Make the compute_viscosity function 'const'.

git-svn-id: https://svn.dealii.org/trunk@18312 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/examples/step-31/step-31.cc b/deal.II/examples/step-31/step-31.cc
index 77d795f16f5b39eccfc6845fcf0edccce7be0763..0d1da76c1611ba6f3d258ed102efae7c7ca7edc7 100644 (file)
--- a/deal.II/examples/step-31/step-31.cc
+++ b/deal.II/examples/step-31/step-31.cc
@@ -604,7 +604,7 @@ class BoussinesqFlowProblem
                      const std::vector<double>          &gamma_values,
                      const double                        global_u_infty,
                      const double                        global_T_variation,
-                     const double                        cell_diameter);
+                     const double                        cell_diameter) const;
 
 
     Triangulation<dim>                  triangulation;
@@ -984,7 +984,7 @@ compute_viscosity (const std::vector<double>          &old_temperature,
                   const std::vector<double>          &gamma_values,
                   const double                        global_u_infty,
                   const double                        global_T_variation,
-                  const double                        cell_diameter)
+                  const double                        cell_diameter) const
 {
   const double beta = 0.015 * dim;
   const double alpha = 1;