From: Joa L. <li...@jo...> - 2009-10-14 15:12:31
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So returning to the "fix" using the constraint equations... I don't quite understand the idea behind this. If my hanging node no longer is at the right position, my mesh is broken, no? So fixing this with the constraint equations is a way of making the calculations go on, assuming that the error we introduced this way is small, and not a complete solution to the problem? This is way I came up with the idea of moving the nodes in groups... Joa Joa On Wed, Oct 14, 2009 at 08:38:59AM -0500, Roy Stogner wrote: > > On Wed, 14 Oct 2009, Joa Ljungvall wrote: > > >When I loop over the nodes, find a face that is on the boundary, and > >then move the nodes the problem is, if I understood it correct, that > >I might move a hanging node out of the line between the nodes of the > >not so refined neighbour. > > This is not the only possible failure case: You also might move a > vertex node without moving a hanging node (even a non-boundary hanging > node) that depends on it. That's the only failure mode in 2D, in > fact. > > >But I can check if this is the case, and instead of moving only the > >hanging node I move all three nodes keeping them on a line to > >minimize the error vis-a-vis the geometry. > > Or move all 6 nodes, in case you moved node A which depends on node B > and C, node C depends on D and E, and node F depends on nodes B and G? > In 3D this is not an extremely unlikely possibility, even with tets. > > That's why I suggested just fixing things with the constraint > equations. It sounds great to optimize the geometry error, but one > step at a time. > > >If this is a region where the solution changes fast this not so > >refined element will be refined allowing an improved description of > >the geometry. > > Also, in 3D "this not so refined element" may be "these not so refined > elements", since any number of tets can share a boundary node or a > boundary edge. > --- > Roy |