Hi Michael, The problem here is that “scratch.solution_grads_u_total” is initialised with the cell FEValues, and so has n_cell_quadrature_points entries. You need to pass "scratch.fe_face_values_ref[u_fe].get_function_gradients(scratch.solution_total, scratch.solution_grads_u_total);” something that has size n_face_quadrature_points. That’s what this error is informing you.
As a side note, Physics::Transformations::nansons_formula() <https://dealii.org/developer/doxygen/deal.II/namespacePhysics_1_1Transformations.html#aa82925b742c3708f625a48a7abc440bc> can compute the transformation of the normal vector + area change for you, should you like the traction direction to follow the moving boundary surface as well. Best, Jean-Paul > On 1. Aug 2021, at 20:05, Michael Lee <lianxi...@gmail.com> wrote: > > fe_face_values.get_function_gradients returns a rank 2 tensor as the solution > is the displacement vector. > > Let me be more specific. In the code gallery " Quasi-Static Finite-Strain > Compressible Elasticity (The deal.II Library: The 'Quasi-Static Finite-Strain > Compressible Elasticity' code gallery program (dealii.org) > <https://www.dealii.org/current/doxygen/deal.II/code_gallery_Quasi_static_Finite_strain_Compressible_Elasticity.html> > ). It does not consider the follower force as described in the > documentation: " > // We specify the traction in reference configuration. > // For this problem, a defined total vertical force is applied > // in the reference configuration. > // The direction of the applied traction is assumed not to > // evolve with the deformation of the domain." > > So I made a modification to consider the effect of the deformed area on the > traction as follows according to the formula da/dA = J sqrt(N C^-1 N) . > > void > assemble_neumann_contribution_one_cell(const typename > DoFHandler<dim>::active_cell_iterator &cell, > ScratchData_ASM &scratch, > PerTaskData_ASM &data) > { > // Aliases for data referenced from the Solid class > const unsigned int &n_q_points_f = data.solid->n_q_points_f; > const unsigned int &dofs_per_cell = data.solid->dofs_per_cell; > const Time &time = data.solid->time; > const FESystem<dim> &fe = data.solid->fe; > const unsigned int &u_dof = data.solid->u_dof; > const FEValuesExtractors::Vector &u_fe = data.solid->u_fe; > > // Next we assemble the Neumann contribution. We first check to see it > the > // cell face exists on a boundary on which a traction is applied and add > // the contribution if this is the case. > for (unsigned int face = 0; face < GeometryInfo<dim>::faces_per_cell; > ++face) > if (cell->face(face)->at_boundary() == true > && cell->face(face)->boundary_id() == 11) > { > scratch.fe_face_values_ref.reinit(cell, face); > > scratch.fe_face_values_ref[u_fe].get_function_gradients(scratch.solution_total, > > scratch.solution_grads_u_total); > > for (unsigned int f_q_point = 0; f_q_point < n_q_points_f; > ++f_q_point) > { > // Note that the contributions to the right hand side vector > we > // compute here only exist in the displacement components of > the > // vector. > const double time_ramp = (time.current() / time.end()); > const double magnitude = 0.5*1.95*1000*0.32*0.32*time_ramp; > // (Total force) / (RHS surface area) > Tensor<1,dim> dir; > dir[0] = 1.0; > Tensor<1,dim> face_normal = > scratch.fe_face_values_ref.normal_vector(f_q_point); > > const Tensor<2,dim,NumberType> &grad_u = > scratch.solution_grads_u_total[f_q_point]; > const Tensor<2,dim,NumberType> F = > Physics::Elasticity::Kinematics::F(grad_u); > const SymmetricTensor<2,dim,NumberType> C = > Physics::Elasticity::Kinematics::C(F); > const SymmetricTensor<2,dim,NumberType> C_inv = invert(C); > const Tensor<1, dim> traction = magnitude*dir; > > for (unsigned int i = 0; i < dofs_per_cell; ++i) > { > const unsigned int i_group = > fe.system_to_base_index(i).first.first; > > if (i_group == u_dof) > { > const unsigned int component_i = > fe.system_to_component_index(i).first; > const double Ni = > scratch.fe_face_values_ref.shape_value(i, > f_q_point); > const double JxW = > scratch.fe_face_values_ref.JxW(f_q_point); > > data.cell_rhs(i) += (Ni * traction[component_i]) > * sqrt(face_normal * C_inv * > face_normal) > * JxW; > } > } > } > } > } > > > The errors I got are as follows: > If I set the parameters as: set Polynomial degree = 2 set Quadrature > order = 2 > An error occurred in line <645> of file > </home/michael/dealii-9.2.0/source/fe/fe_values.cc <http://fe_values.cc/>> in > function > void dealii::FEValuesViews::internal::do_function_derivatives(const > dealii::ArrayView<Number>&, const dealii::Table<2, dealii::Tensor<order, > spacedim> >&, const std::vector<typename dealii::FEValuesViews::Vector<dim, > spacedim>::ShapeFunctionData>&, std::vector<typename > dealii::ProductType<Number, dealii::Tensor<(order + 1), spacedim> >::type>&) > [with int order = 1; int dim = 3; int spacedim = 3; Number = double; typename > dealii::FEValuesViews::Vector<dim, spacedim>::ShapeFunctionData = > dealii::FEValuesViews::Vector<3, 3>::ShapeFunctionData; typename > dealii::ProductType<Number, dealii::Tensor<(order + 1), spacedim> >::type = > dealii::Tensor<2, 3, double>] > The violated condition was: > static_cast<typename ::dealii::internal::argument_type<void( typename > std::common_type<decltype(derivatives.size()), > decltype(n_quadrature_points)>::type)>::type>(derivatives.size()) == > static_cast<typename ::dealii::internal::argument_type<void( typename > std::common_type<decltype(derivatives.size()), > decltype(n_quadrature_points)>::type)>::type>(n_quadrature_points) > Additional information: > Dimension 8 not equal to 4. > > If I use set Polynomial degree = 2 set Quadrature order = 1 > An error occurred in line <335> of file > </home/michael/dealii-9.2.0/source/lac/sparse_direct.cc > <http://sparse_direct.cc/>> in function > void dealii::SparseDirectUMFPACK::factorize(const Matrix&) [with Matrix = > dealii::SparseMatrix<double>] > The violated condition was: > status == UMFPACK_OK > Additional information: > UMFPACK routine umfpack_dl_numeric returned error status 1. > > On Sunday, August 1, 2021 at 12:08:37 AM UTC-6 peterr...@gmail.com > <http://gmail.com/> wrote: > The return type should be `Tensor<2,dim,NumberType>` shouldn't it? > > Hope this helps. If not, could describe how the code does not work? It it not > compiling? Is the result wrong? > > PM > > On Sunday, 1 August 2021 at 04:09:45 UTC+2 lian...@gmail.com > <applewebdata://077135A6-7F9A-4355-B67F-C1A09CC2AECF> wrote: > Dear All, > > I want to do a surface integration which needs to evaluate the gradients of > the solution on the face. The following code does not work > > fe_face_values.get_function_gradients(solution, solution_grads); > for (unsigned int f_q_point = 0; f_q_point < n_q_points_f; > ++f_q_point) > { > const Tensor<2,dim,NumberType> &grad_u = > solution_grads[f_q_point]; > ... > } > > Can anybody give a hint on that? > > Thanks, > Michael > > -- > The deal.II project is located at http://www.dealii.org/ > <http://www.dealii.org/> > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > <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 > <mailto:dealii+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/3b018015-206e-41f7-9ff3-88c909927af7n%40googlegroups.com > > <https://groups.google.com/d/msgid/dealii/3b018015-206e-41f7-9ff3-88c909927af7n%40googlegroups.com?utm_medium=email&utm_source=footer>. -- 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. 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