Roy Stogner wrote: > > > On Thu, 8 Apr 2010, David Knezevic wrote: > >>> Oh, and even if adaptivity is working, you'll definitely need the >>> coarse mesh to match up. Otherwise there's no way to enforce >>> periodic continuity without "locking" destroying your accuracy. >> >> Thanks for the info Roy. We're not doing adaptivity, we just generated >> a mesh (using gmsh) for a periodic channel flow, but the mesh >> generator doesn't necessarily match up inflow and outflow nodes so it >> sounds like that is a problem? > > Definitely. Imagine a grid of piecewise linears or bilinears, > intended to be periodic from left to right, and offset the nodes on > the right side down by just a little bit. For strict C0 continuity, > then, the slope on the left bottom element must match the slopes on > the two right bottom elements. But the slope on the > second-from-bottom element on the right must match the > second-from-bottom on the left, etc., and by the time you're done your > "piecewise bilinear" mesh has been constrained to a single linear > along that entire edge. Disaster.
Very clear explanation, thanks. > Your only hope in that case is to enforce periodicity weakly: use a DG > term or mortar method or some such on those boundaries, remembering > that you'd have to add the appropriate terms to the send_list & > sparsity pattern by hand. It would probably be easier to fix up the > mesh generator output. Yes, the latter option is definitely easier. Dave ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
