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Magnetostatic Help
Posted Jan 29, 2012, 4:23 p.m. EST Low-Frequency Electromagnetics Version 4.2a 1 Reply
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Hello everyone,
I'm relatively new to COMSOL and I'm teaching myself through the books we have at our university. I'm trying to model the torque between two disks containing a ring of magnets as a function of their angular offset. I looked through the permanent magnet tutorial model, and used a similar setup. My results that I get are not what I would expect, the torque curve is very scattered and is not largest about my rotating axis. Is there anyone who might be able to give me some help with this, maybe look over my model and see if you see anything wrong, or give me some ideas?
Thanks
Devin
I'm relatively new to COMSOL and I'm teaching myself through the books we have at our university. I'm trying to model the torque between two disks containing a ring of magnets as a function of their angular offset. I looked through the permanent magnet tutorial model, and used a similar setup. My results that I get are not what I would expect, the torque curve is very scattered and is not largest about my rotating axis. Is there anyone who might be able to give me some help with this, maybe look over my model and see if you see anything wrong, or give me some ideas?
Thanks
Devin
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1 Reply Last Post Jan 29, 2012, 4:38 p.m. EST
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Posted:
1 decade ago
Hi
some suggestions: check your mesh and see if the scatter is not from a mesh density distribution (try to double the density), and try to use points on the results lines, on the mesh without interpolation/smoothing (check your plot node settings)
Then be aware that forces are extracted from derivatives (gradients) of the resulting dependent variable and that these become quite "noisy" particularly around sharp edges and for low mesh densisties. You could also try to increase the "shape" functions in the discretization tab (must be turned on in the preferences to be visible) this gives a better derivative estimation, but still on a vertex, what is the flux direction ? along one of the edges, normal to some plane ? you have in anycase a "singularity" for the flux on shaprt edges and vertexes. Adding some fillets helps, but increases highly the mesh density, then often one run out of RAM
Another thing, consider usign symmetry, this would reduce the model size, hence allow you to increase drastically the mesh density without RAM excess
--
Good luck
Ivar
some suggestions: check your mesh and see if the scatter is not from a mesh density distribution (try to double the density), and try to use points on the results lines, on the mesh without interpolation/smoothing (check your plot node settings)
Then be aware that forces are extracted from derivatives (gradients) of the resulting dependent variable and that these become quite "noisy" particularly around sharp edges and for low mesh densisties. You could also try to increase the "shape" functions in the discretization tab (must be turned on in the preferences to be visible) this gives a better derivative estimation, but still on a vertex, what is the flux direction ? along one of the edges, normal to some plane ? you have in anycase a "singularity" for the flux on shaprt edges and vertexes. Adding some fillets helps, but increases highly the mesh density, then often one run out of RAM
Another thing, consider usign symmetry, this would reduce the model size, hence allow you to increase drastically the mesh density without RAM excess
--
Good luck
Ivar