Menu

Discussion Forum

New Discussion
Filtrer

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Internal error in geometry decompositon: problem with just 2 elements in model!

Posted 15 avr. 2013, 18:21 UTC−4 Version 4.3a 3 Replies

Sri Puranam
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi Everyone:

I am trying to build a complicated 3-D model with many channels and such but I ran into a problem very early on. I just have one block attached to one hexaheadron. I am unable to form a union. I must be missing something very basic. Could someone help me out? I have attached my mph file.

Thanks!
Sri.

Attachments:

3 Replies Last Post 16 avr. 2013, 11:55 UTC−4
John H.
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 16 avr. 2013, 08:13 UTC−4
The documentation of the "Hexahedron" geometry object says "Vertices 1–4 are the vertices of the bottom face in clockwise order." It makes a similar statement about the top face. Now, I have no idea what "clockwise order" is supposed to mean in this context, but I went ahead and just inversed the order of the vertices (both faces). Suddenly it worked.

I noticed that the geometry sequence also works with the vertices in the original order if you switch from the "CAD Import Module" geometry kernel to the "Comsol" kernel. Looks like a bug to me...

The documentation of the "Hexahedron" geometry object says "Vertices 1–4 are the vertices of the bottom face in clockwise order." It makes a similar statement about the top face. Now, I have no idea what "clockwise order" is supposed to mean in this context, but I went ahead and just inversed the order of the vertices (both faces). Suddenly it worked. I noticed that the geometry sequence also works with the vertices in the original order if you switch from the "CAD Import Module" geometry kernel to the "Comsol" kernel. Looks like a bug to me...

Attachments:

Sergei Yushanov Certified Consultant
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 16 avr. 2013, 08:43 UTC−4
Sri,

Another way to get around “Form Union” issue in your geometry is to use Work Plane Geometry and Extrude options, as shown in the attached mph file. For better visualization of your geometry, clear “Preserve aspect ratio” in the Camera View, as shown in the attached picture.

Please realize that extra care should be taken to build good quality mesh for this type of geometry.

Regards,
Sergei
Sri, Another way to get around “Form Union” issue in your geometry is to use Work Plane Geometry and Extrude options, as shown in the attached mph file. For better visualization of your geometry, clear “Preserve aspect ratio” in the Camera View, as shown in the attached picture. Please realize that extra care should be taken to build good quality mesh for this type of geometry. Regards, Sergei
Sri Puranam
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 16 avr. 2013, 11:55 UTC−4
John: I fixed the geometry by switching the order of the verticies and it worked for me too. Thanks for the tip!

Sergei: My final geometry is a complex 3-D geometry which does not lend itself easily to extrusion. Just for these two elements, I tried extrusion and it worked. There were no errors. I have to now decide which of the two proposed solutions I will end up using.

Thanks to both of you.
Sri.
John: I fixed the geometry by switching the order of the verticies and it worked for me too. Thanks for the tip! Sergei: My final geometry is a complex 3-D geometry which does not lend itself easily to extrusion. Just for these two elements, I tried extrusion and it worked. There were no errors. I have to now decide which of the two proposed solutions I will end up using. Thanks to both of you. Sri.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content