[Gmsh] Joining two pipes

Martin Vymazal martin.vymazal at vki.ac.be
Fri Aug 6 11:07:47 CEST 2010

Hi Dave,

  ok, thanks for the info.

  Best regards,

   Martin Vymazal

P.S. Do you have any idea what open source software might be able to  
edit stl geometry? Salome maybe?

Quoting David Colignon <David.Colignon at ulg.ac.be>:

> On 04/08/10 20:06, Martin Vymazal wrote:
>> Hello,
>> I would like to ask if anyone has an idea how (if at all) to join  
>> two cylindrical surfaces in gmsh. I have an 'msh' file
>> after conversion from CAD data. The file contains 2 pipes which  
>> have the same axis but slightly different diameters, one
>> following after the other. There's a small gap between the end of  
>> the first pipe and the beginning of the second pipe
>> that I'd like to cover with a surface mesh, thus joining the two pipes.
>> I have a circle (elementary entity number 1), which is the 'outlet  
>> ring' of the first pipe and another circle
>> (elementary entity # 2) - 'inlet ring' of the second pipe.  
>> Moreover, there's a line number 3 joining one point of the
>> first circle with another point on the second circle. These three  
>> lines form sort of a 'conical outline' - I have 2
>> bases with slightly different radiuses and one surface line  
>> connecting them. I thought I could write this in my geo file
>> (after merging the mesh with the two pipes):
>> l1 = newreg;
>> Line Loop(l1) = {1,2,3};
>> Ruled Surface(newreg) = {l1};
>> Unfortunately, gmsh meshes only the surface defined by circle 1,  
>> instead of meshing the conical surface that I tried to
>> define.
>> Could you please tell if what I'm trying to do is feasible? If so,  
>> do you have an idea how to do it?
> Hi Martin,
> I am not sure that Gmsh is able to understand the topology of the  
> surface you want to create, especially with the line n°3 joining the  
> two circles... Moreover Gmsh doesn't like arc circles greater than  
> PI ...
> The best solution would be to divide each circle in two parts, and  
> having a second line joining the two half circles...
> Regards,
> Dave
>> Best regards,
>> Martin Vymazal
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