Discussion Forum

For those unfamiliar, and axicon is apparently an unusual type of lens.

Geometries that cannot be successfully meshed automatically can usually be meshed using the advanced options. See https://www.comsol.com/learning-center/building-the-mesh-for-a-model-geometry-in-comsol-multiphysics.

https://www.comsol.com/learning-center/building-the-mesh-for-a-model-geometry-in-comsol-multiphysic

Thank you.I actually have watched this video but for me it doesn't seem to work because of the geometry which has open ends.I am struggling to create the axicon because whenever i tried to do it,the geometry has open ends because of the sweeping of helix through the cone.I swept one face of the cone through the helix and this face seems to have the problem and I am still stuck on it.Do you have any other resources on how to tackle this situation?

At first the question seemed to concern meshing. Now it is perhaps a problem with construction of the geometry.

Only in very rare cases is it possible to provide useful advice without looking at the .mph file. Apparently this is not one of those rare cases. OP should post the file (perhaps with some explanation of the geometry he is trying to construct) OR consult a colleague who is familar with FEM calculations.

A review of other posts will show that posts that do not include an attached file rarely result in replies.

Hi, Thanks again for your reply.I have posted the file so that you can take a look.I can't really tackle this issue so any help would be appreciated.

If I am understanding the desired geometry correctly this is an interesting puzzle.

See attached. Even if not exactly what you want it may help you go in the right direction. I made surfaces using the 3D Parameterized Surface node, with some kludges that help avoid the dreaded Internal Error in Geometry Decomposition.

If I am understanding the desired geometry correctly this is an interesting puzzle.

See attached. Even if not exactly what you want it may help you go in the right direction. I made surfaces using the 3D Parameterized Surface node, with some kludges that help avoid the dreaded Internal Error in Geometry Decomposition.

Thank you so much for your support on this case.Yeah it is a complex geometry and thats why i think it shows meshing error.Can you please explain more about how you got the geometry without these internal errors?I tried to design it using parametric surface node and I got almost the desired shape but still getting meshing errors.But your geometry looks interesting though it is not the desired shape but I guess if I could tailor it in the right way,this seems a positive approach.I'm attaching my geometry based on parametric surface node here.I would like to get your opinion on it as I guess you've got the right knowledge to guide me on this.Once again thank you.

I thought you were trying to make a solid object like a lens. Your recent file produces a bunch of surfaces, not a solid.

As to geometry decomposition errors- it's not clear why they happen but I eliminated them by (1) making my surface (or tool for partitioning) from two partial surfaces and (2) making the surface a bit bigger than the cylinder.

I thought you were trying to make a solid object like a lens. Your recent file produces a bunch of surfaces, not a solid.

As to geometry decomposition errors- it's not clear why they happen but I eliminated them by (1) making my surface (or tool for partitioning) from two partial surfaces and (2) making the surface a bit bigger than the cylinder.

I wanted to create the helical axicon as a solid object.I am quite new to COMSOL,so thats why I am a bit confused sometimes.I thought it became a solid but I guess I could just put a cone to make it a solid,isnt it?I really dont understand how to proceed.When i tried to do the computation,it shows "Variables property does not include all variables in xmesh" but this was the case in my first structure.The last structure with the parametric surface,it shows meshing error.

You can get advice here (especially if you post your .mph file and have an interesting question) but you are not likely to get a complete solution. Some of us like to get paid for that sort of thing.

But anyway, advice. A parametric surface is a surface, not a solid. To make it into a solid you can use it as a tool for partitioning a volume, and then delete one of the partitions. Kind of like making a lens by grinding away part of a larger piece of glass. This is what I did in my example.

I didn't think sweeping with the helix was the way to go. If you want to explore this I recommend exaggerating the pitch so you can see what is happening. (And I don't see why you want to make 3 turns!).

Your issue right now is constructing the right volume, which is not really a Comsol issue. The same sort of tools for geometry construction are used in other applications.

Good luck, I think you have enough tips to get moving in the right direction.