[Gmsh] Problems with mesh quality

[Alexander Sjögren]

Hi,
I'm pretty new to GMSH and my problem may be due to a basic mistake,
nevertheless I'm really stuck. I'm trying to make a mesh of the volume
around a spacecraft. The spacecraft consists of an almost cubic body, large
solar panels and two booms. The most interesting volumes for my simulations
are around the two booms, so the mesh around the booms need to be in good
quality. The program I'm doing my simulation in needs the quite large
simulation box (ellipsoidal in the pictures).

The problem is that when I make a 3D mesh of the volume around the
spacecraft, the mesh around the two booms consists largely of straight lines
to the booms, not of a mesh in all (random) directions. I've tried using
different characteristic lengths for the booms, both making it larger and
smaller than the characteristic length for the ellipsoid and rest of the
spacecraft. I've also tried using the two different meshing algorithms
(Tetgen+Delaunay and Netgen), the result looks maybe a little bit better
with Netgen but the problem is still there. The result of the mesh-problem
is that when I run simulations you can tell from the results that the mesh
affects the result, too much, in a bad way.

Does anyone have an idea of what I'm doing wrong and what I can do to make
my mesh better? I've attached three pictures:

1.jpg: This is the spacecraft inside the ellipsoid I'm using for the
calculations.
2.jpg: A close-up of one of the booms.
3.jpg: Same as 2.jpg, now with the mesh that I'm not happy with.

Thanks in advance for your help and your time!

Best regards
Alexander Sjögren, Uppsala, Sweden
alex.ph.sjogren at gmail.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20090213/288dbad5/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 1.jpg
Type: image/jpeg
Size: 180269 bytes
Desc: not available
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20090213/288dbad5/attachment.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 2.jpg
Type: image/jpeg
Size: 141932 bytes
Desc: not available
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20090213/288dbad5/attachment-0001.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 3.jpg
Type: image/jpeg
Size: 518481 bytes
Desc: not available
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20090213/288dbad5/attachment-0002.jpg>