1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
3 Module: FGAtmosphere.cpp
5 Implementation of 1959 Standard Atmosphere added by Tony Peden
7 Purpose: Models the atmosphere
10 ------------- Copyright (C) 1999 Jon S. Berndt (jon@jsbsim.org) -------------
12 This program is free software; you can redistribute it and/or modify it under
13 the terms of the GNU Lesser General Public License as published by the Free Software
14 Foundation; either version 2 of the License, or (at your option) any later
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 Lesser General Public License for more
22 You should have received a copy of the GNU Lesser 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.
26 Further information about the GNU Lesser General Public License can also be found on
27 the world wide web at http://www.gnu.org.
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.
35 --------------------------------------------------------------------------------
37 07/23/99 TP Added implementation of 1959 Standard Atmosphere
38 Moved calculation of Mach number to FGPropagate
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
46 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
48 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
50 #include "FGAtmosphere.h"
51 #include "FGAircraft.h"
52 #include "FGPropagate.h"
53 #include "FGInertial.h"
54 #include "FGAuxiliary.h"
55 #include "FGFDMExec.h"
56 #include "input_output/FGPropertyManager.h"
64 static const char *IdSrc = "$Id: FGAtmosphere.cpp,v 1.41 2010/11/30 12:19:57 jberndt Exp $";
65 static const char *IdHdr = ID_ATMOSPHERE;
67 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
69 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
71 FGAtmosphere::FGAtmosphere(FGFDMExec* fdmex) : FGModel(fdmex)
73 Name = "FGAtmosphere";
84 htab[7]=278385.0; //ft.
86 MagnitudedAccelDt = MagnitudeAccel = Magnitude = 0.0;
87 // SetTurbType( ttCulp );
88 SetTurbType( ttNone );
92 spike = target_time = strength = 0.0;
93 wind_from_clockwise = 0.0;
94 SutherlandConstant = 198.72; // deg Rankine
95 Beta = 2.269690E-08; // slug/(sec ft R^0.5)
97 T_dev_sl = T_dev = delta_T = 0.0;
98 StandardTempOnly = false;
100 vGustNED.InitMatrix();
101 vTurbulenceNED.InitMatrix();
103 // Milspec turbulence model
104 windspeed_at_20ft = 0.;
105 probability_of_exceedence_index = 0;
106 POE_Table = new FGTable(7,12);
107 // this is Figure 7 from p. 49 of MIL-F-8785C
108 // rows: probability of exceedance curve index, cols: altitude in ft
110 << 500.0 << 1750.0 << 3750.0 << 7500.0 << 15000.0 << 25000.0 << 35000.0 << 45000.0 << 55000.0 << 65000.0 << 75000.0 << 80000.0
111 << 1 << 3.2 << 2.2 << 1.5 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0
112 << 2 << 4.2 << 3.6 << 3.3 << 1.6 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0
113 << 3 << 6.6 << 6.9 << 7.4 << 6.7 << 4.6 << 2.7 << 0.4 << 0.0 << 0.0 << 0.0 << 0.0 << 0.0
114 << 4 << 8.6 << 9.6 << 10.6 << 10.1 << 8.0 << 6.6 << 5.0 << 4.2 << 2.7 << 0.0 << 0.0 << 0.0
115 << 5 << 11.8 << 13.0 << 16.0 << 15.1 << 11.6 << 9.7 << 8.1 << 8.2 << 7.9 << 4.9 << 3.2 << 2.1
116 << 6 << 15.6 << 17.6 << 23.0 << 23.6 << 22.1 << 20.0 << 16.0 << 15.1 << 12.1 << 7.9 << 6.2 << 5.1
117 << 7 << 18.7 << 21.5 << 28.4 << 30.2 << 30.7 << 31.0 << 25.2 << 23.1 << 17.5 << 10.7 << 8.4 << 7.2;
123 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
125 FGAtmosphere::~FGAtmosphere()
130 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
132 bool FGAtmosphere::InitModel(void)
134 if (!FGModel::InitModel()) return false;
136 UseInternal(); // this is the default
139 StdSLtemperature = SLtemperature = 518.67;
140 StdSLpressure = SLpressure = 2116.22;
141 StdSLdensity = SLdensity = 0.00237767;
142 StdSLsoundspeed = SLsoundspeed = sqrt(SHRatio*Reng*StdSLtemperature);
143 rSLtemperature = 1.0/StdSLtemperature;
144 rSLpressure = 1.0/StdSLpressure;
145 rSLdensity = 1.0/StdSLdensity;
146 rSLsoundspeed = 1.0/StdSLsoundspeed;
151 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
153 bool FGAtmosphere::Run(void)
155 if (FGModel::Run()) return true;
156 if (FDMExec->Holding()) return false;
161 h = FDMExec->GetPropagate()->GetAltitudeASL();
176 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
180 void FGAtmosphere::Calculate(double altitude)
182 double slope, reftemp, refpress;
185 if (altitude < htab[lastIndex]) {
191 while (htab[i] > altitude) i--;
193 } else if (altitude > htab[lastIndex+1]) {
194 if (altitude >= htab[7]) {
199 while (htab[i+1] < altitude) i++;
205 slope = -0.00356616; // R/ft.
