From: Manav B. <manav@u.washington.edu> - 2007-01-16 22:04:32
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Hi, Kindly you help me with a hint about the basic concept of the MeshSmoother class? In my understanding, it does not affect the boundary nodes, but changes some of the domain interior node locations after a refinement/ coarsening. What is the need for this? Thanks, Manav |
From: Roy S. <roy...@ic...> - 2007-01-16 22:11:38
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On Tue, 16 Jan 2007, Manav Bhatia wrote: > Kindly you help me with a hint about the basic concept of the > MeshSmoother class? > In my understanding, it does not affect the boundary nodes, but > changes some of the domain interior node locations after a refinement/ > coarsening. What is the need for this? Mesh generators, as well as mesh-distorting formulations for high-deformation mechanics problems, often produce meshes with elements that are more distorted than optimal for a finite element solver, or even too distorted to solve on at all. Running such a mesh through a good smoother algorithm is intended to fix that. A mesh smoother may affect boundary as well as interior nodes, just so long as the domain of the mesh remains relatively unchanged. In practice what I've seen is that smoothers will allow nodes to "slide" along flat boundaries, but will keep nodes on corners, edges, or curves pinned in place. --- Roy |
From: Derek G. <fri...@gm...> - 2007-01-16 22:25:57
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Hmmm.... I finally got my office setup at home... I should really put some time into getting my mesh smoother stuff in a working state and checked in... The problem is that WoW: Burning Crusade came out today ;-) We'll see which one wins in the fight for my time.... Derek On 1/16/07, Roy Stogner <roy...@ic...> wrote: > On Tue, 16 Jan 2007, Manav Bhatia wrote: > > > Kindly you help me with a hint about the basic concept of the > > MeshSmoother class? > > In my understanding, it does not affect the boundary nodes, but > > changes some of the domain interior node locations after a refinement/ > > coarsening. What is the need for this? > > Mesh generators, as well as mesh-distorting formulations for > high-deformation mechanics problems, often produce meshes with > elements that are more distorted than optimal for a finite element > solver, or even too distorted to solve on at all. Running such a mesh > through a good smoother algorithm is intended to fix that. > > A mesh smoother may affect boundary as well as interior nodes, just so > long as the domain of the mesh remains relatively unchanged. In > practice what I've seen is that smoothers will allow nodes to "slide" > along flat boundaries, but will keep nodes on corners, edges, or > curves pinned in place. > --- > Roy > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Libmesh-users mailing list > Lib...@li... > https://lists.sourceforge.net/lists/listinfo/libmesh-users > |
From: li p. <li...@ya...> - 2007-01-17 09:10:07
|
hi, I'm using tet4 to simulate large distortion. I usually get inversed tet during the calculation. Is that possible to smooth the mesh and correct the inversed tet with MeshSmoother? pan --- Roy Stogner <roy...@ic...> wrote: > On Tue, 16 Jan 2007, Manav Bhatia wrote: > > > Kindly you help me with a hint about the basic > concept of the > > MeshSmoother class? > > In my understanding, it does not affect the > boundary nodes, but > > changes some of the domain interior node locations > after a refinement/ > > coarsening. What is the need for this? > > Mesh generators, as well as mesh-distorting > formulations for > high-deformation mechanics problems, often produce > meshes with > elements that are more distorted than optimal for a > finite element > solver, or even too distorted to solve on at all. > Running such a mesh > through a good smoother algorithm is intended to fix > that. > > A mesh smoother may affect boundary as well as > interior nodes, just so > long as the domain of the mesh remains relatively > unchanged. In > practice what I've seen is that smoothers will allow > nodes to "slide" > along flat boundaries, but will keep nodes on > corners, edges, or > curves pinned in place. > --- > Roy > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get > the chance to share your > opinions on IT & business topics through brief > surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Libmesh-users mailing list > Lib...@li... > https://lists.sourceforge.net/lists/listinfo/libmesh-users > ____________________________________________________________________________________ Be a PS3 game guru. Get your game face on with the latest PS3 news and previews at Yahoo! Games. http://videogames.yahoo.com/platform?platform=120121 |
From: Roy S. <roy...@ic...> - 2007-01-17 14:56:06
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On Wed, 17 Jan 2007, li pan wrote: > I'm using tet4 to simulate large distortion. I usually > get inversed tet during the calculation. Is that > possible to smooth the mesh and correct the inversed > tet with MeshSmoother? It's possible up to a point. From what I've seen in other people's results, if the distortion is large enough you'll always have to remesh eventually, but using a smoother can extend the number of timesteps you can run between remeshings. Of course, until Derek gets the variational smoother he integrated committed to CVS, the only smoother we have available is pretty simple, so I'm not sure how much help it will be. Oh, and needless to say, when you do smooth the mesh you'll need to project the solution onto the new mesh, not just keep the same degree of freedom values on the smoother-displaced nodes. --- Roy |
