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Magnetic force imposing on magnetic fluid in 3D magnetostatic field (no currents)

Posted Sep 2, 2012, 6:09 a.m. EDT Low-Frequency Electromagnetics, Fluid & Heat Version 3.5a 6 Replies

Homeland
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Hi

Everyone

I try to do with a simulation of magnetic fluid imposed on magnetic force in magnetostatic field (no

currents), but the results show that there seems to be no magnetic force on magnetic fluid.

Equations of magnetic force are expressed as:

Fx= mu0_emqa*(Mx_emqa*d(Hx_emqa,x)+My_emqa*d(Hx_emqa,y)+Mz_emqa*d(Hx_emqa,z))

Fy= mu0_emqa*(Mx_emqa*d(Hy_emqa,x)+My_emqa*d(Hy_emqa,y)+Mz_emqa*d(Hy_emqa,z))

Fz= mu0_emqa*(Mx_emqa*d(Hz_emqa,x)+My_emqa*d(Hz_emqa,y)+Mz_emqa*d(Hz_emqa,z))

I am sorry that I could find out what went wrong, and your help is highly appreciated!

Thanks!

Best wishes

Hongliang Zhou
6 Replies Last Post Nov 9, 2012, 8:01 a.m. EST
Bodong Li
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Posted: 1 decade ago Sep 5, 2012, 1:24 p.m. EDT
What magnetic force equations you are following?
What magnetic force equations you are following?
Homeland
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Posted: 1 decade ago Sep 5, 2012, 9:09 p.m. EDT

What magnetic force equations you are following?


The equation is:

F=mu0*M*(detaH)

Do you have any suggestions?

I am looking forward to your replies.

Best regards
[QUOTE] What magnetic force equations you are following? [/QUOTE] The equation is: F=mu0*M*(detaH) Do you have any suggestions? I am looking forward to your replies. Best regards
Jaehak Lee
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Posted: 1 decade ago Nov 6, 2012, 6:51 a.m. EST
did you find the answer? i'm finding exact same one as yours
did you find the answer? i'm finding exact same one as yours
Homeland
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Posted: 1 decade ago Nov 6, 2012, 8:48 p.m. EST

did you find the answer? i'm finding exact same one as yours


Thanks for your attention!

I am sorry that I still could not find the answer, and I am wondering if the magnetic force is related to the distribution

of magnetic field intensity and magnetization, foe the reason that the magnetic force is defined from the relation

F=mu0*M*(detaH).

What is more, would you mind giving me some suggestions about the yield stress simulated with COMSOL?

I am looking forward to your replies.

Best regards

[QUOTE] did you find the answer? i'm finding exact same one as yours [/QUOTE] Thanks for your attention! I am sorry that I still could not find the answer, and I am wondering if the magnetic force is related to the distribution of magnetic field intensity and magnetization, foe the reason that the magnetic force is defined from the relation F=mu0*M*(detaH). What is more, would you mind giving me some suggestions about the yield stress simulated with COMSOL? I am looking forward to your replies. Best regards
Alexander Weddemann
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Posted: 1 decade ago Nov 9, 2012, 6:41 a.m. EST
Hi,
I don't know if this helps, but one thing you should check is the spatial derivatives of the magnetic field H. Is every single one of them zero by itself? This is for example the case, if you are solving in some sort of magnetostatic mode, the governing equations are formulated for a scalar potential phi and the field follows from H = - grad phi. Therefore, all the components in the force expressions are indeed second order derivatives.

An easy work around is to add additional (auxiliary) variables (Hx, Hy, Hz) which are defined as, e.g. Hx = - diff(phi,x). This way, you should be able to evaluate all expressions diff(Hx,x) and so on.

Alex
Hi, I don't know if this helps, but one thing you should check is the spatial derivatives of the magnetic field H. Is every single one of them zero by itself? This is for example the case, if you are solving in some sort of magnetostatic mode, the governing equations are formulated for a scalar potential phi and the field follows from H = - grad phi. Therefore, all the components in the force expressions are indeed second order derivatives. An easy work around is to add additional (auxiliary) variables (Hx, Hy, Hz) which are defined as, e.g. Hx = - diff(phi,x). This way, you should be able to evaluate all expressions diff(Hx,x) and so on. Alex
Homeland
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Posted: 1 decade ago Nov 9, 2012, 8:01 a.m. EST

Hi,
I don't know if this helps, but one thing you should check is the spatial derivatives of the magnetic field H. Is every single one of them zero by itself? This is for example the case, if you are solving in some sort of magnetostatic mode, the governing equations are formulated for a scalar potential phi and the field follows from H = - grad phi. Therefore, all the components in the force expressions are indeed second order derivatives.

An easy work around is to add additional (auxiliary) variables (Hx, Hy, Hz) which are defined as, e.g. Hx = - diff(phi,x). This way, you should be able to evaluate all expressions diff(Hx,x) and so on.

Alex


Dear Alex,

Thanks fou your suggestions, I will try my best to do it as what you said.

Best wishes,

Hongliang
[QUOTE] Hi, I don't know if this helps, but one thing you should check is the spatial derivatives of the magnetic field H. Is every single one of them zero by itself? This is for example the case, if you are solving in some sort of magnetostatic mode, the governing equations are formulated for a scalar potential phi and the field follows from H = - grad phi. Therefore, all the components in the force expressions are indeed second order derivatives. An easy work around is to add additional (auxiliary) variables (Hx, Hy, Hz) which are defined as, e.g. Hx = - diff(phi,x). This way, you should be able to evaluate all expressions diff(Hx,x) and so on. Alex [/QUOTE] Dear Alex, Thanks fou your suggestions, I will try my best to do it as what you said. Best wishes, Hongliang

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