206 reftemp = 518.67; // in degrees Rankine, 288.15 Kelvin
207 refpress = 2116.22; // psf
208 //refdens = 0.00237767; // slugs/cubic ft.
210 case 1: // 36089 ft. or 11 km
212 reftemp = 389.97; // in degrees Rankine, 216.65 Kelvin
214 //refdens = 0.000706032;
216 case 2: // 65616 ft. or 20 km
218 reftemp = 389.97; // in degrees Rankine, 216.65 Kelvin
220 //refdens = 0.000171306;
222 case 3: // 104986 ft. or 32 km
224 reftemp = 411.57; // in degrees Rankine, 228.65 Kelvin
226 //refdens = 1.18422e-05;
228 case 4: // 154199 ft. 47 km
230 reftemp = 487.17; // in degrees Rankine, 270.65 Kelvin
232 //refdens = 4.00585e-7;
234 case 5: // 167322 ft. or 51 km
235 slope = -0.001536192;
236 reftemp = 487.17; // in degrees Rankine, 270.65 Kelvin
238 //refdens = 8.17102e-7;
240 case 6: // 232940 ft. or 71 km
242 reftemp = 386.368; // in degrees Rankine, 214.649 Kelvin
244 //refdens = 8.77702e-9;
246 case 7: // 278385 ft. or 84.8520 km
248 reftemp = 336.5; // in degrees Rankine, 186.94 Kelvin
250 //refdens = 2.19541e-10;
252 default: // sea level
253 slope = -0.00356616; // R/ft.
254 reftemp = 518.67; // in degrees Rankine, 288.15 Kelvin
255 refpress = 2116.22; // psf
256 //refdens = 0.00237767; // slugs/cubic ft.
261 // If delta_T is set, then that is our temperature deviation at any altitude.
262 // If not, then we'll estimate a deviation based on the sea level deviation (if set).
264 if(!StandardTempOnly) {
266 if (delta_T != 0.0) {
269 if ((altitude < 36089.239) && (T_dev_sl != 0.0)) {
270 T_dev = T_dev_sl * ( 1.0 - (altitude/36089.239));
277 intTemperature = reftemp;
278 intPressure = refpress*exp(-FDMExec->GetInertial()->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
279 intDensity = intPressure/(Reng*intTemperature);
281 intTemperature = reftemp+slope*(altitude-htab[i]);
282 intPressure = refpress*pow(intTemperature/reftemp,-FDMExec->GetInertial()->SLgravity()/(slope*Reng));
283 intDensity = intPressure/(Reng*intTemperature);
289 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
290 // Calculate parameters derived from T, P and rho
291 // Sum gust and turbulence values in NED frame into the wind vector.
