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Second order tetrahedral mesh elements

Posted 07.04.2011, 10:55 GMT-4 Version 4.2 5 Replies

Tanja Etzelstorfer
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Hello all!

Is there a possibility to use second order tetrahedral mesh elements (one node at the corners and an additional node in the middle of the edges = 10 nodes per element)?

I can not find this option in COMSOL 4.1.

Any help is much appreciated!

Best,
Tanja
5 Replies Last Post 24.10.2011, 11:46 GMT-4
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 07.04.2011, 15:28 GMT-4
I believe that's what COMSOL uses by default when you generate a tetrahedral mesh in Solid Mechanics.

Nagi Elabbasi
Veryst Engineering
I believe that's what COMSOL uses by default when you generate a tetrahedral mesh in Solid Mechanics. Nagi Elabbasi Veryst Engineering
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 08.04.2011, 01:17 GMT-4
Hi

COMSOL uses "shape functions" on the mesh elements of 1st, 2nd, 3rd or even higher order, default is generally 2nd (but not always depend on the variables, check your main physics nodes) this corresponds more or less to "traditional FEM programmes" to Tri 3,4,6,7 ... Quad 4,5,8,9 ... or Tet 4,10,11 ...

--
Good luck
Ivar
Hi COMSOL uses "shape functions" on the mesh elements of 1st, 2nd, 3rd or even higher order, default is generally 2nd (but not always depend on the variables, check your main physics nodes) this corresponds more or less to "traditional FEM programmes" to Tri 3,4,6,7 ... Quad 4,5,8,9 ... or Tet 4,10,11 ... -- Good luck Ivar
Tanja Etzelstorfer
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Posted: 1 decade ago 11.04.2011, 09:36 GMT-4
Hello Ivar!

I can not find this options.
But if this is default, how can I access this information within the Matlab environment? I only get the corner nodes and the data values at that position.

Best wishes,
Tanja
Hello Ivar! I can not find this options. But if this is default, how can I access this information within the Matlab environment? I only get the corner nodes and the data values at that position. Best wishes, Tanja
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 11.04.2011, 09:41 GMT-4
Hi

the option is in the GUI, main physics node "Discretization", but I'm not sure where and how you catch it now in matlab with V4.

On the other hand, I do neither not know if these "extra points" are accessed via matlab, as I'm not sure they are part of the matrices. COMSOL has a more modern and different generic approach, with a cleaner separation between physics and (FEM) maths, in my view, than older traditional FEM programmes.

For the time being I have managed without matlab since I got CM V4, even if I have it ready in case, but there are many new things to learn there too with the v4 (r)evolution, so I'm lacking behind ;)

--
Good luck
Ivar
Hi the option is in the GUI, main physics node "Discretization", but I'm not sure where and how you catch it now in matlab with V4. On the other hand, I do neither not know if these "extra points" are accessed via matlab, as I'm not sure they are part of the matrices. COMSOL has a more modern and different generic approach, with a cleaner separation between physics and (FEM) maths, in my view, than older traditional FEM programmes. For the time being I have managed without matlab since I got CM V4, even if I have it ready in case, but there are many new things to learn there too with the v4 (r)evolution, so I'm lacking behind ;) -- Good luck Ivar
kodanda
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Posted: 1 decade ago 24.10.2011, 11:46 GMT-4
Hi,

Can anybody point out to the resource on how the nodes are ordered for a "tet2" element (quadratic tetrahedral element with 10 nodes)?

When I export the mesh directly (no changes made) from COMSOL to ABAQUS, I see a problem with the mid-side nodes.

FYI: this is the node ordering in ABAQUS:
abaqusdoc.ucalgary.ca/v6.9/books/usb/default.htm?startat=pt06ch24s01.html#usbgencont

Best regards,
Kodanda
Hi, Can anybody point out to the resource on how the nodes are ordered for a "tet2" element (quadratic tetrahedral element with 10 nodes)? When I export the mesh directly (no changes made) from COMSOL to ABAQUS, I see a problem with the mid-side nodes. FYI: this is the node ordering in ABAQUS: http://abaqusdoc.ucalgary.ca/v6.9/books/usb/default.htm?startat=pt06ch24s01.html#usbgencont Best regards, Kodanda

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