Hi all, I have one comment about Wolfgang's summary:
Before expanding to a FE field and then interpolating back to the new quadrature point locations, you first need to make sure that a mathematically sound FE field can be found. It is one of those cases where it is easy to do but not necessarily correct to. For example, in the worst case of an unknown nonlinear function, the value at a quadrature point might have no formal relationship to the value at another point. The actual situation would probably not be this bad, because if the original FEM problem was properly posed then presumably there must be some assumptions already made that can be applied. This loose phrasing is about as far as my experience of FEM, the type of problems people tackle with it and the maths involved goes, but the main warning I want to make is that the handy FE field which is already lying around may not be the right one to use for the process. Hopefully a good look at the formal maths setting will show what is required. Cheers, Michael On Sat, Feb 5, 2011 at 8:35 AM, Wolfgang Bangerth <[email protected]> wrote: > >> There are various other options to transfer quadrature point data in >> problems where one classically has an evolution equation for an internal >> variable that is satisfied at the level of the quadrature point (e.g. >> return mapping algorithms in plasticity). I would be keen to help with >> these once you need them. > > And Andrew is the person to go to with these sort of questions :-) > > Just for completeness (and in order to leave this in the mailing list > archives): When you have internal variables and want to get them from one mesh > to the next, the natural way to do this would be > - to expand these variables that are only defined at quadrature points to > a FE field that is defined everywhere > - move this field by interpolation to the next mesh > - restrict the field again to quadrature points on individual cells > > There are functions and classes for each of these steps: > - FETools::compute_projection_from_quadrature_points_matrix > - SolutionTransfer > - FETools::compute_interpolation_to_quadrature_points_matrix > > Hope this helps! > W. > > ------------------------------------------------------------------------- > Wolfgang Bangerth email: [email protected] > www: http://www.math.tamu.edu/~bangerth/ > _______________________________________________ > dealii mailing list http://poisson.dealii.org/mailman/listinfo/dealii > _______________________________________________ dealii mailing list http://poisson.dealii.org/mailman/listinfo/dealii
