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Zero Magnetic Scalar Potential, which boundaries to define?

Posted Nov 6, 2013, 7:29 p.m. EST Low-Frequency Electromagnetics Version 4.3b 6 Replies

Antoine Courtois
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Hello there!

I am actually studying ferrofluids, and their use in the sorting of non-magnetic particles. I am right now at the step of simulating the magnetic field in the micro-channel, where the particles are sorted.

I have created the model, but I have doubts about many things. I am first of all trying to understand the zero magnetic scalar potential.
What is its use exactly? What does it define?
In my case, the magnetization is directed through the sickness of the magnet, so i define the magnetization on y axis.

It is said in the papers that I am studying that "The magnetic field component perpendicular to the region boundary all went to zero at the boundaries".
I have no clue of how to interpret this piece of information.

I would really appreciate your help!

Thank you very much,

Cheers

Antoine Courtois

PS: The mesh and studies are done in another file, but I can't put it here, it is 100 Mo! :)

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6 Replies Last Post Apr 6, 2017, 4:41 p.m. EDT
Jens Krause
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Posted: 1 decade ago Nov 7, 2013, 2:36 a.m. EST
Hi Antoine,

setting the scalar potential Vm=0 on boundaries will make field intensity H be perpendicular to the surface (ie paralell to the normal vector). I guess that is not what you want: the flux density should be tangential. This is achieved by the natural boundary condition, called "magnetic insulation" in Comsol.

However, you need to fix Vm to something. It is sufficient to fix Vm to zero at a single point (Points/Zero Magnetic scalar potential), and you are done.

Regards

Jens
Hi Antoine, setting the scalar potential Vm=0 on boundaries will make field intensity H be perpendicular to the surface (ie paralell to the normal vector). I guess that is not what you want: the flux density should be tangential. This is achieved by the natural boundary condition, called "magnetic insulation" in Comsol. However, you need to fix Vm to something. It is sufficient to fix Vm to zero at a single point (Points/Zero Magnetic scalar potential), and you are done. Regards Jens
Antoine Courtois
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Posted: 1 decade ago Nov 10, 2013, 7:19 p.m. EST
Hi,
thanks for the answer!

First of all, what are the boundaries that I should set with the magnetic insulation? If I understand, it should be the external boundaries of the cube defining the air...is that it?
Which point should I set Vm=0? Any point is good?

Cheers

Antoine
Hi, thanks for the answer! First of all, what are the boundaries that I should set with the magnetic insulation? If I understand, it should be the external boundaries of the cube defining the air...is that it? Which point should I set Vm=0? Any point is good? Cheers Antoine
Jens Krause
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Posted: 1 decade ago Nov 11, 2013, 2:40 a.m. EST
Yes, to both question:
+ all external boundaries for magnetic insulation
+ any point for Vm=0 is good (but only one)

Regards

Jens
Yes, to both question: + all external boundaries for magnetic insulation + any point for Vm=0 is good (but only one) Regards Jens
Antoine Courtois
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Posted: 1 decade ago Nov 11, 2013, 2:43 a.m. EST
Okay thanks a lot!

Is that normal if I don't have any magnetic field strength visible in the microchannel block? It seems that it is only the magnetic flux density that is visible...my electromagnetism background is really really old!

Cheers
Okay thanks a lot! Is that normal if I don't have any magnetic field strength visible in the microchannel block? It seems that it is only the magnetic flux density that is visible...my electromagnetism background is really really old! Cheers
Antoine Courtois
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Posted: 1 decade ago Nov 11, 2013, 7:34 p.m. EST
Hi there,

By doing a 1D plot on my microchannel, I can plot a magnetic field strength, so there is definitely one but I can't visualize it on my 3D plot.

Do you have an idea why?

Cheers

Antoine
Hi there, By doing a 1D plot on my microchannel, I can plot a magnetic field strength, so there is definitely one but I can't visualize it on my 3D plot. Do you have an idea why? Cheers Antoine
Santosh Srivatsa Gunturi
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Posted: 8 years ago Apr 6, 2017, 4:41 p.m. EDT
Hey,

I'm working on a similar kind of model and I'm struck. Are you still working on the model or something?

Regards,
Santosh.
Hey, I'm working on a similar kind of model and I'm struck. Are you still working on the model or something? Regards, Santosh.

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