293 void FGAtmosphere::CalculateDerived(void)
295 T_dev = (*temperature) - GetTemperature(h);
297 if (T_dev == 0.0) density_altitude = h;
298 else density_altitude = 518.67/0.00356616 * (1.0 - pow(GetDensityRatio(),0.235));
300 if (turbType != ttNone) Turbulence();
302 vTotalWindNED = vWindNED + vGustNED + vTurbulenceNED;
304 // psiw (Wind heading) is the direction the wind is blowing towards
305 if (vWindNED(eX) != 0.0) psiw = atan2( vWindNED(eY), vWindNED(eX) );
306 if (psiw < 0) psiw += 2*M_PI;
308 soundspeed = sqrt(SHRatio*Reng*(*temperature));
310 intViscosity = Beta * pow(intTemperature, 1.5) / (SutherlandConstant + intTemperature);
311 intKinematicViscosity = intViscosity / intDensity;
315 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
316 // Get the standard atmospheric properties at a specified altitude
318 void FGAtmosphere::GetStdAtmosphere(double altitude) {
319 StandardTempOnly = true;
321 StandardTempOnly = false;
322 atmosphere.Temperature = intTemperature;
323 atmosphere.Pressure = intPressure;
324 atmosphere.Density = intDensity;
326 // Reset the internal atmospheric state
330 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
331 // Get the standard pressure at a specified altitude
333 double FGAtmosphere::GetPressure(double altitude) {
334 GetStdAtmosphere(altitude);
335 return atmosphere.Pressure;
338 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
339 // Get the standard temperature at a specified altitude
341 double FGAtmosphere::GetTemperature(double altitude) {
342 GetStdAtmosphere(altitude);
343 return atmosphere.Temperature;
346 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
347 // Get the standard density at a specified altitude
349 double FGAtmosphere::GetDensity(double altitude) {
350 GetStdAtmosphere(altitude);
351 return atmosphere.Density;
355 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
356 // square a value, but preserve the original sign
358 static inline double square_signed (double value)
361 return value * value * -1;
363 return value * value;
366 /// simply square a value
367 static inline double sqr(double x) { return x*x; }
369 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
371 // psi is the angle that the wind is blowing *towards*
373 void FGAtmosphere::SetWindspeed(double speed)
375 if (vWindNED.Magnitude() == 0.0) {
377 vWindNED(eNorth) = speed;
379 vWindNED(eNorth) = speed * cos(psiw);
380 vWindNED(eEast) = speed * sin(psiw);
381 vWindNED(eDown) = 0.0;
385 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
387 double FGAtmosphere::GetWindspeed(void) const
389 return vWindNED.Magnitude();
392 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
394 // psi is the angle that the wind is blowing *towards*
396 void FGAtmosphere::SetWindPsi(double dir)
398 double mag = GetWindspeed();
403 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
405 void FGAtmosphere::Turbulence(void)
407 const double DeltaT = rate*FDMExec->GetDeltaT();
408 const double wingspan = FDMExec->GetAircraft()->GetWingSpan();
409 const double HOverBMAC = FDMExec->GetAuxiliary()->GetHOverBMAC();
410 const FGMatrix33& Tl2b = FDMExec->GetPropagate()->GetTl2b();
411 const double HTailArm = FDMExec->GetAircraft()->GetHTailArm();
412 const double VTailArm = FDMExec->GetAircraft()->GetVTailArm();
416 // TurbGain = TurbGain * TurbGain * 100.0; // what is this!?
418 vDirectiondAccelDt(eX) = 1 - 2.0*(double(rand())/double(RAND_MAX));
419 vDirectiondAccelDt(eY) = 1 - 2.0*(double(rand())/double(RAND_MAX));
420 vDirectiondAccelDt(eZ) = 1 - 2.0*(double(rand())/double(RAND_MAX));
422 MagnitudedAccelDt = 1 - 2.0*(double(rand())/double(RAND_MAX)) - Magnitude;
423 // Scale the magnitude so that it moves
424 // away from the peaks
425 MagnitudedAccelDt = ((MagnitudedAccelDt - Magnitude) /
426 (1 + fabs(Magnitude)));
427 MagnitudeAccel += MagnitudedAccelDt*TurbRate*DeltaT;
428 Magnitude += MagnitudeAccel*DeltaT;
429 Magnitude = fabs(Magnitude);
431 vDirectiondAccelDt.Normalize();
433 // deemphasise non-vertical forces
434 vDirectiondAccelDt(eX) = square_signed(vDirectiondAccelDt(eX));
435 vDirectiondAccelDt(eY) = square_signed(vDirectiondAccelDt(eY));
437 vDirectionAccel += vDirectiondAccelDt*TurbRate*DeltaT;
438 vDirectionAccel.Normalize();
439 vDirection += vDirectionAccel*DeltaT;
441 vDirection.Normalize();
443 // Diminish turbulence within three wingspans
445 vTurbulenceNED = TurbGain * Magnitude * vDirection;
447 vTurbulenceNED *= (HOverBMAC / 3.0) * (HOverBMAC / 3.0);
449 // I don't believe these next two statements calculate the proper gradient over
450 // the aircraft body. One reason is because this has no relationship with the
451 // orientation or velocity of the aircraft, which it must have. What is vTurbulenceGrad
452 // supposed to represent? And the direction and magnitude of the turbulence can change,
453 // so both accelerations need to be accounted for, no?
