On 02/05/2013 03:51 PM, Adrien Girard wrote:
Hello,
I just finish university and I am now working as a mechanical engineer and
I am still confused with some points of FEM theory.
I have to make the complete thermal analysis of a rectangular box, I
decided to use the symetry of the problem and thus modelise only 1/8 of the
box. But now, I wonder when I have to add the symetry to the problem.
- 1) to the mechanical model ? (before the simulation)
- 2) at the simulation phase ?
- 3) only for the post process, to visualise the result ?
It's the 1st one: before the simulation.
The main point of taking advantage of a model's symmetry is to cut down
the computational costs of getting a solution to the problem it
describes. In your example, if you only analyze 1/8th of a thermal
model then it will have approximately 1/8th of the degrees of freedom
that it would otherwise require. Considering that the computational
complexity of the algorithms which dominate the whole computational
process, as it tends to lie somewhere between either O(n^2) or O(n^3),
(n) being the number of degrees of freedom, you can get an idea of how
much more efficient the whole process becomes.
Taking advantage of a model's symmetry can also eases the computational
requirements of the whole visualization process, but in general, when
compared with the previous point, this detail is pretty much a
non-issue. There are plenty of ways to skin this proverbial cat, and
symmetry doesn't tend to come up in the conversation.
Hope this helps,
Rui Maciel
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