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Magnetic field of a permanent magnet (incl. rotation)

Posted 3 oct. 2014, 04:45 UTC−4 Low-Frequency Electromagnetics Version 4.4 3 Replies

Kathy
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Dear all

I am quite new to Comsol so please excuse my lack of knowledge. I am trying to model a disk magnet (symmetry axis is the z-axis at first) and visualize the magnetic field. So far so good. On a second step I want to define a point under the magnet, for example the origin, where I measure the magnetic flux density in z direction. Now the magnet is rotated a bit so the new symmetry axis forms a angle (Variable alpha) with the z-axis.

How can I make a plot that shows the magnetic flux density (in z-direction) at the origin depending on alpha varying from 0 to 90 degrees?

Do I have to model the magnet using "moving mesh" like it is done in a few tutorials?

Thank you for your help!
Kathy
3 Replies Last Post 6 oct. 2014, 12:10 UTC−4
Robert Koslover Certified Consultant
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Posted: 10 years ago 3 oct. 2014, 17:54 UTC−4
No, you don't need a moving mesh. And you don't even need to rotate the magnet. Just create a curve, or set of points in space, where you can compute your fields.
I've attached a simple example for you to modify. You can plot whatever vector component (or combination of vector components) of B that you want.

No, you don't need a moving mesh. And you don't even need to rotate the magnet. Just create a curve, or set of points in space, where you can compute your fields. I've attached a simple example for you to modify. You can plot whatever vector component (or combination of vector components) of B that you want.

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Kathy
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Posted: 10 years ago 6 oct. 2014, 03:52 UTC−4
Thank you for your answer, I looked into it and played around a bit. But I think the thought with the arc would only be right if I needed the magnetic flux density norm. Since I only want to measure Bz (like a sensor under the magnet) measuring Bz on a point on the arc is not the same as measuring Bz when the magnet is rotated (The angle between magnet and measurement direction is not the same). So I think I need to rotate the magnet after all? How would I do that (Including the nice alpha-Bz-Lineplot)? Or can I manage that with a combination of components?


No, you don't need a moving mesh. And you don't even need to rotate the magnet. Just create a curve, or set of points in space, where you can compute your fields.
I've attached a simple example for you to modify. You can plot whatever vector component (or combination of vector components) of B that you want.


Thank you for your answer, I looked into it and played around a bit. But I think the thought with the arc would only be right if I needed the magnetic flux density norm. Since I only want to measure Bz (like a sensor under the magnet) measuring Bz on a point on the arc is not the same as measuring Bz when the magnet is rotated (The angle between magnet and measurement direction is not the same). So I think I need to rotate the magnet after all? How would I do that (Including the nice alpha-Bz-Lineplot)? Or can I manage that with a combination of components? [QUOTE] No, you don't need a moving mesh. And you don't even need to rotate the magnet. Just create a curve, or set of points in space, where you can compute your fields. I've attached a simple example for you to modify. You can plot whatever vector component (or combination of vector components) of B that you want. [/QUOTE]
Robert Koslover Certified Consultant
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Posted: 10 years ago 6 oct. 2014, 12:10 UTC−4
Comsol allows you to plot any component, or combination of components, of B that you want. The code computes both Bz and Br. (Bphi = 0). There are pull-down menus in many places in the post-processing that allow you to choose components to plot. You can type in, and compute, the component of B along any other direction via elementary trigonometry.
Comsol allows you to plot any component, or combination of components, of B that you want. The code computes both Bz and Br. (Bphi = 0). There are pull-down menus in many places in the post-processing that allow you to choose components to plot. You can type in, and compute, the component of B along any other direction via elementary trigonometry.

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