Added functions to initialise an entropy floor and to compute the floor for a given density.

src/cooling.c

@@ -67,7 +67,7 @@ void cooling_struct_dump(const struct cooling_function_data* cooling,
 }
 
 /**
- * @brief Restore a hydro_props struct from the given FILE as a stream of
+ * @brief Restore a cooling_function struct from the given FILE as a stream of
  * bytes.
  *
  * @param cooling the struct

src/entropy_floor.h

@@ -35,4 +35,3 @@
 #endif
 
 #endif /* SWIFT_ENTROPY_FLOOR_H */
-

src/entropy_floor/EAGLE/entropy_floor.h

@@ -19,10 +19,217 @@
 #ifndef SWIFT_ENTROPY_FLOOR_EAGLE_H
 #define SWIFT_ENTROPY_FLOOR_EAGLE_H
 
+#include "adiabatic_index.h"
+#include "cosmology.h"
+#include "hydro_properties.h"
+#include "parser.h"
+#include "units.h"
+
 /**
  * @file src/entropy_floor/EAGLE/entropy_floor.h
  * @brief Entropy floor used in the EAGLE model
  */
 
+/**
+ * @brief Properties of the entropy floor in the EAGLE model.
+ */
+struct entropy_floor_properties {
+
+  /*! Density threshold for the Jeans floor in Hydrogen atoms per cubic cm */
+  float Jeans_density_threshold_H_p_cm3;
+
+  /*! Density threshold for the Jeans floor in internal units */
+  float Jeans_density_threshold;
+
+  /*! Inverse of the density threshold for the Jeans floor in internal units */
+  float Jeans_density_threshold_inv;
+
+  /*! Over-density threshold for the Jeans floor */
+  float Jeans_over_density_threshold;
+
+  /*! Slope of the Jeans floor power-law */
+  float Jeans_gamma_effective;
+
+  /*! Temperature of the Jeans floor at the density threshold in Kelvin */
+  float Jeans_temperature_norm_K;
+
+  /*! Temperature of the Jeans floor at the density thresh. in internal units */
+  float Jeans_temperature_norm;
+
+  /*! Pressure of the Jeans floor at the density thresh. in internal units */
+  float Jeans_pressure_norm;
+
+  /*! Density threshold for the Cool floor in Hydrogen atoms per cubic cm */
+  float Cool_density_threshold_H_p_cm3;
+
+  /*! Density threshold for the Cool floor in internal units */
+  float Cool_density_threshold;
+
+  /*! Inverse of the density threshold for the Cool floor in internal units */
+  float Cool_density_threshold_inv;
+
+  /*! Over-density threshold for the Cool floor */
+  float Cool_over_density_threshold;
+
+  /*! Slope of the Cool floor power-law */
+  float Cool_gamma_effective;
+
+  /*! Temperature of the Cool floor at the density threshold in Kelvin */
+  float Cool_temperature_norm_K;
+
+  /*! Temperature of the Cool floor at the density thresh. in internal units */
+  float Cool_temperature_norm;
+
+  /*! Pressure of the Cool floor at the density thresh. in internal units */
+  float Cool_pressure_norm;
+};
+
+/**
+ * @brief Compute the entropy floor of a given #part.
+ *
+ * Note that the particle is not updated!!
+ *
+ * @param p The #part.
+ * @param cosmo The cosmological model.
+ * @param props The properties of the entropy floor.
+ */
+float entropy_floor(const struct part *p, const struct cosmology *cosmo,
+                    const struct entropy_floor_properties *props) {
+
+  /* Physical density in internal units */
+  const float rho = hydro_get_physical_density(p, cosmo);
+
+  /* Critical density at this redshift.
+   * Recall that this is 0 in a non-cosmological run */
+  const float rho_crit = cosmo->critical_density;
+
+  float pressure = 0.;
+
+  /* Are we in the regime of the Jeans equation of state? */
+  if ((rho > rho_crit * props->Jeans_over_density_threshold) &&
+      (rho > props->Jeans_density_threshold)) {
+
+    const float pressure_Jeans = props->Jeans_pressure_norm *
+                                 powf(rho * props->Jeans_density_threshold_inv,
+                                      props->Jeans_gamma_effective);
+
+    pressure = max(pressure, pressure_Jeans);
+  }
+
+  /* Are we in the regime of the Cool equation of state? */
+  if ((rho > rho_crit * props->Cool_over_density_threshold) &&
+      (rho > props->Cool_density_threshold)) {
+
+    const float pressure_Cool = props->Cool_pressure_norm *
+                                powf(rho * props->Cool_density_threshold_inv,
+                                     props->Cool_gamma_effective);
+
+    pressure = max(pressure, pressure_Cool);
+  }
+
+  /* Convert to an entropy.
+   * (Recall that the entropy is the same in co-moving and phycial frames) */
+  return gas_entropy_from_pressure(rho, pressure);
+}
+
+/**
