aero_rep_single_particle.c

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/* Copyright (C) 2021 Barcelona Supercomputing Center and University of
 * Illinois at Urbana-Champaign
 * SPDX-License-Identifier: MIT
 *
 * Single particle aerosol representation functions
 *
 */
/** \file
 * \brief Single particle aerosol representation functions
 */
#include <stdio.h>
#include <stdlib.h>
#include <camp/aero_phase_solver.h>
#include <camp/aero_reps.h>
#include <camp/camp_solver.h>
 
// TODO Lookup environmental indicies during initialization
#define TEMPERATURE_K_ env_data[0]
#define PRESSURE_PA_ env_data[1]
 
#define UPDATE_NUMBER 0
 
#define NUM_LAYERS_ int_data[0]
#define AERO_REP_ID_ int_data[1]
#define MAX_PARTICLES_ int_data[2]
#define PARTICLE_STATE_SIZE_ int_data[3]
#define NUMBER_CONC_(x) aero_rep_env_data[x]
#define NUM_INT_PROP_ 4
#define NUM_FLOAT_PROP_ 0
#define NUM_ENV_PARAM_ MAX_PARTICLES_
#define LAYER_PHASE_START_(l) (int_data[NUM_INT_PROP_+l]-1)
#define LAYER_PHASE_END_(l) (int_data[NUM_INT_PROP_+NUM_LAYERS_+l]-1)
#define TOTAL_NUM_PHASES_ (LAYER_PHASE_END_(NUM_LAYERS_-1)-LAYER_PHASE_START_(0)+1)
#define NUM_PHASES_(l) (LAYER_PHASE_END_(l)-LAYER_PHASE_START_(l)+1)
#define PHASE_STATE_ID_(l,p) (int_data[NUM_INT_PROP_+2*NUM_LAYERS_+LAYER_PHASE_START_(l)+p]-1)
#define PHASE_MODEL_DATA_ID_(l,p) (int_data[NUM_INT_PROP_+2*NUM_LAYERS_+TOTAL_NUM_PHASES_+LAYER_PHASE_START_(l)+p]-1)
#define PHASE_NUM_JAC_ELEM_(l,p) int_data[NUM_INT_PROP_+2*NUM_LAYERS_+2*TOTAL_NUM_PHASES_+LAYER_PHASE_START_(l)+p]
 
/** \brief Flag Jacobian elements used in calcualtions of mass and volume
 *
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param model_data Pointer to the model data
 * \param aero_phase_idx Index of the aerosol phase to find elements for
 * \param jac_struct 1D array of flags indicating potentially non-zero
 *                   Jacobian elements. (The dependent variable should have
 *                   been chosen by the calling function.)
 * \return Number of Jacobian elements flagged
 */
 
int aero_rep_single_particle_get_used_jac_elem(ModelData *model_data,
                                               int aero_phase_idx,
                                               int *aero_rep_int_data,
                                               double *aero_rep_float_data,
                                               bool *jac_struct) {
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  int n_jac_elem = 0;
  int i_part = aero_phase_idx / TOTAL_NUM_PHASES_;
 
  // Each phase in a single particle has the same jac elements
  // (one for each species in each phase in the particle)
  for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
    for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {
      PHASE_NUM_JAC_ELEM_(i_layer,i_phase) = aero_phase_get_used_jac_elem(
          model_data, PHASE_MODEL_DATA_ID_(i_layer,i_phase),
          i_part * PARTICLE_STATE_SIZE_ + PHASE_STATE_ID_(i_layer,i_phase), jac_struct);
      n_jac_elem += PHASE_NUM_JAC_ELEM_(i_layer,i_phase);
     }
  }
  return n_jac_elem;
}
 
/** \brief Flag elements on the state array used by this aerosol representation
 *
 * The single particle aerosol representation functions do not use state array
 * values
 *
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param state_flags Array of flags indicating state array elements used
 */
 
void aero_rep_single_particle_get_dependencies(int *aero_rep_int_data,
                                               double *aero_rep_float_data,
                                               bool *state_flags) {
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  
  return;
}
 
