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 "FGAircraft.h"
  54 #include "FGPosition.h"
  55 #include "FGInertial.h"
  56 #include "FGPropertyManager.h"
  57
  58 namespace JSBSim {
  59
  60 static const char *IdSrc = "$Id$";
  61 static const char *IdHdr = ID_ATMOSPHERE;
  62
  63 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  64 CLASS IMPLEMENTATION
  65 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  66
  67
  68 FGAtmosphere::FGAtmosphere(FGFDMExec* fdmex) : FGModel(fdmex)
  69 {
  70   Name = "FGAtmosphere";
  71   lastIndex = 0;
  72   h = 0.0;
  73   psiw = 0.0;
  74   htab[0]=0;
  75   htab[1]=36089.239;
  76   htab[2]=65616.798;
  77   htab[3]=104986.878;
  78   htab[4]=154199.475;
  79   htab[5]=170603.675;
  80   htab[6]=200131.234;
  81   htab[7]=259186.352; //ft.
  82
  83   MagnitudedAccelDt = MagnitudeAccel = Magnitude = 0.0;
  84 //   turbType = ttNone;
  85   turbType = ttStandard;
  86 //   turbType = ttBerndt;
  87   TurbGain = 0.0;
  88   TurbRate = 1.0;
  89
  90   bind();
  91   Debug(0);
  92 }
  93
  94 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  95
  96 FGAtmosphere::~FGAtmosphere()
  97 {
  98   unbind();
  99   Debug(1);
 100 }
 101
 102 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 103
 104 bool FGAtmosphere::InitModel(void)
 105 {
 106   FGModel::InitModel();
 107
 108   Calculate(h);
 109   SLtemperature = intTemperature;
 110   SLpressure    = intPressure;
 111   SLdensity     = intDensity;
 112   SLsoundspeed  = sqrt(SHRatio*Reng*intTemperature);
 113   rSLtemperature = 1.0/intTemperature;
 114   rSLpressure    = 1.0/intPressure;
 115   rSLdensity     = 1.0/intDensity;
 116   rSLsoundspeed  = 1.0/SLsoundspeed;
 117   temperature=&intTemperature;
 118   pressure=&intPressure;
 119   density=&intDensity;
 120
 121   useExternal=false;
 122
 123   return true;
 124 }
 125
 126 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 127
 128 bool FGAtmosphere::Run(void)
 129 {
 130   if (!FGModel::Run()) {                 // if false then execute this Run()
 131     //do temp, pressure, and density first
 132     if (!useExternal) {
 133       h = Position->Geth();
 134       Calculate(h);
 135     }
 136
 137     if (turbType != ttNone) {
 138       Turbulence();
 139       vWindNED += vTurbulence;
 140     }
 141
 142     if (vWindNED(1) != 0.0) psiw = atan2( vWindNED(2), vWindNED(1) );
 143
 144     if (psiw < 0) psiw += 2*M_PI;
 145
 146     soundspeed = sqrt(SHRatio*Reng*(*temperature));
 147
 148     Debug(2);
 149
 150     return false;
 151   } else {                               // skip Run() execution this time
 152     return true;
 153   }
 154 }
 155
 156 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 157 //
 158 // See reference 1
 159
 160 void FGAtmosphere::Calculate(double altitude)
 161 {
 162   double slope, reftemp, refpress;
 163   int i = 0;
 164
 165   i = lastIndex;
 166   if (altitude < htab[lastIndex]) {
 167     if (altitude <= 0) {
 168       i = 0;
 169       altitude=0;
 170     } else {
 171        i = lastIndex-1;
 172        while (htab[i] > altitude) i--;
 173     }
 174   } else if (altitude > htab[lastIndex+1]) {
 175     if (altitude >= htab[7]) {
 176       i = 7;
 177       altitude = htab[7];
 178     } else {
 179       i = lastIndex+1;
 180       while (htab[i+1] < altitude) i++;
 181     }
 182   }
 183
 184   switch(i) {
 185   case 1:     // 36089 ft.
 186     slope     = 0;
 187     reftemp   = 389.97;
 188     refpress  = 472.452;
 189     //refdens   = 0.000706032;
 190     break;
 191   case 2:     // 65616 ft.
 192     slope     = 0.00054864;
 193     reftemp   = 389.97;
 194     refpress  = 114.636;
 195     //refdens   = 0.000171306;
 196     break;
 197   case 3:     // 104986 ft.
 198     slope     = 0.00153619;
 199     reftemp   = 411.57;
 200     refpress  = 8.36364;
 201     //refdens   = 1.18422e-05;
 202     break;
 203   case 4:     // 154199 ft.
