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Help creating a ring geometry
Posted Feb 24, 2012, 10:44 p.m. EST Geometry, Parameters, Variables, & Functions, Structural Mechanics 1 Reply
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I'm new to COMSOL and pretty much just learning the basics of building within it for right now. What I'm trying to figure out how to do is to create two cylinders one within the other but just a little bit shorter in diameter and then to extrude them the same amount and kind of remove the middle piece in order to create a circular channel through which I can let a fluid flow. I know it's pretty basic, but I'm learning on my own for the most part so any help would be appreciated. I can creat both the cylinders (by making them in a 2D plane and then extruding them) but I'm not sure how to remove the center so that I only have a channel or a ring left.
1 Reply Last Post Feb 25, 2012, 8:25 a.m. EST
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Posted:
1 decade ago
Hi
you have at least 2 simple ways: deine a workplane in 3D open it draw a circle, then under the Layer tab, enter a thickness for your wall and you will have the second cylinder, alternative you duplicate your circle and change the radius., then you extrude. With this you get 2 concentric cylinders (note you could have made directly the 2 cylinders in 3D with the cylinder volume (including the layer).
Like this your model is set up for a tube (external) with water inside, hence you have 2 entities (domains in this case) that you may select in the FEM physics section.
If you have no fluid in the middle, and want a hollow cylinder you have also a few options, either you do a difference large_cylinder - small cylinder (or you do it on the circels before you extrude).
Often what people do is to make the hollow cylinder and the add again the fluid in the middle. This is not required, as when you pass the "Geometry Finish" line you geometrical object are analysed and transformed into numbered and unique Entities (domains, boundaries, edges points, to which you can attach physics or BC ...)) ANd passing the Finish line both methodes give 2 domains, but the second method has a few extra operations one can as well skip. The geoemtry objects has nothing to do with the final physics, the mapping to the physical parts is done on the Entities after having united and analysed the geometry
Hope I'm clair enough, this operation took me some time to really catch, but once you have got the principle, it feels all natural
--
Good luck
Ivar
you have at least 2 simple ways: deine a workplane in 3D open it draw a circle, then under the Layer tab, enter a thickness for your wall and you will have the second cylinder, alternative you duplicate your circle and change the radius., then you extrude. With this you get 2 concentric cylinders (note you could have made directly the 2 cylinders in 3D with the cylinder volume (including the layer).
Like this your model is set up for a tube (external) with water inside, hence you have 2 entities (domains in this case) that you may select in the FEM physics section.
If you have no fluid in the middle, and want a hollow cylinder you have also a few options, either you do a difference large_cylinder - small cylinder (or you do it on the circels before you extrude).
Often what people do is to make the hollow cylinder and the add again the fluid in the middle. This is not required, as when you pass the "Geometry Finish" line you geometrical object are analysed and transformed into numbered and unique Entities (domains, boundaries, edges points, to which you can attach physics or BC ...)) ANd passing the Finish line both methodes give 2 domains, but the second method has a few extra operations one can as well skip. The geoemtry objects has nothing to do with the final physics, the mapping to the physical parts is done on the Entities after having united and analysed the geometry
Hope I'm clair enough, this operation took me some time to really catch, but once you have got the principle, it feels all natural
--
Good luck
Ivar