Thanks, Roy. It means that one needs to judge which triangle (which three vertices) of an element is on boundary for Neumann or Robin type boundary conditions?
Regards, Yujie On Sun, Oct 25, 2009 at 7:35 PM, Roy Stogner <[email protected]>wrote: > > On Sun, 25 Oct 2009, Yujie wrote: > > for each element, we have >> " >> for (unsigned int i=0; i<phi.size(); i++) >> Fe(i) += JxW[qp]*fxy*phi[i][qp]; >> " >> for each boundary side, we have correspondingly >> " >> for (unsigned int i=0; i<phi_face.size(); i++) >> Fe(i) += JxW_face[qp]*penalty*value*phi_face[i][qp]; >> " >> Assuming that we use tetrahedral element and linear Lagrange shape >> function, >> in this case, for an element, there are 4 vertices, that is i=0, 1, 2, 3. >> for a boundary side, how to guarantee the vertices (i=0, 1, 2) on the >> boundary? Thanks a lot. >> > > Simple: we don't guarantee that i is a boundary vertex. In fact, > that would be an easy source of error when integrating Neumann or > Robin type boundary conditions, where the interior vertices affect the > gradients being integrated and you can't leave them out. > > But for Dirichlet conditions, the terms where i is an interior vertex > don't matter, because phi_face is evaluated on boundary sides and > we have phi_face[i_interior][qp] = 0. > --- > Roy > ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
