added documentation and updated parameter example

doc/RTD/source/RadiativeTransfer/GEAR_RT.rst

@@ -49,15 +49,18 @@ You need to provide the following runtime parameters in the yaml file:
 
    GEARRT:
        photon_groups_Hz: [3.288e15, 5.945e15, 13.157e15]  # Photon frequency group bin edges in Hz
-       use_const_emission_rates: 1 
-       star_emission_rates_LSol: [1., 1., 1.]             # stellar emission rates for each photon 
-                                                          # frequency bin in units of solar luminosity
+       stellar_spectrum_type: 0                           # Which radiation spectrum to use. 
+                                                          #   0: constant. 
+                                                          #   1: blackbody spectrum.
+       stellar_luminosity_model: const                    # Which Luminosity model to use.
+       const_stellar_luminosities_LSol: [1., 1., 1.]      # stellar emission rates for each photon 
+                                                          #   frequency bin in units of solar luminosity
+                                                          #   for the 'const' luminosity model
        f_reduce_c: 1e-3                                   # reduce the speed of light by this factor
        CFL_condition: 0.9                                 # CFL condition for time integration
        hydrogen_mass_fraction:  0.76                      # total hydrogen (H + H+) mass fraction in the 
                                                           # metal-free portion of the gas
 
-       stellar_spectrum_type: 0                           # Which radiation spectrum to use. 0: constant. 1: blackbody spectrum.
 
    TimeIntegration:
        max_nr_rt_subcycles: 128         # maximal number of RT subcycles per hydro step
@@ -70,17 +73,18 @@ need to be sorted in increasing order. The final upper edge is defined in a
 different manner, and depends on the stellar spectrum type you assume (see below
 for more details).
 
+To specify the radiation emitted by stars, there are two main parameters:
+``stellar_luminosity_model`` defines which model to use to obtain star 
+luminosities, while ``stellar_spectrum_type`` determines the spectrum of the
+radiation.
 At the moment, the only way to define star emission rates is to use constant
-star emission rates that need to be provided in the parameter file. The star 
-emission rates need to be defined for each photon frequency group individually.
-Each star particle will then emit the given energies, independent of their other 
-properties, i.e. the spectrum is currently independent of stellar age, metallicity, 
-redshift, etc.
-
-Furthermore, even though the parameter ``use_const_emission_rates`` is 
-intended to be optional in the future, **for now it needs to be set to 1**., and
-it requires you to manually set the stellar emission rates via the
-``star_emission_rates_LSol`` parameter.
+stellar luminosities by setting ``stellar_luminosity_model: const``. [#f3]_
+The constant star emission rates need to be provided in the parameter file and
+to be defined for each photon frequency group individually using the 
+``const_stellar_luminosities_LSol`` parameter. The luminosities are expected to
+be in units of solar luminosities. Each star particle will then emit the given 
+luminosities, independent of their other properties, i.e. the spectrum is 
+currently independent of stellar age, metallicity, redshift, etc.
 
 When solving the thermochemistry, we need to assume some form of stellar
 spectrum so we may integrate over frequency bins to obtain average interaction
@@ -410,4 +414,7 @@ useful:
    This is the state of things at 08.2022, with grackle being at version 3.2 (commit
    ``a089c837b8649c97b53ed3c51c84b1decf5073d8``)
     
-
+.. [#f3] Technically there is also the model used for "Test 4" from the 
+   `I. Iliev et al. 2006 <https://ui.adsabs.harvard.edu/abs/2006MNRAS.369.1625I>`_ 
+   paper, but that is very specialized and shouldn't have much use in real 
+   applications.

examples/parameter_example.yml

@@ -766,8 +766,8 @@ GEARRT:
   CFL_condition: 0.9                                # CFL condition for RT, independent of hydro
   f_limit_cooling_time: 0.9                         # (Optional) multiply the cooling time by this factor when estimating maximal next time step. Set to 0.0 to turn computation of cooling time off.
   photon_groups_Hz: [3.288e15, 5.945e15, 13.157e15] # Lower photon frequency group bin edges in Hz. Needs to have exactly N elements, where N is the configured number of bins --with-RT=GEAR_N
-  use_const_emission_rates: 1                       # (Optional) use constant emission rates for stars as defined with star_emission_rates_LSol parameter
-  star_emission_rates_LSol: [1., 1., 1.]            # (Optional) constant star emission rates for each photon frequency group to use if use_constant_emission_rates is set, in units of Solar Luminosity.
+  stellar_luminosity_model: const                   # Which model to use to determine the stellar luminosities.
+  const_stellar_luminosities_LSol: [1., 1., 1.]     # (Conditional) constant star luminosities for each photon frequency group to use if stellar_luminosity_model:const is set, in units of Solar Luminosity.
   hydrogen_mass_fraction:  0.76                     # total hydrogen (H + H+) mass fraction in the metal-free portion of the gas
   set_equilibrium_initial_ionization_mass_fractions: 0   # (Optional) set the initial ionization fractions depending on gas temperature assuming ionization equilibrium.
   set_initial_ionization_mass_fractions: 0          # (Optional) manually overwrite initial mass fraction of each species (using the values you set below)