Approximation of non-axisymmetric geometry

["niallcaldwell" <niall.caldwell@xxxxxxxx>]

Hi all,

Firstly thanks to David Meeker for writing such a great program- I was
using ANSYS for years, writing scripts for parametric optimisation of
solenoid valves. It is very powerful but a complete pig to use. I 
have moved to femm because it is so much quicker to set up and change
geometry. The inclusion of Lua means it is just as good as ANSYS for
most design optimisation.

My question is not really femm-specific, but maybe some of you have
tackled it before...

I have a mainly axisymmetric solenoid valve. The moving pole in real
life has radial slits in it (for non-magnetic reasons) leaving it only
50% solid in places. I am wondering what the best way is to
approximate this non axisymmetry.

One thought I have had is to define a new steel, based on the B-H
curve of 1006 but with the B values divided by half (making sure that
the final gradient equals mu0). I would use this new 50% steel over
the slitted area. By building a library of 30%, 50%, 70% etc. steel I
could model the slitting percentage across the radius of the moving
pole by dividing it into zones of different material.

I suspect there is a fatal flaw in this somewhere.... anyone got a
better idea (apart from 3D modelling that is!)

thanks

Niall Caldwell