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                                                vDirectiondAccelDt(3),
  74                                                vDirectionAccel(3),
  75                                                vDirection(3),
  76                                                vTurbulence(3),
  77                                                vTurbulenceGrad(3),
  78                                                vBodyTurbGrad(3),
  79                                                vTurbPQR(3)
  80 {
  81   Name = "FGAtmosphere";
  82   lastIndex=0;
  83   h = 0;
  84   htab[0]=0;
  85   htab[1]=36089.239;
  86   htab[2]=65616.798;
  87   htab[3]=104986.878;
  88   htab[4]=154199.475;
  89   htab[5]=170603.675;
  90   htab[6]=200131.234;
  91   htab[7]=259186.352; //ft.
  92
  93   MagnitudedAccelDt = MagnitudeAccel = Magnitude = 0.0;
  94   turbType = ttNone;
  95 //  turbType = ttBerndt; // temporarily disable turbulence until fully tested
  96   TurbGain = 100.0;
  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::InitModel(void)
 111 {
 112   FGModel::InitModel();
 113
 114   Calculate(h);
 115   SLtemperature = temperature;
 116   SLpressure    = pressure;
 117   SLdensity     = density;
 118   SLsoundspeed  = sqrt(SHRatio*Reng*temperature);
 119   rSLtemperature = 1.0/temperature;
 120   rSLpressure    = 1.0/pressure;
 121   rSLdensity     = 1.0/density;
 122   rSLsoundspeed  = 1.0/SLsoundspeed;
 123   useExternal=false;
 124
 125   return true;
 126 }
 127
 128 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 129
 130 bool FGAtmosphere::Run(void)
 131 {
 132   if (!FGModel::Run()) {                 // if false then execute this Run()
 133     //do temp, pressure, and density first
 134     if (!useExternal) {
 135       h = Position->Geth();
 136       Calculate(h);
 137     } else {
 138       density = exDensity;
 139       pressure = exPressure;
 140       temperature = exTemperature;
 141     }
 142
 143     if (turbType != ttNone) {
 144       Turbulence();
 145       vWindNED += vTurbulence;
 146     }
 147
 148     if (vWindNED(1) != 0.0) psiw = atan2( vWindNED(2), vWindNED(1) );
 149
 150     if (psiw < 0) psiw += 2*M_PI;
 151
 152     soundspeed = sqrt(SHRatio*Reng*temperature);
 153
 154     State->Seta(soundspeed);
 155
 156     if (debug_lvl > 1) Debug();
 157
 158   } else {                               // skip Run() execution this time
 159   }
 160
 161   return false;
 162 }
 163
 164 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 165 //
 166 // See reference 1
 167
 168 void FGAtmosphere::Calculate(double altitude)
 169 {
 170   double slope, reftemp, refpress;
 171   int i = 0;
 172   bool lookup = false;
 173
 174   i = lastIndex;
 175   if (altitude < htab[lastIndex]) {
 176     if (altitude <= 0) {
 177       i = 0;
 178       altitude=0;
 179     } else {
 180        i = lastIndex-1;
 181        while (htab[i] > altitude) i--;
 182     }
 183   } else if (altitude > htab[lastIndex+1]){
 184     if (altitude >= htab[7]){
 185       i = 7;
 186       altitude = htab[7];
 187     } else {
 188       i = lastIndex+1;
 189       while(htab[i+1] < altitude) i++;
 190     }
 191   }
 192
 193   switch(i) {
 194   case 0:     // sea level
 195     slope     = -0.00356616; // R/ft.
 196     reftemp   = 518.67;    // R
 197     refpress  = 2116.22;    // psf
 198     //refdens   = 0.00237767;  // slugs/cubic ft.
 199     break;
 200   case 1:     // 36089 ft.
 201     slope     = 0;
 202     reftemp   = 389.97;
 203     refpress  = 472.452;
 204     //refdens   = 0.000706032;
 205     break;
 206   case 2:     // 65616 ft.
 207     slope     = 0.00054864;
 208     reftemp   = 389.97;
 209     refpress  = 114.636;
 210     //refdens   = 0.000171306;
 211     break;
 212   case 3:     // 104986 ft.