/** \brief Update aerosol representation data for new environmental conditions
 *
 * The single particle aerosol representation does not use environmental
 * conditions
 *
 * \param model_data Pointer to the model data
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_update_env_state(ModelData *model_data,
                                               int *aero_rep_int_data,
                                               double *aero_rep_float_data,
                                               double *aero_rep_env_data) {
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  double *env_data = model_data->grid_cell_env;
 
  return;
}
 
/** \brief Update aerosol representation data for a new state
 *
 * \param model_data Pointer to the model data, include the state array
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_update_state(ModelData *model_data,
                                           int *aero_rep_int_data,
                                           double *aero_rep_float_data,
                                           double *aero_rep_env_data) {
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
 
  return;
}
 
/** \brief Get the effective radius of a specified layer \f$r_{layer}\f$ (m)
 *
 * \param model_data Pointer to the model data, including the state array
 * \param aero_phase_idx Index of the aerosol phase within the representation
 * \param layer_radius Effective layer radius (m)
 * \param partial_deriv \f$\frac{\partial r_{eff}}{\partial y}\f$ where \f$y\f$
 *                      are species on the state array
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_get_effective_layer_radius__m(
    ModelData *model_data, int aero_phase_idx, double *layer_radius,
    double *partial_deriv, int *aero_rep_int_data, double *aero_rep_float_data,
    double *aero_rep_env_data) {
 
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  int i_part = aero_phase_idx / TOTAL_NUM_PHASES_;
  double *curr_partial = NULL;
  int aero_phase_idx_temp = aero_phase_idx;
  aero_phase_idx_temp -= i_part * TOTAL_NUM_PHASES_;
  
  int i_layer_radius = -1;
  for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
   if (LAYER_PHASE_START_(i_layer) <= aero_phase_idx_temp &&
      aero_phase_idx_temp <= LAYER_PHASE_END_(i_layer)) {
      i_layer_radius = i_layer;
      break;
    }
  }
 
  *layer_radius = 0.0;
  if (partial_deriv) curr_partial = partial_deriv;
  for (int i_layer = 0; i_layer <= i_layer_radius; ++i_layer) {
    for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {
      double *state = (double *)(model_data->grid_cell_state);
      state += i_part * PARTICLE_STATE_SIZE_ + PHASE_STATE_ID_(i_layer,i_phase);
      double volume;
      aero_phase_get_volume__m3_m3(model_data, PHASE_MODEL_DATA_ID_(i_layer,i_phase),
                                   state, &(volume), curr_partial);
      if (partial_deriv) curr_partial += PHASE_NUM_JAC_ELEM_(i_layer,i_phase);
      *layer_radius += volume;
    }
  }
  *layer_radius = pow(((*layer_radius) * 3.0 / 4.0 / 3.14159265359), 1.0 / 3.0);
  if (!partial_deriv) return;
  for (int i_layer = 0; i_layer <= i_layer_radius; ++i_layer) {
    for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {
      for (int i_spec = 0; i_spec < PHASE_NUM_JAC_ELEM_(i_layer,i_phase); ++i_spec) {
        *partial_deriv =
            1.0 / 4.0 / 3.14159265359 * pow(*layer_radius, -2.0) * (*partial_deriv);
        ++partial_deriv;
      }
    }
  }
  return;
}
 
/** \brief Get the effective particle radius \f$r_{eff}\f$ (m)
 * Finds the radius of the largest layer in specified particle.
 *
 * \param model_data Pointer to the model data, including the state array
 * \param aero_phase_idx Index of the aerosol phase within the representation
 * \param radius Effective particle radius (m)
 * \param partial_deriv \f$\frac{\partial r_{eff}}{\partial y}\f$ where \f$y\f$
 *                      are species on the state array
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_get_effective_radius__m(
    ModelData *model_data, int aero_phase_idx, double *radius,
    double *partial_deriv, int *aero_rep_int_data, double *aero_rep_float_data,
    double *aero_rep_env_data) {
 
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  double *curr_partial = NULL;
  
