Hi all, Apologies if this is somewhere in the documentation and I missed it. I am trying to update the "Newmark system and the Wave Equation" example. I have successfully updated the example to use time dependent Dirichlet (essential) boundary conditions and I am working on doing something similar in the Neumann (natural) case.
The problem with just updating the assemble function to make the Neumann BCs time dependent in the example is the matrix is only assembled once so instead of having time dependent boundary conditions the initial evaluation is treated as constant Neumann BCs. Doing a reinit() and assemble() each timestep doesn't work for the Newmark case (and seems inefficient). Finally, I tried to change the "fill_dirichlet_bc" function to "fill_neumann_bc". The new version ingrates the Neumann BC over the boundary sides of each boundary element and adds the result to the RHS vector. This seems to make the BC time dependent but the wrong magnitude. I am confident in the integration scheme (the same one is working perfectly in the constant BC and the non transient case). I thought maybe adding the result to the "force" vector (rather than rhs) would make the algorithm work properly but that seems to have the same effect. I haven't been able to back engineer from the code where to add the time dependent Neumann BCs to get the Newmark timestepper to work properly. Does anyone know? or is there an example I can look at? Again, sorry if this is described somewhere; I didn't see it in the examples or in my searches of the email list. Thanks again for your help! Andy ------------------------------------------------------------------------------ LIMITED TIME SALE - Full Year of Microsoft Training For Just $49.99! 1,500+ hours of tutorials including VisualStudio 2012, Windows 8, SharePoint 2013, SQL 2012, MVC 4, more. BEST VALUE: New Multi-Library Power Pack includes Mobile, Cloud, Java, and UX Design. Lowest price ever! Ends 9/20/13. http://pubads.g.doubleclick.net/gampad/clk?id=58041151&iu=/4140/ostg.clktrk _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