455 // Need to determine the turbulence change in body axes between two time points.
457 vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
458 vBodyTurbGrad = Tl2b*vTurbulenceGrad;
461 vTurbPQR(eP) = vBodyTurbGrad(eY)/wingspan;
463 vTurbPQR(eP) = vBodyTurbGrad(eY)/30.0;
465 // if (HTailArm != 0.0)
466 // vTurbPQR(eQ) = vBodyTurbGrad(eZ)/HTailArm;
468 // vTurbPQR(eQ) = vBodyTurbGrad(eZ)/10.0;
471 vTurbPQR(eR) = vBodyTurbGrad(eX)/VTailArm;
473 vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
475 // Clear the horizontal forces
476 // actually felt by the plane, now
477 // that we've used them to calculate
480 // vTurbulenceNED(eX) = 0.0;
481 // vTurbulenceNED(eY) = 0.0;
485 case ttBerndt: { // This is very experimental and incomplete at the moment.
487 vDirectiondAccelDt(eX) = GaussianRandomNumber();
488 vDirectiondAccelDt(eY) = GaussianRandomNumber();
489 vDirectiondAccelDt(eZ) = GaussianRandomNumber();
491 MagnitudedAccelDt = GaussianRandomNumber();
492 MagnitudeAccel += MagnitudedAccelDt * DeltaT;
493 Magnitude += MagnitudeAccel * DeltaT;
495 Magnitude += GaussianRandomNumber() * DeltaT;
497 vDirectiondAccelDt.Normalize();
498 vDirectionAccel += TurbRate * vDirectiondAccelDt * DeltaT;
499 vDirectionAccel.Normalize();
500 vDirection += vDirectionAccel*DeltaT;
502 // Diminish z-vector within two wingspans of the ground
503 if (HOverBMAC < 2.0) vDirection(eZ) *= HOverBMAC / 2.0;
505 vDirection.Normalize();
507 vTurbulenceNED = TurbGain*Magnitude * vDirection;
508 vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
510 vBodyTurbGrad = Tl2b * vTurbulenceGrad;
511 vTurbPQR(eP) = vBodyTurbGrad(eY) / wingspan;
513 vTurbPQR(eQ) = vBodyTurbGrad(eZ) / HTailArm;
515 vTurbPQR(eQ) = vBodyTurbGrad(eZ) / 10.0;
518 vTurbPQR(eR) = vBodyTurbGrad(eX) / VTailArm;
520 vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
526 vTurbPQR(eP) = wind_from_clockwise;
527 if (TurbGain == 0.0) return;
529 // keep the inputs within allowable limts for this model
530 if (TurbGain < 0.0) TurbGain = 0.0;
531 if (TurbGain > 1.0) TurbGain = 1.0;
532 if (TurbRate < 0.0) TurbRate = 0.0;
533 if (TurbRate > 30.0) TurbRate = 30.0;
534 if (Rhythmicity < 0.0) Rhythmicity = 0.0;
535 if (Rhythmicity > 1.0) Rhythmicity = 1.0;
537 // generate a sine wave corresponding to turbulence rate in hertz
538 double time = FDMExec->GetSimTime();
539 double sinewave = sin( time * TurbRate * 6.283185307 );
542 if (target_time == 0.0) {
543 strength = random = 1 - 2.0*(double(rand())/double(RAND_MAX));
544 target_time = time + 0.71 + (random * 0.5);
546 if (time > target_time) {
551 // max vertical wind speed in fps, corresponds to TurbGain = 1.0
554 vTurbulenceNED(1) = vTurbulenceNED(2) = vTurbulenceNED(3) = 0.0;
555 double delta = strength * max_vs * TurbGain * (1-Rhythmicity) * spike;
557 // Vertical component of turbulence.
558 vTurbulenceNED(3) = sinewave * max_vs * TurbGain * Rhythmicity;
559 vTurbulenceNED(3)+= delta;
561 vTurbulenceNED(3) *= HOverBMAC * 0.3333;
563 // Yaw component of turbulence.
564 vTurbulenceNED(1) = sin( delta * 3.0 );
565 vTurbulenceNED(2) = cos( delta * 3.0 );
567 // Roll component of turbulence. Clockwise vortex causes left roll.
