Re: [Libmesh-users] Defining duplicate nodes on refinement

[Simone R. <sim...@gm...>]

I fixed it looping over the mesh elements using the active elements iterator.
Thanks,
Simone

> On Sep 12, 2018, at 7:25 PM, Simone Rossi <sim...@gm...> wrote:
> 
> I tried adding a new node to the mesh.
> If I call:
> 
> MeshTools::Generation::build_cube(mesh, 2, 2, 0, -1.0, 1.0, -1.0, 1.0, -1.0, 1.0,TRI3);
> 
> I simply add a new (copied) node to the mesh and change it in one element. That gives me the desired mesh with 10 vertices. Defining a system of linear Lagrangian elements on this mesh, the solution vector has 10 entries. All good.
> 
> On the other hand, if before adding the node, I call
> 
> MeshTools::Generation::build_cube(mesh, 1, 1, 0, -1.0, 1.0, -1.0, 1.0, -1.0, 1.0,TRI3);
> MeshRefinement refinement(mesh);
> refinement.uniformly_refine();
> 
> then the mesh object sees 10 vertices, but the solution vector has only 9 entries. Also the exporter does not recognize the additional node in the mesh.
> 
> This is how I’m adding the node in both scenarios:
> 
> Node * node = mesh.node_ptr(0);
> auto nodeID = mesh.node_ptr(0)->id();
> Node * new_node = new Node(*node);
> new_node -> set_id(100);
> mesh.add_node(new_node);
> 
> bool stop = false;
> for (int elc = 0; elc < mesh.n_elem() ; ++elc)
> {
>    Elem * elem = mesh.elem_ptr(elc);
>    for(int nn = 0; nn < elem->n_nodes(); ++nn)
>    {
>        int ID = elem->node_ptr(nn)->id();
>        if(ID == nodeID)
>        {
>            elem->set_node(nn) = new_node;
>            stop = true;
>            break;
>        }
>    }
>    if(stop) break;
> }
> 
> Do you have any suggestion?
> Thanks for the help,
> Simone
> 
> 
>> On Sep 11, 2018, at 12:58 PM, Roy Stogner <roy...@ic...> wrote:
>> 
>> 
>> On Tue, 11 Sep 2018, Rossi, Simone wrote:
>> 
>>>> If you start with the 10 node mesh
>>>> on top and refine, then you will always have continuity of any C0 (or
>>>> C1) solution variables at the two shared domain corner nodes.
>>> This is what I would like to have. The idea is to introduce some random “cuts” in the mesh, where I can apply some boundary conditions.
>>> I thought the easiest way to achieve this would have been adding new duplicated nodes on the side using AMR.
>> 
>> Yeah, if that's the effect you want, then a single refinement followed
>> by duplicating the non-corner internal boundary nodes is exactly what
>> you want to do.
>> 
>>> Could I “break” the mesh, use AMR, and then stitch back the nodes together?
>> 
>> You could but it would be more of a pain.  Just do one refinement and
>> then break it afterward.  Or, actually, you could also use TRI6
>> instead of TRI3 and break the middle node between the two triangles.
>> ---
>> Roy
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