[Gmsh] Refining a 4th order mesh to a 2nd order mesh

[Christophe Geuzaine]

> On 21 May 2019, at 09:23, Aman Saxena <amansaxena.iitg at gmail.com> wrote:
> 
> I have a 4th order mesh(with 5 points defining the lines) and I want to refine it twice. As I refine it once, I get a linear mesh and all other points except for the nodes forming the elements are lost.
> So when I refine it for the second time it splits and gives me points on the linear mesh which are not on the actual boundary. If I can get a 2nd order mesh after refining the 4th order mesh, further refinement could have given me points on the actual boundary. 
> 
> Thus how to get a 2nd order mesh from the fourth order mesh?
> 

There's no built-in function for this. But you could code it yourself quite easily with the Gmsh api.

Christophe

> I have attached a file to demonstrate this, figure 1 shows the boundary element of fourth order mesh while second figure shows the boundary element(linear) I get after one refinement and the last figure shows the kind of element(quadratic -- degree 2) I want to have after one refinement.
> 
> I have also attached the mesh file.
> 
> Thanks.
> 
>  btc0-NLR-L3.v2.m4.msh.gz
> 
> <boundaryElement.pdf>_______________________________________________
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine