On Mon, Mar 4, 2013 at 3:34 PM, Roy Stogner <royst...@ices.utexas.edu>wrote:
> > On Sun, 3 Mar 2013, Ataollah Mesgarnejad wrote: > > > I need some advice on how to implement an inhomogeneous Dirichlet BC > > for elastic-rigid contact. This BC is a bit weird since it doesn't > > apply to all of the faces of a boundary_id rather it applies to > > faces within the contact range (changes with time) and all the other > > faces should have natural (traction free) BCs. > > > > - can this be done using new Dirichlet API? and how? > > You can add and remove boundary_ids from sides, sides can have > multiple (or no) boundary ids at any given time, and Dirichlet > constraints can be regenerated with a reinit(). So although the > DirichletBoundary API requires an id, you can still control the extent > of a time-varying boundary with that id. > > But what this implementation would do to your time and space orders of > accuracy, I don't know. A selectively applied equality constraint may > not be a decent substitute for the true inequality constraint. > > It wouldn't be impossible to extend the current constraints system to > allow for true inequalities that could then be enforced within the > nonlinear solver rather than the time integration. That's probably > not near the top of any of the main developers' todo lists, though. > There are plans to extend PETSc VI solvers to allow bounds on constraints (functionals of the state), in addition to bounds on the state variables themselves. However, to add these systematically, Lagrange multipliers living on the contact services would need to be introduced into libMesh. Another tricky part would be matrix preallocation corresponding to those nodes (the same, I believe, as in the case of dynamically added/removed Dirichlet nodes). The SNESVI extension plans are a bit on the back burner, but could be moved up if, for example, Moose were to use this formulation as one of its options for doing contact. That, again, would depend on having surface variables. Dmitry. > --- > Roy > > > ------------------------------------------------------------------------------ > Everyone hates slow websites. So do we. > Make your web apps faster with AppDynamics > Download AppDynamics Lite for free today: > http://p.sf.net/sfu/appdyn_d2d_feb > _______________________________________________ > Libmesh-users mailing list > Libmesh-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/libmesh-users > ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_feb _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
