## incorrect magnetic force in 2D axisymmetric magnetic model

Numerical methods and mathematical models of Elmer
Yeonho Jeong
Posts: 4
Joined: 24 Apr 2018, 03:33
Antispam: Yes

### incorrect magnetic force in 2D axisymmetric magnetic model

I'm a beginner in Elmer.
So far, I have tested many cases on the magnetic analysis using Elmer.
But, I failed to get the magnetic forces in 2D Axisymmetric model.

As a example, I have tried it using a double C-core model with a coil.
Model.png (24.35 KiB) Viewed 1933 times
In the results, I got force(1,2,3) = 6.562606332450E+001 1.881623416445E+003 0.000000000000E+000.
Results of FEMM(another 2D FEM solver) are 0 67.3566 0.

I attach the sif and mesh file.
Please inform me on what is wrong.
GapCoreAxi.zip
AnalysisFile

Yeonho Jeong
Posts: 4
Joined: 24 Apr 2018, 03:33
Antispam: Yes

### Re: incorrect magnetic force in 2D axisymmetric magnetic model

Also, the distributed patterns of Vector potential line are different in FEMM and Elmer(using Paraview) as followings.

[Elmer <Paraview>]
Fluxline_ElmerFEM.png (433.03 KiB) Viewed 1933 times
[FEMM]
Fluxline_FEMM.png (246.51 KiB) Viewed 1933 times

Why different ????

mzenker
Posts: 1991
Joined: 07 Dec 2009, 11:49
Location: Germany

### Re: incorrect magnetic force in 2D axisymmetric magnetic model

Hi,

it seems like one of the solvers makes a mistake here, or both have not been fed with the same input parameters.
If I were you, I would sit back and try to find out what would be the expected physical result. I don't see it right away, and I don't have the time right now to think about it and look into my electromagnetics textbook...
Maybe you could build a simpler geometry where the result can be calculated analytically?

HTH,

Matthias

pavel
Posts: 34
Joined: 17 Apr 2014, 17:08
Antispam: Yes

### Re: incorrect magnetic force in 2D axisymmetric magnetic model

Hi,

have you tried increasing

BR, Pavel

Takala
Posts: 183
Joined: 23 Aug 2009, 23:59

### Re: incorrect magnetic force in 2D axisymmetric magnetic model

Yeonho Jeong wrote:Also, the distributed patterns of Vector potential line are different in FEMM and Elmer(using Paraview) as followings.

Why different ????
Note that in case you have an axisymmetric case, in Paraview, you need to multiply the vector potential with 2 * pi * r if you wish to plot the magnetic field lines.

So you should take the contour plot from a new variable "a_cont = 2 * pi * coordsX* a" (this you can compute with the Calculator in Paraview). Look at the attached countour plot.
contours_axi.png
Magnetic field lines