Now I understand more about the mechanism of refinement tool with import mesh/grid. Thank you for such clear and detailed explanation and the suggestion as well.
Regards, Thang. Vào lúc 14:00:30 UTC+9 ngày Thứ Tư, 1 tháng 9, 2021, Jean-Paul Pelteret đã viết: > Dear Truong, > > To supplement Bruno’s remarks, and answer this question in particular: > > I guess a procedure like associating the surface boundaries (from meshing > software) to the manifolds would also only works for meshing refinement, > not for mesh coarsening. > > > It would work for mesh coarsening as well, but only up to the coarsest > mesh that is read into deal.II. So if you do some initial refinement within > deal.II itself, then both refinement and subsequent coarsening respect the > attached manifold geometries. > > The point to be understood is that deal.II does not, and cannot, have any > more fundamental knowledge of the discretisation other than what you pass > it in the original mesh. It does not know the steps that you took to get > that mesh — the underlying CAD geometry, whether the mesh is cartesian or > structured, has an even or odd number of divisions on each edge, etc. All > of this information, which would be critical to determine how the mesh > *might* be coarsened using the child-parent cell approach to adaptivity > that deal.II adopts. So one always needs to consider a read in mesh to be > “flattened”, i.e. at its coarsest state, and the benefits of mesh > adaptivity may then be maximised when the read in grid is as coarse as > possible and one is able to produce a satisfactorily refined mesh using the > built in refinement tools (and possibly connecting the mesh to a CAD model > or manifold geometries to provide information of boundary and interface > curvature). > > Best, > Jean-Paul > > On 1. Sep 2021, at 03:32, Thang W Pham <truongthangp...@gmail.com> wrote: > > Thanks for your instant and helpful answer. So, the grid from other mesh > generator cannot be made coarser at all. As I referred from step-5 > tutorial, I guess a procedure like associating the surface boundaries (from > meshing software) to the manifolds would also only works for meshing > refinement, not for mesh coarsening. > Vào lúc 00:09:00 UTC+9 ngày Thứ Tư, 1 tháng 9, 2021, blais...@gmail.com đã > viết: > >> Dear Truong, >> My understanding is that the triangulation in deal.II works like a >> quad/oct-forest.That is, the mesh that is generated or read serves as the >> forest and each cell is a tree. Consequently, it is not possible to coarsen >> a mesh more than it's initial configuration. >> >> For a lot of meshes generated by deal.II, this is not a problem since >> they contain a very low number of cells (for example, a cubic grid has 1 >> cell in it's coarsest level, hence it is a forest with once tree). However, >> if you read your mesh from an external source, you cannot make it coarser >> than it is when you have read it. >> >> My suggestions would be to make a coarse abacus mesh, then you refine it >> within deal.II. This way you would have a coarsest level with as few cell a >> possible, then you could refine it adaptively. As far as I know, it is not >> possible to coarsen a mesh below it's level 0, because this would imply >> "merging cell". >> >> I hope that was sufficiently clear. >> Best of luck! >> Bruno >> >> On Tuesday, August 31, 2021 at 9:26:32 a.m. UTC-4 >> truongthangp...@gmail.com wrote: >> >>> Hello everyone, >>> I am new to deal.II and I am playing around with the grid of L-shape >>> which is imported from Abaqus input file using GridIn::read_abaqus(). The >>> grid has been successfully read as well as the boundary indicators ( from >>> the surface with the name of "SS1" and "SS2"). However, when I try to do >>> coarsening the grid by setting cell->set_coarsen_flag(), nothing happened. >>> I also tested with adaptive refinement as in step-6, only a figure of the >>> new cell has been generated, none has been coarsened even I set the >>> coarsening ratio to high value. >>> I wonder what is wrong here or is there something that I misunderstand >>> with the code. Thanks in advance. >>> >>> [image: Capture.PNG] >>> [image: Capture.PNG] >>> >> > -- > The deal.II project is located at http://www.dealii.org/ > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > --- > You received this message because you are subscribed to the Google Groups > "deal.II User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to dealii+un...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/c674a25b-0daa-4cdf-bd78-c64a90a5a86fn%40googlegroups.com > > <https://groups.google.com/d/msgid/dealii/c674a25b-0daa-4cdf-bd78-c64a90a5a86fn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. 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