Detailed Description

Encapsulates the aerodynamic calculations.

This class owns and contains the list of force/coefficients that define the aerodynamic properties of an aircraft. Here also, such unique phenomena as ground effect, aerodynamic reference point shift, and maximum lift curve tailoff are handled.

Configuration File Format for <aerodynamics> Section:

<aerodynamics>
   <alphalimits unit="{RAD | DEG}">
     <min> {number} </min>
     <max> {number} </max>
   </alphalimits>
   <hysteresis_limits unit="{RAD | DEG}">
     <min> {number} </min>
     <max> {number} </max>
   </hysteresis_limits>
   <aero_ref_pt_shift_x>  
     <function>
       {function contents}
     </function> 
   </aero_ref_pt_shift_x>  
   <function>
     {function contents}
   </function>
   <axis name="{LIFT | DRAG | SIDE | ROLL | PITCH | YAW}">
     {force or moment definitions}
   </axis>
   {additional axis definitions}
</aerodynamics>

Optionally two other coordinate systems may be used.

1) Body coordinate system:

2) Axial-Normal coordinate system:

Systems may NOT be combined, or a load error will occur.

Author: Jon S. Berndt, Tony Peden

Version

Revision: 1.30

Definition at line 113 of file FGAerodynamics.h.

#include <FGAerodynamics.h>

Inheritance diagram for FGAerodynamics:

Collaboration diagram for FGAerodynamics:

Classes
struct	Inputs

Public Member Functions
	FGAerodynamics (FGFDMExec *Executive)
	Constructor. More...

	~FGAerodynamics () override
	Destructor.

std::vector< FGFunction * > *	GetAeroFunctions (void) const

std::string	GetAeroFunctionStrings (const std::string &delimeter) const
	Gets the strings for the current set of aero functions. More...

std::string	GetAeroFunctionValues (const std::string &delimeter) const
	Gets the aero function values. More...

double	GetAlphaCLMax (void) const

double	GetAlphaCLMin (void) const

double	GetAlphaW (void) const

double	GetBI2Vel (void) const

double	GetCI2Vel (void) const

double	GetClSquared (void) const
	Retrieves the square of the lift coefficient.

double	GetForces (int n) const
	Gets the aerodynamic force for an axis. More...

const FGColumnVector3 &	GetForces (void) const
	Gets the total aerodynamic force vector. More...

double	GetForcesInStabilityAxes (int n) const
	Retrieves the aerodynamic forces in the stability axes, given an axis. More...

FGColumnVector3	GetForcesInStabilityAxes (void) const
	Retrieves the aerodynamic forces in the stability axes. More...

double	GetHysteresisParm (void) const

double	GetLoD (void) const
	Retrieves the lift over drag ratio.

double	GetMoments (int n) const
	Gets the aerodynamic moment about the CG for an axis. More...

const FGColumnVector3 &	GetMoments (void) const
	Gets the total aerodynamic moment vector about the CG. More...

double	GetMomentsInStabilityAxes (int n) const
	Gets the aerodynamic moment about the CG for an axis. More...

FGColumnVector3	GetMomentsInStabilityAxes (void) const
	Gets the total aerodynamic moment vector about the CG in the stability axes. More...

double	GetMomentsInWindAxes (int n) const
	Gets the aerodynamic moment about the CG for an axis. More...

FGColumnVector3	GetMomentsInWindAxes (void) const
	Gets the total aerodynamic moment vector about the CG in the wind axes. More...

double	GetMomentsMRC (int n) const
	Gets the aerodynamic moment about the Moment Reference Center for an axis. More...

const FGColumnVector3 &	GetMomentsMRC (void) const
	Gets the total aerodynamic moment vector about the Moment Reference Center. More...

double	GetStallWarn (void) const

double	GetvFw (int axis) const
	Retrieves the aerodynamic forces in the wind axes, given an axis. More...

const FGColumnVector3 &	GetvFw (void) const
	Retrieves the aerodynamic forces in the wind axes. More...

bool	InitModel (void) override

bool	Load (Element *element) override
	Loads the Aerodynamics model. More...

bool	Run (bool Holding) override
	Runs the Aerodynamics model; called by the Executive Can pass in a value indicating if the executive is directing the simulation to Hold. More...

void	SetAlphaCLMax (double tt)

void	SetAlphaCLMin (double tt)

Public Member Functions inherited from FGModel
	FGModel (FGFDMExec *)
	Constructor.

