[Dune] globalRefine and ALUGRID_SIMPLEX

[Martin Nolte]

There are 3 different ways of subdividing a tetrahedron into 8 smaller 
tetrahedra. Depending on the chosen variant, this leads to different centers. 
As far as I know ALUGrid, chosen variant depends on the order of the vertices.
It may be a clever idea to sort them such that version produce the same 
output. This might need some complex change in the DGFGridFactory of ALUGrid, 
though.

By the way: The number of tetrahedra is the same for both DGF files, since 6*8 
= 8*6 (i.e. make6 + red refinement = red refinement + make6).

Martin

Andreas Dedner wrote:
> Hi.
> This would really be a surprising error in the refinement strategy of 
> ALU - which I have difficulties to believe.
> Again your tow test cases cannot lead to the same grid -
> are we agreed on that?
> 
> Perhaps you could reduce the test case by starting with one tetrahedron
> and calling globalRefine - since you have analyzed the problem so far
> it should be easy enough to write a dgf file which only contains
> one of the six tetrahedron ALU starts with and then we have only
> 8 tetrahedrons after refinement. This grid should be easy to
> visualize.
> 
> Andreas
> 
> Dragan Vidovic wrote:>
>> This is difficult to see because it
>> looks all right from the outside, but four of the 48 tetrahedra in my
>> final grid have cell centres at z=0.5, which means that they are not
>> similar to the big tetrahedra that they were made from.
> Could you explain this argument at bit more?
> 
> 
> _______________________________________________
> Dune mailing list
> Dune at dune-project.org
> http://lists.dune-project.org/mailman/listinfo/dune

-- 
Martin Nolte <nolte at mathematik.uni-freiburg.de>

Universität Freiburg                                   phone: +49-761-203-5642
Abteilung für angewandte Mathematik                    fax:   +49-761-203-5632
Hermann-Herder-Straße 10
79104 Freiburg, Germany