  // Adjust aero_phase_idx to the last phase in the particle.
  // Add 1 to aero_phase_idx/TOTAL_NUM_PHASES_ to account for c indexing starting at 0.
  int offset = (TOTAL_NUM_PHASES_*((aero_phase_idx / TOTAL_NUM_PHASES_)+1)) - aero_phase_idx;
  aero_phase_idx += offset;
  aero_rep_single_particle_get_effective_layer_radius__m(
      model_data, 
      aero_phase_idx-1, // Adjusted to last phase in particle.
      radius,
      partial_deriv,
      int_data, 
      float_data, 
      aero_rep_env_data);
 
  return;
}
 
/** \brief Get the volume of a specified phase in the corresponding layer
 * 
 * \param model_data Pointer to the model data, including the state array
 * \param aero_phase_idx Index of the aerosol phase within the representation
 * \param phase_volume Volume of the phase (m^3)
 * \param partial_deriv \f$\frac{\partial V}{\partial y}\f$ where \f$y\f$
 *                     are species on the state array
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                           floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                         environment-dependent parameters
 */
 
 void aero_rep_single_particle_get_phase_volume__m3_m3(
    ModelData *model_data, int aero_phase_idx, double *phase_volume,
    double *partial_deriv, int *aero_rep_int_data, double *aero_rep_float_data,
    double *aero_rep_env_data) {
 
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  int i_part = aero_phase_idx / TOTAL_NUM_PHASES_;
  double *curr_partial = NULL;
  int aero_phase_idx_temp = aero_phase_idx;
  aero_phase_idx_temp -= i_part * TOTAL_NUM_PHASES_;
  
  int i_layer_phase = -1;
  for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
   if (LAYER_PHASE_START_(i_layer) <= aero_phase_idx_temp &&
      aero_phase_idx_temp <= LAYER_PHASE_END_(i_layer)) {
      i_layer_phase = i_layer;
      break;
    }
  }
  
  if (i_layer_phase == -1) {
    printf("\n\nERROR: aero_rep_single_particle_get_phase_volume__m3_m3: Could not determine i_layer_phase ");
    printf("for aero_phase_idx=%d.\n\n", aero_phase_idx);
    exit(1);
  }
 
  int total_phases_previous_layers = 0;
  for (int i_layer = 0; i_layer < i_layer_phase; ++i_layer) {
    total_phases_previous_layers += NUM_PHASES_(i_layer);
  }
  int i_phase = aero_phase_idx_temp - total_phases_previous_layers;
 
  if (partial_deriv) curr_partial = partial_deriv;
  double *state = (double *)(model_data->grid_cell_state);
  state += i_part * PARTICLE_STATE_SIZE_ + PHASE_STATE_ID_(i_layer_phase,i_phase);
  aero_phase_get_volume__m3_m3(model_data, PHASE_MODEL_DATA_ID_(i_layer_phase,i_phase),
                                state, phase_volume, curr_partial);
  if (partial_deriv) curr_partial += PHASE_NUM_JAC_ELEM_(i_layer_phase,i_phase);
    
  }
 
/** \brief Get the surface area of specified particle layer \f$r_{eff}\f$ (m)
 *
 * Solve for the surface area of the interfacial layer that exists between the 
 * two phases considered in aerosol phase mass tranfer between layers. When more
 * than one phase exists in a layer, a "fractional volume overlap" configuration 
 * is applied (see the single particle description in the Fortran script and 
 * CAMP Github Documentation for details).
 * 
 * \param model_data Pointer to the model data, including the state array
 * \param aero_phase_idx_first Index of the first aerosol phase within the representation
 * \param aero_phase_idx_second Index of the second aerosol phase within the representation
 * \param surface_area Pointer to surface area of inner layer (m^2)
 * \param partial_deriv \f$\frac{\partial sa_{eff}}{\partial y}\f$ where \f$y\f$
 *                      are species on the state array
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_get_interface_surface_area__m2(
    ModelData *model_data, int aero_phase_idx_first, int aero_phase_idx_second, 
    double *surface_area, double *partial_deriv, 
    int *aero_rep_int_data, double *aero_rep_float_data, double *aero_rep_env_data) {
 
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  double *curr_partial = NULL;
  int layer_first = -1;
  int layer_second = -1;
  int layer_interface = -1;
  int phase_model_data_id_first = -1;
  int phase_model_data_id_second = -1;
  double radius;
  int i_part = aero_phase_idx_first / TOTAL_NUM_PHASES_;
  aero_phase_idx_first -= i_part * TOTAL_NUM_PHASES_;
  aero_phase_idx_second -= i_part * TOTAL_NUM_PHASES_;
 