	~FGModel () override
	Destructor.

virtual SGPath	FindFullPathName (const SGPath &path) const

FGFDMExec *	GetExec (void)

const std::string &	GetName (void)

unsigned int	GetRate (void)
	Get the output rate for the model in frames.

bool	InitModel (void) override

void	SetPropertyManager (std::shared_ptr< FGPropertyManager > fgpm)

void	SetRate (unsigned int tt)
	Set the ouput rate for the model in frames.

Public Member Functions inherited from FGModelFunctions
std::string	GetFunctionStrings (const std::string &delimeter) const
	Gets the strings for the current set of functions. More...

std::string	GetFunctionValues (const std::string &delimeter) const
	Gets the function values. More...

std::shared_ptr< FGFunction >	GetPreFunction (const std::string &name)
	Get one of the "pre" function. More...

bool	Load (Element el, FGFDMExec fdmex, std::string prefix="")

void	PostLoad (Element el, FGFDMExec fdmex, std::string prefix="")

void	PreLoad (Element el, FGFDMExec fdmex, std::string prefix="")

void	RunPostFunctions (void)

void	RunPreFunctions (void)

Public Member Functions inherited from FGJSBBase
	FGJSBBase ()
	Constructor for FGJSBBase.

virtual	~FGJSBBase ()
	Destructor for FGJSBBase.

void	disableHighLighting (void)
	Disables highlighting in the console output.

Public Attributes
struct JSBSim::FGAerodynamics::Inputs	in

Additional Inherited Members
Public Types inherited from FGJSBBase
enum	{ eL = 1 , eM , eN }
	Moments L, M, N.

enum	{ eP = 1 , eQ , eR }
	Rates P, Q, R.

enum	{ eU = 1 , eV , eW }
	Velocities U, V, W.

enum	{ eX = 1 , eY , eZ }
	Positions X, Y, Z.

enum	{ ePhi = 1 , eTht , ePsi }
	Euler angles Phi, Theta, Psi.

enum	{ eDrag = 1 , eSide , eLift }
	Stability axis forces, Drag, Side force, Lift.

enum	{ eRoll = 1 , ePitch , eYaw }
	Local frame orientation Roll, Pitch, Yaw.

enum	{ eNorth = 1 , eEast , eDown }
	Local frame position North, East, Down.

enum	{ eLat = 1 , eLong , eRad }
	Locations Radius, Latitude, Longitude.

enum	{ inNone = 0 , inDegrees , inRadians , inMeters , inFeet }
	Conversion specifiers.

Static Public Member Functions inherited from FGJSBBase
static const std::string &	GetVersion (void)
	Returns the version number of JSBSim. More...

static constexpr double	KelvinToFahrenheit (double kelvin)
	Converts from degrees Kelvin to degrees Fahrenheit. More...

static constexpr double	CelsiusToRankine (double celsius)
	Converts from degrees Celsius to degrees Rankine. More...

static constexpr double	RankineToCelsius (double rankine)
	Converts from degrees Rankine to degrees Celsius. More...

static constexpr double	KelvinToRankine (double kelvin)
	Converts from degrees Kelvin to degrees Rankine. More...

static constexpr double	RankineToKelvin (double rankine)
	Converts from degrees Rankine to degrees Kelvin. More...

static constexpr double	FahrenheitToCelsius (double fahrenheit)
	Converts from degrees Fahrenheit to degrees Celsius. More...

static constexpr double	CelsiusToFahrenheit (double celsius)
	Converts from degrees Celsius to degrees Fahrenheit. More...

static constexpr double	CelsiusToKelvin (double celsius)
	Converts from degrees Celsius to degrees Kelvin. More...

static constexpr double	KelvinToCelsius (double kelvin)
	Converts from degrees Kelvin to degrees Celsius. More...

static constexpr double	FeetToMeters (double measure)
	Converts from feet to meters. More...

static bool	EqualToRoundoff (double a, double b)
	Finite precision comparison. More...

static bool	EqualToRoundoff (float a, float b)
	Finite precision comparison. More...

