who I could ask, whether implementing laplaceFaceDecomposition to OpenFOAM 1.6.x is a reallistic opportunity?

Thanks,

Albrecht
vonboett is offline   Reply With Quote

Old   August 17, 2010, 21:10
Default
  #11
Senior Member
 
Sandeep Menon
Join Date: Mar 2009
Location: Amherst, MA
Posts: 386
Rep Power: 15
deepsterblue will become famous soon enough
The tetDecomposition solvers are probably non-trivial to port to OF-1.6, but I've never really tried, so I can't say for certain. Are you dealing with a tet-mesh?
__________________
Sandeep Menon
University of Massachusetts Amherst
https://github.com/smenon
deepsterblue is offline   Reply With Quote

Old   August 18, 2010, 17:31
Default
  #12
Senior Member
 
Albrecht vBoetticher
Join Date: Aug 2010
Location: Zürich, Swizerland
Posts: 183
Rep Power: 7
vonboett is on a distinguished road
Ok, I see. I use hexahedral blocks created with blockMesh.
vonboett 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
vtk mesh or Abaqus mesh to OpenFOAM bigphil Open Source Meshers: Gmsh, Netgen, CGNS, ... 19 August 16, 2011 04:14
unv mesh corrupted after createPatch maddalena OpenFOAM Mesh Utilities 1 February 18, 2010 08:43
2d irregular grid Remy Main CFD Forum 1 December 22, 2008 05:49
fluent add additional zones for the mesh file SSL FLUENT 2 January 26, 2008 12:55
basic of mesh refinement arya CFX 4 June 19, 2007 12:21


All times are GMT -4. The time now is 22:26.