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What is "the direction of a boundary"?

Posted 4 feb 2011, 12:19 GMT-5 Version 4.0 3 Replies

Xiaoyi Yu
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When I read the instructions about "Direction of the Normal Component on Interior Boundaries" in Users' Guide, I saw such descriptions:
In 2D:
- unx and uny for the up direction
- dnx and dny for the down direction
The upside is defined as the left side with respect to the direction of the boundary.

What is the direction of the boundary? The direction of the arrow pointing to? (we can see that there is an arrow for each boundary)
3 Replies Last Post 5 feb 2011, 02:24 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 4 feb 2011, 13:40 GMT-5
Hi

the direction of a boundary in 2D, its easy to see, it is the direction of the arrow showing how "s" varies from 0 to 1

but in 3D the directions are not that easy to represent on boundaries = surfaces, as there are s1 and s2 the tangeant directions, try the boundarys arrow ploting of V4 to visualise them (and the new ones in v4.1)

--
Good luck
Ivar
Hi the direction of a boundary in 2D, its easy to see, it is the direction of the arrow showing how "s" varies from 0 to 1 but in 3D the directions are not that easy to represent on boundaries = surfaces, as there are s1 and s2 the tangeant directions, try the boundarys arrow ploting of V4 to visualise them (and the new ones in v4.1) -- Good luck Ivar
Xiaoyi Yu
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Posted: 1 decade ago 4 feb 2011, 15:08 GMT-5

Hi

the direction of a boundary in 2D, its easy to see, it is the direction of the arrow showing how "s" varies from 0 to 1

but in 3D the directions are not that easy to represent on boundaries = surfaces, as there are s1 and s2 the tangeant directions, try the boundarys arrow ploting of V4 to visualise them (and the new ones in v4.1)

--
Good luck
Ivar


Thank you, Ivar!
I can see the arrow at the end of a boundary, but I don't understand "showing how 's' varies from 0 to 1", what is 's' ? where can I see it?
Thank you!
[QUOTE] Hi the direction of a boundary in 2D, its easy to see, it is the direction of the arrow showing how "s" varies from 0 to 1 but in 3D the directions are not that easy to represent on boundaries = surfaces, as there are s1 and s2 the tangeant directions, try the boundarys arrow ploting of V4 to visualise them (and the new ones in v4.1) -- Good luck Ivar [/QUOTE] Thank you, Ivar! I can see the arrow at the end of a boundary, but I don't understand "showing how 's' varies from 0 to 1", what is 's' ? where can I see it? Thank you!
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 5 feb 2011, 02:24 GMT-5
Hi

chek your doc ;) "s" is in fact the "ds" boundary length elementary items

--
Good luck
Ivar
Hi chek your doc ;) "s" is in fact the "ds" boundary length elementary items -- Good luck Ivar

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