static bool	EqualToRoundoff (float a, double b)
	Finite precision comparison. More...

static bool	EqualToRoundoff (double a, float b)
	Finite precision comparison. More...

static constexpr double	Constrain (double min, double value, double max)
	Constrain a value between a minimum and a maximum value.

static constexpr double	sign (double num)

Static Public Attributes inherited from FGJSBBase
static char	highint [5] = {27, '[', '1', 'm', '\0' }
	highlights text

static char	halfint [5] = {27, '[', '2', 'm', '\0' }
	low intensity text

static char	normint [6] = {27, '[', '2', '2', 'm', '\0' }
	normal intensity text

static char	reset [5] = {27, '[', '0', 'm', '\0' }
	resets text properties

static char	underon [5] = {27, '[', '4', 'm', '\0' }
	underlines text

static char	underoff [6] = {27, '[', '2', '4', 'm', '\0' }
	underline off

static char	fgblue [6] = {27, '[', '3', '4', 'm', '\0' }
	blue text

static char	fgcyan [6] = {27, '[', '3', '6', 'm', '\0' }
	cyan text

static char	fgred [6] = {27, '[', '3', '1', 'm', '\0' }
	red text

static char	fggreen [6] = {27, '[', '3', '2', 'm', '\0' }
	green text

static char	fgdef [6] = {27, '[', '3', '9', 'm', '\0' }
	default text

static short	debug_lvl = 1

Protected Member Functions inherited from FGModel
bool	Upload (Element *el, bool preLoad)
	Uploads this model in memory. More...

Static Protected Member Functions inherited from FGJSBBase
static std::string	CreateIndexedPropertyName (const std::string &Property, int index)

Protected Attributes inherited from FGModel
unsigned int	exe_ctr

FGFDMExec *	FDMExec

std::string	Name

std::shared_ptr< FGPropertyManager >	PropertyManager

unsigned int	rate

Protected Attributes inherited from FGModelFunctions
FGPropertyReader	LocalProperties

std::vector< std::shared_ptr< FGFunction > >	PostFunctions

std::vector< std::shared_ptr< FGFunction > >	PreFunctions

Static Protected Attributes inherited from FGJSBBase
static constexpr double	radtodeg = 180. / M_PI

static constexpr double	degtorad = M_PI / 180.

static constexpr double	hptoftlbssec = 550.0

static constexpr double	psftoinhg = 0.014138

static constexpr double	psftopa = 47.88

static constexpr double	fttom = 0.3048

static constexpr double	ktstofps = 1852./(3600*fttom)

static constexpr double	fpstokts = 1.0 / ktstofps

static constexpr double	inchtoft = 1.0/12.0

static constexpr double	m3toft3 = 1.0/(fttomfttomfttom)

static constexpr double	in3tom3 = inchtoftinchtoftinchtoft/m3toft3

static constexpr double	inhgtopa = 3386.38

static constexpr double	slugtolb = 32.174049
	Note that definition of lbtoslug by the inverse of slugtolb and not to a different constant you can also get from some tables will make lbtoslug*slugtolb == 1 up to the magnitude of roundoff. More...

static constexpr double	lbtoslug = 1.0/slugtolb

static constexpr double	kgtolb = 2.20462

static constexpr double	kgtoslug = 0.06852168

static const std::string	needed_cfg_version = "2.0"

static const std::string	JSBSim_version = JSBSIM_VERSION " " __DATE__ " " __TIME__

Constructor & Destructor Documentation

◆ FGAerodynamics()

FGAerodynamics ( FGFDMExec * Executive )

Constructor.

Parameters

Executive a pointer to the parent executive object

Definition at line 51 of file FGAerodynamics.cpp.