  // Find the layer each phase (first and second) exist in 
  int i_phase_count = 0;
  for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
    for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {
      if (LAYER_PHASE_START_(i_layer) <= aero_phase_idx_first && 
          aero_phase_idx_first <= LAYER_PHASE_END_(i_layer) && 
          i_phase_count == aero_phase_idx_first) {
        layer_first = i_layer;
        phase_model_data_id_first = PHASE_MODEL_DATA_ID_(i_layer, i_phase);
      } else if (LAYER_PHASE_START_(i_layer) <= aero_phase_idx_second &&
                 aero_phase_idx_second <= LAYER_PHASE_END_(i_layer) &&
                 i_phase_count == aero_phase_idx_second) {
        layer_second = i_layer;
        phase_model_data_id_second = PHASE_MODEL_DATA_ID_(i_layer, i_phase);
      }
      ++i_phase_count;
    }
  }
  if (layer_first == -1 || layer_second == -1) {
    printf("\n\nERROR: aero_rep_single_particle_get_interface_surface_area__m2: ");
    printf("Could not determine layer_first and layer_second for ");
    printf("aero_phase_idx_first=%d and aero_phase_idx_second=%d.\n\n", aero_phase_idx_first, aero_phase_idx_second);
    exit(1);
  }
 
  if (layer_second < layer_first) {
    printf("\n\nERROR: aero_rep_single_particle_get_interface_surface_area__m2: ");
    printf("layer_second is less than layer_first for ");
    printf("aero_phase_idx_first=%d and aero_phase_idx_second=%d.\n\n", aero_phase_idx_first, aero_phase_idx_second);
    exit(1);
  }
 
  // Find the interface between the first and second layer
  layer_interface = layer_first > layer_second ? layer_second : layer_first;
 
  /* Solve for the total volume, total volume of the layer with the first phase, 
   * total volume of the layer with the second phase, volume of first phase (within
   * first layer) and volume of second phase (within second layer).
   */ 
  double interface_volume = 0.0;
  double total_volume_layer_first = 0.0;
  double total_volume_layer_second = 0.0;
  double volume_phase_first = 0.0;
  double volume_phase_second = 0.0;
  i_phase_count = 0;
  if (partial_deriv) curr_partial = partial_deriv;
  for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
    for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {
      double *state = (double *)(model_data->grid_cell_state);
      state += PARTICLE_STATE_SIZE_ + PHASE_STATE_ID_(i_layer,i_phase);
      double volume;
      aero_phase_get_volume__m3_m3(model_data, PHASE_MODEL_DATA_ID_(i_layer,i_phase),
                                   state, &(volume), curr_partial);
      if (i_layer == layer_first) total_volume_layer_first += volume;
      if (i_phase_count == aero_phase_idx_first && 
          PHASE_MODEL_DATA_ID_(i_layer, i_phase) == 
          phase_model_data_id_first) volume_phase_first = volume;
      if (i_layer == layer_second) total_volume_layer_second += volume;
      if (i_phase_count == aero_phase_idx_second && 
          PHASE_MODEL_DATA_ID_(i_layer, i_phase) == 
          phase_model_data_id_second) volume_phase_second = volume;
      if (i_layer <= layer_interface) interface_volume += volume;
      if (partial_deriv) curr_partial += PHASE_NUM_JAC_ELEM_(i_layer,i_phase);
      ++i_phase_count;
    }
  }
 
  /* Calculate the fractional volume of first and second phase in their 
  * assocaited layers. Calculate the radius and surface area of the interface
  * between the first and second layer.
  */ 
  double f_first = volume_phase_first / total_volume_layer_first;
  double f_second = volume_phase_second / total_volume_layer_second;
  radius = pow(((interface_volume) * 3.0 / 4.0 / M_PI), 1.0 / 3.0);
  *surface_area = f_first * f_second * 4 * M_PI * pow(radius, 2.0);
 
