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Point load on the axisymmetry

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Pablo Suarez

Pablo Suarez

July 30, 2010 5:04pm UTC

Point load on the axisymmetry

Hi to all,

I am new to COMSOL and I keep struggling with things I think should be straightforward.
I have a sphere in an axisymmetric domain. In this domain this is simply half a circle with radius R
Now I want to put a point load on the axis of symmetry but COMSOL states this is not applicable.
Another way to do this is to put a load on one of the boundaries and make this boundary very small
for instance making the arc of the circle 1/180 \pi R .
Unfortunately I do not know of any easy way to have the circle break up into 180 pieces as by default
COMSOL only allows 4 boundaries.

Any ideas appreciated.


Best regards,

Pablo

Attachments:   my_sphere.mph  

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0 votes
Ivar Kjelberg

Ivar Kjelberg
Moderator

July 31, 2010 10:17am UTC in response to Pablo Suarez

Re: Point load on the axisymmetry

Hi
one way is to add a line, probably for you starting at the origine and that intersects the circle (might be longer too), normally this would add up an internal boundary and your edge will be split so that you can add an edge load (you might need to coerce the all to a single CO. (Note: an edge load in 2D-axi is a surface load by the "2*pi*r" multipicant, check your units and the doc on 2D axis if you are in doubt)

Point loads are always delicate, they represent normally a singularity. Furthermore, any object on the axis is even worse, as COMSOL rearranges Axi physics to remove the natural origine singularity by multiplying the equations by "r" and then remove this "r" for the postprocessing. Therefore, you have less freedom to select point boundary conditions on the axis, than anwhere else

--
Good luck
Ivar

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