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                  Later updated to '76 model
  40 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  41 COMMENTS, REFERENCES,  and NOTES
  42 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  43 [1]   Anderson, John D. "Introduction to Flight, Third Edition", McGraw-Hill,
  44       1989, ISBN 0-07-001641-0
  45
  46 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  47 INCLUDES
  48 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  49
  50 #include "FGAtmosphere.h"
  51 #include "FGState.h"
  52 #include "FGFDMExec.h"
  53 #include "FGFCS.h"
  54 #include "FGAircraft.h"
  55 #include "FGTranslation.h"
  56 #include "FGRotation.h"
  57 #include "FGPosition.h"
  58 #include "FGAuxiliary.h"
  59 #include "FGOutput.h"
  60 #include "FGMatrix33.h"
  61 #include "FGColumnVector3.h"
  62 #include "FGColumnVector4.h"
  63 #include "FGPropertyManager.h"
  64
  65 namespace JSBSim {
  66
  67 static const char *IdSrc = "$Id$";
  68 static const char *IdHdr = ID_ATMOSPHERE;
  69
  70 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  71 CLASS IMPLEMENTATION
  72 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  73
  74
  75 FGAtmosphere::FGAtmosphere(FGFDMExec* fdmex) : FGModel(fdmex)
  76 {
  77   Name = "FGAtmosphere";
  78   lastIndex = 0;
  79   h = 0.0;
  80   psiw = 0.0;
  81   htab[0]=0;
  82   htab[1]=36089.239;
  83   htab[2]=65616.798;
  84   htab[3]=104986.878;
  85   htab[4]=154199.475;
  86   htab[5]=170603.675;
  87   htab[6]=200131.234;
  88   htab[7]=259186.352; //ft.
  89
  90   MagnitudedAccelDt = MagnitudeAccel = Magnitude = 0.0;
  91 //   turbType = ttNone;
  92   turbType = ttStandard;
  93 //   turbType = ttBerndt;
  94   TurbGain = 0.0;
  95   TurbRate = 1.0;
  96
  97   bind();
  98   Debug(0);
  99 }
 100
 101 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 102
 103 FGAtmosphere::~FGAtmosphere()
 104 {
 105   unbind();
 106   Debug(1);
 107 }
 108
 109 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 110
 111 bool FGAtmosphere::InitModel(void)
 112 {
 113   FGModel::InitModel();
 114
 115   Calculate(h);
 116   SLtemperature = intTemperature;
 117   SLpressure    = intPressure;
 118   SLdensity     = intDensity;
 119   SLsoundspeed  = sqrt(SHRatio*Reng*intTemperature);
 120   rSLtemperature = 1.0/intTemperature;
 121   rSLpressure    = 1.0/intPressure;
 122   rSLdensity     = 1.0/intDensity;
 123   rSLsoundspeed  = 1.0/SLsoundspeed;
 124   temperature=&intTemperature;
 125   pressure=&intPressure;
 126   density=&intDensity;
 127
 128   useExternal=false;
 129
 130   return true;
 131 }
 132
 133 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 134
 135 bool FGAtmosphere::Run(void)
 136 {
 137   if (!FGModel::Run()) {                 // if false then execute this Run()
 138     //do temp, pressure, and density first
 139     if (!useExternal) {
 140       h = Position->Geth();
 141       Calculate(h);
 142     }
 143
 144     if (turbType != ttNone) {
 145       Turbulence();
 146       vWindNED += vTurbulence;
 147     }
 148
 149     if (vWindNED(1) != 0.0) psiw = atan2( vWindNED(2), vWindNED(1) );
 150
 151     if (psiw < 0) psiw += 2*M_PI;
 152
 153     soundspeed = sqrt(SHRatio*Reng*(*temperature));
 154
 155     State->Seta(soundspeed);
 156
 157     Debug(2);
 158
 159     return false;
 160   } else {                               // skip Run() execution this time
 161     return true;
 162   }
 163 }
 164
 165 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 166 //
 167 // See reference 1
 168
 169 void FGAtmosphere::Calculate(double altitude)
 170 {
 171   double slope, reftemp, refpress;
 172   int i = 0;
 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 1:     // 36089 ft.
 195     slope     = 0;
 196     reftemp   = 389.97;
 197     refpress  = 472.452;
 198     //refdens   = 0.000706032;
 199     break;
 200   case 2:     // 65616 ft.
 201     slope     = 0.00054864;
 202     reftemp   = 389.97;
 203     refpress  = 114.636;
 204     //refdens   = 0.000171306;
 205     break;
 206   case 3:     // 104986 ft.