From: Derek G. <fri...@gm...> - 2007-01-17 16:09:49
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> Oh, and needless to say, when you do smooth the mesh you'll need to > project the solution onto the new mesh, not just keep the same degree > of freedom values on the smoother-displaced nodes. Which is actually non-trivial... so watch out for that! (man I need to get off my butt and check in a function for doing the solution projection to a smoothed mesh... football is almost over so then I should have some time! ;-) Derek PS: WoW won last night ;-) On 1/17/07, Roy Stogner <roy...@ic...> wrote: > On Wed, 17 Jan 2007, li pan wrote: > > > I'm using tet4 to simulate large distortion. I usually > > get inversed tet during the calculation. Is that > > possible to smooth the mesh and correct the inversed > > tet with MeshSmoother? > > It's possible up to a point. From what I've seen in other people's > results, if the distortion is large enough you'll always have to > remesh eventually, but using a smoother can extend the number of > timesteps you can run between remeshings. Of course, until Derek gets > the variational smoother he integrated committed to CVS, the only > smoother we have available is pretty simple, so I'm not sure how much > help it will be. > > Oh, and needless to say, when you do smooth the mesh you'll need to > project the solution onto the new mesh, not just keep the same degree > of freedom values on the smoother-displaced nodes. > --- > Roy > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Libmesh-users mailing list > Lib...@li... > https://lists.sourceforge.net/lists/listinfo/libmesh-users > |
From: John P. <pet...@cf...> - 2007-01-18 02:18:42
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Derek Gaston writes: > > PS: WoW won last night ;-) Just please tell us you weren't one of these poor saps, er I mean players, that shelled out $90 for the collector's edition! And this for a game that you pay $15/month to play!! -J |
From: Manav B. <manav@u.washington.edu> - 2007-01-16 22:40:34
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Thanks Roy, for your reply. I have additional questions related to the aspect of boundary conditions with AMR. Is there a consistent way of handling the issue of applying dirichlet boundary conditions on a mesh that is being refined/coarsened? For instance, if a portion of the boundary has dirichlet bc applied to it, and gets refined, then the new nodes created inside that portion also should have the same bc applied to it. One way to do this is to check for nodes on that boundary and apply bc on them. Do you have a recommendation on this? Similarly, with the case of Neumann bcs...? Thanks, Manav On Jan 16, 2007, at 2:12 PM, Roy Stogner wrote: > On Tue, 16 Jan 2007, Manav Bhatia wrote: > >> Kindly you help me with a hint about the basic concept of the >> MeshSmoother class? >> In my understanding, it does not affect the boundary nodes, but >> changes some of the domain interior node locations after a >> refinement/ >> coarsening. What is the need for this? > > Mesh generators, as well as mesh-distorting formulations for > high-deformation mechanics problems, often produce meshes with > elements that are more distorted than optimal for a finite element > solver, or even too distorted to solve on at all. Running such a mesh > through a good smoother algorithm is intended to fix that. > > A mesh smoother may affect boundary as well as interior nodes, just so > long as the domain of the mesh remains relatively unchanged. In > practice what I've seen is that smoothers will allow nodes to "slide" > along flat boundaries, but will keep nodes on corners, edges, or > curves pinned in place. > --- > Roy |
From: Roy S. <roy...@ic...> - 2007-01-16 22:54:00
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On Tue, 16 Jan 2007, Manav Bhatia wrote: > Is there a consistent way of handling the issue of applying dirichlet > boundary conditions on a mesh that is being refined/coarsened? > For instance, if a portion of the boundary has dirichlet bc applied to it, > and gets refined, then the new nodes created inside that portion also should > have the same bc applied to it. One way to do this is to check for nodes on > that boundary and apply bc on them. Do you have a recommendation on this? > > Similarly, with the case of Neumann bcs...? I usually just have some if statements or switch statements that get applied to each quadrature point on a boundary side. If your boundary conditions are applied on regions that don't precisely break down onto element boundaries, then that's what you have to do, but it's not a great idea for robust code, because it means your boundary conditions have to be hard-coded in C++. For more sophisticated software, what you want to do is set boundary_id values on boundary sides of your coarse mesh, then in your assembly routine call boundary_id() on each boundary side you iterate over. The library will make sure that the ids remain correct through refinement and coarsening. See example 13 or example 18. --- Roy |