Hi developers and users,
Can I set neumann/natural BC to my square model? I have gone through all
examples, which all set the Dirichlet BC. except the ex15(Biharmonic
Equation). There is a flux boundary condition in ex15 because of the
4th-order PDE, so May I just take the 'Gradient flux' idea then apply it
to my 2nd-order PDE? Thanks!
Liang
copied from ex15 B.C. part:
{
perf_log.start_event (*"BCs"*);
*const* Real penalty = 1e10;
*const* Real penalty2 = 1e10;
*for* (*unsigned* *int* s=0; s<elem->n_sides(); s++)
*if* (elem->neighbor(s) == NULL)
{
*const* std::vector<std::vector<Real> >& phi_face =
fe_face->get_phi();
*const* std::vector<std::vector<RealGradient> >& dphi_face =
fe_face->get_dphi();
*const* std::vector<Real>& JxW_face = fe_face->get_JxW();
*const* std::vector<Point>& qface_point = fe_face->get_xyz();
*const* std::vector<Point>& face_normals =
fe_face->get_normals();
fe_face->reinit(elem, s);
*for* (*unsigned* *int* qp=0; qp<qface->n_points(); qp++)
{
Number value = exact_solution(qface_point[qp],
es.parameters, *"null"*,
*"void"*);
Gradient flux = exact_2D_derivative(qface_point[qp],
es.parameters,
*"null"*, *"void"*);
*for* (*unsigned* *int* i=0; i<phi_face.size(); i++)
*for* (*unsigned* *int* j=0; j<phi_face.size(); j++)
Ke(i,j) += JxW_face[qp] *
(penalty * phi_face[i][qp] *
phi_face[j][qp] + penalty2
* (dphi_face[i][qp] *
face_normals[qp]) *
(dphi_face[j][qp] *
face_normals[qp]));
*for* (*unsigned* *int* i=0; i<phi_face.size(); i++)
Fe(i) += JxW_face[qp] *
(penalty * value * phi_face[i][qp]
+ penalty2 *
(flux * face_normals[qp])
* (dphi_face[i][qp]
* face_normals[qp]));
}
}
perf_log.stop_event (*"BCs"*);
}
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