# [Gmsh] Surface mesh with holes

Martin Aunskjær maaudk at yahoo.dk
Sun Mar 30 09:58:20 CEST 2008

```Hi,

I'm just starting to use gmsh. I want to generate a
surface mesh of a rocket, but I'm having two problems.

(1)
surface of the rocket into distinct sections, ie.
nosetip, upper body etc. Barring fins the rocket is
rotationally symmetric, so I proceeded to model the
generating curve of each section in the longitudinal
direction either as a spline or a line. Along the
circumference, I subdivide the two bounding circles of
each section into a number of circular arcs. I then
construct the surface of each section as a series of
line loops consisting of two rotated versions of the
longitudinal spline/line curves and two end circle
arcs. These surface pacthes are set up by the 'Ruled
Surface' primitive.

The problem with this approach is that unless I
subdivide each section into the same number of
circular segments, gmsh will generate a nonconforming
2d surface mesh, i.e. the boundary nodes of triangles
on one rocket section will not match of with boundary
nodes of triangles on a neighboring section.

If you want to see the problem, try and generate a
surface mesh from the two included .geo files.

My question is, if this is not the intended way of
constructing such a surface? Could I do it another way
so I wouldn't have to worry about non-conforming
surface meshes ?

(2)

The lower part of the rocket I haven't done yet has
three fins separated by 120 deg attached to the lower,
curved body. It is not clear to me - keeping the
problems mentioned above in mind - how I could
generate surface patches for the lower body and still
avoid non-conformancy.

The missing lower body is similar to the mirror of the
upper curved section. What I need to do is to carve
three holes of some small width in it where the fins
should be attached. But how can I carve holes in a
Ruled Surface?

for it.

Martin Aunskjaer

________________________________________________________
Audi, Fiat, Peugeot, Skoda, Porsche, Toyota, Ford - Kelkoo har brugte biler til en hver smag! Klik her for at sammenligne priser.(http://dk.yahoo.com/r/pat/mmb)
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```