+ * @brief Initialise the entropy floor by reading the parameters and converting
+ * to internal units.
+ *
+ * @param params The YAML parameter file.
+ * @param us The system of units used internally.
+ * @param phys_cont The physical constants.
+ * @param props The entropy floor properties to fill.
+ */
+void entropy_floor_init(struct swift_params *params,
+                        const struct unit_system *us,
+                        const struct phys_const *phys_const,
+                        const struct hydro_props *hydro_props,
+                        struct entropy_floor_properties *props) {
+
+  /* Read the parameters in the units they are set */
+  props->Jeans_density_threshold_H_p_cm3 = parser_get_param_float(
+      params, "EAGLEEntropyFloor:Jeans_density_threshold_H_p_cm3");
+  props->Jeans_over_density_threshold = parser_get_param_float(
+      params, "EAGLEEntropyFloor:Jeans_over_density_threshold");
+  props->Jeans_temperature_norm_K = parser_get_param_float(
+      params, "EAGLEEntropyFloor:Jeans_temperature_norm_K");
+  props->Jeans_gamma_effective =
+      parser_get_param_float(params, "EAGLEEntropyFloor:Jeans_gamma_effective");
+
+  props->Cool_density_threshold_H_p_cm3 = parser_get_param_float(
+      params, "EAGLEEntropyFloor:Cool_density_threshold_H_p_cm3");
+  props->Cool_over_density_threshold = parser_get_param_float(
+      params, "EAGLEEntropyFloor:Cool_over_density_threshold");
+  props->Cool_temperature_norm_K = parser_get_param_float(
+      params, "EAGLEEntropyFloor:Cool_temperature_norm_K");
+  props->Cool_gamma_effective =
+      parser_get_param_float(params, "EAGLEEntropyFloor:Cool_gamma_effective");
+
+  /* Initial Hydrogen abundance (mass fraction) */
+  const float X_H = hydro_props->hydrogen_mass_fraction;
+
+  /* Now convert to internal units */
+  props->Jeans_temperature_norm =
+      props->Jeans_temperature_norm_K /
+      units_cgs_conversion_factor(us, UNIT_CONV_TEMPERATURE);
+  props->Jeans_density_threshold =
+      props->Jeans_density_threshold /
+      units_cgs_conversion_factor(us, UNIT_CONV_VOLUME) *
+      phys_const->const_proton_mass / X_H;
+
+  props->Cool_temperature_norm =
+      props->Cool_temperature_norm_K /
+      units_cgs_conversion_factor(us, UNIT_CONV_TEMPERATURE);
+  props->Cool_density_threshold =
+      props->Cool_density_threshold /
+      units_cgs_conversion_factor(us, UNIT_CONV_VOLUME) *
+      phys_const->const_proton_mass / X_H;
+
+  /* We assume neutral gas */
+  const float mean_molecular_weight = hydro_props->mu_neutral;
+
+  /* Get the common terms */
+  props->Jeans_density_threshold_inv = 1.f / props->Jeans_density_threshold;
+  props->Cool_density_threshold_inv = 1.f / props->Cool_density_threshold;
+
+  /* P_norm = (k_B * T) / (m_p * mu) * rho_threshold */
+  props->Jeans_pressure_norm =
+      (phys_const->const_boltzmann_k * props->Jeans_temperature_norm) /
+      (phys_const->const_proton_mass * mean_molecular_weight) *
+      props->Jeans_density_threshold;
+
+  props->Cool_pressure_norm =
+      (phys_const->const_boltzmann_k * props->Cool_temperature_norm) /
+      (phys_const->const_proton_mass * mean_molecular_weight) *
+      props->Cool_density_threshold;
+}
+
+/**
+ * @brief Write an entropy floor struct to the given FILE as a stream of bytes.
+ *
+ * @param props the struct
+ * @param stream the file stream
+ */
+void entropy_floor_struct_dump(const struct entropy_floor_properties *props,
+                               FILE *stream) {
+
+  restart_write_blocks((void *)props, sizeof(struct entropy_floor_properties),
+                       1, stream, "entropy floor", "entropy floor properties");
+}
+
+/**
+ * @brief Restore a entropy floor struct from the given FILE as a stream of
+ * bytes.
+ *
+ * @param props the struct
+ * @param stream the file stream
+ */
+void entropy_floor_struct_restore(struct entropy_floor_properties *props,
+                                  FILE *stream) {
+
+  restart_read_blocks((void *)props, sizeof(struct entropy_floor_properties), 1,
+                      stream, NULL, "entropy floor properties");
+}
 
 #endif /* SWIFT_ENTROPY_FLOOR_EAGLE_H */

src/entropy_floor/none/entropy_floor.h

@@ -25,5 +25,4 @@
  * floors.
  */
 
-
 #endif /* SWIFT_ENTROPY_FLOOR_NONE_H */

src/runner.c

@@ -48,6 +48,7 @@
 #include "debug.h"
 #include "drift.h"
 #include "engine.h"
+#include "entropy_floor.h"
 #include "error.h"
 #include "gravity.h"
 #include "hydro.h"