[Gmsh] Ruled surface interpolation

[Christophe Geuzaine]

Martin Aunskjær wrote:
> Hello,
> 
> I've used Gmsh to generate a 3D mesh around a body
> made of lots of ruled surfaces. All the triangular
> faces on these surfaces receive special treatment in
> my fluid dynamics solver, since they must be modified
> from being flat to being curved. This procedure
> involves projecting a lot of Gauss integration points
> inside each surface triangle onto the real, curved
> surface.
> 
> I do this by using the InterpolateSurface() routine in
> Geo.cpp. This seems to work fine, except in those
> cases where a ruled surface has holes. Say, the
> definition is like this:
> 
> Ruled Surface(177) = {156, 175};
> 
> Then any point inside a surface triangle on surface
> 177 will be projected onto a surface defined by the
> generatrices of edge loop 156, the hole is not taken
> into account (holes are skipped in the interpolation
> routine). This way, the projected point will in fact
> not be on surface 177.
> 
> My question is, how can I solve this problem? 
> 

Someone will have to implement e.g. trimmed nurbs interpolation...

(At the moment the native ".geo" language only uses transfinite 
interpolation (using 3 or 4 borders) to interpolate curved surfaces. For 
more complex case we usually import STEP or similar files.)




> The surface meshing routines seems to be capable of
> correctly inserting points on ruled surfaces with
> holes. Is there some mechanism in the meshing routines
> that I can reuse to project my surface triangle
> integration points correctly onto any surface ?
> 
> Thanks,
> Martin 
> 
> 
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine