On Mon, Mar 4, 2013 at 4:14 PM, Ataollah Mesgarnejad <ames...@tigers.lsu.edu > wrote:
> Thanks for all your responses, > > Roy, what you said is true about real elastic contact. My > implementation(& my geometry) for elastic-rigid contact problem is still > very elementary. If someone wanted to do a real elastic contact with for > example "conforming profiles" (e.g. a ball on a curve or something > similar) then they needed to use inequality bounds and what not. > > Right now I implemented these using a penalty method. It's not pretty nor > does any good for my condition number but does the trick for me. > On the other hand if I wanted to use the API how would you suggest > updating the ID? Should I do a loop over all the elements and then faces > and add faces that are in contact zone to an ID? If so can a face have two > IDs? And is there a place in the source code you do something similar so I > can look and get an idea? > > Dimtry, on a slightly different subject, Since they removed > DMSetFunction/Jacobian from petsc-dev can libMesh DM be built with > petsc-dev right now? > It should build with petsc-dev as of this morning after my pull request fixing the API mismatch was accepted. Let me know if there are any problems, though. Dmitry. > > Best, > Ata > > > On Mar 4, 2013, at 4:42 PM, Dmitry Karpeev <karp...@mcs.anl.gov> wrote: > > > > 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
