src/FDM/JSBSim/FGAtmosphere.cpp

   1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   2
   3  Module:       FGAtmosphere.cpp
   4  Author:       Jon Berndt
   5                Implementation of 1959 Standard Atmosphere added by Tony Peden
   6  Date started: 11/24/98
   7  Purpose:      Models the atmosphere
   8  Called by:    FGSimExec
   9
  10  ------------- Copyright (C) 1999  Jon S. Berndt (jsb@hal-pc.org) -------------
  11
  12  This program is free software; you can redistribute it and/or modify it under
  13  the terms of the GNU General Public License as published by the Free Software
  14  Foundation; either version 2 of the License, or (at your option) any later
  15  version.
  16
  17  This program is distributed in the hope that it will be useful, but WITHOUT
  18  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  19  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
  20  details.
  21
  22  You should have received a copy of the GNU General Public License along with
  23  this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  24  Place - Suite 330, Boston, MA  02111-1307, USA.
  25
  26  Further information about the GNU General Public License can also be found on
  27  the world wide web at http://www.gnu.org.
  28
  29 FUNCTIONAL DESCRIPTION
  30 --------------------------------------------------------------------------------
  31 Models the atmosphere. The equation used below was determined by a third order
  32 curve fit using Excel. The data is from the ICAO atmosphere model.
  33
  34 HISTORY
  35 --------------------------------------------------------------------------------
  36 11/24/98   JSB   Created
  37 07/23/99   TP    Added implementation of 1959 Standard Atmosphere
  38                  Moved calculation of Mach number to FGTranslation
  39 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  40 COMMENTS, REFERENCES,  and NOTES
  41 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  42 [1]   Anderson, John D. "Introduction to Flight, Third Edition", McGraw-Hill,
  43       1989, ISBN 0-07-001641-0
  44
  45 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  46 INCLUDES
  47 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  48
  49 #include "FGAtmosphere.h"
  50 #include "FGState.h"
  51 #include "FGFDMExec.h"
  52 #include "FGFCS.h"
  53 #include "FGAircraft.h"
  54 #include "FGTranslation.h"
  55 #include "FGRotation.h"
  56 #include "FGPosition.h"
  57 #include "FGAuxiliary.h"
  58 #include "FGOutput.h"
  59 #include "FGDefs.h"
  60 #include "FGMatrix.h"
  61
  62 static const char *IdSrc = "$Id$";
  63 static const char *IdHdr = ID_ATMOSPHERE;
  64
  65 extern short debug_lvl;
  66
  67 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  68 CLASS IMPLEMENTATION
  69 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  70
  71
  72 FGAtmosphere::FGAtmosphere(FGFDMExec* fdmex) : FGModel(fdmex),
  73                                                     vWindNED(3)
  74 {
  75   Name = "FGAtmosphere";
  76   h = 0;
  77   Calculate(h);
  78   SLtemperature = temperature;
  79   SLpressure    = pressure;
  80   SLdensity     = density;
  81   SLsoundspeed  = sqrt(SHRATIO*Reng*temperature);
  82   useExternal=false;
  83   vWindNED(1)=0;vWindNED(2)=0;vWindNED(3)=0;
  84
  85   if (debug_lvl & 2) cout << "Instantiated: " << Name << endl;
  86 }
  87
  88 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  89
  90 FGAtmosphere::~FGAtmosphere()
  91 {
  92   if (debug_lvl & 2) cout << "Destroyed:    FGAtmosphere" << endl;
  93 }
  94
  95 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  96
  97 bool FGAtmosphere::Run(void)
  98 {
  99   //cout << "In FGAtmosphere::Run(void)" << endl;
 100   if (!FGModel::Run()) {                 // if false then execute this Run()
 101     //do temp, pressure, and density first
 102     if (!useExternal) {
 103       //cout << "Atmosphere: Using internal model, altitude= ";
 104       h = Position->Geth();
 105
 106       Calculate(h);
 107     } else {
 108       density = exDensity;
 109       pressure = exPressure;
 110       temperature = exTemperature;
 111     }
 112
 113     psiw = atan2( vWindNED(2), vWindNED(1) );
 114
 115     if (psiw < 0) psiw += 2*M_PI;
 116
 117     soundspeed = sqrt(SHRATIO*Reng*temperature);
 118     //cout << "Atmosphere: soundspeed: " << soundspeed << endl;
 119     State->Seta(soundspeed);
 120
 121   } else {                               // skip Run() execution this time
 122   }
 123   return false;
 124 }
 125
 126 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 127
 128 void FGAtmosphere::Calculate(float altitude)
 129 {
 130   //see reference [1]
 131
 132   float slope,reftemp,refpress,refdens;
 133   int i=0;
 134   float htab[]={0,36089,82020,154198,173882,259183,295272,344484}; //ft.
