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

blockMesh for bigger mesh

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

Like Tree3Likes
  • 2 Post By bigphil
  • 1 Post By eugene

Reply
 
LinkBack Thread Tools Display Modes
Old   October 12, 2010, 11:42
Default blockMesh for bigger mesh
  #1
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 10
gwierink is on a distinguished road
Dear all,

I am trying to generate a blockMesh with 6.75 million cells and have some trouble:
Code:
new cannot satisfy memory request.
This does not necessarily mean you have run out of virtual memory.
It could be due to a stack violation caused by e.g. bad use of pointers or an out of date shared library
Aborted
I read in these threads (DNS mesh and Trouble with blockMesh) that it should be possible, but I did not really find an answer. Up to 2 million cells blockMesh builds the mesh, but more cells won't work. I am using 64 bit machine with 8 GB of memory (actually a cluster node since I can forget about it on my desktop). Would anyone have any tips? Many thanks!
__________________
Regards, Gijs
gwierink is offline   Reply With Quote

Old   October 13, 2010, 08:36
Default
  #2
Senior Member
 
Jens Höpken
Join Date: Apr 2009
Location: Duisburg, Germany
Posts: 156
Rep Power: 9
jhoepken is on a distinguished road
Send a message via Skype™ to jhoepken
Hi Gijs,

I cannot say anything about blockMesh, but I've observed a similar barrier with snappyHexMesh. By using a machine with 12GB of RAM, I was able to obtain a mesh consisting of approximately 3.3 Mio cells. Maybe there is no alternative as to use more memory? I'm glad if anybody has an other suggestion?

Jens
jhoepken is offline   Reply With Quote

Old   October 13, 2010, 12:48
Default
  #3
Senior Member
 
bigphil's Avatar
 
Philip Cardiff
Join Date: Mar 2009
Location: Dublin,Ireland
Posts: 598
Rep Power: 20
bigphil will become famous soon enoughbigphil will become famous soon enough
Hi,

You could split up your geometry into smaller parts and then mesh each part, then merge and stitch the part meshes together with the mergeMeshes and stitchMesh utilities.

This is not a very nice way of doing it, but if you can't figure anything else out then it might be an option.

Philip
solefire and mgg like this.
bigphil is offline   Reply With Quote

Old   October 14, 2010, 03:17
Default
  #4
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 10
gwierink is on a distinguished road
Hi guys,

@Jens: That's a long time ago, how's life? Hope you're doing well! Hmm, it seems that brute force (or actually memory) is the only way ... I'll let you know if I find something out.

@Philip: Thanks for the suggestion, good idea. Would a renumberMesh be helpful after I merge and stitch?
__________________
Regards, Gijs
gwierink is offline   Reply With Quote

Old   October 14, 2010, 06:45
Default
  #5
Senior Member
 
bigphil's Avatar
 
Philip Cardiff
Join Date: Mar 2009
Location: Dublin,Ireland
Posts: 598
Rep Power: 20
bigphil will become famous soon enoughbigphil will become famous soon enough
Gijs,

I'm not very familiar with renumberMesh but it seems to give you a more efficient mesh, so yes it probably would be a good idea after merging and stitching.
I'll keep that in mind the next time I use merge and stitch!

Philip
bigphil is offline   Reply With Quote

Old   October 14, 2010, 07:39
Default
  #6
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 10
gwierink is on a distinguished road
Hi Philip,

I used renumberMesh after converting Fluent meshes to OpenFOAM. After the conversion the cellID numbering is not the most efficient for use in OF. renumberMesh renumbers the cellIDs for more efficient calculation, it can speed up the calculation time actually. However, I heard it doesn't work with MRF meshes. Maybe there are some tricks for that ...
__________________
Regards, Gijs
gwierink is offline   Reply With Quote

Old   October 14, 2010, 08:33
Default
  #7
Senior Member
 
bigphil's Avatar
 
Philip Cardiff
Join Date: Mar 2009
Location: Dublin,Ireland
Posts: 598
Rep Power: 20
bigphil will become famous soon enoughbigphil will become famous soon enough
Quote:
Originally Posted by gwierink View Post
Hi Philip,

I used renumberMesh after converting Fluent meshes to OpenFOAM. After the conversion the cellID numbering is not the most efficient for use in OF. renumberMesh renumbers the cellIDs for more efficient calculation, it can speed up the calculation time actually. However, I heard it doesn't work with MRF meshes. Maybe there are some tricks for that ...
Thanks Gijs,
I will keep it in mind when I convert meshes from Gambit.

Philip
bigphil is offline   Reply With Quote

Old   October 14, 2010, 10:44
Default
  #8
Senior Member
 
Jens Höpken
Join Date: Apr 2009
Location: Duisburg, Germany
Posts: 156
Rep Power: 9
jhoepken is on a distinguished road
Send a message via Skype™ to jhoepken
<offtopic>
So renumberMesh can help to use Fluent meshes? Does this work for the export of ICEM grids in the Fluent format as well? I've hat a lot of trouble with that in the past.