                                                  : FGModel(FDMExec)
 {
   Name = "FGAerodynamics";
  
   AxisIdx["DRAG"]   = 0;
   AxisIdx["SIDE"]   = 1;
   AxisIdx["LIFT"]   = 2;
   AxisIdx["ROLL"]   = 3;
   AxisIdx["PITCH"]  = 4;
   AxisIdx["YAW"]    = 5;
  
   AxisIdx["AXIAL"]  = 0;
   AxisIdx["NORMAL"] = 2;
  
   AxisIdx["X"] = 0;
   AxisIdx["Y"] = 1;
   AxisIdx["Z"] = 2;
  
   forceAxisType = atNone;
   momentAxisType = atNone;
  
   AeroFunctions = new AeroFunctionArray[6];
   AeroFunctionsAtCG = new AeroFunctionArray[6];
  
   impending_stall = stall_hyst = 0.0;
   alphaclmin = alphaclmax = 0.0;
   alphaclmin0 = alphaclmax0 = 0.0;
   alphahystmin = alphahystmax = 0.0;
   clsq = lod = 0.0;
   alphaw = 0.0;
   bi2vel = ci2vel = 0.0;
   AeroRPShift = 0;
   vDeltaRP.InitMatrix();
  
   bind();
  
   Debug(0);
 }

Member Function Documentation

◆ GetAeroFunctionStrings()

string GetAeroFunctionStrings ( const std::string & delimeter ) const

Gets the strings for the current set of aero functions.

Parameters

delimeter either a tab or comma string depending on output type

Returns: a string containing the descriptive names for all aero functions

Definition at line 544 of file FGAerodynamics.cpp.

 {
   string AeroFunctionStrings = "";
   bool firstime = true;
   unsigned int axis, sd;
  
   for (axis = 0; axis < 6; axis++) {
     for (sd = 0; sd < AeroFunctions[axis].size(); sd++) {
       if (firstime) {
         firstime = false;
       } else {
         AeroFunctionStrings += delimeter;
       }
       AeroFunctionStrings += AeroFunctions[axis][sd]->GetName();
     }
   }
  
   string FunctionStrings = FGModelFunctions::GetFunctionStrings(delimeter);
  
   if (!FunctionStrings.empty()) {
     if (!AeroFunctionStrings.empty()) {
       AeroFunctionStrings += delimeter + FunctionStrings;
     } else {
       AeroFunctionStrings = FunctionStrings;
     }
   }
  
   return AeroFunctionStrings;
 }

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◆ GetAeroFunctionValues()

string GetAeroFunctionValues ( const std::string & delimeter ) const

Gets the aero function values.

Parameters

delimeter either a tab or comma string depending on output type

Returns: a string containing the numeric values for the current set of aero functions

Definition at line 576 of file FGAerodynamics.cpp.

 {
   ostringstream buf;
  
   for (unsigned int axis = 0; axis < 6; axis++) {
     for (unsigned int sd = 0; sd < AeroFunctions[axis].size(); sd++) {
       if (buf.tellp() > 0) buf << delimeter;
       buf << AeroFunctions[axis][sd]->GetValue();
     }
   }
  
   string FunctionValues = FGModelFunctions::GetFunctionValues(delimeter);
  
   if (!FunctionValues.empty()) {
     if (!buf.str().empty()) {
       buf << delimeter << FunctionValues;
     } else {
       buf << FunctionValues;
     }
   }
  
   return buf.str();
 }

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◆ GetForces() [1/2]

double GetForces ( int n ) const

inline

Gets the aerodynamic force for an axis.

Parameters

n	Axis index. This could be 0, 1, or 2, or one of the axis enums: eX, eY, eZ.

Returns: the force acting on an axis

Definition at line 149 of file FGAerodynamics.h.

149 {return vForces(n);}

◆ GetForces() [2/2]

const FGColumnVector3& GetForces ( void ) const

inline

Gets the total aerodynamic force vector.

Returns: a force vector reference.

Definition at line 143 of file FGAerodynamics.h.

143 {return vForces;}

◆ GetForcesInStabilityAxes() [1/2]

double GetForcesInStabilityAxes ( int n ) const

inline

Retrieves the aerodynamic forces in the stability axes, given an axis.

Parameters

axis	the axis to return the force for (eX, eY, eZ).

Returns: a reference to a column vector containing the requested stability axis force.

Definition at line 187 of file FGAerodynamics.h.

187 { return GetForcesInStabilityAxes()(n); }

JSBSim::FGAerodynamics::GetForcesInStabilityAxes

FGColumnVector3 GetForcesInStabilityAxes(void) const

Retrieves the aerodynamic forces in the stability axes.

