[Gmsh] Hybrid mesh and combine triangles in quadrilaterals

[Fabian]

Hi,

I just saw the geometry and wonder, if there is a chance to extrude the 
surfaces and create a transfinite volume?
It's probably not working due to more than six surfaces building the 
volumen!? Would be nice, if this would work, though...

Fabian

Christophe Geuzaine wrote:
> Durufle Marc wrote:
>   
>> Hi,
>> I have two questions :
>>
>> 1- How do you create hybrid meshes in 2-D (quad-dominant with a few 
>> triangles) ?
>> Until now, I am using the Recombine option, but often I get non-convex 
>> quadrilaterals.
>> In the picture attached to this message, you can see that two elements 
>> (in black) are non-convex
>> quads and that's a problem ... So, often I change the characterisc 
>> length in the hope that I will have only
>> fine quadrilaterals. Is it possible to require that all quadrilaterals 
>> are convex ?
>>
>>     
>
> Yes. In your file you use
>
> Recombine Surface {1,s0[0]} = 100;
>
> which means that you allow quads with angles between 90-100 and 90+100 
> degrees (which does not make sense).
>
> Use
>
> Recombine Surface {1,s0[0]} = 45;
>
> instead, which will allow angles between 90-45=45 and 90+45=135 degrees. 
> (45 is the default if you don't specify anything, i.e., with just 
> "Recombine Surface {1,s0[0]}".)
>
> We are working on an automatic full quad algorithm, but it's not ready 
> yet. In the meantime for simple geometries you could also use 
> Transfinite meshes to generate a full quad mesh (see attached file).
>
>
>   
>> 2- In 3-D, when I try "Recombine Volume", it doesn't work. So, how is it 
>> possible with gmsh
>> to create 3-D hexahedral-dominant meshes (with some tets, pyramids and 
>> wedges) ?
>>     
>
> Non. Your only choices for generating hex/prism/pyramid meshes are 
> extruded (see "Extrude Surface") or transfinite (see "Transfinite 
> Volume") grids.
>
>
>
>   
>> Thank you for your help.
>>
>> PS : I am using gmsh 2.24
>>
>>
>>
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>>     
>
>
>   
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