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
  84   if (debug_lvl & 2) cout << "Instantiated: " << Name << endl;
  85 }
  86
  87 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  88
  89 FGAtmosphere::~FGAtmosphere()
  90 {
  91   if (debug_lvl & 2) cout << "Destroyed:    FGAtmosphere" << endl;
  92 }
  93
  94 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  95
  96 bool FGAtmosphere::Run(void)
  97 {
  98   //cout << "In FGAtmosphere::Run(void)" << endl;
  99   if (!FGModel::Run()) {                 // if false then execute this Run()
 100     //do temp, pressure, and density first
 101     if (!useExternal) {
 102       //cout << "Atmosphere: Using internal model, altitude= ";
 103       h = Position->Geth();
 104
 105       Calculate(h);
 106     } else {
 107       density = exDensity;
 108       pressure = exPressure;
 109       temperature = exTemperature;
 110     }
 111
 112     if (vWindNED(1) != 0.0) psiw = atan2( vWindNED(2), vWindNED(1) );
 113
 114     if (psiw < 0) psiw += 2*M_PI;
 115
 116     soundspeed = sqrt(SHRATIO*Reng*temperature);
 117     //cout << "Atmosphere: soundspeed: " << soundspeed << endl;
 118     State->Seta(soundspeed);
 119
 120   } else {                               // skip Run() execution this time
 121   }
 122   return false;
 123 }
 124
 125 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 126
 127 void FGAtmosphere::Calculate(float altitude)
 128 {
 129   //see reference [1]
 130
 131   float slope,reftemp,refpress,refdens;
 132   int i=0;
 133   float htab[]={0,36089,82020,154198,173882,259183,295272,344484}; //ft.
 134   // cout << "Atmosphere:  h=" << altitude << " rho= " << density << endl;
 135   if (altitude <= htab[0]) {
 136     altitude=0;
 137   } else if (altitude >= htab[7]){
 138     i = 7;
 139     altitude = htab[7];
 140   } else {
 141     while (htab[i+1] < altitude) {
 142       i++;
 143     }
 144   }
 145
 146   switch(i) {
 147   case 0:     // sea level
 148     slope     = -0.0035662; // R/ft.
 149     reftemp   = 518.688;    // R
 150     refpress  = 2116.17;    // psf
 151     refdens   = 0.0023765;  // slugs/cubic ft.
 152     break;
 153   case 1:     // 36089 ft.
 154     slope     = 0;
 155     reftemp   = 389.988;
 156     refpress  = 474.1;
 157     refdens   = 0.0007078;
 158     break;
 159   case 2:     // 82020 ft.
 160     slope     = 0.00164594;
 161     reftemp   = 389.988;
 162     refpress  = 52.7838;
 163     refdens   = 7.8849E-5;
 164     break;
 165   case 3:     // 154198 ft.
 166     slope     = 0;
 167     reftemp   = 508.788;
 168     refpress  = 2.62274;
 169     refdens   = 3.01379E-6;
 170     break;
 171   case 4:     // 173882 ft.
 172     slope     = -0.00246891;
 173     reftemp   = 508.788;
 174     refpress  = 1.28428;
 175     refdens   = 1.47035e-06;
 176     break;
 177   case 5:     // 259183 ft.
 178     slope     = 0;
 179     reftemp   = 298.188;
 180     refpress  = 0.0222008;
 181     refdens   = 4.33396e-08;
 182     break;
 183   case 6:     // 295272 ft.
 184     slope     = 0.00219459;
 185     reftemp   = 298.188;
 186     refpress  = 0.00215742;
 187     refdens   = 4.21368e-09;
 188     break;
 189   case 7:     // 344484 ft.
 190     slope     = 0;
 191     reftemp   = 406.188;
 192     refpress  = 0.000153755;
 193     refdens   = 2.20384e-10;
 194     break;
 195   }
 196
 197   if (slope == 0) {
 198     temperature = reftemp;
 199     pressure = refpress*exp(-GRAVITY/(reftemp*Reng)*(altitude-htab[i]));
 200     density = refdens*exp(-GRAVITY/(reftemp*Reng)*(altitude-htab[i]));
 201   } else {
 202     temperature = reftemp+slope*(altitude-htab[i]);
 203     pressure = refpress*pow(temperature/reftemp,-GRAVITY/(slope*Reng));
 204     density = refdens*pow(temperature/reftemp,-(GRAVITY/(slope*Reng)+1));
 205   }
 206
 207   //cout << "Atmosphere:  h=" << altitude << " rho= " << density << endl;
 208
 209 }
 210
 211 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 212
 213 void FGAtmosphere::Debug(void)
 214 {
 215     //TODO: Add your source code here
 216 }
 217