Definition: FGAerodynamics.cpp:320

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◆ GetForcesInStabilityAxes() [2/2]

FGColumnVector3 GetForcesInStabilityAxes ( void ) const

Retrieves the aerodynamic forces in the stability axes.

Returns: a reference to a column vector containing the stability axis forces.

Definition at line 320 of file FGAerodynamics.cpp.

 {
   FGColumnVector3 vFs = Tb2s*vForces;
   // Need sign flips since drag is positive and lift is positive in stability axes
   vFs(eDrag) *= -1; vFs(eLift) *= -1;
  
   return vFs;
 }

◆ GetMoments() [1/2]

double GetMoments ( int n ) const

inline

Gets the aerodynamic moment about the CG for an axis.

Returns: the moment about a single axis (as described also in the similar call to GetForces(int n).

Definition at line 158 of file FGAerodynamics.h.

158 {return vMoments(n);}

◆ GetMoments() [2/2]

const FGColumnVector3& GetMoments ( void ) const

inline

Gets the total aerodynamic moment vector about the CG.

Returns: a moment vector reference.

Definition at line 153 of file FGAerodynamics.h.

153 {return vMoments;}

◆ GetMomentsInStabilityAxes() [1/2]

double GetMomentsInStabilityAxes ( int n ) const

inline

Gets the aerodynamic moment about the CG for an axis.

Returns: the moment about a single axis (as described also in the similar call to GetForces(int n).

Definition at line 196 of file FGAerodynamics.h.

196 { return GetMomentsInStabilityAxes()(n); }

JSBSim::FGAerodynamics::GetMomentsInStabilityAxes

FGColumnVector3 GetMomentsInStabilityAxes(void) const

Gets the total aerodynamic moment vector about the CG in the stability axes.

Definition: FGAerodynamics.h:191

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◆ GetMomentsInStabilityAxes() [2/2]

FGColumnVector3 GetMomentsInStabilityAxes ( void ) const

inline

Gets the total aerodynamic moment vector about the CG in the stability axes.

Returns: a moment vector reference.

Definition at line 191 of file FGAerodynamics.h.

191 { return Tb2s*vMoments; }

◆ GetMomentsInWindAxes() [1/2]

double GetMomentsInWindAxes ( int n ) const

inline

Gets the aerodynamic moment about the CG for an axis.

Returns: the moment about a single axis (as described also in the similar call to GetForces(int n).

Definition at line 205 of file FGAerodynamics.h.

205 { return GetMomentsInWindAxes()(n); }

JSBSim::FGAerodynamics::GetMomentsInWindAxes

FGColumnVector3 GetMomentsInWindAxes(void) const

Gets the total aerodynamic moment vector about the CG in the wind axes.

Definition: FGAerodynamics.h:200

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◆ GetMomentsInWindAxes() [2/2]

FGColumnVector3 GetMomentsInWindAxes ( void ) const

inline

Gets the total aerodynamic moment vector about the CG in the wind axes.

Returns: a moment vector reference.

Definition at line 200 of file FGAerodynamics.h.

200 { return in.Tb2w*vMoments; }

◆ GetMomentsMRC() [1/2]

double GetMomentsMRC ( int n ) const

inline

Gets the aerodynamic moment about the Moment Reference Center for an axis.

Returns: the moment about a single axis (as described also in the similar call to GetForces(int n).

Definition at line 167 of file FGAerodynamics.h.

167 {return vMomentsMRC(n);}

◆ GetMomentsMRC() [2/2]

const FGColumnVector3& GetMomentsMRC ( void ) const

inline

Gets the total aerodynamic moment vector about the Moment Reference Center.

Returns: a moment vector reference.

Definition at line 162 of file FGAerodynamics.h.

162 {return vMomentsMRC;}

◆ GetvFw() [1/2]

double GetvFw ( int axis ) const

inline

Retrieves the aerodynamic forces in the wind axes, given an axis.

Parameters

axis	the axis to return the force for (eX, eY, eZ).

Returns: a reference to a column vector containing the requested wind axis force.

Definition at line 177 of file FGAerodynamics.h.

177 { return vFw(axis); }

◆ GetvFw() [2/2]

const FGColumnVector3& GetvFw ( void ) const

inline

Retrieves the aerodynamic forces in the wind axes.

