Dear Wen,
If it is a 2D elastostatic problem, you have 3 rigid displacements (2
translations and 1 rotation). So you have to prescribe 3 constraints.
The constraints you added only prescribe the two translations. So, you
have to add another points for instance [0,1] with the direction [1 0]
if it is inside the domain, of course.
Yves.
Le 20/01/2014 16:48, Wen Jiang a écrit :
> Dear all,
>
> I was trying to add the pointwise constraints for a pure Neumann
> problem. In elastostatic.cc example, I eliminated the Dirichelet bc's
> and added pointwise constraints, see below
>
> /***************************************************************/
> /* top and bottom are selected as Neumann bc's*/
> void elastostatic_problem::select_boundaries(void) {
> size_type N = mesh.dim();
> getfem::mesh_region border_faces;
> getfem::outer_faces_of_mesh(mesh, border_faces);
> for (getfem::mr_visitor i(border_faces); !i.finished(); ++i) {
> base_node un = mesh.normal_of_face_of_convex(i.cv
> <http://i.cv>(), i.f());
> un /= gmm::vect_norm2(un);
> if (gmm::abs(un[0] - 0.0) < 0.1) { // new Neumann face
> mesh.region(NEUMANN_BOUNDARY_NUM).add(i.cv
> <http://i.cv>(), i.f());
> }
> }
> }
> /***************************************************************/
>
> /***************************************************************/
> /* add pointwise constraint
> fixed the x and y components of (0.0,0.0) point */
>
> std::vector<scalar_type> cpoints(4);
> cpoints[0] = 0.0; cpoints[1] = 0.0;
> cpoints[2] = 0.0; cpoints[3] = 0.0;
> std::vector<scalar_type> cunitv(4);
> cunitv[0] = 1.0; cunitv[1] = 0.0;
> cunitv[2] = 0.0; cunitv[3] = 1.0;
> model.add_initialized_fixed_size_data("cpoints", cpoints);
> model.add_initialized_fixed_size_data("cunitv",cunitv);
>
> getfem::add_pointwise_constraints_with_multipliers(model,"u","cpoints","cunitv");
> /***************************************************************/
>
>
> The output is
> /***************************************************************/
> Number of dof for u: 51842
> Total number of variables : 51844
> Trace 2 in ../getfem_models.cc, line 3265: Stiffness matrix assembly
> for isotropic linearized elasticity
> Trace 2 in ../getfem_models.cc, line 1522: Source term assembly
> Trace 2 in ../getfem_models.cc, line 1657: source term assembly
> Level 1 Warning in ../getfem_superlu.cc, line 216: SuperLU solve
> failed: info =51845condition number: 8.47747e+17
>
> terminate called after throwing an instance of 'gmm::gmm_error'
> what(): Error in ../elastostatic.cc, line 542 int main(int, char**):
> Solve has failed
> /***************************************************************/
>
> It seems that the rigid displacements are not correctly enforced.
> Could anyone tell me where I was wrong? Thanks.
>
> Regards,
> Wen
>
>
> _______________________________________________
> 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
---------
_______________________________________________
Getfem-users mailing list
[email protected]
https://mail.gna.org/listinfo/getfem-users