 
  // Calculate the partial derivatives for each layer/phase combination. 
  if (!partial_deriv) return;
  i_phase_count = 0;
  for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
    for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {
      double *state = (double *)(model_data->grid_cell_state);
      state += PARTICLE_STATE_SIZE_ + PHASE_STATE_ID_(i_layer,i_phase);
      double volume_phase;
      aero_phase_get_volume__m3_m3(model_data, PHASE_MODEL_DATA_ID_(i_layer,i_phase),
                                       state, &(volume_phase), NULL);
      for (int i_spec = 0; i_spec < PHASE_NUM_JAC_ELEM_(i_layer,i_phase); ++i_spec) {
        // layer = layer_first, phase = aero_phase_idx_first 
        if (i_layer == layer_first && i_phase_count == aero_phase_idx_first) {
          *partial_deriv =
              (((total_volume_layer_first - volume_phase_first) * 
              pow(total_volume_layer_first, -2.0) * f_second * (*surface_area)) +
              2.0 * f_first * f_second * pow(radius, -1.0))  * (*partial_deriv);
          ++partial_deriv;
        }
        // layer = layer_first, phase != aero_phase_idx_first
        else if (i_layer == layer_first && i_phase_count != aero_phase_idx_first) {
          *partial_deriv =
              (((-1 * volume_phase) * pow(total_volume_layer_first, -2.0) * 
              f_second * (*surface_area)) + 2.0 * f_first * f_second * 
              pow(radius, -1.0))  * (*partial_deriv);
          ++partial_deriv;
        }
        // layer = layer_second, phase = aero_phase_idx_second
        else if (i_layer == layer_second && i_phase_count == aero_phase_idx_second) {
          *partial_deriv =
              (((total_volume_layer_second - volume_phase_second) *
              pow(total_volume_layer_second, -2.0) * f_first * (*surface_area)) +
              2.0 * f_first * f_second * pow(radius, -1.0))  * (*partial_deriv);
          ++partial_deriv;
        }
        // layer = layer_second, phase != aero_phase_idx_second
        else if (i_layer == layer_second && i_phase_count != aero_phase_idx_second) {
          *partial_deriv =
              (((-1 * volume_phase) * pow(total_volume_layer_second, -2.0) *
              f_first * (*surface_area)) + 2.0 * f_first * f_second *
              pow(radius, -1.0))  * (*partial_deriv);
          ++partial_deriv;
        }
        else if (i_layer < layer_first) {
          *partial_deriv = 2.0 * f_first * f_second * pow(radius, -1.0) * (*partial_deriv);
          ++partial_deriv;
        }
        // Set partial_derivative = 0 for all other layers. 
        else if (i_layer > layer_second) {
          *(partial_deriv++) = ZERO;
        }
        else {
            printf("\n\nERROR No conditions met for surface area partial derivative.\n\n");
            exit(1);
        }
      }
    ++i_phase_count;
    }
  }
  return;
}
 
/** \brief Get the thickness of a particle layer (m)
 *
 * \param model_data Pointer to the model data, including the state array
 * \param aero_phase_idx Index of the aerosol phase within the representation
 * \param layer_thickness Effective layer thickness (m)
 * \param partial_deriv \f$\frac{\partial r_{eff}}{\partial y}\f$ where \f$y\f$
 *                      are species on the state array
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_get_layer_thickness__m(
    ModelData *model_data, int aero_phase_idx, double *layer_thickness,
    double *partial_deriv, int *aero_rep_int_data, double *aero_rep_float_data,
    double *aero_rep_env_data) {
 
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  int jac_size = PARTICLE_STATE_SIZE_;
  double radius_inner, radius_outer;
  int i_part = aero_phase_idx / TOTAL_NUM_PHASES_;
  int aero_phase_idx_temp = aero_phase_idx;
  aero_phase_idx_temp -= i_part * TOTAL_NUM_PHASES_;
  
