nice getdp results and some questions

Christophe Geuzaine Christophe.Geuzaine at
Wed Sep 6 12:17:02 CEST 2000

Samuel Kvasnica wrote:
> Hi Christophe,
> this week a had again some time to play with getdp. All the problems with cyl. axis seem to be
> really away after specifying that "Dimension 2" option. Now I'm going to simulate a magnetron
> we've constructed few years ago. I made some measurements using an F.W.Bell gaussmeter
> to compare the getdp output with reality (well, also to find out Br of used magnets). I
> measured
> Br and Bz at ~70mm lines in r direction at distance z=2,5,10,20mm from magnetron. After I used
> nonlinear BH curve, I started to get quite good results, look at complete.eps. I used just
> generic BH curve for steel. I could fit that curve by H=a*(1-exp(-b*B))+c*B in 0-0.4T region.
> Unfortunatelly I could not find out how to put it into getdp (how to get unity vector for B,
> any hint ? ) so I finally aproximated it by 5th degree polynome and extracted B to get nu[B].

Hi Samuel,

I use 'Unit[{d a}]'. But you could also write something like
'Vector[CompX[{d a}]/Norm[{d a}]], CompY[{d a}]/Norm[{d a}], CompZ[{d
a}]/Norm[{d a}]]]'.

> Btw, could you give me an advice for some good source of material property data - e.g.
> magnetization curves for standard materials ?

That is a good question. In fact, we are quite often confronted to the
same problem, and I don't know any good compilation of such
characteristics. So we often interpolate on measurement points.

> Well, regarding the second attached picture singular.eps, there still seems to be some problem
> with interpolation. I generated data for B at line going exactly through iron-air boundary
> (magenta color, at z=-6mm  in umag1.geo) and there seems to be some funny noise in Br, Bz is
> ok. It seems to correspond to mesh points someway.
> The same with line at 3.5mm (cyan), which touches the middle pole, but there's just slight
> noise visible.
> Do you think it's a bug ?

Could you send me the files in an archive? My mail application made a
mess with your attached postscript file.

My best,

Christophe Geuzaine

Tel: +32-(0)4-366.37.10    mailto:Christophe.Geuzaine at
Fax: +32-(0)4-366.29.10