Returns: a reference to a column vector containing the wind axis forces.

Definition at line 171 of file FGAerodynamics.h.

171 { return vFw; }

◆ Load()

bool Load ( Element * element )

overridevirtual

Loads the Aerodynamics model.

The Load function for this class expects the XML parser to have found the aerodynamics keyword in the configuration file.

Parameters

element pointer to the current XML element for aerodynamics parameters.

Returns: true if successful

Reimplemented from FGModel.

Definition at line 331 of file FGAerodynamics.cpp.

 {
   string axis;
   string scratch_unit="";
   Element *temp_element, *axis_element, *function_element;
  
   Name = "Aerodynamics Model: " + document->GetAttributeValue("name");
  
   // Perform base class Pre-Load
   if (!FGModel::Upload(document, true))
     return false;
  
   DetermineAxisSystem(document); // Determine if Lift/Side/Drag, etc. is used.
  
   Debug(2);
  
   if ((temp_element = document->FindElement("alphalimits"))) {
     scratch_unit = temp_element->GetAttributeValue("unit");
     if (scratch_unit.empty()) scratch_unit = "RAD";
     alphaclmin0 = temp_element->FindElementValueAsNumberConvertFromTo("min", scratch_unit, "RAD");
     alphaclmax0 = temp_element->FindElementValueAsNumberConvertFromTo("max", scratch_unit, "RAD");
     alphaclmin = alphaclmin0;
     alphaclmax = alphaclmax0;
   }
  
   if ((temp_element = document->FindElement("hysteresis_limits"))) {
     scratch_unit = temp_element->GetAttributeValue("unit");
     if (scratch_unit.empty()) scratch_unit = "RAD";
     alphahystmin = temp_element->FindElementValueAsNumberConvertFromTo("min", scratch_unit, "RAD");
     alphahystmax = temp_element->FindElementValueAsNumberConvertFromTo("max", scratch_unit, "RAD");
   }
  
   if ((temp_element = document->FindElement("aero_ref_pt_shift_x"))) {
     function_element = temp_element->FindElement("function");
     AeroRPShift = new FGFunction(FDMExec, function_element);
   }
  
   axis_element = document->FindElement("axis");
   while (axis_element) {
     AeroFunctionArray ca;
     AeroFunctionArray ca_atCG;
     axis = axis_element->GetAttributeValue("name");
     function_element = axis_element->FindElement("function");
     while (function_element) {
       string current_func_name = function_element->GetAttributeValue("name");
       bool apply_at_cg = false;
       if (function_element->HasAttribute("apply_at_cg")) {
         if (function_element->GetAttributeValue("apply_at_cg") == "true") apply_at_cg = true;
       }
       if (!apply_at_cg) {
       try {
         ca.push_back( new FGFunction(FDMExec, function_element) );
       } catch (const string& str) {
         cerr << endl << axis_element->ReadFrom()
              << endl << fgred << "Error loading aerodynamic function in "
              << current_func_name << ":" << str << " Aborting." << reset << endl;
         return false;
       }
       } else {
         try {
           ca_atCG.push_back( new FGFunction(FDMExec, function_element) );
         } catch (const string& str) {
           cerr << endl << axis_element->ReadFrom()
                << endl << fgred << "Error loading aerodynamic function in "
                << current_func_name << ":" << str << " Aborting." << reset << endl;
           return false;
         }
       }
       function_element = axis_element->FindNextElement("function");
     }
     AeroFunctions[AxisIdx[axis]] = ca;
     AeroFunctionsAtCG[AxisIdx[axis]] = ca_atCG;
     axis_element = document->FindNextElement("axis");
   }
  
   PostLoad(document, FDMExec); // Perform base class Post-Load
  
   return true;
 }

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◆ Run()

bool Run ( bool Holding )

overridevirtual

Runs the Aerodynamics model; called by the Executive Can pass in a value indicating if the executive is directing the simulation to Hold.

Parameters

Holding if true, the executive has been directed to hold the sim from advancing time. Some models may ignore this flag, such as the Input model, which may need to be active to listen on a socket for the "Resume" command to be given.

Returns: false if no error

Reimplemented from FGModel.

Definition at line 132 of file FGAerodynamics.cpp.