  // Temporary Jacobians
  double *jac_inner = NULL;
  double *jac_outer = NULL;
 
  if (partial_deriv) {
      jac_inner = (double *)calloc(jac_size, sizeof(double));
      jac_outer = (double *)calloc(jac_size, sizeof(double));
  }
 
  int i_layer_inner = -1;
  int i_layer_outer = -1;
  int i_phase_inner = -1;
  int i_phase_outer = -1;
  for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
   if (LAYER_PHASE_START_(i_layer) <= aero_phase_idx_temp &&
      aero_phase_idx_temp <= LAYER_PHASE_END_(i_layer)) {
      i_layer_outer = i_layer;
      if (i_layer - 1 >= 0 ) {
        i_layer_inner = i_layer - 1;
      } else if (i_layer - 1 < 0 ) {
        i_layer_inner = i_layer;
      }
    }
  }
  int offset = aero_phase_idx_temp - (i_part * LAYER_PHASE_START_(i_layer_outer));
  int aero_phase_idx_inner = -1;
  if (i_layer_inner == i_layer_outer) {
    aero_phase_idx_inner = aero_phase_idx;
  } else {
    aero_phase_idx_inner = aero_phase_idx - (offset+1);
  }
 
  aero_rep_single_particle_get_effective_layer_radius__m(
      model_data, 
      aero_phase_idx,      
      &radius_outer,
      jac_outer,
      int_data, 
      float_data, 
      aero_rep_env_data);
 
  aero_rep_single_particle_get_effective_layer_radius__m(
      model_data,
      aero_phase_idx_inner,
      &radius_inner,
      jac_inner,
      int_data,
      float_data,
      aero_rep_env_data);
 
  if (i_layer_inner == i_layer_outer) {
    *layer_thickness = radius_inner;
  } else {
    *layer_thickness = radius_outer - radius_inner;
  }
 
  if (partial_deriv) {
      for (int i = 0; i < jac_size; ++i) {
          partial_deriv[i] = jac_outer[i] - jac_inner[i];
      }
  }
 
  free(jac_inner);
  free(jac_outer);
  return;
}
 
/** \brief Get the particle number concentration \f$n\f$
 * (\f$\mbox{\si{\#\per\cubic\metre}}\f$)
 *
 * This single particle number concentration is set by the aerosol model prior
 * to solving the chemistry. Thus, all \f$\frac{\partial n}{\partial y}\f$ are
 * zero. Also, there is only one set of particles in the single particle
 * representation, so the phase index is not used.
 *
 * \param model_data Pointer to the model data, including the state array
 * \param aero_phase_idx Index of the aerosol phase within the representation
 *                       (not used)
 * \param number_conc Particle number concentration, \f$n\f$
 *                    (\f$\mbox{\si{\#\per\cubic\metre}}\f$)
 * \param partial_deriv \f$\frac{\partial n}{\partial y}\f$ where \f$y\f$ are
 *                      the species on the state array
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_get_number_conc__n_m3(
    ModelData *model_data, int aero_phase_idx, double *number_conc,
    double *partial_deriv, int *aero_rep_int_data, double *aero_rep_float_data,
    double *aero_rep_env_data) {
 
 
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  int i_part = aero_phase_idx / TOTAL_NUM_PHASES_;
 
  *number_conc = NUMBER_CONC_(i_part);
 
  if (partial_deriv) {
    for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
      for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {
        for (int i_spec = 0; i_spec < PHASE_NUM_JAC_ELEM_(i_layer,i_phase); ++i_spec)
          *(partial_deriv++) = ZERO;
      }
    }
  }
  return;
}
 
/** \brief Get the type of aerosol concentration used.
 *
 * Single particle concentrations are per-particle.
 *
 * \param aero_phase_idx Index of the aerosol phase within the representation
 * \param aero_conc_type Pointer to int that will hold the concentration type
 *                       code (0 = per particle mass concentrations;
 *                       1 = total particle mass concentrations)
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_get_aero_conc_type(int aero_phase_idx,
                                                 int *aero_conc_type,
                                                 int *aero_rep_int_data,
                                                 double *aero_rep_float_data,
                                                 double *aero_rep_env_data) {
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
 
