// Normalize the eigenfunction representing the neutron flux so that the total
// power it generates equals to 'desired_power' [W].
void normalize_to_power(Space* space, double desired_power)
{
// Calculate total power generated by the computed flux 'u':
// P(u) = \eps \int_\Omega \Sigma_f(x) u(x).
double P = eps * calc_fission_yield(space) / nu;
// Calculate normalization constant 'c', so that P(c u) = 'desired_power'.
double c = desired_power / P;
// Multiply the computed flux by the normalization constant.
multiply_dofs_with_constant(space, c);
}
int main()
{
// Create space.
// Transform input data to the format used by the "Space" constructor.
SpaceData *md = new SpaceData(verbose);
Space* space = new Space(md->N_macroel, md->interfaces, md->poly_orders, md->material_markers, md->subdivisions, N_GRP, N_SLN);
delete md;
// Enumerate basis functions, info for user.
int ndof = Space::get_num_dofs(space);
info("ndof: %d", ndof);
// Plot the space.
space->plot("space.gp");
// Initial approximation of the dominant eigenvalue.
double K_EFF = 1.0;
// Initial approximation of the dominant eigenvector.
double init_val = 1.0;
for (int g = 0; g < N_GRP; g++)
{
set_vertex_dofs_constant(space, init_val, g);
space->set_bc_right_dirichlet(g, flux_right_surf[g]);
}
// Initialize the weak formulation.
WeakForm wf(2);
wf.add_matrix_form(0, 0, jacobian_fuel_0_0, NULL, fuel);
wf.add_matrix_form(0, 0, jacobian_water_0_0, NULL, water);
wf.add_matrix_form(0, 1, jacobian_fuel_0_1, NULL, fuel);
wf.add_matrix_form(0, 1, jacobian_water_0_1, NULL, water);
wf.add_matrix_form(1, 0, jacobian_fuel_1_0, NULL, fuel);
wf.add_matrix_form(1, 0, jacobian_water_1_0, NULL, water);
wf.add_matrix_form(1, 1, jacobian_fuel_1_1, NULL, fuel);
wf.add_matrix_form(1, 1, jacobian_water_1_1, NULL, water);
wf.add_vector_form(0, residual_fuel_0, NULL, fuel);
wf.add_vector_form(0, residual_water_0, NULL, water);
wf.add_vector_form(1, residual_fuel_1, NULL, fuel);
wf.add_vector_form(1, residual_water_1, NULL, water);
wf.add_vector_form_surf(0, residual_surf_left_0, BOUNDARY_LEFT);
wf.add_vector_form_surf(1, residual_surf_left_1, BOUNDARY_LEFT);
// Initialize the FE problem.
bool is_linear = false;
DiscreteProblem *dp = new DiscreteProblem(&wf, space, is_linear);
Linearizer l(space);
char solution_file[32];
// Source iteration
int i;
int current_solution = 0, previous_solution = 1;
double K_EFF_old;
for (i = 0; i < Max_SI; i++)
{
// Plot the critical (i.e. steady-state) flux in the actual iteration.
sprintf(solution_file, "solution_%d.gp", i);
l.plot_solution(solution_file);
// Store the previous solution (used at the right-hand side).
for (int g = 0; g < N_GRP; g++)
copy_dofs(current_solution, previous_solution, space, g);
// Obtain the number of degrees of freedom.
int ndof = Space::get_num_dofs(space);
// Fill vector coeff_vec using dof and coeffs arrays in elements.
double *coeff_vec = new double[Space::get_num_dofs(space)];
get_coeff_vector(space, coeff_vec);
// Set up the solver, matrix, and rhs according to the solver selection.
SparseMatrix* matrix = create_matrix(matrix_solver);
Vector* rhs = create_vector(matrix_solver);
Solver* solver = create_linear_solver(matrix_solver, matrix, rhs);
int it = 1;
while (1)
{
// Obtain the number of degrees of freedom.
int ndof = Space::get_num_dofs(space);
// Assemble the Jacobian matrix and residual vector.
dp->assemble(coeff_vec, matrix, rhs);
// Calculate the l2-norm of residual vector.
double res_l2_norm = get_l2_norm(rhs);
// Info for user.
info("---- Newton iter %d, ndof %d, res. l2 norm %g", it, Space::get_num_dofs(space), res_l2_norm);
// If l2 norm of the residual vector is within tolerance, then quit.
// NOTE: at least one full iteration forced
// here because sometimes the initial
// residual on fine mesh is too small.
if(res_l2_norm < NEWTON_TOL && it > 1) break;
// Multiply the residual vector with -1 since the matrix
// equation reads J(Y^n) \deltaY^{n+1} = -F(Y^n).
for(int i=0; i<ndof; i++) rhs->set(i, -rhs->get(i));
// Solve the linear system.
if(!solver->solve())
error ("Matrix solver failed.\n");
// Add \deltaY^{n+1} to Y^n.
for (int i = 0; i < ndof; i++) coeff_vec[i] += solver->get_solution()[i];
// If the maximum number of iteration has been reached, then quit.
if (it >= NEWTON_MAX_ITER) error ("Newton method did not converge.");
// Copy coefficients from vector y to elements.
set_coeff_vector(coeff_vec, space);
it++;
}
// Cleanup.
delete matrix;
delete rhs;
delete solver;
delete [] coeff_vec;
// Update the eigenvalue.
K_EFF_old = K_EFF;
K_EFF = calc_total_reaction_rate(space, nSf, 0., 40.);
// Convergence test.
if (fabs(K_EFF - K_EFF_old)/K_EFF < TOL_SI) break;
// Normalize total neutron flux to one fission neutron.
multiply_dofs_with_constant(space, 1./K_EFF, current_solution);
if (verbose) info("K_EFF_%d = %.8f", i+1, K_EFF);
}
// Print the converged eigenvalue.
info("K_EFF = %.8f, err= %.8f%%", K_EFF, 100*(K_EFF-1));
// Plot the converged critical neutron flux.
sprintf(solution_file, "solution.gp");
l.plot_solution(solution_file);
// Comparison with analytical results (see the reference above).
double flux[N_GRP], J[N_GRP], R;
get_solution_at_point(space, 0.0, flux, J);
R = flux[0]/flux[1];
info("phi_fast/phi_therm at x=0 : %.4f, err = %.2f%%", R, 100*(R-2.5332)/2.5332);
get_solution_at_point(space, 40.0, flux, J);
R = flux[0]/flux[1];
info("phi_fast/phi_therm at x=40 : %.4f, err = %.2f%%", R, 100*(R-1.5162)/1.5162);
info("Done.");
return 0;
}
