Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

In the Maxwell Surface Stress Tensor in Boundary Integration

Please login with a confirmed email address before reporting spam

Hi all

I don`t understand the meaning of the equation in the Maxwell Surface Stress Tensor in Boundary Integration
upside and downside in the AC/DC magneto static module.

The boundary equation is

-0.5*(Bx_emqa_up*Hx_emqa_up+By_emqa_up*Hy_emqa_up)*dny+(dnx*Hx_emqa_up+dny*Hy_emqa_up)*By_emqa_up

and the Bx_emqa_up is the problem.

The manual said this is upside of the boundary but what is the exact meaning of upside?
The normal vector direction of the boundary?

Is there somebody tell me the meaning of the upside?

2 Replies Last Post 3 sept. 2010, 06:21 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 28 août 2010, 05:22 UTC−4
Hi

Check the doc for up and down, but basically (if I'm not getting it up side ;) "up" is out of a closed domain and "down" is inward.

If you have a continuity conditions (default interiour boundaries) the normal up & down macth so you do not need to distinguish them, but if you have some specific physics happening on the border you need to distinguish the two sides.

Boundaries have directions too, i.e. in 2D you have the "s" variable travelling along the edge from 0 to 1, but there is also it's sign that you can put in evidence either with an arrow graph (once the model have been solved at least to the initial values condition) or by the graphical view by enabling boundary condition signs (3.5a)

for boundary normals you can also show them with the arrow graph by using the (nx ny nz) vectors, and then replacing by the respective "up" and "down" values

--
Good luck
Ivar
Hi Check the doc for up and down, but basically (if I'm not getting it up side ;) "up" is out of a closed domain and "down" is inward. If you have a continuity conditions (default interiour boundaries) the normal up & down macth so you do not need to distinguish them, but if you have some specific physics happening on the border you need to distinguish the two sides. Boundaries have directions too, i.e. in 2D you have the "s" variable travelling along the edge from 0 to 1, but there is also it's sign that you can put in evidence either with an arrow graph (once the model have been solved at least to the initial values condition) or by the graphical view by enabling boundary condition signs (3.5a) for boundary normals you can also show them with the arrow graph by using the (nx ny nz) vectors, and then replacing by the respective "up" and "down" values -- Good luck Ivar

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 3 sept. 2010, 06:21 UTC−4
Thanks Ivar. Your help is really helpful. ^^
Thanks Ivar. Your help is really helpful. ^^

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.