Discussion Forum

I am getting to grips with using Comsol and have been following the "Permanent Magnet" tutorial model. I have adapted the model slightly so that the magnet is now just a bar at the centre of a cube of air and the iron rod is removed. I am able to use Magnetic Insulation as the boundary condition at the sides of the air cube and do get a reasonable result, but if I use a streamline plot of the magnetic flux density the effects of the relatively small size block of air become obvious.

I have been trying to implement infinite boundary conditions using the "Infinite Elements" option to prevent this distortion, but I find that the two help pages in the manual useless in explaining the feature. I do not know if I should be just applying the condition to the air block, or capping each axis in the model with an air block with the infinite element condition applied as indicated by the images in the manual.

When I attempt to solve the problem with Infinite Elements enabled I receive an error: "Feature: Stationary Solver 1 (sol1/s1), Error: Undefined value found.". I still want to use the boundary condition of magnetic insulation at infinity, but the only condition available under "Infinite Elements I" is Magnetic Flux Conservation. I suspect that this is the problem, but can anyone help in identifying the correct way to set the infinite boundary conditions for this model?

Thank you for any help you can provide.

Jo Rushton