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 "FGMatrix33.h"
  61 #include "FGColumnVector3.h"
  62 #include "FGColumnVector4.h"
  63
  64 static const char *IdSrc = "$Id$";
  65 static const char *IdHdr = ID_ATMOSPHERE;
  66
  67 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  68 CLASS IMPLEMENTATION
  69 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  70
  71
  72 FGAtmosphere::FGAtmosphere(FGFDMExec* fdmex) : FGModel(fdmex),
  73                                                vWindNED(3)
  74 {
  75   Name = "FGAtmosphere";
  76   lastIndex=0;
  77   h = 0;
  78   htab[0]=0;
  79   htab[1]=36089.239;
  80   htab[2]=65616.798;
  81   htab[3]=104986.878;
  82   htab[4]=154199.475;
  83   htab[5]=170603.675;
  84   htab[6]=200131.234;
  85   htab[7]=259186.352; //ft.
  86
  87   Calculate(h);
  88   SLtemperature = temperature;
  89   SLpressure    = pressure;
  90   SLdensity     = density;
  91   SLsoundspeed  = sqrt(SHRATIO*Reng*temperature);
  92   rSLtemperature = 1.0/temperature;
  93   rSLpressure    = 1.0/pressure;
  94   rSLdensity     = 1.0/density;
  95   rSLsoundspeed  = 1.0/SLsoundspeed;
  96   useExternal=false;
  97
  98   if (debug_lvl & 2) cout << "Instantiated: " << Name << endl;
  99 }
 100
 101 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 102
 103 FGAtmosphere::~FGAtmosphere()
 104 {
 105   if (debug_lvl & 2) cout << "Destroyed:    FGAtmosphere" << endl;
 106 }
 107
 108 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 109
 110 bool FGAtmosphere::Run(void)
 111 {
 112   if (!FGModel::Run()) {                 // if false then execute this Run()
 113     //do temp, pressure, and density first
 114     if (!useExternal) {
 115       h = Position->Geth();
 116       Calculate(h);
 117     } else {
 118       density = exDensity;
 119       pressure = exPressure;
 120       temperature = exTemperature;
 121     }
 122
 123     if (vWindNED(1) != 0.0) psiw = atan2( vWindNED(2), vWindNED(1) );
 124
 125     if (psiw < 0) psiw += 2*M_PI;
 126
 127     soundspeed = sqrt(SHRATIO*Reng*temperature);
 128
 129     State->Seta(soundspeed);
 130
 131   } else {                               // skip Run() execution this time
 132   }
 133   return false;
 134 }
 135
 136 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 137
 138 void FGAtmosphere::Calculate(float altitude)
 139 {
 140   //see reference [1]
 141
 142   float slope,reftemp,refpress;
 143   int i=0; bool lookup = false;
 144   // cout << "Atmosphere:  h=" << altitude << " rho= " << density << endl;
 145   i=lastIndex;
 146   if(altitude < htab[lastIndex]) {
 147     if (altitude <= 0) {
 148       i=0; altitude=0;
 149     } else {
 150        i=lastIndex-1;
 151        while (htab[i] > altitude) { i--; }
 152     }
 153   } else if (altitude > htab[lastIndex+1]){
 154     if (altitude >= htab[7]){
 155       i = 7; altitude = htab[7];
 156     } else {
 157       i=lastIndex+1;
 158       while(htab[i+1] < altitude) { i++; }
 159     }
 160   }
 161
 162   switch(i) {
 163   case 0:     // sea level
 164     slope     = -0.00356616; // R/ft.
 165     reftemp   = 518.67;    // R
 166     refpress  = 2116.22;    // psf
 167     //refdens   = 0.00237767;  // slugs/cubic ft.
 168     break;
 169   case 1:     // 36089 ft.
 170     slope     = 0;
 171     reftemp   = 389.97;
 172     refpress  = 472.452;
 173     //refdens   = 0.000706032;
 174     break;
 175   case 2:     // 65616 ft.
 176     slope     = 0.00054864;
 177     reftemp   = 389.97;
 178     refpress  = 114.636;
 179     //refdens   = 0.000171306;
 180     break;
 181   case 3:     // 104986 ft.
 182     slope     = 0.00153619;
 183     reftemp   = 411.57;
 184     refpress  = 8.36364;
 185     //refdens   = 1.18422e-05;
 186     break;
 187   case 4:     // 154199 ft.
 188     slope     = 0;
 189     reftemp   = 487.17;
 190     refpress  = 0.334882;
 191     //refdens   = 4.00585e-7;
 192     break;
 193   case 5:     // 170603 ft.
 194     slope     = -0.00109728;
 195     reftemp   = 487.17;
 196     refpress  = 0.683084;
 197     //refdens   = 8.17102e-7;
 198     break;
 199   case 6:     // 200131 ft.
 200     slope     = -0.00219456;
 201     reftemp   = 454.17;
 202     refpress  = 0.00684986;
 203     //refdens   = 8.77702e-9;
 204     break;
 205   case 7:     // 259186 ft.
 206     slope     = 0;
 207     reftemp   = 325.17;
 208     refpress  = 0.000122276;
 209     //refdens   = 2.19541e-10;
 210     break;
 211   }
 212
 213   if (slope == 0) {
 214     temperature = reftemp;
 215     pressure = refpress*exp(-GRAVITY/(reftemp*Reng)*(altitude-htab[i]));
 216     //density = refdens*exp(-GRAVITY/(reftemp*Reng)*(altitude-htab[i]));
 217     density = pressure/(Reng*temperature);
 218   } else {
 219     temperature = reftemp+slope*(altitude-htab[i]);
 220     pressure = refpress*pow(temperature/reftemp,-GRAVITY/(slope*Reng));
 221     //density = refdens*pow(temperature/reftemp,-(GRAVITY/(slope*Reng)+1));
 222     density = pressure/(Reng*temperature);
 223   }
 224   lastIndex=i;
 225   //cout << "Atmosphere:  h=" << altitude << " rho= " << density << endl;
 226 }
 227
 228 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 229
 230 void FGAtmosphere::Debug(void)
 231 {
 232     //TODO: Add your source code here
 233 }
 234