Importing Mesh from COMSOL

General Discussion
1

Has anyone extracted a mesh from COMSOL and imported it into FreeFem?

I am exporting a 2d mesh from COMSOL. There are different formats that I can extract. I extract and tried all of them, but I cannot import it into FreeFem.

Does anyone know what format I should do and what procedure I should follow?

I appreciate your help.
Best

2

What format did you try?

3

Thank you for your reply. I tried all the formats.
mphbin, mphtxt: these two weren’t useful because freefem and also Gmsh cannot open them.

.nas: I could open this with Gmsh and save it as msh file. But I wasn’t able to open it with code.

.vtu: THis one was also not readable in freefem.

Could you please tell me what to do? Thank you.

4

If you can open with Gmsh and then export to .mesh or .msh, then that should be alright.

5

Thank you again.

I saved it .msh file, but it is not opening if freefem.

Here:
load “gmsh”
mesh Th=gmshload(“Mesh4.msh”);

this is the error:
mshptg bug in number of points 1 > 1 == max nb points
Sorry Error build delaunay triangle error = 1
current line = 3
Exec error : Error mshptg8_
– number :1
Exec error : Error mshptg8_
– number :1
err code 8 , mpirank 0
try getConsole C:\Users\ava\Desktop\My FreeFem\reading.edp
save log in : ‘C:\Users\ava\Desktop\My FreeFem\reading.log’
wait enter ?

Please let me know what I should do.

6

Can I give you my .nas or .msh file and you check it, please?

7

Sure, upload the .msh.

8

Thank you.

I appreciate your help.
Mesh1.mesh (836.8 KB)

9

Your mesh has no boundary elements, so it cannot be read by FreeFEM. You need to define the surface of the circle.

10

Could you please help me how I can do that?

The file that I sent you is the result of gmsh from .nas of the COMSOL.

11

Some time ago I used feconv to convert a 3D mesh from mphtxt format to gmsh format. Check out the software. Maybe it also works for 2D meshes.

1 Like
12

Hello,
I recently have tried feconv that @henkel suggested and it worked! Thanks to him!
I wanted to import in freefem a mesh of a 2d square with a slit from COMSOL.

Firstly, you need to choose .mphtxt and check all the 4 first v’s on the export menu, that is:

  • domain elements
  • boundary elements
  • vertex elements
  • geometric entity information

But then all I had to do was to write in cmd (though installing feconv is a bit hard):

  1. cd <go to a place where feconv is>
  2. feconv -ff <yourfile.mphtxt> <newfile.msh>
    -ff is for when .msh file appears, you choose for freefem. You could also write -gm for gmsh.
  3. And then you just read it in freefem:
    mesh Th = readmesh("newfile.msh");
    plot(Th, wait=1);

P.S. At least that’s what I had come to, through trying and failing.

P.S.S. If you need to deal with labels, I just printed them out with cout << labels(Th)<< endl; and it’s just numbers. I deformed the square by the numbers one by one until I finally discovered every sides’ labels.

P.S.S.S. If you read somewhere that for importing 2d-mesh you need to remove z-axis from your file because freefem can’t read because of it, don’t trust them. Freefem reads 2d meshes just fine with readmesh().