568 vTurbPQR(eP) += delta * 0.04;
575 double V = FDMExec->GetAuxiliary()->GetVt(); // true airspeed in ft/s
577 // an index of zero means turbulence is disabled
578 // airspeed occurs as divisor in the code below
579 if (probability_of_exceedence_index == 0 || V == 0) {
580 vTurbulenceNED(1) = vTurbulenceNED(2) = vTurbulenceNED(3) = 0.0;
581 vTurbPQR(1) = vTurbPQR(2) = vTurbPQR(3) = 0.0;
585 // Turbulence model according to MIL-F-8785C (Flying Qualities of Piloted Aircraft)
587 h = FDMExec->GetPropagate()->GetDistanceAGL(),
589 L_u, L_w, sig_u, sig_w;
591 if (b_w == 0.) b_w = 30.;
593 // clip height functions at 10 ft
594 if (h <= 10.) h = 10;
596 // Scale lengths L and amplitudes sigma as function of height
598 L_u = h/pow(0.177 + 0.000823*h, 1.2); // MIL-F-8785c, Fig. 10, p. 55
600 sig_w = 0.1*windspeed_at_20ft;
601 sig_u = sig_w/pow(0.177 + 0.000823*h, 0.4); // MIL-F-8785c, Fig. 11, p. 56
602 } else if (h <= 2000) {
603 // linear interpolation between low altitude and high altitude models
604 L_u = L_w = 1000 + (h-1000.)/1000.*750.;
605 sig_u = sig_w = 0.1*windspeed_at_20ft
606 + (h-1000.)/1000.*(POE_Table->GetValue(probability_of_exceedence_index, h) - 0.1*windspeed_at_20ft);
608 L_u = L_w = 1750.; // MIL-F-8785c, Sec. 3.7.2.1, p. 48
609 sig_u = sig_w = POE_Table->GetValue(probability_of_exceedence_index, h);
612 // keep values from last timesteps
613 // TODO maybe use deque?
615 xi_u_km1 = 0, nu_u_km1 = 0,
616 xi_v_km1 = 0, xi_v_km2 = 0, nu_v_km1 = 0, nu_v_km2 = 0,
617 xi_w_km1 = 0, xi_w_km2 = 0, nu_w_km1 = 0, nu_w_km2 = 0,
618 xi_p_km1 = 0, nu_p_km1 = 0,
619 xi_q_km1 = 0, xi_r_km1 = 0;
623 T_V = DeltaT, // for compatibility of nomenclature
624 sig_p = 1.9/sqrt(L_w*b_w)*sig_w, // Yeager1998, eq. (8)
625 sig_q = sqrt(M_PI/2/L_w/b_w), // eq. (14)
626 sig_r = sqrt(2*M_PI/3/L_w/b_w), // eq. (17)
627 L_p = sqrt(L_w*b_w)/2.6, // eq. (10)
628 tau_u = L_u/V, // eq. (6)
629 tau_w = L_w/V, // eq. (3)
630 tau_p = L_p/V, // eq. (9)
631 tau_q = 4*b_w/M_PI/V, // eq. (13)
632 tau_r =3*b_w/M_PI/V, // eq. (17)
633 nu_u = GaussianRandomNumber(),
634 nu_v = GaussianRandomNumber(),
635 nu_w = GaussianRandomNumber(),
636 nu_p = GaussianRandomNumber(),
637 xi_u=0, xi_v=0, xi_w=0, xi_p=0, xi_q=0, xi_r=0;
639 // values of turbulence NED velocities
641 if (turbType == ttTustin) {
642 // the following is the Tustin formulation of Yeager's report
644 omega_w = V/L_w, // hidden in nomenclature p. 3
645 omega_v = V/L_u, // this is defined nowhere
646 C_BL = 1/tau_u/tan(T_V/2/tau_u), // eq. (19)
647 C_BLp = 1/tau_p/tan(T_V/2/tau_p), // eq. (22)
648 C_BLq = 1/tau_q/tan(T_V/2/tau_q), // eq. (24)
649 C_BLr = 1/tau_r/tan(T_V/2/tau_r); // eq. (26)
651 // all values calculated so far are strictly positive, except for
652 // the random numbers nu_*. This means that in the code below, all
653 // divisors are strictly positive, too, and no floating point
654 // exception should occur.
