add to docs

Author: BenWibking

docs/markdown/parameters.md

@@ -26,6 +26,8 @@ These parameters are read in the `AMRSimulation<problem_t>::readParameters()` fu
 | derived_vars                | String        | A list of the names of derived variables that should be included in the plotfile and Ascent outputs.                                                                                                            |
 | regrid_interval             | Integer       | The number of timesteps between AMR regridding.                                                                                                                                                                 |
 | density_floor               | Float         | The minimum density value allowed in the simulation. Enforced through EnforceLimits.                                                                                                                            |
+| density_floor_expr          | String        | Optional AMReX parser expression for a spatially varying density floor. Variables: x, y, z, base_density_floor. When set, this overrides the constant floor.                                             |
+| debug_density_floor_plot    | Boolean (0/1) | If set to 1, adds a derived field `density_floor_dbg` to plotfiles to visualize the spatially varying density floor. Default: 0 (disabled).                                                                 |
 | temperature_floor           | Float         | The minimum temperature value allowed in the simulation. Enforced through EnforceLimits.                                                                                                                        |
 | max_walltime                | String        | The maximum walltime for the simulation in the format DD:HH:SS (days/hours/seconds). After 90% of this walltime elapses, the simulation will automatically stop and exit.                                       |
 | dt_cutoff                   | Float         | Timestep drop detector threshold. If the timestep drops below dt_cutoff \* current_time, the simulation aborts with an error message. This helps detect numerical instabilities early. Default: 0.0 (disabled). |