[Getdp] Forces

[Ruth Vazquez Sabariego]

Dear Anton,

I’ve gone through your files. The Maxwell Stress Tensor you are using is not correct. You should use exactly the same expression as the one in magnets.pro,
https://gitlab.onelab.info/doc/tutorials/wikis/Magnetic-forces
that is

// Maxwell stress tensor (valid for both formulations and linear materials
  TM[] = ( SquDyadicProduct[$1] - SquNorm[$1] * TensorDiag[0.5, 0.5, 0.5] ) / mu[] ;


The 0.5 factor comes from the theory not from the geometry.

See e.g.

@ARTICLE{2004JCoAM.168..235H,

   author = {{Henrotte}, F. and {Hameyer}, K.},
    title = "{Computation of electromagnetic force densities: Maxwell stress tensor vs. virtual work principle}",
  journal = {Journal of Computational and Applied Mathematics},
 keywords = {Electromechanical coupling, Electromagnetic force density, Finite element, Maxwell stress tensor, Virtual work principle},
     year = 2004,
    month = jul,
   volume = 168,
    pages = {235-243},
   adsurl = {https://ui.adsabs.harvard.edu/abs/2004JCoAM.168..235H},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}

or any other reference dealing with the MST computation.

Besides that, the idea of using a shell for bounding the computational domain has to do with using a transformation in the shell and that you can only apply if the two spheres limiting the domain are concentric. If the center is not (0,0,0), you will have to add the center for applying the transformation.

HTH,

Ruth





—
Prof. Ruth V. Sabariego
KU Leuven, Dept. Electrical Engineering ESAT/Electa, EnergyVille
http://www.esat.kuleuven.be/electa
http://www.energyville.be








On 26 May 2019, at 22:06, Panteleev, Anton <anton.panteleev at haw-hamburg.de<mailto:anton.panteleev at haw-hamburg.de>> wrote:

dear Ruth,


in my previous letter, namely in the pro. file I made a thousand mistakes and therefore it did not work for me,
now I have finished this file and it gives me all the forces in all three planes Fx,Fy,Fz).
I hope that these forces are calculated correctly.

best regards
Anton Panteleev

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