Le 13-févr.-09 à 11:04, Alexander Sjögren a écrit :
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 do
You shoud define a size field. By default, Gmsh interpolates mesh
sizes from boundaries :
-) in 1D mesh, we take mesh sizes at vertices and interpolate linearly
-) in 2D, we use edge sizes at boundaries and interpolate using
baricentric coordinates
-) in 3D, we use triangle sizes and interpolate using baricentric
coordinates
If you have huge sizes in your outside box, this causes gmsh to
believe that the initial
3D mesh is ok.
JF
ing 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
[email protected]
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Prof. Jean-Francois Remacle
Universite catholique de Louvain (UCL)
Tel : +32-10-472082 -- Mobile : +32-473-909930
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