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Magnetic Flux Function

Posted 8 janv. 2015, 15:27 UTC−5 Low-Frequency Electromagnetics, RF & Microwave Engineering, Results & Visualization Version 4.4, Version 5.0, Version 5.2 6 Replies

Chris Barlog
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Hello,

I'm working with the magnetic fields, no currents module to create an axially symmetric model. I'm verifying past work done by a colleague. He used another program to plot the flux function of the model (see attached image).

Does Comsol have similar functionality? I have modelled the same item, but I only seem able to plot the flux density, not the flux function (see second attached). Ideally I would like the two attached images to match fairly closely.

My understanding is that the flux function, Phi, is a function of the flux density, B:
Phi = Integral( B dA)

Any help is greatly appreciated!

Thanks,
Chris
6 Replies Last Post 14 août 2017, 04:33 UTC−4
Mohsen
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Posted: 10 years ago 8 janv. 2015, 18:18 UTC−5
Hi

I checked it seems that magnetic flux is not an explicit output in COMSOL. I think you should integral B(x,y,z) over the your model surfaces. You can use "More derived values" option in the "Results" menu to take a surface integration.
Hi I checked it seems that magnetic flux is not an explicit output in COMSOL. I think you should integral B(x,y,z) over the your model surfaces. You can use "More derived values" option in the "Results" menu to take a surface integration.
Chris Barlog
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Posted: 10 years ago 8 janv. 2015, 22:47 UTC−5
Thanks MAEQEng,

That definitely seems like a step in the right direction. Now my problem is integrating the flux density vector. Your suggestion seems to work fine to integrate any single component of the vector, but how do I tell COMSOL that I want an expression for the flux at every point? Currently it is giving me a scalar value which I'm assuming is the flux through the entire area of my model. Obviously, this doesn't lend itself well to a contour plot.

Any additional thoughts you could provide on this would be greatly appreciated!

Thanks,
Chris
Thanks MAEQEng, That definitely seems like a step in the right direction. Now my problem is integrating the flux density vector. Your suggestion seems to work fine to integrate any single component of the vector, but how do I tell COMSOL that I want an expression for the flux at every point? Currently it is giving me a scalar value which I'm assuming is the flux through the entire area of my model. Obviously, this doesn't lend itself well to a contour plot. Any additional thoughts you could provide on this would be greatly appreciated! Thanks, Chris
Edgar J. Kaiser Certified Consultant
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Posted: 10 years ago 9 janv. 2015, 05:57 UTC−5
Chris,

you are somehow mixing things here. You correctly state that flux is the integral of the flux density vector over a surface. So flux is not a function of a point. The integration of the flux density vector gives a flux vector, not a scalar.
It is unclear what you mean with 'magnetic flux function'. The COMSOL plot shows flux density contours. There isn't something like flux contours, remember flux is an integral. Maybe you want streamlines, which can be a visualisation of flux. They are available in COMSOL, but you have to be careful about the choice of the start points otherways streamlines can be misleading. Make sure you understand what streamlines actually are!

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Chris, you are somehow mixing things here. You correctly state that flux is the integral of the flux density vector over a surface. So flux is not a function of a point. The integration of the flux density vector gives a flux vector, not a scalar. It is unclear what you mean with 'magnetic flux function'. The COMSOL plot shows flux density contours. There isn't something like flux contours, remember flux is an integral. Maybe you want streamlines, which can be a visualisation of flux. They are available in COMSOL, but you have to be careful about the choice of the start points otherways streamlines can be misleading. Make sure you understand what streamlines actually are! Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Mark Harradine
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Posted: 10 years ago 12 janv. 2015, 10:02 UTC−5
Hi Chris,

it is perfectly possible to generate a flux plot in Comsol. I have attached a model which shows the result you are after. You can use the same settings in your model to generate a similar plot.

Regards,

Mark
Hi Chris, it is perfectly possible to generate a flux plot in Comsol. I have attached a model which shows the result you are after. You can use the same settings in your model to generate a similar plot. Regards, Mark
Yecheng Shen
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Posted: 7 years ago 14 août 2017, 03:01 UTC−4
Hi, Mohsen

Do you know the expression of B(x,y,z), because I cannot find the flux density related to the position.

Thanks
Hi, Mohsen Do you know the expression of B(x,y,z), because I cannot find the flux density related to the position. Thanks
Wajid Ali
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Posted: 7 years ago 14 août 2017, 04:33 UTC−4
Hi,
I am sorry for irrelevant reply but i am very much upset with this problem facing in comsol i.e.

"How to incorporate the constant external magnetic field in RF module for the case of Scattering off gold nanosphere" .


Any help will be greatly appreciated.

Best
Ali
Hi, I am sorry for irrelevant reply but i am very much upset with this problem facing in comsol i.e. "How to incorporate the constant external magnetic field in RF module for the case of Scattering off gold nanosphere" . Any help will be greatly appreciated. Best Ali

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