 213     slope     = 0.00153619;
 214     reftemp   = 411.57;
 215     refpress  = 8.36364;
 216     //refdens   = 1.18422e-05;
 217     break;
 218   case 4:     // 154199 ft.
 219     slope     = 0;
 220     reftemp   = 487.17;
 221     refpress  = 0.334882;
 222     //refdens   = 4.00585e-7;
 223     break;
 224   case 5:     // 170603 ft.
 225     slope     = -0.00109728;
 226     reftemp   = 487.17;
 227     refpress  = 0.683084;
 228     //refdens   = 8.17102e-7;
 229     break;
 230   case 6:     // 200131 ft.
 231     slope     = -0.00219456;
 232     reftemp   = 454.17;
 233     refpress  = 0.00684986;
 234     //refdens   = 8.77702e-9;
 235     break;
 236   case 7:     // 259186 ft.
 237     slope     = 0;
 238     reftemp   = 325.17;
 239     refpress  = 0.000122276;
 240     //refdens   = 2.19541e-10;
 241     break;
 242   }
 243
 244   if (slope == 0) {
 245     temperature = reftemp;
 246     pressure = refpress*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 247     //density = refdens*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 248     density = pressure/(Reng*temperature);
 249   } else {
 250     temperature = reftemp+slope*(altitude-htab[i]);
 251     pressure = refpress*pow(temperature/reftemp,-Inertial->SLgravity()/(slope*Reng));
 252     //density = refdens*pow(temperature/reftemp,-(Inertial->SLgravity()/(slope*Reng)+1));
 253     density = pressure/(Reng*temperature);
 254   }
 255   lastIndex=i;
 256   //cout << "Atmosphere:  h=" << altitude << " rho= " << density << endl;
 257 }
 258
 259 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 260
 261 void FGAtmosphere::Turbulence(void)
 262 {
 263   switch (turbType) {
 264   case ttBerndt:
 265     vDirectiondAccelDt(eX) = 1 - 2.0*(((double)(rand()))/RAND_MAX);
 266     vDirectiondAccelDt(eY) = 1 - 2.0*(((double)(rand()))/RAND_MAX);
 267     vDirectiondAccelDt(eZ) = 1 - 2.0*(((double)(rand()))/RAND_MAX);
 268
 269     MagnitudedAccelDt = 1 - 2.0*(((double)(rand()))/RAND_MAX);
 270     MagnitudeAccel    += MagnitudedAccelDt*rate*State->Getdt();
 271     Magnitude         += MagnitudeAccel*rate*State->Getdt();
 272
 273     vDirectiondAccelDt.Normalize();
 274     vDirectionAccel += vDirectiondAccelDt*rate*State->Getdt();
 275     vDirectionAccel.Normalize();
 276     vDirection      += vDirectionAccel*rate*State->Getdt();
 277     vDirection.Normalize();
 278
 279     vTurbulence = TurbGain*Magnitude * vDirection;
 280     vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
 281
 282     vBodyTurbGrad = State->GetTl2b()*vTurbulenceGrad;
 283     vTurbPQR(eP) = vBodyTurbGrad(eY)/Aircraft->GetWingSpan();
 284     if (Aircraft->GetHTailArm() != 0.0)
 285       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/Aircraft->GetHTailArm();
 286     else
 287       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/10.0;
 288
 289     if (Aircraft->GetVTailArm())
 290       vTurbPQR(eR) = vBodyTurbGrad(eX)/Aircraft->GetVTailArm();
 291     else
 292       vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
 293
 294     break;
 295   default:
 296     break;
 297   }
 298 }
 299
 300 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 301
 302 void FGAtmosphere::Debug(void)
 303 {
 304   if (frame == 0) {
 305     cout << "vTurbulence(X), vTurbulence(Y), vTurbulence(Z), "
 306          << "vTurbulenceGrad(X), vTurbulenceGrad(Y), vTurbulenceGrad(Z), "
 307          << "vDirection(X), vDirection(Y), vDirection(Z), "
 308          << "Magnitude, "
 309          << "vTurbPQR(P), vTurbPQR(Q), vTurbPQR(R), " << endl;
 310   } else {
 311     cout << vTurbulence << ", " << vTurbulenceGrad << ", " << vDirection << ", " << Magnitude << ", " << vTurbPQR << endl;
 312   }
 313 }
 314