Hi Wolfgang, thank you for your reply. I've had another look at the functions available and i'm stuck on how to implement these in this case.
The whole point of not imposing zero for all components in a Dirichlet sense is that I am testing for a case where I have inhomogeneous normal component of the normal stress, with the tangential stress being zero on some boundaries. On some boundaries, I have zero normal flux and zero tangential stress but I'm pretty sure this doesn't amount to the actual components being zero anyway. Can you suggest a way to implement this if I algorithmically, what I was doing previously wouldn't work? Thank you - I will keep having a look mathematically if there is some manipulation I might be able to do. Many thanks On Monday, November 27, 2017 at 10:53:14 PM UTC, Wolfgang Bangerth wrote: > > On 11/27/2017 01:16 PM, Jane Lee wrote: > > I'm trying to apply some partial boundary conditions to the step-22 > > stokes problem. I can't seem to find much further help on this and when > > I try and implement it, it solves but solution is clearly unstable/blows > > up. > > > > I am trying the basics before i impose inhomogeneous quantities, and > > using no normal flux on the boundary, which constrains one component, > > and then allow no tangential stresses either, which should constrain the > > other two. Can anyone spot where I'm going wrong? > > I don't think you can do it that way -- this would constrain the normal > component in terms of the tangential components, and then somehow try to > find a coordinate system in which to constrain the tangential > components, but I can completely see how this leads to circular > dependencies and all sorts of other weirdness. If you want a zero > boundary condition, then just impose zero for all components. > > I'll add that *theoretically* things should work this way -- you are > constraining all components. But *algorithmically*, I don't think that's > a useful approach. > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: bang...@colostate.edu > <javascript:> > www: http://www.math.colostate.edu/~bangerth/ > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