655 xi_u = -(1 - C_BL*tau_u)/(1 + C_BL*tau_u)*xi_u_km1
656 + sig_u*sqrt(2*tau_u/T_V)/(1 + C_BL*tau_u)*(nu_u + nu_u_km1); // eq. (18)
657 xi_v = -2*(sqr(omega_v) - sqr(C_BL))/sqr(omega_v + C_BL)*xi_v_km1
658 - sqr(omega_v - C_BL)/sqr(omega_v + C_BL) * xi_v_km2
659 + sig_u*sqrt(3*omega_v/T_V)/sqr(omega_v + C_BL)*(
660 (C_BL + omega_v/sqrt(3.))*nu_v
661 + 2/sqrt(3.)*omega_v*nu_v_km1
662 + (omega_v/sqrt(3.) - C_BL)*nu_v_km2); // eq. (20) for v
663 xi_w = -2*(sqr(omega_w) - sqr(C_BL))/sqr(omega_w + C_BL)*xi_w_km1
664 - sqr(omega_w - C_BL)/sqr(omega_w + C_BL) * xi_w_km2
665 + sig_w*sqrt(3*omega_w/T_V)/sqr(omega_w + C_BL)*(
666 (C_BL + omega_w/sqrt(3.))*nu_w
667 + 2/sqrt(3.)*omega_w*nu_w_km1
668 + (omega_w/sqrt(3.) - C_BL)*nu_w_km2); // eq. (20) for w
669 xi_p = -(1 - C_BLp*tau_p)/(1 + C_BLp*tau_p)*xi_p_km1
670 + sig_p*sqrt(2*tau_p/T_V)/(1 + C_BLp*tau_p) * (nu_p + nu_p_km1); // eq. (21)
671 xi_q = -(1 - 4*b_w*C_BLq/M_PI/V)/(1 + 4*b_w*C_BLq/M_PI/V) * xi_q_km1
672 + C_BLq/V/(1 + 4*b_w*C_BLq/M_PI/V) * (xi_w - xi_w_km1); // eq. (23)
673 xi_r = - (1 - 3*b_w*C_BLr/M_PI/V)/(1 + 3*b_w*C_BLr/M_PI/V) * xi_r_km1
674 + C_BLr/V/(1 + 3*b_w*C_BLr/M_PI/V) * (xi_v - xi_v_km1); // eq. (25)
676 } else if (turbType == ttMilspec) {
677 // the following is the MIL-STD-1797A formulation
678 // as cited in Yeager's report
679 xi_u = (1 - T_V/tau_u) *xi_u_km1 + sig_u*sqrt(2*T_V/tau_u)*nu_u; // eq. (30)
680 xi_v = (1 - 2*T_V/tau_u)*xi_v_km1 + sig_u*sqrt(4*T_V/tau_u)*nu_v; // eq. (31)
681 xi_w = (1 - 2*T_V/tau_w)*xi_w_km1 + sig_w*sqrt(4*T_V/tau_w)*nu_w; // eq. (32)
682 xi_p = (1 - T_V/tau_p) *xi_p_km1 + sig_p*sqrt(2*T_V/tau_p)*nu_p; // eq. (33)
683 xi_q = (1 - T_V/tau_q) *xi_q_km1 + M_PI/4/b_w*(xi_w - xi_w_km1); // eq. (34)
684 xi_r = (1 - T_V/tau_r) *xi_r_km1 + M_PI/3/b_w*(xi_v - xi_v_km1); // eq. (35)
687 // rotate by wind azimuth and assign the velocities
688 double cospsi = cos(psiw), sinpsi = sin(psiw);
689 vTurbulenceNED(1) = cospsi*xi_u + sinpsi*xi_v;
690 vTurbulenceNED(2) = -sinpsi*xi_u + cospsi*xi_v;
691 vTurbulenceNED(3) = xi_w;
693 vTurbPQR(1) = cospsi*xi_p + sinpsi*xi_q;
694 vTurbPQR(2) = -sinpsi*xi_p + cospsi*xi_q;
697 // vTurbPQR is in the body fixed frame, not NED
698 vTurbPQR = Tl2b*vTurbPQR;
700 // hand on the values for the next timestep
701 xi_u_km1 = xi_u; nu_u_km1 = nu_u;
702 xi_v_km2 = xi_v_km1; xi_v_km1 = xi_v; nu_v_km2 = nu_v_km1; nu_v_km1 = nu_v;
703 xi_w_km2 = xi_w_km1; xi_w_km1 = xi_w; nu_w_km2 = nu_w_km1; nu_w_km1 = nu_w;
704 xi_p_km1 = xi_p; nu_p_km1 = nu_p;
714 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
716 void FGAtmosphere::UseExternal(void)
718 temperature=&exTemperature;
719 pressure=&exPressure;
724 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
726 void FGAtmosphere::UseInternal(void)
728 temperature=&intTemperature;
729 pressure=&intPressure;
734 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
736 void FGAtmosphere::bind(void)
738 typedef double (FGAtmosphere::*PMF)(int) const;
739 typedef double (FGAtmosphere::*PMFv)(void) const;
740 typedef int (FGAtmosphere::*PMFt)(void) const;
741 typedef void (FGAtmosphere::*PMFd)(int,double);
742 typedef void (FGAtmosphere::*PMFi)(int);