 {
  
   if (FGModel::Run(Holding)) return true;
   if (Holding) return false; // if paused don't execute
  
   unsigned int axis_ctr;
   const double twovel=2*in.Vt;
  
   // The lift coefficient squared (property aero/cl-squared) is computed before
   // the aero functions are called to make sure that they use the same value for
   // qbar.
   if ( in.Qbar > 1.0) {
     // Skip the computation if qbar is close to zero to avoid huge values for
     // aero/cl-squared when a non-null lift coincides with a very small aero
     // velocity (i.e. when qbar is close to zero).
     clsq = vFw(eLift) / (in.Wingarea*in.Qbar);
     clsq *= clsq;
   }
  
   RunPreFunctions();
  
   // calculate some oft-used quantities for speed
  
   if (twovel != 0) {
     bi2vel = in.Wingspan / twovel;
     ci2vel = in.Wingchord / twovel;
   }
   alphaw = in.Alpha + in.Wingincidence;
   qbar_area = in.Wingarea * in.Qbar;
  
   if (alphaclmax != 0) {
     if (in.Alpha > 0.85*alphaclmax) {
       impending_stall = 10*(in.Alpha/alphaclmax - 0.85);
     } else {
       impending_stall = 0;
     }
   }
  
   if (alphahystmax != 0.0 && alphahystmin != 0.0) {
     if (in.Alpha > alphahystmax) {
       stall_hyst = 1;
     } else if (in.Alpha < alphahystmin) {
       stall_hyst = 0;
     }
   }
  
   vFw.InitMatrix();
   vFnative.InitMatrix();
   vFnativeAtCG.InitMatrix();
  
   BuildStabilityTransformMatrices();
  
   for (axis_ctr = 0; axis_ctr < 3; ++axis_ctr) {
     AeroFunctionArray::iterator f;
  
     AeroFunctionArray* array = &AeroFunctions[axis_ctr];
     for (f=array->begin(); f != array->end(); ++f) {
       // Tell the Functions to cache values, so when the function values are
       // being requested for output, the functions do not get calculated again
       // in a context that might have changed, but instead use the values that
       // have already been calculated for this frame.
       (*f)->cacheValue(true);
       vFnative(axis_ctr+1) += (*f)->GetValue();
     }
  
     array = &AeroFunctionsAtCG[axis_ctr];
     for (f=array->begin(); f != array->end(); ++f) {
       (*f)->cacheValue(true); // Same as above
       vFnativeAtCG(axis_ctr+1) += (*f)->GetValue();
     }
   }
  
   switch (forceAxisType) {
   case atBodyXYZ:       // Forces already in body axes; no manipulation needed
     vForces = vFnative;
     vForcesAtCG = vFnativeAtCG;
     break;
   case atWind:      // Copy forces into wind axes
     vFnative(eDrag)*=-1; vFnative(eLift)*=-1;
     vForces = in.Tw2b*vFnative;
  
     vFnativeAtCG(eDrag)*=-1; vFnativeAtCG(eLift)*=-1;
     vForcesAtCG = in.Tw2b*vFnativeAtCG;
     break;
   case atBodyAxialNormal:   // Convert native forces into Axial|Normal|Side system
     vFnative(eX)*=-1; vFnative(eZ)*=-1;
     vForces = vFnative;
  
     vFnativeAtCG(eX)*=-1; vFnativeAtCG(eZ)*=-1;
     vForcesAtCG = vFnativeAtCG;
     break;
   case atStability:   // Convert from stability axes to both body and wind axes
     vFnative(eDrag) *= -1; vFnative(eLift) *= -1;
     vForces = Ts2b*vFnative;
  
     vFnativeAtCG(eDrag) *= -1; vFnativeAtCG(eLift) *= -1;
     vForcesAtCG = Ts2b*vFnativeAtCG;
     break;
   default:
     {
       stringstream s;
       s << "  A proper axis type has NOT been selected. Check "
         << "your aerodynamics definition.";
       cerr << endl << s.str() << endl;
       throw BaseException(s.str());
     }
   }
   // Calculate aerodynamic reference point shift, if any. The shift takes place
   // in the structual axis. That is, if the shift is positive, it is towards the
   // back (tail) of the vehicle. The AeroRPShift function should be
   // non-dimensionalized by the wing chord. The calculated vDeltaRP will be in
   // feet.
   if (AeroRPShift) vDeltaRP(eX) = AeroRPShift->GetValue()*in.Wingchord;
  
