Problem meshing an object.

Student_21133

Hello,

I have an issue with meshing an object.

I try to mesh a plane model obtained with 3DS Max, which provides a .stl file.

This .stl file is read as a mesh by Feko ("Import/Mesh") :

In order to mesh it correctly, I set a frequency (100MHz) then right click on the mesh ("Use model mesh") :

Apparently, the model is correctly meshed :

, but flaws appear on closer inspection :

One can see that there are holes in the meshing, and even stranger, some triangles are not complete :

I've tried all the settings in the "Meshing/Modify Mesh" tab, but I can't get a correct mesh.

Would anyone recognize a well known error and have a way to solve it ?

Thank you in advance.

BrianWoods

HI @Student ,

Maybe one other observation that may be causing confusion here:

I see that you have the Overlay display mode on and you are (therefore) seeing both the mesh and the geometry at the same time in the 3D view. In some places, the mesh view is being obscured by the underlying geometry. 

If you change the display mode to only show the mesh

- Either on the Ribbon under Display Options, so that the setting is as follows:

 

- Or in the quick actions available at the bottom of the CADFEKO windows (as shown below):

I believe that you may be able to see the mesh more correctly and you may find that the mesh is infact 'good'.

Torben Voigt

Hi @Student ,

Unfortunately, it is not uncommon for CAD data to be unsuitable for EM simulations. It is often due to errors in the data, such as inaccuracies in the definition of surfaces, or extremely small geometric details that lead to very small mesh elements. The usual workflow is then actually via pre-conditioning tools such as HyperMesh. There you will find the necessary tools to create a valid mesh from CAD data, no matter how faulty it may be

Of course, you can also do fourl in CADFEKO yourself (CAD repair tools, regeneration of defective faces, etc.), but this can be a lengthy process depending on the data. If you like, I can take a look at your model. Maybe I'm lucky and can fix the problems quickly.

Maybe it will also help you to use the Airbus model from the Component Library in CADFEKO?

Best regards,
Torben

BrianWoods

HI @Student ,

Maybe one other observation that may be causing confusion here:

I see that you have the Overlay display mode on and you are (therefore) seeing both the mesh and the geometry at the same time in the 3D view. In some places, the mesh view is being obscured by the underlying geometry. 

If you change the display mode to only show the mesh

- Either on the Ribbon under Display Options, so that the setting is as follows:

 

- Or in the quick actions available at the bottom of the CADFEKO windows (as shown below):

I believe that you may be able to see the mesh more correctly and you may find that the mesh is infact 'good'.

Student_21133

Hi Brian,
You've found the right trick.
I changed the display mode to show the mesh only, as you explained, and my mesh looks fine now :

... but now I have a more common problem when launching the solver : 
"ERROR 832: Segmentation rules violated (two triangles touching without a common edge)".
I'll try to solve it myself... and bother an expert again if I can't.
Thanks a lot for your help (and thanks also to Torben for his dedication and good advice !)
Good day to you both.

Torben Voigt

Hi Student,

As I said, such problems are unfortunately not uncommon. Did you activate Connectivity (Display Settings)? This highlights open edges and often is useful to find overlappnig faces in CADFEKO.

The only way to find the faulty mesh triangles would be to open the model in POSTFEKO and search for the triangles mentioned in the .out file (also see https://www.youtube.com/watch?v=i4AjhQ003BY&t=11s).

I would be happy to take a look at your model. 

Best regards,
Torben

Student_21133

Hi Torben,
I followed your advice : I watched your interesting video about mesh problems and how to solve them, and I applied the procedure (with "connectivity" enabled). Unfortunately, I can't produce a correct mesh because the original file comes from an unusual source : in CADFeko, my triangles are not easily accessible. 
I have seen that there are real aeroplanes in Feko (like the A380 you showed me), but I have to concentrate on a specific model.
So I'm going to start working with HyperWorks, but I'd also be grateful if you could take a look at my file, as you offered.
I can't post my file on a public forum : it's not copyright free as it comes from my organisation. Can I open a support ticket?
Thank you very much.

Torben Voigt

Student_21133 said:

Hi Torben,
I followed your advice : I watched your interesting video about mesh problems and how to solve them, and I applied the procedure (with "connectivity" enabled). Unfortunately, I can't produce a correct mesh because the original file comes from an unusual source : in CADFeko, my triangles are not easily accessible. 
I have seen that there are real aeroplanes in Feko (like the A380 you showed me), but I have to concentrate on a specific model.
So I'm going to start working with HyperWorks, but I'd also be grateful if you could take a look at my file, as you offered.
I can't post my file on a public forum : it's not copyright free as it comes from my organisation. Can I open a support ticket?
Thank you very much.

Hi Student,

of course you can create a Support ticket.