743 PropertyManager->Tie("atmosphere/T-R", this, (PMFv)&FGAtmosphere::GetTemperature);
744 PropertyManager->Tie("atmosphere/rho-slugs_ft3", this, (PMFv)&FGAtmosphere::GetDensity);
745 PropertyManager->Tie("atmosphere/P-psf", this, (PMFv)&FGAtmosphere::GetPressure);
746 PropertyManager->Tie("atmosphere/a-fps", this, &FGAtmosphere::GetSoundSpeed);
747 PropertyManager->Tie("atmosphere/T-sl-R", this, &FGAtmosphere::GetTemperatureSL);
748 PropertyManager->Tie("atmosphere/rho-sl-slugs_ft3", this, &FGAtmosphere::GetDensitySL);
749 PropertyManager->Tie("atmosphere/P-sl-psf", this, &FGAtmosphere::GetPressureSL);
750 PropertyManager->Tie("atmosphere/a-sl-fps", this, &FGAtmosphere::GetSoundSpeedSL);
751 PropertyManager->Tie("atmosphere/theta", this, &FGAtmosphere::GetTemperatureRatio);
752 PropertyManager->Tie("atmosphere/sigma", this, &FGAtmosphere::GetDensityRatio);
753 PropertyManager->Tie("atmosphere/delta", this, &FGAtmosphere::GetPressureRatio);
754 PropertyManager->Tie("atmosphere/a-ratio", this, &FGAtmosphere::GetSoundSpeedRatio);
755 PropertyManager->Tie("atmosphere/psiw-rad", this, &FGAtmosphere::GetWindPsi, &FGAtmosphere::SetWindPsi);
756 PropertyManager->Tie("atmosphere/delta-T", this, &FGAtmosphere::GetDeltaT, &FGAtmosphere::SetDeltaT);
757 PropertyManager->Tie("atmosphere/T-sl-dev-F", this, &FGAtmosphere::GetSLTempDev, &FGAtmosphere::SetSLTempDev);
758 PropertyManager->Tie("atmosphere/density-altitude", this, &FGAtmosphere::GetDensityAltitude);
760 PropertyManager->Tie("atmosphere/wind-north-fps", this, eNorth, (PMF)&FGAtmosphere::GetWindNED,
761 (PMFd)&FGAtmosphere::SetWindNED);
762 PropertyManager->Tie("atmosphere/wind-east-fps", this, eEast, (PMF)&FGAtmosphere::GetWindNED,
763 (PMFd)&FGAtmosphere::SetWindNED);
764 PropertyManager->Tie("atmosphere/wind-down-fps", this, eDown, (PMF)&FGAtmosphere::GetWindNED,
765 (PMFd)&FGAtmosphere::SetWindNED);
766 PropertyManager->Tie("atmosphere/wind-mag-fps", this, &FGAtmosphere::GetWindspeed,
767 &FGAtmosphere::SetWindspeed);
768 PropertyManager->Tie("atmosphere/total-wind-north-fps", this, eNorth, (PMF)&FGAtmosphere::GetTotalWindNED);
769 PropertyManager->Tie("atmosphere/total-wind-east-fps", this, eEast, (PMF)&FGAtmosphere::GetTotalWindNED);
770 PropertyManager->Tie("atmosphere/total-wind-down-fps", this, eDown, (PMF)&FGAtmosphere::GetTotalWindNED);
772 PropertyManager->Tie("atmosphere/gust-north-fps", this, eNorth, (PMF)&FGAtmosphere::GetGustNED,
773 (PMFd)&FGAtmosphere::SetGustNED);
774 PropertyManager->Tie("atmosphere/gust-east-fps", this, eEast, (PMF)&FGAtmosphere::GetGustNED,
775 (PMFd)&FGAtmosphere::SetGustNED);
776 PropertyManager->Tie("atmosphere/gust-down-fps", this, eDown, (PMF)&FGAtmosphere::GetGustNED,
777 (PMFd)&FGAtmosphere::SetGustNED);
779 PropertyManager->Tie("atmosphere/turb-north-fps", this, eNorth, (PMF)&FGAtmosphere::GetTurbNED,
780 (PMFd)&FGAtmosphere::SetTurbNED);
781 PropertyManager->Tie("atmosphere/turb-east-fps", this, eEast, (PMF)&FGAtmosphere::GetTurbNED,
782 (PMFd)&FGAtmosphere::SetTurbNED);
783 PropertyManager->Tie("atmosphere/turb-down-fps", this, eDown, (PMF)&FGAtmosphere::GetTurbNED,