@gijs: Life is great so far
</offtopic>
jhoepken is offline   Reply With Quote

Old   October 14, 2010, 10:57
Default
  #9
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 10
gwierink is on a distinguished road
Hi Jens,

Good to hear you are well .
I have seen this effect with Gambit meshes (the .msh extension), converted to OF. I suppose that other meshing tools also do not necessarily generate the mesh cellID order that is most optimal for OF to calculate with. Some codes work with "x-y-z", but OF "stacks" cells on a pile based on cellID. Of course, OF also uses "x-y-z", but perhaps in a slightly different way. I am not sure, but my guess is that renumberMesh may also be effective for meshes generated by other tools, e.g. ICEM.
__________________
Regards, Gijs
gwierink is offline   Reply With Quote

Old   October 15, 2010, 03:11
Default
  #10
Senior Member
 
Jens Höpken
Join Date: Apr 2009
Location: Duisburg, Germany
Posts: 156
Rep Power: 9
jhoepken is on a distinguished road
Send a message via Skype™ to jhoepken
Thanks Gijs I'll give it a try, on the next ICEM mesh I need to use for the simulations.
jhoepken is offline   Reply With Quote

Old   October 15, 2010, 10:26
Default
  #11
Senior Member
 
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 13
eugene is on a distinguished road
One way to make bigger blockMeshes is to make a smallish blockMesh, decompose it and then use snappyHexMesh with volume refinement to refine it into a bigger mesh.

The memory requirements of snappy are large because it always stores 2 meshes (new and old) and each processor in a parallel run contains the entire set of surface meshes used to define the geometry. It could be better though.
mgg likes this.
eugene is offline   Reply With Quote

Old   October 26, 2010, 10:17
Default
  #12
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 10
gwierink is on a distinguished road
Ah great, thanks Eugene, I will give it a try.

We do have a larger machine available, but it uses multiple cores on a single node. Does anyone know whether blockMesh is multithreaded so it could run with the full amount of memory on the node? Thanks in advance!
__________________
Regards, Gijs
gwierink is offline   Reply With Quote

Old   October 26, 2010, 16:04
Default
  #13
Senior Member
 
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 13
eugene is on a distinguished road
blockMesh is single core only. Just about all multi-socket nodes these days have a shared memory architecture though, so each core can use all the memory on the node if required.
eugene is offline   Reply With Quote

Old   October 27, 2010, 03:37
Default
  #14
Senior Member
 
Gijsbert Wierink
Join Date: Mar 2009
Posts: 383
Rep Power: 10
gwierink is on a distinguished road
Thanks, Eugene, I will have a try
__________________
Regards, Gijs
gwierink is offline   Reply With Quote

Old   November 29, 2010, 00:51
Default
  #15
pkr
Member
 
Join Date: Nov 2010
Posts: 33
Rep Power: 6
pkr is an unknown quantity at this point
I just started using OpenFoam for evaluating it for multi-core/many-core machines. I need to create a mesh with large number of cells (~2 million).

So I was looking at nonnewtonianIcofoam. I refined the mesh using refineMesh utility. The current mesh structure is as follows:

Mesh stats
points: 14884
internal points: 0
faces: 29042
internal faces: 14182
cells: 7200
boundary patches: 6
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 7180
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 20


I would like to increase the number of cells and faces in this mesh to a large value. How can it be done using blockMesh? Please suggest the required changes. It will be great if I can get some kind of help. Thanks!!
pkr is offline   Reply With Quote

Old   July 8, 2014, 05:53
Default
  #16
Senior Member
 
Julien
Join Date: Jun 2012
Location: France
Posts: 152
Rep Power: 5
Djub is on a distinguished road
Hello everybody,
it makes a long time that you wrote into this subject. Today four years later, I have the same kind of problem. I would like a ~18 Mcells blockMesh. Do I need only to ask more memory on my cluster ? I am asking for 8000mb and it is still too few...
Any idea / suggestion / comment ?
Djub 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
[ICEM] surface mesh merging problem everest ANSYS Meshing & Geometry 44 April 14, 2016 06:41
SnappyHexMesh for internal Flow vishwa OpenFOAM Native Meshers: snappyHexMesh and Others 23 August 6, 2014 03:50
2d irregular grid Remy Main CFD Forum 1 December 22, 2008 05:49
basic of mesh refinement arya CFX 4 June 19, 2007 12:21
Does blockMesh create mesh vertices in any particular order brooksmoses OpenFOAM Native Meshers: blockMesh 3 December 12, 2005 21:26


All times are GMT -4. The time now is 20:57.