  *aero_conc_type = 0;
 
  return;
}
 
/** \brief Get the total mass in an aerosol phase \f$m\f$
 * (\f$\mbox{\si{\kilogram\per\cubic\metre}}\f$)
 *
 * The single particle mass is set for each new state as the sum of the masses
 * of the aerosol phases that compose the particle
 *
 * \param model_data Pointer to the model data, including the state array
 * \param aero_phase_idx Index of the aerosol phase within the representation
 * \param aero_phase_mass Total mass in the aerosol phase, \f$m\f$
 *                        (\f$\mbox{\si{\kilogram\per\cubic\metre}}\f$)
 * \param partial_deriv \f$\frac{\partial m}{\partial y}\f$ where \f$y\f$ are
 *                      the species on the state array
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_get_aero_phase_mass__kg_m3(
    ModelData *model_data, int aero_phase_idx, double *aero_phase_mass,
    double *partial_deriv, int *aero_rep_int_data, double *aero_rep_float_data,
    double *aero_rep_env_data) {
 
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  int i_part = aero_phase_idx / TOTAL_NUM_PHASES_;
  aero_phase_idx -= i_part * TOTAL_NUM_PHASES_;
 
  int i_total_phase = 0; 
  for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
    for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {  
      if ( i_total_phase == aero_phase_idx ) {
        double *state = (double *)(model_data->grid_cell_state);
        state += i_part * PARTICLE_STATE_SIZE_ + PHASE_STATE_ID_(i_layer,i_phase);
        double mw;
        aero_phase_get_mass__kg_m3(model_data, PHASE_MODEL_DATA_ID_(i_layer,i_phase),
                                   state, aero_phase_mass, &mw, partial_deriv, NULL);
        if (partial_deriv) partial_deriv += PHASE_NUM_JAC_ELEM_(i_layer,i_phase);
      } else if (partial_deriv) {
        for (int i_spec = 0; i_spec < PHASE_NUM_JAC_ELEM_(i_layer,i_phase); ++i_spec)
          *(partial_deriv++) = ZERO;
      }
      ++i_total_phase;
    }
  }
  return;
}
 
/** \brief Get the average molecular weight in an aerosol phase
 **        \f$m\f$ (\f$\mbox{\si{\kilo\gram\per\mol}}\f$)
 *
 * The single particle mass is set for each new state as the sum of the masses
 * of the aerosol phases that compose the particle
 *
 * \param model_data Pointer to the model data, including the state array
 * \param aero_phase_idx Index of the aerosol phase within the representation
 * \param aero_phase_avg_MW Average molecular weight in the aerosol phase
 *                          (\f$\mbox{\si{\kilogram\per\mole}}\f$)
 * \param partial_deriv \f$\frac{\partial m}{\partial y}\f$ where \f$y\f$ are
 *                      the species on the state array
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 */
 
void aero_rep_single_particle_get_aero_phase_avg_MW__kg_mol(
    ModelData *model_data, int aero_phase_idx, double *aero_phase_avg_MW,
    double *partial_deriv, int *aero_rep_int_data, double *aero_rep_float_data,
    double *aero_rep_env_data) {
 
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
  int i_part = aero_phase_idx / TOTAL_NUM_PHASES_;
  aero_phase_idx -= i_part * TOTAL_NUM_PHASES_;
  
  int i_total_phase = 0;
  for (int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer) {
    for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {
      if ( i_total_phase == aero_phase_idx ) {
        double *state = (double *)(model_data->grid_cell_state);
        state += i_part * PARTICLE_STATE_SIZE_ + PHASE_STATE_ID_(i_layer,i_phase);
        double mass;
        aero_phase_get_mass__kg_m3(model_data, PHASE_MODEL_DATA_ID_(i_layer,i_phase),
                                   state, &mass, aero_phase_avg_MW, NULL, partial_deriv);
        if (partial_deriv) partial_deriv += PHASE_NUM_JAC_ELEM_(i_layer,i_phase);
      } else if (partial_deriv) {
        for (int i_spec = 0; i_spec < PHASE_NUM_JAC_ELEM_(i_layer,i_phase); ++i_spec)
          *(partial_deriv++) = ZERO;
      }
      ++i_total_phase;
    }
  }
  return;
}
 
