Discussion Forum

You will need to draw that triangle on the surface, either in the CAD package (SolidWorks, for you) before you import it into COMSOL, or in COMSOL. See www.comsol.com/community/forums/general/thread/15263/#p246712 regarding the latter.
Best,
Jeff

Hi,

As long as the boundary condition is of Neumann type, another possibility is to write the load as a boolean expression based on the coordinates. Something like

17.4*(x>0.2)*(x<0.35)*(y<0.12)

This is of course only feasible for simple geometrical shapes of the loaded area. Also, the mesh must be fine enough, so that the discretization errors are small.

Actually the same idea can be used also for Dirichlet type boundary conditions, but with a little trick. If the degree of freedom is 'u', then the following expression for the value of a Dirichlet condition will prescribe u to 12 inside an area, and let u be free elsewhere:

if((x>0.2)*(x<0.35)*(y<0.12),12, u)

If anyone is curious about how this expression works, a Dirichlet condition is implemented as u - prescribed_value. But if the prescribed value happens to be 'u' itself, u - u will cancel during the symbolic evaluation and the constraint magically disappears.

Regards,
Henrik

Hi Henrik

Thanks for the nice trick, then it should also apply to other cases, such as T for temperature (in K) etc
Worth a Blog presentation with several examples on different physics, for me :)

--
Good luck
Ivar

Thank you very much. I'll try that immediately

Hi Ivar,

The blog post that you suggested is now published!

www.comsol.com/blogs/how-to-make-boundary-conditions-conditional-in-your-simulation/

Regards,
Henrik