~amcg-stokes/fluidity/multimaterial_diagnostic_dependencies

              ## The default free_surface implements the physical boundary

              ## condition p=0 (this is full pressure without subtracting the hydrostatic component)

              ## For viscous fluids the correct boundary condition is a no normal

              ## stress condition, which includes a viscosity term. When using

              ## this option a prognostic FreeSurface field is required.

              element no_normal_stress {

                 ## Treat the free surface evolution equation separately from the momentum equation.  

                 ## i.e. stagger the solves.

                 ##

                 ## Requires a prognostic FreeSurface field.

                 element explicit {

                   empty

                 }?

              }?,

              ## When selected the density at the surface is calculated using the Density field.  Therefore

              ## this requires a Density field!

              element variable_density {

                 empty

              }?,

              ## When selected a hydrostatic pressure distribution on the outside is assumed

              ## using the specified density, i.e. instead of applying p=0 (resp.

              ## normal_stress=0) we apply p=p_external (resp. normal_stress=p_external) where p_external is determined by dp_external/dz=external_density*g

              element external_density {

                 real

              }?,

         }|

         ## Flux boundary condition. 

         ##

         ## Weakly enforces a flux across a boundary

         element type {

            attribute name { "flux" },

            element align_bc_with_cartesian {

               element x_component {

                  input_choice_real_bc_component

               }?,

               element y_component {

                  input_choice_real_bc_component

               }?,

               element z_component {

                  input_choice_real_bc_component

               }?

            }

         ## Use in combination with a free_surface boundary condition on velocity

         ## Without the no_normal_stress option, this field should be diagnostic

         ## and is optional. With the no_normal_stress option this field is required

         ## and should be prognostic.

               ## field, without the no_normal_stress_option.

               ## It gives you a full dimensional field (constant over the vertical)

               }|

               ## Free Surface

               ## NOTE: the prognostic FreeSurface field only works in combination

               ## with the free_surface boundary condition applied to the Velocity

               ## field in combination with the no_normal_stress_option.

               ## It gives you a full dimensional field (constant over the vertical)

               ## of the free surface elevation. Initial and boundary conditions

               ## for free surface should be set on this field.

               element prognostic {

                  ## Must be on the same mesh as Pressure

                  pressure_mesh_choice,

                  (

                     ## Initial condition for WholeMesh

                     ##

                     ## Only specify one condition if not using mesh regions.

                     ## Otherwise select other initial_condition option, specify region_ids

                     ## and distinct names.  Then add extra intial conditions for other regions.

                     element initial_condition {

                        attribute name { "WholeMesh" },

                        input_choice_initial_condition_real

                     }|

                     ## Multiple initial_conditions are allowed if specifying

                     ## different values in different

                     ## regions of the mesh (defined by region_ids).  In this case

                     ## each initial_condition

                     ## requires a distinct name for the options dictionary.

                     element initial_condition {

                        attribute name { string },

                        region_ids?,

                        input_choice_initial_condition_real

                     }

                  )+,

                  ## Solver - only necessary in combination with an explicit no_normal_stress free_surface bc under Velocity.

                  element solver {

                     linear_solver_options_sym

                  },

                  prognostic_scalar_output_options,

                  prognostic_scalar_stat_options,

                  scalar_convergence_options,

                  prognostic_detector_options,

                  scalar_steady_state_options,

                  adaptivity_options_prognostic_scalar_field,

                  interpolation_algorithm_scalar