 207     slope     = 0.00153619;
 208     reftemp   = 411.57;
 209     refpress  = 8.36364;
 210     //refdens   = 1.18422e-05;
 211     break;
 212   case 4:     // 154199 ft.
 213     slope     = 0;
 214     reftemp   = 487.17;
 215     refpress  = 0.334882;
 216     //refdens   = 4.00585e-7;
 217     break;
 218   case 5:     // 170603 ft.
 219     slope     = -0.00109728;
 220     reftemp   = 487.17;
 221     refpress  = 0.683084;
 222     //refdens   = 8.17102e-7;
 223     break;
 224   case 6:     // 200131 ft.
 225     slope     = -0.00219456;
 226     reftemp   = 454.17;
 227     refpress  = 0.00684986;
 228     //refdens   = 8.77702e-9;
 229     break;
 230   case 7:     // 259186 ft.
 231     slope     = 0;
 232     reftemp   = 325.17;
 233     refpress  = 0.000122276;
 234     //refdens   = 2.19541e-10;
 235     break;
 236   case 0:
 237   default:     // sea level
 238     slope     = -0.00356616; // R/ft.
 239     reftemp   = 518.67;    // R
 240     refpress  = 2116.22;    // psf
 241     //refdens   = 0.00237767;  // slugs/cubic ft.
 242     break;
 243
 244   }
 245
 246   if (slope == 0) {
 247     intTemperature = reftemp;
 248     intPressure = refpress*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 249     //intDensity = refdens*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 250     intDensity = intPressure/(Reng*intTemperature);
 251   } else {
 252     intTemperature = reftemp+slope*(altitude-htab[i]);
 253     intPressure = refpress*pow(intTemperature/reftemp,-Inertial->SLgravity()/(slope*Reng));
 254     //intDensity = refdens*pow(intTemperature/reftemp,-(Inertial->SLgravity()/(slope*Reng)+1));
 255     intDensity = intPressure/(Reng*intTemperature);
 256   }
 257   lastIndex=i;
 258   //cout << "Atmosphere:  h=" << altitude << " rho= " << intDensity << endl;
 259 }
 260
 261 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 262
 263 // square a value, but preserve the original sign
 264 static inline double
 265 square_signed (double value)
 266 {
 267     if (value < 0)
 268         return value * value * -1;
 269     else
 270         return value * value;
 271 }
 272
 273 void FGAtmosphere::Turbulence(void)
 274 {
 275   switch (turbType) {
 276   case ttStandard: {
 277     vDirectiondAccelDt(eX) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 278     vDirectiondAccelDt(eY) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 279     vDirectiondAccelDt(eZ) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 280
 281     MagnitudedAccelDt = 1 - 2.0*(double(rand())/double(RAND_MAX)) - Magnitude;
 282                                 // Scale the magnitude so that it moves
 283                                 // away from the peaks
 284     MagnitudedAccelDt = ((MagnitudedAccelDt - Magnitude) /
 285                          (1 + fabs(Magnitude)));
 286     MagnitudeAccel    += MagnitudedAccelDt*rate*TurbRate*State->Getdt();
 287     Magnitude         += MagnitudeAccel*rate*State->Getdt();
 288
 289     vDirectiondAccelDt.Normalize();
 290
 291                                 // deemphasise non-vertical forces
 292     vDirectiondAccelDt(eX) = square_signed(vDirectiondAccelDt(eX));
 293     vDirectiondAccelDt(eY) = square_signed(vDirectiondAccelDt(eY));
 294
 295     vDirectionAccel += vDirectiondAccelDt*rate*TurbRate*State->Getdt();
 296     vDirectionAccel.Normalize();
 297     vDirection      += vDirectionAccel*rate*State->Getdt();
 298
 299     vDirection.Normalize();
 300
 301                                 // Diminish turbulence within three wingspans
 302                                 // of the ground
 303     vTurbulence = TurbGain * Magnitude * vDirection;
 304     double HOverBMAC = Position->GetHOverBMAC();
 305     if (HOverBMAC < 3.0)
 306         vTurbulence *= (HOverBMAC / 3.0) * (HOverBMAC / 3.0);
 307
 308     vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
 309
 310     vBodyTurbGrad = State->GetTl2b()*vTurbulenceGrad;
 311     vTurbPQR(eP) = vBodyTurbGrad(eY)/Aircraft->GetWingSpan();
 312 //     if (Aircraft->GetHTailArm() != 0.0)
 313 //       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/Aircraft->GetHTailArm();
 314 //     else
 315 //       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/10.0;
 316
 317     if (Aircraft->GetVTailArm())
 318       vTurbPQR(eR) = vBodyTurbGrad(eX)/Aircraft->GetVTailArm();
 319     else
 320       vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
 321
 322                                 // Clear the horizontal forces
 323                                 // actually felt by the plane, now
 324                                 // that we've used them to calculate
 325                                 // moments.
