Dear Bianca, The answer is not so easy. The implementation of Xfem in Getfem is quite general and support the multi-level-sets case. Thi means that an element can be cut by an arbitrary number of level-sets. A finite element shape function whose support is (completely) cut by n level-sets will be duplicated the necessary number of time (max 2^n). It corresponds to Hansbo's strategy but generalized to the multi-level-sets case. In the case of a unique level-set, each shape function whose support is completely cut by the level-set is duplicated into two, each degree of freedom representing the finite element field on one side of the level-set (this means that there is not the standard degree of freedom and the enriched one). Of course, this is equivalent to the standard Xfem strategy and a linear combination of the two degrees of freedom can give you the non-enriched and enriched degree of freedom of the standard Xfem.
The information for each dof that it is enriched or not can be retreived by pdof_description pdd = mf.fem_of_element(cv)->dof_types()[i]; where i is the local (to the element) dof number and pdd is a pointer on a structure describing the type of dof (see the file src/getfem_fem.cc) The function dof_xfem_index(pdd) will return the index of enrichement (0 : non eneriched, n : first zone, n+1 : second zone ...) where n is typically 1000. Concerning tip enrichement, this is taken into account in a very different way. It uses a global mesh_fem (i.e. not really linked to a mesh), see src/getfem/getfem_mesh_fem_global_function.h and a mesh_fem_sum object. This is a quite tricky part of Getfem which would have to be optimized. Similarly, such dofs can be detected since they are declared as "global dofs", see getfem_mesh_fem_global_functions. Best regards, Yves. Le 24/06/2015 18:39, Bianca Giovanardi a écrit : > Dear Yves, > I am a PhD student at Politecnico di Milano and I am using Getfem++ > for the numerical simulations involved in my thesis about crack > propagation. > I have compiled and tested crack.cc <http://crack.cc>. To perform some > post processing computations on the displacement, I need to know how > the degrees of freedom are enumerated in the vector of the enriched > displacement. > I have understood that the even elements of the vector correspond to > an x component and the odd ones correspond to a y component, but it is > not clear to me in which order the non enriched DOFs, the Heaviside > enriched DOFs and the tip enriched DOFs are set. > I hope I managed to explain myself and that you can help me. > I thank you very much for your time, > > Bianca Giovanardi > > MOX - Modeling and Scientific Computing > Department of Mathematics "Francesco Brioschi" > Politecnico di Milano > Via Bonardi 9, 20133 Milano, Italy > > > > _______________________________________________ > Getfem-users mailing list > [email protected] > https://mail.gna.org/listinfo/getfem-users -- Yves Renard ([email protected]) tel : (33) 04.72.43.87.08 Pole de Mathematiques, INSA-Lyon fax : (33) 04.72.43.85.29 20, rue Albert Einstein 69621 Villeurbanne Cedex, FRANCE http://math.univ-lyon1.fr/~renard ---------
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