[Dune] parametrized AMR and cell divergence

Marco Cisternino marco.cisternino at optimad.it
Tue Feb 24 17:35:07 CET 2015

Absolutely non conforming. 
I know I have a hanging node, but I cannot understand what you say: why do you talk about coarse and fine intersections?? 
If I move a hanging node I'm moving 4 intersections, isn't it? And my coarse element has 9 intersections, right? 
Through its intersections the coarse element knows about the hanging node or not? 
If not I cannot imagine the use of intersections. 

Thanks again. 

----- Messaggio originale -----

Da: "Andreas Dedner" <a.s.dedner at warwick.ac.uk> 
A: "Marco Cisternino" <marco.cisternino at optimad.it>, dune at dune-project.org 
Inviato: Martedì, 24 febbraio 2015 16:55:38 
Oggetto: Re: [Dune] parametrized AMR and cell divergence 

Conforming or non conforming? If non conforming you have a hanging 
node and if you move coarse and fine intersections will not match (the 
coarse grid element does not know about the hanging nor where it 
is). Could that be your problem? 

On 24/02/15 15:39, Marco Cisternino wrote: 

Hi Andreas, thank you for your reply. 
I'm using GeometryGrid and ALU together. I provide ALU with a DiscreteDeformationFunction (my coarse element parametrization). Any time a new point appears in the mesh after a refinement I move that point using the DiscreteDeformationFunction. 
The problem appears for local refinement. On the other hand, if I globally refine the mesh I have no problem about the divergence of the cells: it is zero everywhere. 
However, if I refine only a bunch of cells, then the coarse ones, sharing intersection with the fine ones, have non-zero divergence. 
I'm doing all this using the following methods: 
intersection centerOuterUnitNormal 
and codimension 1 volume method (choosing the element face corresponding to the intersection) 
I hope it is clearer. 


----- Messaggio originale -----

Da: "Andreas Dedner" <a.s.dedner at warwick.ac.uk> 
A: dune at dune-project.org 
Inviato: Martedì, 24 febbraio 2015 12:14:33 
Oggetto: Re: [Dune] parametrized AMR and cell divergence 

I'm not quite sure I understand the question. Are you seeing problems 
when refining the grid using ALU's standard globalRefine method or do the problems 
only appear when you use your local parametrization and after moving nodes around 
(I'm not quite clear how you do that with ALU....). 

On 24/02/15 11:00, Marco Cisternino wrote: 


Good morning, 
I would like to ask duners about deformed AMR. 
I'm working with body fitted mesh and ALUGrid. 


In order to refine my mesh I compute a local parametrization for every coarse element, then I refine the mesh moving new nodes using my parametrization. 
Therefore I compute the cell divergence summing over the cell intersection 
normal . flux * area 
where intersection normals and areas are computed by Dune methods centerUnitNormal and volume(this for a face), while flux is (1,1,1) everywhere. 
I expect 0 over the entire mesh and this is true on the coarse grid, but for a refined grid this is not true for coarse cells sharing intersections with finer cells. 
Does anyone see something like this? And is there a cure? Am I doing something wrong? 

Thanks for any hint. 


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