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help on boundary index
Posted Jan 4, 2010, 12:38 a.m. EST 2 Replies
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Hi,
I have a simple 2D heat transfer problem defined on a rectangular geometry of a copper plate. Once I open the history (.m) file of the model saved by COMSOL in matlab editor, I see the boundary index entry which looks something like: bnd.ind = [1,3,2,1]; I understand that these four entries are some way related to the four boundaries of my 2D model. But what do the number [1, 3, 2, 1] possibly mean? Could someone please help me sort out this little mystery. I swamped through the COMSOL manual but did not see any answer.
Thanks,
Sandra
I have a simple 2D heat transfer problem defined on a rectangular geometry of a copper plate. Once I open the history (.m) file of the model saved by COMSOL in matlab editor, I see the boundary index entry which looks something like: bnd.ind = [1,3,2,1]; I understand that these four entries are some way related to the four boundaries of my 2D model. But what do the number [1, 3, 2, 1] possibly mean? Could someone please help me sort out this little mystery. I swamped through the COMSOL manual but did not see any answer.
Thanks,
Sandra
2 Replies Last Post Jan 4, 2010, 1:36 a.m. EST
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Posted:
1 decade ago
Hi
After some trial I could figure it out something but needs confirmation from someone. In the test case I cited, bnd.ind = [1,3,2,1]; the integer index list possibly refers to the grouped boundaries i.e. the boundaries sharing the same settings in COMSOL model. In my case, left and right boundaries have same setting so they get the same list index 1, while the top and the bottom boundaries settings being different, are therefore, indexed as 2 and 3. However, it is still a mystery to me as to how the COMSOL decides their order. Thanks.
Sandra
After some trial I could figure it out something but needs confirmation from someone. In the test case I cited, bnd.ind = [1,3,2,1]; the integer index list possibly refers to the grouped boundaries i.e. the boundaries sharing the same settings in COMSOL model. In my case, left and right boundaries have same setting so they get the same list index 1, while the top and the bottom boundaries settings being different, are therefore, indexed as 2 and 3. However, it is still a mystery to me as to how the COMSOL decides their order. Thanks.
Sandra
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Posted:
1 decade ago
Hi
As you say, the indexes are heavily used in the fem structure, the number are pointers into the next part of the structure, you have the groups, the BC's , index to constants, to their names etc.
I agree that I have also problems to understand this, as I havnt either found many expalanations in the doc, but by playing with simple models, and cross checking what the GUI odes to the fem structure you find your way out.
there are lso few discussions about the fem structure, and the index if you run a search on the forum
Hope it helps
Ivar
As you say, the indexes are heavily used in the fem structure, the number are pointers into the next part of the structure, you have the groups, the BC's , index to constants, to their names etc.
I agree that I have also problems to understand this, as I havnt either found many expalanations in the doc, but by playing with simple models, and cross checking what the GUI odes to the fem structure you find your way out.
there are lso few discussions about the fem structure, and the index if you run a search on the forum
Hope it helps
Ivar