open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi everyone,

I have a large mesh. When I want to add somewhere a piece of mesh, in my case it is the Scheldt Estuary and I want to add somewhere an extra flooding area,I create an outline for the flooding area and use the big mesh as submesh in the mesh generator. I hit the run button and the result is nice. My question is about the processing time: Blue Kenue takes in my case more than 12 hours to compute this new mesh.(When I use a small mesh as submesh, the processing is very quick.) But nothing needs to be changed in the big submesh. What is blue kenue doing all this time? Can I do this faster; is there a faster way?

King regards,
Sven

Hi Sven,

There is something strange going on but I can't tell what it is from your description.
What is the last message on the progress dialog before it goes off for a long time?
How long does it take to produce the original large mesh?

What I can suggest is you try to generate the small mesh separately by supplying a fixed outline that lines up with the nodes in your big mesh and then use "Edit->T3 Mesh->Merge Mesh"

Cheers... Martin

Hi Martin,

the merge mesh thing could be a nice alternative!

Although I don't understand why adding a small part of mesh to a bigger mesh should take such a long time.
The big mesh has about 456000 nodes. It takes a long time to create this one. I wanted to add a small flooding area to it (this would take only 153 nodes).
I use the mesh generator and use a small outline surrounding the flooding area I would like to add and use the big mesh as a submesh. When I run this, it takes some time to 'compute interior nodes' but the process that takes most of the time (I estimate sometimes more than 20 hours) is 'Finalize submesh & island edge connectivity'.
In the end I get a nice result, but if I want to change my mesh in 20 places like this it takes me up to 2 weeks to do this.
It seems to me that BK is recalculating also the whole submesh, while this is not necessary.

I could send you the mesh generator file if necessary.

Thanks!

Sven

Hi Sven,

Ahhh... the infamous "Finalize submesh & island edge connectivity" function. It is a nasty bit of code that I had hoped to throw away at some point. It is a brute force algorithm that was added to fix problems that can arise when long thin islands and long thin submeshes are present in an area where the density object specifies large elements (much larger than the width of the island/submesh). In essence it attempts to recover from inconsistent density specs.

Hopefully my successor Alan will fix this at some point (or provide an option to turn this code off) but for now I think you should look at the Merge Mesh option.

Cheers... Martin

Hi Martin,

thanks for the info. Meanwhile I tried the merge option and this saves me a lot of time indeed!
Thanks for the suggestion!

Cheers,
Sven