.. _program_listing_file_src_modules_fetchr.cpp:

Program Listing for File fetchr.cpp
===================================

|exhale_lsh| :ref:`Return to documentation for file <file_src_modules_fetchr.cpp>` (``src/modules/fetchr.cpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   //
   // Canadian Hydrological Model - The Canadian Hydrological Model (CHM) is a novel
   // modular unstructured mesh based approach for hydrological modelling
   // Copyright (C) 2018 Christopher Marsh
   //
   // This file is part of Canadian Hydrological Model.
   //
   // Canadian Hydrological Model is free software: you can redistribute it and/or
   // modify
   // it under the terms of the GNU General Public License as published by
   // the Free Software Foundation, either version 3 of the License, or
   // (at your option) any later version.
   //
   // Canadian Hydrological Model is distributed in the hope that it will be useful,
   // but WITHOUT ANY WARRANTY; without even the implied warranty of
   // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   // GNU General Public License for more details.
   //
   // You should have received a copy of the GNU General Public License
   // along with Canadian Hydrological Model.  If not, see
   // <http://www.gnu.org/licenses/>.
   //
   
   
   #include "fetchr.hpp"
   REGISTER_MODULE_CPP(fetchr);
   
   fetchr::fetchr(config_file cfg)
           : module_base("fetchr", parallel::data, cfg)
   {
       depends("vw_dir");
   
       provides("fetch");
   
       //number of steps along the search vector to check for a higher point
       steps = cfg.get("steps",10);
       //max distance to search
       max_distance = cfg.get("max_distance",1000.0);
   
       //size of the step to take
       size_of_step = max_distance / steps;
   
       I = cfg.get("I",0.06);
   
       incl_veg = cfg.get("incl_veg",true);
   
       h_IBL = 5;
   
   }
   
   fetchr::~fetchr()
   {
   
   
   }
   
   void fetchr::run(mesh_elem& face)
   {
   
   
       (*face)["fetch"_s]= max_distance;
   
       //direction it is from, need upwind fetch
       double wind_dir = (*face)["vw_dir"_s] ;
   
       //if we are using vegetation and the current face is covered in veg, set the fetch to 0
       if(incl_veg && face->has_vegetation())
       {
   
           double me_Z_CanTop = face->veg_attribute("CanopyHeight");
           if(me_Z_CanTop > 1) // 1m might be too high?
           {
               (*face)["fetch"_s]= 0;
               return;
           }
   
       }
   
       // search along wind_dir azimuth in j step increments
       for (int j = 1; j <= steps; ++j)
       {
           double distance = j * size_of_step;
   
           auto f = face->find_closest_face(wind_dir, distance);
   
           double Z_CanTop = 0;
           if (incl_veg && f->has_vegetation())
           {
   
               Z_CanTop = f->veg_attribute("CanopyHeight");
           }
   
           //include canopy height if available
           double Z_test =  f->center().z()+Z_CanTop;
   
           //equation 1, pg 771, Lapen and Martz 1993
           double Z_core = face->center().z() + distance*I;
   
           double z0_1 = std::max(0.12*Z_CanTop,0.001);
           double z0_2 = 0.001;
           double n=1.0/0.8;
           double h = 5; //IBL height, m
   
           //Kaimal, J., Finnigan, J., 1994. Atmospheric Boundary Layer Flows: Their structure and measurement. Oxford University Press, Toronto.
           //eq 4.2,4.3
           double x_sss  = pow(((33.33333333*h-25.*z0_2)/(log(z0_1/z0_2)*z0_2)),n)*z0_2;
   
           //reset the fetch if there is elevation, but also if we run into vegetation and haven't restablished the IBL (assumed @ 5m)
           if(Z_test >= Z_core ||
                   (incl_veg && distance < x_sss) )
           {
               (*face)["fetch"_s]= distance;
               break;
           }
       }
   
   
   
   
   }