/** \brief Update aerosol representation data
 *
 * Single particle aerosol representation update data is structured as follows:
 *
 *  - \b int aero_rep_id (Id of one or more aerosol representations set by the
 *       host model using the
 *       camp_aero_rep_single_particle::aero_rep_single_particle_t::set_id
 *       function prior to initializing the solver.)
 *  - \b int update_type (Type of update to perform. Can be UPDATE_NUMBER
 *       only.)
 *  - \b double new_value (Either the new radius (m) or the new number
 *       concentration (\f$\mbox{\si{\#\per\cubic\centi\metre}}\f$).)
 *
 * \param update_data Pointer to the updated aerosol representation data
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 * \param aero_rep_env_data Pointer to the aerosol representation
 *                          environment-dependent parameters
 * \return Flag indicating whether this is the aerosol representation to update
 */
 
bool aero_rep_single_particle_update_data(void *update_data,
                                          int *aero_rep_int_data,
                                          double *aero_rep_float_data,
                                          double *aero_rep_env_data) {
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
 
  int *aero_rep_id = (int *)update_data;
  int *update_type = (int *)&(aero_rep_id[1]);
  int *particle_id = (int *)&(update_type[1]);
  double *new_value = (double *)&(update_type[2]);
 
  // Set the new radius or number concentration for matching aerosol
  // representations
  if (*aero_rep_id == AERO_REP_ID_ && AERO_REP_ID_ != 0) {
    if (*update_type == UPDATE_NUMBER) {
      NUMBER_CONC_(*particle_id) = (double)*new_value;
      return true;
    }
  }
 
  return false;
}
 
/** \brief Print the Single Particle reaction parameters
 *
 * \param aero_rep_int_data Pointer to the aerosol representation integer data
 * \param aero_rep_float_data Pointer to the aerosol representation
 *                            floating-point data
 */
 
void aero_rep_single_particle_print(int *aero_rep_int_data,
                                    double *aero_rep_float_data) {
  int *int_data = aero_rep_int_data;
  double *float_data = aero_rep_float_data;
 
  printf("\n\nSingle particle aerosol representation\n");
  printf("\nNumber of phases: %d", TOTAL_NUM_PHASES_);
  printf("\nAerosol representation id: %d", AERO_REP_ID_);
  printf("\nMax computational particles: %d", MAX_PARTICLES_);
  printf("\nParticle state size: %d", PARTICLE_STATE_SIZE_);
  for(int i_layer = 0; i_layer < NUM_LAYERS_; ++i_layer){
    printf("\nLayer: %d", i_layer);
    printf("\n  Start phase: %d End phase: %d", LAYER_PHASE_START_(i_layer), LAYER_PHASE_END_(i_layer));
    printf("\n  Number of phases: %d", NUM_PHASES_(i_layer));
    printf("\n\n   - Phases -");
    for (int i_phase = 0; i_phase < NUM_PHASES_(i_layer); ++i_phase) {
      printf("\n  state id: %d model data id: %d num Jac elements: %d",
             PHASE_STATE_ID_(i_layer,i_phase), PHASE_MODEL_DATA_ID_(i_layer,i_phase),
             PHASE_NUM_JAC_ELEM_(i_layer,i_phase));
    }
  }  
  printf("\n\nEnd single particle aerosol representation\n");
  return;
}
 
 
/** \brief Create update data for new particle number
 *
 * \return Pointer to a new number update data object
 */
void *aero_rep_single_particle_create_number_update_data() {
  int *update_data = (int *)malloc(3 * sizeof(int) + sizeof(double));
  if (update_data == NULL) {
    printf("\n\nERROR allocating space for number update data\n\n");
    exit(1);
  }
  return (void *)update_data;
}
 
/** \brief Set number update data (#/m3)
 *
 * \param update_data Pointer to an allocated number update data object
 * \param aero_rep_id Id of the aerosol representation(s) to update
 * \param particle_id Id of the computational particle
 * \param number_conc New particle number (#/m3)
 */
void aero_rep_single_particle_set_number_update_data__n_m3(void *update_data,
                                                           int aero_rep_id,
                                                           int particle_id,
                                                           double number_conc) {
  int *new_aero_rep_id = (int *)update_data;
  int *update_type = (int *)&(new_aero_rep_id[1]);
  int *new_particle_id = (int *)&(update_type[1]);
  double *new_number_conc = (double *)&(update_type[2]);
  *new_aero_rep_id = aero_rep_id;
  *update_type = UPDATE_NUMBER;
  *new_particle_id = particle_id;
  *new_number_conc = number_conc;
}