   vDXYZcg(eX) = in.RPBody(eX) - vDeltaRP(eX); // vDeltaRP is given in the
   vDXYZcg(eY) = in.RPBody(eY) + vDeltaRP(eY); // structural frame.
   vDXYZcg(eZ) = in.RPBody(eZ) - vDeltaRP(eZ);
  
   vMomentsMRC.InitMatrix();
  
   for (axis_ctr = 0; axis_ctr < 3; axis_ctr++) {
     AeroFunctionArray* array = &AeroFunctions[axis_ctr+3];
     for (AeroFunctionArray::iterator f=array->begin(); f != array->end(); ++f) {
       // Tell the Functions to cache values, so when the function values are
       // being requested for output, the functions do not get calculated again
       // in a context that might have changed, but instead use the values that
       // have already been calculated for this frame.
       (*f)->cacheValue(true);
       vMomentsMRC(axis_ctr+1) += (*f)->GetValue();
     }
   }
  
   // Transform moments to bodyXYZ if the moments are specified in stability or
   // wind axes
   vMomentsMRCBodyXYZ.InitMatrix();
   switch (momentAxisType) {
   case atBodyXYZ:
     vMomentsMRCBodyXYZ = vMomentsMRC;
     break;
   case atStability:
     vMomentsMRCBodyXYZ = Ts2b*vMomentsMRC;
     break;
   case atWind:
     vMomentsMRCBodyXYZ = in.Tw2b*vMomentsMRC;
     break;
   default:
     {
       stringstream s;
       s << "  A proper axis type has NOT been selected. Check "
         << "your aerodynamics definition.";
       cerr << endl << s.str() << endl;
       throw BaseException(s.str());
     }
   }
  
   vMoments = vMomentsMRCBodyXYZ + vDXYZcg*vForces; // M = r X F
  
   // Now add the "at CG" values to base forces - after the moments have been
   // transferred.
   vForces += vForcesAtCG;
  
   // Note that we still need to convert to wind axes here, because it is used in
   // the L/D calculation, and we still may want to look at Lift and Drag.
   //
   // JSB 4/27/12 - After use, convert wind axes to produce normal lift and drag
   // values - not negative ones!
   //
   // As a clarification, JSBSim assumes that drag and lift values are defined in
   // wind axes - BUT with a 180 rotation about the Y axis. That is, lift and
   // drag will be positive up and aft, respectively, so that they are reported
   // as positive numbers. However, the wind axes themselves assume that the X
   // and Z forces are positive forward and down. Same applies to the stability
   // axes.
   vFw = in.Tb2w * vForces;
   vFw(eDrag) *= -1; vFw(eLift) *= -1;
  
   // Calculate Lift over Drag
   if ( fabs(vFw(eDrag)) > 0.0)
     lod = fabs( vFw(eLift) / vFw(eDrag));
  
   RunPostFunctions();
  
   return false;
 }

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The documentation for this class was generated from the following files:

Detailed Description

Configuration File Format for <aerodynamics> Section:

Classes

Public Member Functions

Public Attributes

Additional Inherited Members

Constructor & Destructor Documentation

◆ FGAerodynamics()

Member Function Documentation

◆ GetAeroFunctionStrings()

◆ GetAeroFunctionValues()

◆ GetForces() [1/2]

◆ GetForces() [2/2]

◆ GetForcesInStabilityAxes() [1/2]

◆ GetForcesInStabilityAxes() [2/2]

◆ GetMoments() [1/2]

◆ GetMoments() [2/2]

◆ GetMomentsInStabilityAxes() [1/2]

◆ GetMomentsInStabilityAxes() [2/2]

◆ GetMomentsInWindAxes() [1/2]

◆ GetMomentsInWindAxes() [2/2]

◆ GetMomentsMRC() [1/2]

◆ GetMomentsMRC() [2/2]

◆ GetvFw() [1/2]

◆ GetvFw() [2/2]

◆ Load()

◆ Run()