 204     slope     = 0;
 205     reftemp   = 487.17;
 206     refpress  = 0.334882;
 207     //refdens   = 4.00585e-7;
 208     break;
 209   case 5:     // 170603 ft.
 210     slope     = -0.00109728;
 211     reftemp   = 487.17;
 212     refpress  = 0.683084;
 213     //refdens   = 8.17102e-7;
 214     break;
 215   case 6:     // 200131 ft.
 216     slope     = -0.00219456;
 217     reftemp   = 454.17;
 218     refpress  = 0.00684986;
 219     //refdens   = 8.77702e-9;
 220     break;
 221   case 7:     // 259186 ft.
 222     slope     = 0;
 223     reftemp   = 325.17;
 224     refpress  = 0.000122276;
 225     //refdens   = 2.19541e-10;
 226     break;
 227   case 0:
 228   default:     // sea level
 229     slope     = -0.00356616; // R/ft.
 230     reftemp   = 518.67;    // R
 231     refpress  = 2116.22;    // psf
 232     //refdens   = 0.00237767;  // slugs/cubic ft.
 233     break;
 234
 235   }
 236
 237   if (slope == 0) {
 238     intTemperature = reftemp;
 239     intPressure = refpress*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 240     //intDensity = refdens*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 241     intDensity = intPressure/(Reng*intTemperature);
 242   } else {
 243     intTemperature = reftemp+slope*(altitude-htab[i]);
 244     intPressure = refpress*pow(intTemperature/reftemp,-Inertial->SLgravity()/(slope*Reng));
 245     //intDensity = refdens*pow(intTemperature/reftemp,-(Inertial->SLgravity()/(slope*Reng)+1));
 246     intDensity = intPressure/(Reng*intTemperature);
 247   }
 248   lastIndex=i;
 249   //cout << "Atmosphere:  h=" << altitude << " rho= " << intDensity << endl;
 250 }
 251
 252 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 253
 254 // square a value, but preserve the original sign
 255 static inline double
 256 square_signed (double value)
 257 {
 258     if (value < 0)
 259         return value * value * -1;
 260     else
 261         return value * value;
 262 }
 263
 264 void FGAtmosphere::Turbulence(void)
 265 {
 266   switch (turbType) {
 267   case ttStandard: {
 268     vDirectiondAccelDt(eX) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 269     vDirectiondAccelDt(eY) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 270     vDirectiondAccelDt(eZ) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 271
 272     MagnitudedAccelDt = 1 - 2.0*(double(rand())/double(RAND_MAX)) - Magnitude;
 273                                 // Scale the magnitude so that it moves
 274                                 // away from the peaks
 275     MagnitudedAccelDt = ((MagnitudedAccelDt - Magnitude) /
 276                          (1 + fabs(Magnitude)));
 277     MagnitudeAccel    += MagnitudedAccelDt*rate*TurbRate*State->Getdt();
 278     Magnitude         += MagnitudeAccel*rate*State->Getdt();
 279
 280     vDirectiondAccelDt.Normalize();
 281
 282                                 // deemphasise non-vertical forces
 283     vDirectiondAccelDt(eX) = square_signed(vDirectiondAccelDt(eX));
 284     vDirectiondAccelDt(eY) = square_signed(vDirectiondAccelDt(eY));
 285
 286     vDirectionAccel += vDirectiondAccelDt*rate*TurbRate*State->Getdt();
 287     vDirectionAccel.Normalize();
 288     vDirection      += vDirectionAccel*rate*State->Getdt();
 289
 290     vDirection.Normalize();
 291
 292                                 // Diminish turbulence within three wingspans
 293                                 // of the ground
 294     vTurbulence = TurbGain * Magnitude * vDirection;
 295     double HOverBMAC = Position->GetHOverBMAC();
 296     if (HOverBMAC < 3.0)
 297         vTurbulence *= (HOverBMAC / 3.0) * (HOverBMAC / 3.0);
 298
 299     vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
 300
 301     vBodyTurbGrad = State->GetTl2b()*vTurbulenceGrad;
 302
 303     if (Aircraft->GetWingSpan() > 0) {
 304       vTurbPQR(eP) = vBodyTurbGrad(eY)/Aircraft->GetWingSpan();
 305     } else {
 306       vTurbPQR(eP) = vBodyTurbGrad(eY)/30.0;
 307     }
 308 //     if (Aircraft->GetHTailArm() != 0.0)
 309 //       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/Aircraft->GetHTailArm();
 310 //     else
 311 //       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/10.0;
 312
 313     if (Aircraft->GetVTailArm() > 0)
 314       vTurbPQR(eR) = vBodyTurbGrad(eX)/Aircraft->GetVTailArm();
 315     else
 316       vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
 317
 318                                 // Clear the horizontal forces
 319                                 // actually felt by the plane, now
 320                                 // that we've used them to calculate
 321                                 // moments.