784 (PMFd)&FGAtmosphere::SetTurbNED);
786 PropertyManager->Tie("atmosphere/p-turb-rad_sec", this,1, (PMF)&FGAtmosphere::GetTurbPQR);
787 PropertyManager->Tie("atmosphere/q-turb-rad_sec", this,2, (PMF)&FGAtmosphere::GetTurbPQR);
788 PropertyManager->Tie("atmosphere/r-turb-rad_sec", this,3, (PMF)&FGAtmosphere::GetTurbPQR);
789 PropertyManager->Tie("atmosphere/turb-type", this, (PMFt)&FGAtmosphere::GetTurbType, (PMFi)&FGAtmosphere::SetTurbType);
790 PropertyManager->Tie("atmosphere/turb-rate", this, &FGAtmosphere::GetTurbRate, &FGAtmosphere::SetTurbRate);
791 PropertyManager->Tie("atmosphere/turb-gain", this, &FGAtmosphere::GetTurbGain, &FGAtmosphere::SetTurbGain);
792 PropertyManager->Tie("atmosphere/turb-rhythmicity", this, &FGAtmosphere::GetRhythmicity,
793 &FGAtmosphere::SetRhythmicity);
795 PropertyManager->Tie("atmosphere/turbulence/milspec/windspeed_at_20ft_AGL-fps",
796 this, &FGAtmosphere::GetWindspeed20ft,
797 &FGAtmosphere::SetWindspeed20ft);
798 PropertyManager->Tie("atmosphere/turbulence/milspec/severity",
799 this, &FGAtmosphere::GetProbabilityOfExceedence,
800 &FGAtmosphere::SetProbabilityOfExceedence);
804 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
805 // The bitmasked value choices are as follows:
806 // unset: In this case (the default) JSBSim would only print
807 // out the normally expected messages, essentially echoing
808 // the config files as they are read. If the environment
809 // variable is not set, debug_lvl is set to 1 internally
810 // 0: This requests JSBSim not to output any messages
812 // 1: This value explicity requests the normal JSBSim
814 // 2: This value asks for a message to be printed out when
815 // a class is instantiated
816 // 4: When this value is set, a message is displayed when a
817 // FGModel object executes its Run() method
818 // 8: When this value is set, various runtime state variables
819 // are printed out periodically
820 // 16: When set various parameters are sanity checked and
821 // a message is printed out when they go out of bounds
823 void FGAtmosphere::Debug(int from)
825 if (debug_lvl <= 0) return;
827 if (debug_lvl & 1) { // Standard console startup message output
828 if (from == 0) { // Constructor
831 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
832 if (from == 0) cout << "Instantiated: FGAtmosphere" << endl;
833 if (from == 1) cout << "Destroyed: FGAtmosphere" << endl;
835 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
837 if (debug_lvl & 8 ) { // Runtime state variables
839 if (debug_lvl & 16) { // Sanity checking
841 if (debug_lvl & 128) { // Turbulence
842 if (first_pass && from == 2) {
844 cout << "vTurbulenceNED(X), vTurbulenceNED(Y), vTurbulenceNED(Z), "
845 << "vTurbulenceGrad(X), vTurbulenceGrad(Y), vTurbulenceGrad(Z), "
846 << "vDirection(X), vDirection(Y), vDirection(Z), "
848 << "vTurbPQR(P), vTurbPQR(Q), vTurbPQR(R), " << endl;
851 cout << vTurbulenceNED << ", " << vTurbulenceGrad << ", " << vDirection << ", " << Magnitude << ", " << vTurbPQR << endl;
854 if (debug_lvl & 64) {
855 if (from == 0) { // Constructor
856 cout << IdSrc << endl;
857 cout << IdHdr << endl;
862 } // namespace JSBSim