 326     vTurbulence(eX) = 0.0;
 327     vTurbulence(eY) = 0.0;
 328
 329     break;
 330   }
 331   case ttBerndt: {
 332     vDirectiondAccelDt(eX) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 333     vDirectiondAccelDt(eY) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 334     vDirectiondAccelDt(eZ) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 335
 336
 337     MagnitudedAccelDt = 1 - 2.0*(double(rand())/double(RAND_MAX)) - Magnitude;
 338     MagnitudeAccel    += MagnitudedAccelDt*rate*State->Getdt();
 339     Magnitude         += MagnitudeAccel*rate*State->Getdt();
 340
 341     vDirectiondAccelDt.Normalize();
 342     vDirectionAccel += vDirectiondAccelDt*rate*State->Getdt();
 343     vDirectionAccel.Normalize();
 344     vDirection      += vDirectionAccel*rate*State->Getdt();
 345
 346                                 // Diminish z-vector within two wingspans
 347                                 // of the ground
 348     double HOverBMAC = Position->GetHOverBMAC();
 349     if (HOverBMAC < 2.0)
 350         vDirection(eZ) *= HOverBMAC / 2.0;
 351
 352     vDirection.Normalize();
 353
 354     vTurbulence = TurbGain*Magnitude * vDirection;
 355     vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
 356
 357     vBodyTurbGrad = State->GetTl2b()*vTurbulenceGrad;
 358     vTurbPQR(eP) = vBodyTurbGrad(eY)/Aircraft->GetWingSpan();
 359     if (Aircraft->GetHTailArm() != 0.0)
 360       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/Aircraft->GetHTailArm();
 361     else
 362       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/10.0;
 363
 364     if (Aircraft->GetVTailArm())
 365       vTurbPQR(eR) = vBodyTurbGrad(eX)/Aircraft->GetVTailArm();
 366     else
 367       vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
 368
 369     break;
 370   }
 371   default:
 372     break;
 373   }
 374 }
 375
 376 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 377
 378 void FGAtmosphere::UseExternal(void) {
 379   temperature=&exTemperature;
 380   pressure=&exPressure;
 381   density=&exDensity;
 382   useExternal=true;
 383 }
 384
 385 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 386
 387 void FGAtmosphere::UseInternal(void) {
 388   temperature=&intTemperature;
 389   pressure=&intPressure;
 390   density=&intDensity;
 391   useExternal=false;
 392 }
 393
 394
 395 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 396
 397 void FGAtmosphere::bind(void)
 398 {
 399   typedef double (FGAtmosphere::*PMF)(int) const;
 400   PropertyManager->Tie("atmosphere/T-R", this,
 401                        &FGAtmosphere::GetTemperature);
 402   PropertyManager->Tie("atmosphere/rho-slugs_ft3", this,
 403                        &FGAtmosphere::GetDensity);
 404   PropertyManager->Tie("atmosphere/P-psf", this,
 405                        &FGAtmosphere::GetPressure);
 406   PropertyManager->Tie("atmosphere/a-fps", this,
 407                        &FGAtmosphere::GetSoundSpeed);
 408   PropertyManager->Tie("atmosphere/T-sl-R", this,
 409                        &FGAtmosphere::GetTemperatureSL);
 410   PropertyManager->Tie("atmosphere/rho-sl-slugs_ft3", this,
 411                        &FGAtmosphere::GetDensitySL);
 412   PropertyManager->Tie("atmosphere/P-sl-psf", this,
 413                        &FGAtmosphere::GetPressureSL);
 414   PropertyManager->Tie("atmosphere/a-sl-fps", this,
 415                        &FGAtmosphere::GetSoundSpeedSL);
 416   PropertyManager->Tie("atmosphere/theta-norm", this,
 417                        &FGAtmosphere::GetTemperatureRatio);
 418   PropertyManager->Tie("atmosphere/sigma-norm", this,
 419                        &FGAtmosphere::GetDensityRatio);
 420   PropertyManager->Tie("atmosphere/delta-norm", this,
 421                        &FGAtmosphere::GetPressureRatio);
 422   PropertyManager->Tie("atmosphere/a-norm", this,
 423                        &FGAtmosphere::GetSoundSpeedRatio);
