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Hi

normally its rather simple, if your donut is a what I call a simple torus:

open 3D geometry with Geom1 by default, call in a 2D workplane (Draw WokPlane Settings) which creates a 2D Geom2, draw a circle of the radius of the torus section (and for simplicity lets define the torus revolution rotation axis at (0,0) and vector direction (0,1), so the centre of the 2D cercle is to be drawn on the torus revolution radius).

Then mesh the 2D circle, call out the "Revolve Mesh" extrusion into Geom1 (here you define the point vector of the revolve axis)

OK and there you go

still need to set up your physics etc, but that's another story

hope it helps
Good luck
Ivar

Thank you for your reply.

Thats what I did.
But as soon as I add more geometries in my model the mesh of the donut disappears.

Another way I tried:
I finish my geometry and try to revolve the mesh in the end. I receive an error message:

Error: 2222
Geometry to revolve may not cross axis of revolution

(I did not do this mistake in th error message)

and I cannot select to revolve the mesh in geometry 1. I just can select to relvolve in a new geometry.
(Comsol 3.5)

Cheers

Thomas

It does not seem like the staff at COMSOL have answered this question.

I am having the same problem. If you do the following it works:

1) Create new 3D geometry
2) Add a 2D working plane
3) Draw object in 2D, mesh, then revolve the mesh into the first geometry
4) Switch to geometry 1, select the new subdomain and apply the physics to the object.

Then you can solve the problem.

But if you do something logically similar, but slightly out of order, it won't work:
1) Create 2D geometry
2) Draw object in 2D, mesh, then revolve the mesh into a new geometry
3) Switch to geometry 1, select the new subdomain and TRY to apply the physics to the object. However you can't because the Physics menu items are all greyed out. Why? This is a glaring bug and should be fixed. It gets worse.
4) Use the newly created 3D geometry and now add a 2D working plane (you can delete or keep the original 2D geometry, it has no effect). Delete all object in the 3D geometry. In the 2D geometry, draw object, mesh, then revolve the mesh into the 3D geometry.
5) Switch into 3D and select the subdomain, but you still can't select the physics submenus.

The only way that I have been able to make this work is if I make the 3D geometry first. AFAIC, this is either a bug or poor programming.

Cheers,
Steve

Hi Steven

Thanks for the clear explanations, these are useful for many of us.

To make another thing clear, on the Forum there are few COMSOL "staff" as their priority is, the way I understand it, to reply first of all to the mails sent to the COMSOL "support".
When they have some time left they answer here, which does not mean they are not reading and observing carefully what we are doing and saying ;)

Most of us, even several of the "Moderators", are ordinary users, as I understand you are too, we want just to have an active Forum, and at least for myself, I learn a lot by analysing and answering the questions here, when I beleive I can, so pls joing the group.

Sincerely
Ivar

Hello Stephen,
About that "glaring bug": I will venture to guess that you have not selected an application mode for your 3D geometry (although you may have for the 2D geometry). Once you do, the Physics items will no longer be grayed out.
Best,
Jeff