GetDP

[Samuel Kvasnica]

Hi Christophe,

After few more hours I spent with getDP I have (stupid) questions again:

Is getDP bound someway to SI units or are units given just by constants used in .pro files ?
Are coordinates used in .geo files in mm or meters ? Is there some command to rescale the whole drawing ?

I tried to compute Br and Bz components of magnectic field on a line in 5mm distance
from magnetron using the OnLine type for postoperation. Results seem to be correct,
but not very smoothly - rather hairy (at ~2000) mesh nodes. I tried to incrrease the node
density and got better results (at ~15000) nodes, but I could still imagine better graph.
Could you give me an advice how to reach more continuous results ?
When I tried to increase node density again (~25000), the solution seemed to diverge and
I've got _very_ strange results. Another problem is, that at certain combinations of node
densities on surfaces gmsh tends to segfault. I looked at coredump with debugger and
it seems to crash usually in PtInTriangle,file 2d_bricks.c, line 295 or 298. I unfortunatelly
don't have the sources so it's up to you.

> > I tried both gmsh and gnuplot formats, last one is most suitable for me.
> > But I don't understand what does the first field 'type' mean. Then, why the
> > comments like # type x[1] y[1] z[1] value[1] must be generated for each line
>
> Try gnuplot2. But I agree that all those things should be redefined...

This one was better. Anyway, awk seems to be the optimal processing tool in this case.


> Well, this is a bit strange. I work daily with gmsh (OK, not under linux
> but under DEC), and daily manipulate (without any major difficulty) data
> sets of 200000 to 500000 elements. Is the drawing so slow on your linux
> box ?

Hmm, maybe openGL works faster with some dedicated hardware on your computer. But on my 200Mhz 6x86
with 128MB RAM it takes ~10 seconds till e.g. merged .pos file for Az is diplayed in case of my geometry,
with only 2000 nodes.
And the main problem is, gmsh renders the data also when it is not needed, e.g. when you drag another
window
over gmsh and back and gmsh gets repaint message from X server. It should save rendered data into pixmap
and update
window contents from that pixmap. (Btw, what does the strange message 'Overlay visual not available' on
gmsh startup mean ?)
The same problem is when i try to move or rotate drawing or set any options, each
mouse click causes long delays. to solve this there should be some button to enable/disable auto
rendering. It's surely
not problem of Motif itself, but I meant other toolkits like Qt/KDE give programmer more time for to play
with usefull
things than fighting with Motif interface. Is somebody still working on gmsh ?

> >> Btw, would it be possible to use getDP also for fluidics and fluidics-thermal simulations ?
> >
>
> Well, it depends on the methods you want/have to use to solve these
> problems. For example, nothing about upwinding is implemented for the
> moment in GetDP.

Particulary I meant some solver for Navier-Stokes equations. I was just asking because colleague sitting
next to me is interrested in CFD and likes getDP. I've noticed there's software called TOCHNOG from
university of Twente dedicated to CFD. Is there such a big difference in numerical methods used for CFD
and electromagnetics that software packages usually support only one of these ?

And the last one:  Is there a trivial way to display magnetic field line by giving coordinates of 1 point?



Ragards,

Sam

--
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Mag.Samuel Kvasnica
IAEE TU-WIEN
Gusshausstrase 27-29 / 359   email: kvasnica at iaee.tuwien.ac.at
1040 Wien                    tel:   +43-1-58801-35914
Austria                      fax:   +43-1-58801-35997
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