 135   // cout << "Atmosphere:  h=" << altitude << " rho= " << density << endl;
 136   if (altitude <= htab[0]) {
 137     altitude=0;
 138   } else if (altitude >= htab[7]){
 139     i = 7;
 140     altitude = htab[7];
 141   } else {
 142     while (htab[i+1] < altitude) {
 143       i++;
 144     }
 145   }
 146
 147   switch(i) {
 148   case 0:     // sea level
 149     slope     = -0.0035662; // R/ft.
 150     reftemp   = 518.688;    // R
 151     refpress  = 2116.17;    // psf
 152     refdens   = 0.0023765;  // slugs/cubic ft.
 153     break;
 154   case 1:     // 36089 ft.
 155     slope     = 0;
 156     reftemp   = 389.988;
 157     refpress  = 474.1;
 158     refdens   = 0.0007078;
 159     break;
 160   case 2:     // 82020 ft.
 161     slope     = 0.00164594;
 162     reftemp   = 389.988;
 163     refpress  = 52.7838;
 164     refdens   = 7.8849E-5;
 165     break;
 166   case 3:     // 154198 ft.
 167     slope     = 0;
 168     reftemp   = 508.788;
 169     refpress  = 2.62274;
 170     refdens   = 3.01379E-6;
 171     break;
 172   case 4:     // 173882 ft.
 173     slope     = -0.00246891;
 174     reftemp   = 508.788;
 175     refpress  = 1.28428;
 176     refdens   = 1.47035e-06;
 177     break;
 178   case 5:     // 259183 ft.
 179     slope     = 0;
 180     reftemp   = 298.188;
 181     refpress  = 0.0222008;
 182     refdens   = 4.33396e-08;
 183     break;
 184   case 6:     // 295272 ft.
 185     slope     = 0.00219459;
 186     reftemp   = 298.188;
 187     refpress  = 0.00215742;
 188     refdens   = 4.21368e-09;
 189     break;
 190   case 7:     // 344484 ft.
 191     slope     = 0;
 192     reftemp   = 406.188;
 193     refpress  = 0.000153755;
 194     refdens   = 2.20384e-10;
 195     break;
 196   }
 197
 198   if (slope == 0) {
 199     temperature = reftemp;
 200     pressure = refpress*exp(-GRAVITY/(reftemp*Reng)*(altitude-htab[i]));
 201     density = refdens*exp(-GRAVITY/(reftemp*Reng)*(altitude-htab[i]));
 202   } else {
 203     temperature = reftemp+slope*(altitude-htab[i]);
 204     pressure = refpress*pow(temperature/reftemp,-GRAVITY/(slope*Reng));
 205     density = refdens*pow(temperature/reftemp,-(GRAVITY/(slope*Reng)+1));
 206   }
 207
 208   //cout << "Atmosphere:  h=" << altitude << " rho= " << density << endl;
 209
 210 }
 211
 212 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 213
 214 void FGAtmosphere::Debug(void)
 215 {
 216     //TODO: Add your source code here
 217 }
 218