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 "FGMatrix33.h"
  60 #include "FGColumnVector3.h"
  61 #include "FGColumnVector4.h"
  62
  63 static const char *IdSrc = "$Id$";
  64 static const char *IdHdr = ID_ATMOSPHERE;
  65
  66 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  67 CLASS IMPLEMENTATION
  68 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  69
  70
  71 FGAtmosphere::FGAtmosphere(FGFDMExec* fdmex) : FGModel(fdmex),
  72                                                vWindNED(3)
  73 {
  74   Name = "FGAtmosphere";
  75   lastIndex=0;
  76   h = 0;
  77   htab[0]=0;
  78   htab[1]=36089.239;
  79   htab[2]=65616.798;
  80   htab[3]=104986.878;
  81   htab[4]=154199.475;
  82   htab[5]=170603.675;
  83   htab[6]=200131.234;
  84   htab[7]=259186.352; //ft.
  85
  86   if (debug_lvl & 2) cout << "Instantiated: " << Name << endl;
  87 }
  88
  89 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  90
  91 FGAtmosphere::~FGAtmosphere()
  92 {
  93   if (debug_lvl & 2) cout << "Destroyed:    FGAtmosphere" << endl;
  94 }
  95
  96 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  97
  98 bool FGAtmosphere::InitModel(void)
  99 {
 100   FGModel::InitModel();
 101
 102   Calculate(h);
 103   SLtemperature = temperature;
 104   SLpressure    = pressure;
 105   SLdensity     = density;
 106   SLsoundspeed  = sqrt(SHRatio*Reng*temperature);
 107   rSLtemperature = 1.0/temperature;
 108   rSLpressure    = 1.0/pressure;
 109   rSLdensity     = 1.0/density;
 110   rSLsoundspeed  = 1.0/SLsoundspeed;
 111   useExternal=false;
 112
 113   return true;
 114 }
 115
 116 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 117
 118 bool FGAtmosphere::Run(void)
 119 {
 120   if (!FGModel::Run()) {                 // if false then execute this Run()
 121     //do temp, pressure, and density first
 122     if (!useExternal) {
 123       h = Position->Geth();
 124       Calculate(h);
 125     } else {
 126       density = exDensity;
 127       pressure = exPressure;
 128       temperature = exTemperature;
 129     }
 130
 131     if (vWindNED(1) != 0.0) psiw = atan2( vWindNED(2), vWindNED(1) );
 132
 133     if (psiw < 0) psiw += 2*M_PI;
 134
 135     soundspeed = sqrt(SHRatio*Reng*temperature);
 136
 137     State->Seta(soundspeed);
 138   } else {                               // skip Run() execution this time
 139   }
 140
 141   return false;
 142 }
 143
 144 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 145
 146 void FGAtmosphere::Calculate(double altitude)
 147 {
 148   //see reference [1]
 149
 150   double slope,reftemp,refpress;
 151   int i=0; bool lookup = false;
 152   // cout << "Atmosphere:  h=" << altitude << " rho= " << density << endl;
 153   i=lastIndex;
 154   if(altitude < htab[lastIndex]) {
 155     if (altitude <= 0) {
 156       i=0; altitude=0;
 157     } else {
 158        i=lastIndex-1;
 159        while (htab[i] > altitude) { i--; }
 160     }
 161   } else if (altitude > htab[lastIndex+1]){
 162     if (altitude >= htab[7]){
 163       i = 7; altitude = htab[7];
 164     } else {
 165       i=lastIndex+1;
 166       while(htab[i+1] < altitude) { i++; }
 167     }
 168   }
 169
 170   switch(i) {
 171   case 0:     // sea level
 172     slope     = -0.00356616; // R/ft.
 173     reftemp   = 518.67;    // R
 174     refpress  = 2116.22;    // psf
 175     //refdens   = 0.00237767;  // slugs/cubic ft.
 176     break;
 177   case 1:     // 36089 ft.
 178     slope     = 0;
 179     reftemp   = 389.97;
 180     refpress  = 472.452;
 181     //refdens   = 0.000706032;
 182     break;
 183   case 2:     // 65616 ft.
 184     slope     = 0.00054864;
 185     reftemp   = 389.97;
 186     refpress  = 114.636;
 187     //refdens   = 0.000171306;
 188     break;
 189   case 3:     // 104986 ft.
 190     slope     = 0.00153619;
 191     reftemp   = 411.57;
 192     refpress  = 8.36364;
 193     //refdens   = 1.18422e-05;
 194     break;
 195   case 4:     // 154199 ft.
 196     slope     = 0;
 197     reftemp   = 487.17;
 198     refpress  = 0.334882;
 199     //refdens   = 4.00585e-7;
 200     break;
 201   case 5:     // 170603 ft.
 202     slope     = -0.00109728;
 203     reftemp   = 487.17;
 204     refpress  = 0.683084;
 205     //refdens   = 8.17102e-7;
 206     break;
 207   case 6:     // 200131 ft.
 208     slope     = -0.00219456;
 209     reftemp   = 454.17;
 210     refpress  = 0.00684986;
 211     //refdens   = 8.77702e-9;
 212     break;
 213   case 7:     // 259186 ft.
 214     slope     = 0;
 215     reftemp   = 325.17;
 216     refpress  = 0.000122276;
 217     //refdens   = 2.19541e-10;
 218     break;
 219   }
 220
 221   if (slope == 0) {
 222     temperature = reftemp;
 223     pressure = refpress*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 224     //density = refdens*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 225     density = pressure/(Reng*temperature);
 226   } else {
 227     temperature = reftemp+slope*(altitude-htab[i]);
 228     pressure = refpress*pow(temperature/reftemp,-Inertial->SLgravity()/(slope*Reng));
 229     //density = refdens*pow(temperature/reftemp,-(Inertial->SLgravity()/(slope*Reng)+1));
 230     density = pressure/(Reng*temperature);
 231   }
 232   lastIndex=i;
 233   //cout << "Atmosphere:  h=" << altitude << " rho= " << density << endl;
 234 }
 235
 236 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 237
 238 void FGAtmosphere::Debug(void)
 239 {
 240     //TODO: Add your source code here
 241 }
 242