Add some basic tests for sheath_boundary_simple and refactor

CMakeLists.txt

@@ -236,6 +236,8 @@ if(HERMES_TESTS)
 
   hermes_add_integrated_test(1D-fluid)
   hermes_add_integrated_test(1D-recycling)
+  hermes_add_integrated_test(1D-sheath-simple)
+  hermes_add_integrated_test(1D-sheath)
   hermes_add_integrated_test(diffusion)
   hermes_add_integrated_test(evolve_density)
   hermes_add_integrated_test(neutral_mixed)

docs/sphinx/boundary_conditions.rst

@@ -93,17 +93,17 @@ First, density, temperature and pressure are extrapolated into the target bounda
 The extrapolation method for each can be user set, e.g. `density_boundary_mode`. At the moment, 
 the available modes are:
 
-- 0: LimitFree
+- ``limit_free``
    An exponential extrapolation for decreasing quantities and a Neumann boundary for increasing
    quantities. It is inconsistent between increasing and decreasing values and is not recommended
    unless you have a reason to use it - it's legacy behaviour.
 
-- 1: ExponentialFree
-   An exponential extrapolation. It is more consistent than LimitFree and has the advantage of 
+- ``exponential_free``
+   An exponential extrapolation. It is more consistent than ``limit_free`` and has the advantage of 
    inherently preventing negative values at the target. This is the default and is recommended for most cases.
    It is defined as :math:`guard = (last)^2 / previous`
 
-- 2: LinearFree
+- ``linear_free``
    A linear extrapolation. It can lead to negative values at the target. However, it is the most 
    consistent (the linear extrapolation is what second order differencing reduces to at the wall) and has been shown to 
    reduce "zigzags" or "squiggles" near the target which are common in cell centered codes. Use only
@@ -620,4 +620,4 @@ Note that if you have the density controller enabled, it will work to counteract
    function = 0.01
    source = Pe:source
    source_time_dependent = true
-   source_prefactor = Pe:source_prefactor
+   source_prefactor = Pe:source_prefactor

include/sheath_boundary_simple.hxx

@@ -4,6 +4,10 @@
 
 #include "component.hxx"
 
+#include <bout/bout_enum_class.hxx>
+
+BOUT_ENUM_CLASS(SheathLimitMode, limit_free, exponential_free, linear_free);
+
 /// Boundary condition at the wall in Y
 ///
 /// This is a collective component, because it couples all charged species
@@ -27,7 +31,8 @@ struct SheathBoundarySimple : public Component {
   ///   - secondary_electron_coef  Effective secondary electron emission coefficient
   ///   - sin_alpha                Sine of the angle between magnetic field line and wall surface (0 to 1)
   ///   - always_set_phi           Always set phi field? Default is to only modify if already set
-  SheathBoundarySimple(std::string name, Options &options, Solver *);
+  SheathBoundarySimple(const std::string& name, Options& options,
+                       [[maybe_unused]] Solver* solver);
 
   ///
   /// # Inputs
@@ -90,20 +95,21 @@ private:
   Field3D wall_potential; ///< Voltage of the wall. Normalised units.
 
   Field3D hflux_e;  // Electron heat flux through sheath
-  Field3D phi; // Phi at sheath
-  Field3D ion_sum; // Sum of ion current at sheath
+  Field3D phi;      // Phi at sheath
 
   bool diagnose; // Save diagnostic variables?
   Options diagnostics;   // Options object to store diagnostic fields like a dict
 
   bool no_flow; ///< No flow speed, only remove energy
 
-  BoutReal density_boundary_mode, pressure_boundary_mode, temperature_boundary_mode; ///< BC mode: 0=LimitFree, 1=ExponentialFree, 2=LinearFree
+  SheathLimitMode density_boundary_mode;     ///< BC for density
+  SheathLimitMode pressure_boundary_mode;    ///< BC for pressure
+  SheathLimitMode temperature_boundary_mode; ///< BC for temperature
 };
 
 namespace {
 RegisterComponent<SheathBoundarySimple>
     registercomponentsheathboundarysimple("sheath_boundary_simple");
 }
 
-#endif // SHEATH_BOUNDARY_SIMPLE_H
+#endif // SHEATH_BOUNDARY_SIMPLE_H