 322     vTurbulence(eX) = 0.0;
 323     vTurbulence(eY) = 0.0;
 324
 325     break;
 326   }
 327   case ttBerndt: {
 328     vDirectiondAccelDt(eX) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 329     vDirectiondAccelDt(eY) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 330     vDirectiondAccelDt(eZ) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 331
 332
 333     MagnitudedAccelDt = 1 - 2.0*(double(rand())/double(RAND_MAX)) - Magnitude;
 334     MagnitudeAccel    += MagnitudedAccelDt*rate*State->Getdt();
 335     Magnitude         += MagnitudeAccel*rate*State->Getdt();
 336
 337     vDirectiondAccelDt.Normalize();
 338     vDirectionAccel += vDirectiondAccelDt*rate*State->Getdt();
 339     vDirectionAccel.Normalize();
 340     vDirection      += vDirectionAccel*rate*State->Getdt();
 341
 342                                 // Diminish z-vector within two wingspans
 343                                 // of the ground
 344     double HOverBMAC = Position->GetHOverBMAC();
 345     if (HOverBMAC < 2.0)
 346         vDirection(eZ) *= HOverBMAC / 2.0;
 347
 348     vDirection.Normalize();
 349
 350     vTurbulence = TurbGain*Magnitude * vDirection;
 351     vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
 352
 353     vBodyTurbGrad = State->GetTl2b()*vTurbulenceGrad;
 354     vTurbPQR(eP) = vBodyTurbGrad(eY)/Aircraft->GetWingSpan();
 355     if (Aircraft->GetHTailArm() > 0)
 356       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/Aircraft->GetHTailArm();
 357     else
 358       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/10.0;
 359
 360     if (Aircraft->GetVTailArm() > 0)
 361       vTurbPQR(eR) = vBodyTurbGrad(eX)/Aircraft->GetVTailArm();
 362     else
 363       vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
 364
 365     break;
 366   }
 367   default:
 368     break;
 369   }
 370 }
 371
 372 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 373
 374 void FGAtmosphere::UseExternal(void) {
 375   temperature=&exTemperature;
 376   pressure=&exPressure;
 377   density=&exDensity;
 378   useExternal=true;
 379 }
 380
 381 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 382
 383 void FGAtmosphere::UseInternal(void) {
 384   temperature=&intTemperature;
 385   pressure=&intPressure;
 386   density=&intDensity;
 387   useExternal=false;
 388 }
 389
 390
 391 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 392
 393 void FGAtmosphere::bind(void)
 394 {
 395   typedef double (FGAtmosphere::*PMF)(int) const;
 396   PropertyManager->Tie("atmosphere/T-R", this,
 397                        &FGAtmosphere::GetTemperature);
 398   PropertyManager->Tie("atmosphere/rho-slugs_ft3", this,
 399                        &FGAtmosphere::GetDensity);
 400   PropertyManager->Tie("atmosphere/P-psf", this,
 401                        &FGAtmosphere::GetPressure);
 402   PropertyManager->Tie("atmosphere/a-fps", this,
 403                        &FGAtmosphere::GetSoundSpeed);
 404   PropertyManager->Tie("atmosphere/T-sl-R", this,
 405                        &FGAtmosphere::GetTemperatureSL);
 406   PropertyManager->Tie("atmosphere/rho-sl-slugs_ft3", this,
 407                        &FGAtmosphere::GetDensitySL);
 408   PropertyManager->Tie("atmosphere/P-sl-psf", this,
 409                        &FGAtmosphere::GetPressureSL);
 410   PropertyManager->Tie("atmosphere/a-sl-fps", this,
 411                        &FGAtmosphere::GetSoundSpeedSL);
 412   PropertyManager->Tie("atmosphere/theta-norm", this,
 413                        &FGAtmosphere::GetTemperatureRatio);
 414   PropertyManager->Tie("atmosphere/sigma-norm", this,
 415                        &FGAtmosphere::GetDensityRatio);
 416   PropertyManager->Tie("atmosphere/delta-norm", this,
 417                        &FGAtmosphere::GetPressureRatio);
 418   PropertyManager->Tie("atmosphere/a-norm", this,
 419                        &FGAtmosphere::GetSoundSpeedRatio);
