A bilinear extrapolation seems to be a suitable first try since the shape functions are bilinear. Going this way, I would compute the gradient of the function at a point at the boundary to come up with the extrapolated function value. Call the point outside the grid P, I would project P to the closest at the boundary of the triangulation and evaluate the gradient there.
So, given P, how can I find the closest point at the boundary? Or would you choose a different point at the boundary? -Math Wolfgang Bangerth <bange...@colostate.edu> schrieb am Mi., 7. Juni 2023, 19:23: > On 6/7/23 10:57, Mathieu wrote: > > "Like Bruno already said in other words, you are starting at the wrong > end of > > the question. In a first step, define mathematically *what* it is you > want to > > do (and justify why this is the right choice). Then, in a second step, > one can > > think about *how* to implement this." > > > > [...] > > I want to circumvent this by extrapolating the function somehow > (bilinear, ...). > > You'll need to say what this "somehow" is supposed to be. I can think of a > half-dozen ways of extrapolating functions, but like Bruno already > outlined, > which one is right depends on what you want to do. > > In other words, come up with a *mathematical definition* of the operation > you > want to do, and we can help with how that can be implemented. > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: bange...@colostate.edu > 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. > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/ade0d3bc-05c8-fdc0-6ff1-2ca228dea1a6%40colostate.edu > . > -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/CA%2BwBsdP6ohL7tyshf_n36ig7JcZXT9eumWBreyWiKwmnzoY6Xg%40mail.gmail.com.
