Thanks to David and John for your hints. I need to further digest it. --Junchao Zhang
On Wed, Jan 13, 2016 at 4:33 PM, John Peterson <jwpeter...@gmail.com> wrote: > > > On Wed, Jan 13, 2016 at 3:23 PM, Junchao Zhang <junchao.zh...@gmail.com> > wrote: > >> Hello, >> I tried to follow the textbook to write weak forms of PDEs with Dirichlet >> boundary conditions like some libmesh examples. The textbook usually lets >> u >> = 0 on boundary, making it easy to understand why the boundary term >> vanishes in weak form. But when u is not zero on boundary, I found libmesh >> examples still do not have boundary terms in weak form. Why? >> > > Not sure if this will help, but you can think of the basis functions > associated with the Dirichlet BC degrees of freedom (DOFs) as being "thrown > out" of the test space, i.e. we are not testing against them any more. > > You therefore have to replace the equations that would normally be > associated with those DOFs with some other equations, e.g. penalty terms, > constraints, etc. You have to do this regardless of whether the Dirichlet > value is zero or not. > > -- > John > ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
