On Thu, Jun 12, 2008 at 4:33 PM, Derek Gaston <[EMAIL PROTECTED]> wrote: > Right - maybe I should think about these things before I say them ;-) > > So now the question is... if you were in my place and wanted to set a > u-bc_val type residual for boundary elements... what would you do for > tri's and tets? It seems like a post-processing step is the best way > (so that something from an element with only a node on the boundary > doesn't have a chance to contribute anything). What would that > post-processing step be? Are there any facilities already in libMesh > that could help out? > > I mean, I can certainly loop over the local_active_elements and add > all the nodes on the boundaries to a std::vector<Node *> right after I > read the mesh... but there is a bit of a problem with adaptivity in > this case... and it feels hackish. But I suppose I was hoping that > this is what a BoundaryMesh was... so I guess it's not all that much > different.
BoundaryInfo::build_node_list() does what you suggest. Given the current capabilities of the library, I'd say rebuilding this list after each assembly, and going through and modifying those entries in the residual vector is the way to do it. This should also be done in parallel, i.e. you only set the dof indexes from these nodes which are on your processor. -J > > Thanks, > Derek > > On Thu, Jun 12, 2008 at 3:25 PM, Benjamin Kirk <[EMAIL PROTECTED]> wrote: >>> So how are other people doing boundary conditions with tri's and >>> tets? With Dirichlet you can just use a penalty to swamp everything >>> out. But with Nuemann? >> >> Neumann is not an issue because the BC is in terms of the boundary integral, >> so you only consider it with elements whose sides intersect the boundary. >> The elements who only touch the boundary through a node do not enter into >> the Neumann BC. >> >> > ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
