square pyramid boundary

Loylick

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Dec 11, 2016, 9:14:58 PM12/11/16

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Hello!
I would like to know how to implement a square pyramid boundary with the Dealii library tools? I've looked through the examples but have not found anything alike. Examples are given mostly on hyper cube domains.

Alex

Wolfgang Bangerth

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Dec 11, 2016, 9:48:13 PM12/11/16

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The *boundary* part of the square pyramid is actually pretty simple, because
all faces are flat. So StraightBoundary is the correct boundary description.

But I suspect that you are asking how to create a *mesh* for this geometry, right?

Best
W.

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Wolfgang Bangerth email: bang...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/

Loylick

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Dec 11, 2016, 10:31:18 PM12/11/16

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Hi Wolfgang!
To be precise I need the Triangulation object if it is what you call a *mesh*, that is it.

Jean-Paul Pelteret

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Dec 12, 2016, 2:10:37 AM12/12/16

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Dear Loylick,

For these more complex grids that are not defined in GridGenerator, you have a few options. You can:

1. Use other GridGenerator functions in conjunction with the GridGenerator::merge_triangulations function so assemble it piece-wise

2. Use external meshing software, such as GMsh or Cubit

3. Construct the grid by hand, such as is demonstrated in step-14.

Regards,

Jean-Paul

Loylick

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Dec 12, 2016, 9:08:40 PM12/12/16

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Hi! Thanks for reply.

Following to 1) I have built my square pyramid from 2 simplexes end merged them. Next problem arose immediately. I realized that I did not quite understand which of set_boundary functions to use. Is the following code enough or I should use some more sophisticated approach? Maybe set_all_boundary_ids will do better?

typename Triangulation<dim>::active_cell_iterator

cell = tria.begin_active(),

endc = tria.end();

for (; cell!=endc; ++cell)

{

for (unsigned int face=0; face<GeometryInfo<dim>::faces_per_cell; ++face)

{

if (cell->face(face)->at_boundary()) cell->face(face)->set_boundary_id(1);

Jean-Paul Pelteret

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Dec 13, 2016, 12:57:03 AM12/13/16

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Dear Loylick,

Great, I'm glad you've managed to create a grid using the merge function. The way that you've specified the boundary id's is typically fine. The other function sets the boundary id's of both the faces and edges, which is unnecessary for most cases.