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Meshing in EDITFEKO

Hi,

I have a simple problem. I create a closed cylinder in Cadfeko, union and mesh it. However, when I try it in Editfeko, I create two ellipses and a cylinder and mesh it. The number of triangles in are close ( 2158 vs 2352 ) but the number of points are different (1000 vs 7000). I took the nas output file to draw the mesh and attached in the files below. Since the number of points in Editfeko is too big, I think there is a problem with it, maybe relating to the union. Can anyone explain to me this phenomenon ?

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Altair Forum User

Dear Tuan,

The mesh density depends on the type of mesh being used; please make sure that the mesh type is the same in both EditFEKO and CADFEKO.

Moreover, please ensure the structure are the same in both EditFEKO and CADFEKO.

And yes, structures that touch each other need to be unioned.

It looks like the files were generated using matlab; I do not have access to matlab, can you please send screen snap of the figures?

Also, FEKO only reports the number of triangles, what are the points that you are refereeing to?

Regards,

Aseim

Altair Forum User

Aseim,

I'm pretty sure that the mesh type and size are the same, as well as the dimension of the structure, which is why the numbers of the triangle are close ( 2158 vs 2352 ).

About the union, in Edit FEKO I cannot union so that's why I think the problem comes from.

Cad FEKO reports the number of the triangle, but the output NAS file have the points of each triangle if you want to reconstruct the mesh outside FEKO. Since there are about 2000 triangles, the number of point should be about 1000 like in Cad FEKO mesh, not about 7000 like in Edit FEKO mesh, unless Edit FEKO does not treat the structure as a union.

So basically, my question is how to union in Edit FEKO.

Thank you,

Tuan Nguyen.

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JIF

Hello

Could you send you models? If we have the models, we can take a look.

When building models in EDITFEKO, there is no need to union (no bolean operations are allowed). The model needs to be built so that the nodes align at the borders (if it borders another face). The union in CADFEKO is simply to ensure connectivity so that the correct mesh is generated. When creating models in EDITFEKO, the user needs to ensure that the model is correct.

Regards

JIF

Altair Forum User

I include a CAD and EDIT FEKO model with exactly the same object. Could you take a look at exported nas file to see the difference? In EDIT FEKO model the number of points is exactly three times the number of triangles, which means no points are repeated.

Best regards,

Tuan.

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JIF

Hello Tuan,

I now understand what 'problem' you are referring to. This is simply the difference between the way the FEKO solver exports Nastran files and now CADFEKO exports Nastran files. CADFEKO writes out all the nodes for the mesh model and these will be unique (shared nodes). The FEKO kernel creates Nastran files by writing out the three nodes of a triangle and then the triangle, then the three nodes of the next triangle and then the triangle. Thus, CADFEKO exported Nastran files will have the minimum amount of nodes, while the FEKO kernel would export the same model with 3*(#triangles) nodes. If you need to build your models in EDITFEKO, but want your Nastran files to have unique nodes, I would suggest (as a workaround) to import the FEK file of the EDITFEKO model in CADFEKO and then export it from CADFEKO.

The way the kernel exports the nodes is not optimal, but also not incorrect. I'll log a request to improve the export of Nastran files so that it only exports each node once (unique nodes). Is this a problem for you? We have never received complaints or requests to change this in the past.

By the way, your models are correct (CADFEKO and EDITFEKO models). You don't need to change anything. What you are seeing is simply a difference in the way the two applications export Nastran files.

Kind regards

JIF

Hello Tuan,

I seem to be having problems providing you with a reply - I have replied multiple times already.

Your models are correct. The 'problem' that you are seeing is simply a difference in the way CADFEKO and the kernel export Nastran files. CADFEKO exports the nodes the way you expect - all the unique nodes and then the triangles. The kernel exports the three nodes used by a triangle and then the triangle. This means that the kernel will export 3 nodes for each triangle, even if some of them are spatially coincident. Neither of the exports are incorrect (not a bug), but the CADFEKO export is more optimal. I will log an issue for the developers to look at the kernel Nastran export.

If you need the nodes to be exported the way that CADFEKO exports them, but want to create the mesh in EDITFEKO, you can create the model in EDITFEKO and import the *.fek file in CADFEKO and then export the Nastran file from CADFEKO.

Kind regards

JIF

Altair Forum User

Hello Tuan,

I seem to be having problems providing you with a reply - I have replied multiple times already.

Your models are correct. The 'problem' that you are seeing is simply a difference in the way CADFEKO and the kernel export Nastran files. CADFEKO exports the nodes the way you expect - all the unique nodes and then the triangles. The kernel exports the three nodes used by a triangle and then the triangle. This means that the kernel will export 3 nodes for each triangle, even if some of them are spatially coincident. Neither of the exports are incorrect (not a bug), but the CADFEKO export is more optimal. I will log an issue for the developers to look at the kernel Nastran export.

If you need the nodes to be exported the way that CADFEKO exports them, but want to create the mesh in EDITFEKO, you can create the model in EDITFEKO and import the *.fek file in CADFEKO and then export the Nastran file from CADFEKO.

Kind regards

JIF

Thank you so much for a clear explanation. I want to have the optimal mesh in EDITFEKO because I want to export hundreds of meshed object (one per time frame) from Feko. I'm having the program to export the mesh in EDITFEKO but my solver cannot solve it because of the coincident points. If you know any method to fix the mesh from EDITFEKO even after exporting it out, please help me.

Tuan Nguyen.