Benhour,
I still have problem with implying boundary condition on the curved domain.
consider we produce quarter of a ring in 2D with the function
"quarter_hyper_shell" and want to impose Neumann boundary condition on the
outer surface. In fact we have a force normal to this surface. The other
boundary conditions for straight lines are axisymmetry boundary condition.
What I did is given as follow:
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);
for (unsigned int f_q_point=0; f_q_point<n_q_points_f; ++f_q_point)
{
const double time_ramp = (time.current() / time.end());
const double eta_orderM =
(local_quadrature_point_history[f_q_point].get_eta_boundary_value_mechanic())
* time_ramp; *// The multiplication of Neumann value (for example heat flux
in heat equation or traction force normal to the surface in mechanic) and
time_ramp*.
static const Tensor<1, dim> normals =
scratch.fe_face_values_ref.normal_vector(f_q_point); * // Extracting the
normal vectors of the selected face*
const Tensor<1, dim> neumann_value = eta_orderM * normals;
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 JxW = scratch.fe_face_values_ref.JxW(f_q_point);
data.cell_rhs(i) -= neumann_value[component_i] *
scratch.fe_face_values_ref.shape_value(i, f_q_point) * JxW;
}
}
}
}
The problem is that with changing the sign of the data.cell_rhs(i), the
direction of the force did not change. In fact, The ring is under compression,
however, in the result, it seems that it is under tension.
So you are saying that if you change the sign, the solution does not change?
If so, the term you are adding must be zero! The question is: is it zero? Did
you check this? If it isn't zero, then changing the sign must change the solution.
I also have a question. In
const double eta_orderM = (local_quadrature_point_history[f_q_point].
get_eta_boundary_value_mechanic()) * time_ramp;
Here, f_q_point counts over the quadrature points of the *face* quadrature. Is
`local_quadrature_point_history` only defined for the face, or the cell? If it
is the former, then this code is clearly wrong.
Best
W.
--
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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