[Gmsh] Problem meshing a spur gear

[Christophe Geuzaine]

> On 31 Mar 2020, at 19:30, Carlos Fernandes <carlosmcgfernandes at gmail.com> wrote:
> 
> Dear Gmsh community,
> 
> I am Carlos from Portugal.
> 
> I am working with Gmsh API in order to generate the geometry and automatically mesh spur and helical gears (with a structured mesh). To do so, I make use of setTransfiniteCurve which works perfectly for a 2D situation (see attachement 2D). However, when I extrude the geometry using extrude, one particular area on the tooth doesn't mesh properly (3D_wrong in attachment). The weird thing is, if I use any other gear geometry or even helical gears, the mesh works perfectly both on 2D and 3D. If someone could provide me some hint...
> 
> Another tricky thing that I am facing is making a rotating pattern of the mesh already done. My ideia is to be able to generate the amount of gear teeth according with the type of simulation needs. In certain simulations I use 1 tooth, in others a variable number of tooth up to all the gear (360º). Is there a particular tool in Gmsh API that is efficient in perform this kind of pattern?
> 

In your second picture one can see that the middle-right surface has been split in 2 pieces: you will thus need to adapt the number of nodes on the two-part boundary of the middle surface to make sure that the number of nodes match on the left and right sides. And you will need to specify the corners of the transfinite interpolation manually, as the middle surface has more than 4 points on its boundary. See tutorial/python/t6.py for an example.

Christophe


> Thank you all.
> 
> Best regards,
> Carlos Fernandes
> <2D.png><3D_wrong.png>_______________________________________________
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine