C++ AssemblyContext::get_multiphysics_system方法代码示例

  void ElasticMembranePressure<PressureType>::element_time_derivative
  ( bool compute_jacobian, AssemblyContext & context )
  {
    unsigned int u_var = this->_disp_vars.u();
    unsigned int v_var = this->_disp_vars.v();
    unsigned int w_var = this->_disp_vars.w();

    const unsigned int n_u_dofs = context.get_dof_indices(u_var).size();

    const std::vector<libMesh::Real> &JxW =
      this->get_fe(context)->get_JxW();

    const std::vector<std::vector<libMesh::Real> >& u_phi =
      this->get_fe(context)->get_phi();

    const MultiphysicsSystem & system = context.get_multiphysics_system();

    unsigned int u_dot_var = system.get_second_order_dot_var(u_var);
    unsigned int v_dot_var = system.get_second_order_dot_var(v_var);
    unsigned int w_dot_var = system.get_second_order_dot_var(w_var);

    libMesh::DenseSubVector<libMesh::Number> &Fu = context.get_elem_residual(u_dot_var);
    libMesh::DenseSubVector<libMesh::Number> &Fv = context.get_elem_residual(v_dot_var);
    libMesh::DenseSubVector<libMesh::Number> &Fw = context.get_elem_residual(w_dot_var);

    libMesh::DenseSubMatrix<libMesh::Number>& Kuv = context.get_elem_jacobian(u_dot_var,v_var);
    libMesh::DenseSubMatrix<libMesh::Number>& Kuw = context.get_elem_jacobian(u_dot_var,w_var);

    libMesh::DenseSubMatrix<libMesh::Number>& Kvu = context.get_elem_jacobian(v_dot_var,u_var);
    libMesh::DenseSubMatrix<libMesh::Number>& Kvw = context.get_elem_jacobian(v_dot_var,w_var);

    libMesh::DenseSubMatrix<libMesh::Number>& Kwu = context.get_elem_jacobian(w_dot_var,u_var);
    libMesh::DenseSubMatrix<libMesh::Number>& Kwv = context.get_elem_jacobian(w_dot_var,v_var);

    unsigned int n_qpoints = context.get_element_qrule().n_points();

    // All shape function gradients are w.r.t. master element coordinates
    const std::vector<std::vector<libMesh::Real> >& dphi_dxi =
      this->get_fe(context)->get_dphidxi();

    const std::vector<std::vector<libMesh::Real> >& dphi_deta =
      this->get_fe(context)->get_dphideta();

    const libMesh::DenseSubVector<libMesh::Number>& u_coeffs = context.get_elem_solution( u_var );
    const libMesh::DenseSubVector<libMesh::Number>& v_coeffs = context.get_elem_solution( v_var );
    const libMesh::DenseSubVector<libMesh::Number>& w_coeffs = context.get_elem_solution( w_var );

    const std::vector<libMesh::RealGradient>& dxdxi  = this->get_fe(context)->get_dxyzdxi();
    const std::vector<libMesh::RealGradient>& dxdeta = this->get_fe(context)->get_dxyzdeta();

    for (unsigned int qp=0; qp != n_qpoints; qp++)
      {
        // sqrt(det(a_cov)), a_cov being the covariant metric tensor of undeformed body
        libMesh::Real sqrt_a = sqrt( dxdxi[qp]*dxdxi[qp]*dxdeta[qp]*dxdeta[qp]
                                     - dxdxi[qp]*dxdeta[qp]*dxdeta[qp]*dxdxi[qp] );

        // Gradients are w.r.t. master element coordinates
        libMesh::Gradient grad_u, grad_v, grad_w;
        for( unsigned int d = 0; d < n_u_dofs; d++ )
          {
            libMesh::RealGradient u_gradphi( dphi_dxi[d][qp], dphi_deta[d][qp] );
            grad_u += u_coeffs(d)*u_gradphi;
            grad_v += v_coeffs(d)*u_gradphi;
            grad_w += w_coeffs(d)*u_gradphi;
          }

        libMesh::RealGradient dudxi( grad_u(0), grad_v(0), grad_w(0) );
        libMesh::RealGradient dudeta( grad_u(1), grad_v(1), grad_w(1) );

        libMesh::RealGradient A_1 = dxdxi[qp] + dudxi;
        libMesh::RealGradient A_2 = dxdeta[qp] + dudeta;

        libMesh::RealGradient A_3 = A_1.cross(A_2);

        // Compute pressure at this quadrature point
        libMesh::Real press = (*_pressure)(context,qp);

        // Small optimization
        libMesh::Real p_over_sa = press/sqrt_a;

        /* The formula here is actually
           P*\sqrt{\frac{A}{a}}*A_3, where A_3 is a unit vector
           But, |A_3| = \sqrt{A} so the normalizing part kills
           the \sqrt{A} in the numerator, so we can leave it out
           and *not* normalize A_3.
        */
        libMesh::RealGradient traction = p_over_sa*A_3;

        for (unsigned int i=0; i != n_u_dofs; i++)
          {
            // Small optimization
            libMesh::Real phi_times_jac = u_phi[i][qp]*JxW[qp];

            Fu(i) -= traction(0)*phi_times_jac;
            Fv(i) -= traction(1)*phi_times_jac;
            Fw(i) -= traction(2)*phi_times_jac;

            if( compute_jacobian )
              {
                for (unsigned int j=0; j != n_u_dofs; j++)
//.........这里部分代码省略.........