 420   PropertyManager->Tie("atmosphere/psiw-rad", this,
 421                        &FGAtmosphere::GetWindPsi);
 422   PropertyManager->Tie("atmosphere/p-turb-rad_sec", this,1,
 423                        (PMF)&FGAtmosphere::GetTurbPQR);
 424   PropertyManager->Tie("atmosphere/q-turb-rad_sec", this,2,
 425                        (PMF)&FGAtmosphere::GetTurbPQR);
 426   PropertyManager->Tie("atmosphere/r-turb-rad_sec", this,3,
 427                        (PMF)&FGAtmosphere::GetTurbPQR);
 428 }
 429
 430 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 431
 432 void FGAtmosphere::unbind(void)
 433 {
 434   PropertyManager->Untie("atmosphere/T-R");
 435   PropertyManager->Untie("atmosphere/rho-slugs_ft3");
 436   PropertyManager->Untie("atmosphere/P-psf");
 437   PropertyManager->Untie("atmosphere/a-fps");
 438   PropertyManager->Untie("atmosphere/T-sl-R");
 439   PropertyManager->Untie("atmosphere/rho-sl-slugs_ft3");
 440   PropertyManager->Untie("atmosphere/P-sl-psf");
 441   PropertyManager->Untie("atmosphere/a-sl-fps");
 442   PropertyManager->Untie("atmosphere/theta-norm");
 443   PropertyManager->Untie("atmosphere/sigma-norm");
 444   PropertyManager->Untie("atmosphere/delta-norm");
 445   PropertyManager->Untie("atmosphere/a-norm");
 446   PropertyManager->Untie("atmosphere/psiw-rad");
 447   PropertyManager->Untie("atmosphere/p-turb-rad_sec");
 448   PropertyManager->Untie("atmosphere/q-turb-rad_sec");
 449   PropertyManager->Untie("atmosphere/r-turb-rad_sec");
 450 }
 451
 452 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 453 //    The bitmasked value choices are as follows:
 454 //    unset: In this case (the default) JSBSim would only print
 455 //       out the normally expected messages, essentially echoing
 456 //       the config files as they are read. If the environment
 457 //       variable is not set, debug_lvl is set to 1 internally
 458 //    0: This requests JSBSim not to output any messages
 459 //       whatsoever.
 460 //    1: This value explicity requests the normal JSBSim
 461 //       startup messages
 462 //    2: This value asks for a message to be printed out when
 463 //       a class is instantiated
 464 //    4: When this value is set, a message is displayed when a
 465 //       FGModel object executes its Run() method
 466 //    8: When this value is set, various runtime state variables
 467 //       are printed out periodically
 468 //    16: When set various parameters are sanity checked and
 469 //       a message is printed out when they go out of bounds
 470
 471 void FGAtmosphere::Debug(int from)
 472 {
 473   if (debug_lvl <= 0) return;
 474
 475   if (debug_lvl & 1) { // Standard console startup message output
 476     if (from == 0) { // Constructor
 477     }
 478   }
 479   if (debug_lvl & 2 ) { // Instantiation/Destruction notification
 480     if (from == 0) cout << "Instantiated: FGAtmosphere" << endl;
 481     if (from == 1) cout << "Destroyed:    FGAtmosphere" << endl;
 482   }
 483   if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
 484   }
 485   if (debug_lvl & 8 ) { // Runtime state variables
 486   }
 487   if (debug_lvl & 16) { // Sanity checking
 488   }
 489   if (debug_lvl & 32) { // Turbulence
 490     if (frame == 0 && from == 2) {
 491       cout << "vTurbulence(X), vTurbulence(Y), vTurbulence(Z), "
 492            << "vTurbulenceGrad(X), vTurbulenceGrad(Y), vTurbulenceGrad(Z), "
 493            << "vDirection(X), vDirection(Y), vDirection(Z), "
 494            << "Magnitude, "
 495            << "vTurbPQR(P), vTurbPQR(Q), vTurbPQR(R), " << endl;
 496     } else if (from == 2) {
 497       cout << vTurbulence << ", " << vTurbulenceGrad << ", " << vDirection << ", " << Magnitude << ", " << vTurbPQR << endl;
 498     }
 499   }
 500   if (debug_lvl & 64) {
 501     if (from == 0) { // Constructor
 502       cout << IdSrc << endl;
 503       cout << IdHdr << endl;
 504     }
 505   }
 506 }
 507
 508 } // namespace JSBSim