 424   PropertyManager->Tie("atmosphere/psiw-rad", this,
 425                        &FGAtmosphere::GetWindPsi);
 426   PropertyManager->Tie("atmosphere/p-turb-rad_sec", this,1,
 427                        (PMF)&FGAtmosphere::GetTurbPQR);
 428   PropertyManager->Tie("atmosphere/q-turb-rad_sec", this,2,
 429                        (PMF)&FGAtmosphere::GetTurbPQR);
 430   PropertyManager->Tie("atmosphere/r-turb-rad_sec", this,3,
 431                        (PMF)&FGAtmosphere::GetTurbPQR);
 432 }
 433
 434 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 435
 436 void FGAtmosphere::unbind(void)
 437 {
 438   PropertyManager->Untie("atmosphere/T-R");
 439   PropertyManager->Untie("atmosphere/rho-slugs_ft3");
 440   PropertyManager->Untie("atmosphere/P-psf");
 441   PropertyManager->Untie("atmosphere/a-fps");
 442   PropertyManager->Untie("atmosphere/T-sl-R");
 443   PropertyManager->Untie("atmosphere/rho-sl-slugs_ft3");
 444   PropertyManager->Untie("atmosphere/P-sl-psf");
 445   PropertyManager->Untie("atmosphere/a-sl-fps");
 446   PropertyManager->Untie("atmosphere/theta-norm");
 447   PropertyManager->Untie("atmosphere/sigma-norm");
 448   PropertyManager->Untie("atmosphere/delta-norm");
 449   PropertyManager->Untie("atmosphere/a-norm");
 450   PropertyManager->Untie("atmosphere/psiw-rad");
 451   PropertyManager->Untie("atmosphere/p-turb-rad_sec");
 452   PropertyManager->Untie("atmosphere/q-turb-rad_sec");
 453   PropertyManager->Untie("atmosphere/r-turb-rad_sec");
 454 }
 455
 456 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 457 //    The bitmasked value choices are as follows:
 458 //    unset: In this case (the default) JSBSim would only print
 459 //       out the normally expected messages, essentially echoing
 460 //       the config files as they are read. If the environment
 461 //       variable is not set, debug_lvl is set to 1 internally
 462 //    0: This requests JSBSim not to output any messages
 463 //       whatsoever.
 464 //    1: This value explicity requests the normal JSBSim
 465 //       startup messages
 466 //    2: This value asks for a message to be printed out when
 467 //       a class is instantiated
 468 //    4: When this value is set, a message is displayed when a
 469 //       FGModel object executes its Run() method
 470 //    8: When this value is set, various runtime state variables
 471 //       are printed out periodically
 472 //    16: When set various parameters are sanity checked and
 473 //       a message is printed out when they go out of bounds
 474
 475 void FGAtmosphere::Debug(int from)
 476 {
 477   if (debug_lvl <= 0) return;
 478
 479   if (debug_lvl & 1) { // Standard console startup message output
 480     if (from == 0) { // Constructor
 481     }
 482   }
 483   if (debug_lvl & 2 ) { // Instantiation/Destruction notification
 484     if (from == 0) cout << "Instantiated: FGAtmosphere" << endl;
 485     if (from == 1) cout << "Destroyed:    FGAtmosphere" << endl;
 486   }
 487   if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
 488   }
 489   if (debug_lvl & 8 ) { // Runtime state variables
 490   }
 491   if (debug_lvl & 16) { // Sanity checking
 492   }
 493   if (debug_lvl & 32) { // Turbulence
 494     if (frame == 0 && from == 2) {
 495       cout << "vTurbulence(X), vTurbulence(Y), vTurbulence(Z), "
 496            << "vTurbulenceGrad(X), vTurbulenceGrad(Y), vTurbulenceGrad(Z), "
 497            << "vDirection(X), vDirection(Y), vDirection(Z), "
 498            << "Magnitude, "
 499            << "vTurbPQR(P), vTurbPQR(Q), vTurbPQR(R), " << endl;
 500     } else if (from == 2) {
 501       cout << vTurbulence << ", " << vTurbulenceGrad << ", " << vDirection << ", " << Magnitude << ", " << vTurbPQR << endl;
 502     }
 503   }
 504   if (debug_lvl & 64) {
 505     if (from == 0) { // Constructor
 506       cout << IdSrc << endl;
 507       cout << IdHdr << endl;
 508     }
 509   }
 510 }
 511
 512 } // namespace JSBSim