open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi!

Im trying to create a very large mesh in BK. Number of nodes > 15 000 000
but im having some problems with wierd looking meshes (giant holes etc). I've moved outline etc to origo. Is there a limit to number of nodes/elements for generating mesh in BK?

Regards,
Joanna

Hi Joanna,

There are no explicit hard limits to the size of any object in Blue Kenue.
Data structures are dynamically allocated as required by parameters provided by the user.

There are however practical limits imposed by the operating system.
If you are using a 32 bit OS then there is a 2 GByte limit to virtual memory so make sure you are using Windows/64 and BlueKenue 64 bit edition.

I have never tried to create a mesh with 15 million nodes, but with BlueKenue64 it should be possible although I'm sure it's going to take
a while to generate such a mesh.

The "weird looking mesh" problem is likely related to something else.
Without knowing exactly the inputs/parameters you are providing to the mesher, I have no way of knowing what is happening...

If you turn off the "Auto Smooth Mesh" option, are the "weird" holes still generated?

Cheers... Martin

Hi Martin!

Just some additional information regarding the "holes" in my BK-generated mesh (I use 64 bit by the way). There is no difference when I turn off the "auto smooth". It seems like the problem occur when there are many constraines (several density variations). I'm trying to generate a mesh with 16 M elements and constant edge length right now to see if that works. I'll get back to you. I'll attach the wierd looking mesh (estimated approx 16 M elements) :)

Joanna

Hi Joanna
According to your image, it could be great to have the project to check what is going wrong...
Maybe you could post the T3M file to help us to understand what you've done and where the problem is.

Kind regards

Biensur, see attached files. It would be really nice to know if I'm doing something wrong here, thanks :)

Joanna

Edit: Can you see my attachments? (I can't see them myself which i'm guessing is not a good sign..)

No attachments!
Try with a zip file and check if the size is not too large (the limit on the website is 2M)
Otherwise use an exchange platform or a private message

Regards

Success? :)

Yes
I could load it into BK!
As the process to compute the mesh takes a lot of time, I was wondering what is your main goal with such definition of density?
As I understand, there is 2 main sizes 3m and 50m and on the north and south border, some kind of smooth variation of density...

You really want to have a 3m mesh in all this large area? One of the main advantage of the triangles is the capacity to adapt the size locally...

If you could tell us more about the objective, maybe we could give you some advices to produce a good mesh without so much nodes...

Regards

Hi Joanna,

Your question peeked my curiosity.

So I set out to see if I could generate a mesh this large (> 15 Mil nodes) efficiently. I used my gis2mesh.py script that uses Triangle as the mesh generation engine. I made a 100 m x 100 m box, and asked Triangle to generate a mesh with an area constraint of 0.00075 sq. m (meaning the area of every triangle in the mesh had to be less than this value). This amounts to edge lengths of 25-50 mm.

Triangle generated a mesh having 10,349,741 nodes and 20,686,255 elements in a manner of seconds (including writing the 750 MB nodes and 580 MB element files). Triangle is very fast at this. I couldn't quite make to 15 Mil nodes, as I ran out of memory. Parsing Triangle's output took about 7 min to convert it to an ADCIRC format, and another 7 min to convert ADCIRC mesh to *.vtk format to view it in Paraview. I didn't bother generating a *.slf file, as I wouldn't have a clue what to do with a mesh that large.

Anyhow, if you are working with such large meshes perhaps you could give Triangle mesh generator a try. It is very quick.

Pat

Hi Pat,

I've read your article on using Gmsh and Triangle as mesh generator. I find it very easy to use BK for mesh generating but for my current projects (requiring very large meshes) it seems like I have to start using something else.

Thanks :)

Joanna