Detailed Description

Encapsulates the Buoyant forces calculations.

This class owns and contains the list of force/coefficients that define the Buoyant properties of an air vehicle.

Here's an example of a gas cell specification:

<buoyant_forces>
 
  <!-- Interface properties -->
  <property>ballonets/in-flow-ft3ps[0]</property>
 
  <gas_cell type="HYDROGEN">
    <location unit="M">
      <x> 18.8 </x>
      <y> 0.0 </y>
      <z> 0.0 </z>
    </location>
    <x_radius unit="M"> 22.86 </x_radius>
    <y_radius unit="M">  4.55 </y_radius>
    <z_radius unit="M">  4.55 </z_radius>
    <max_overpressure unit="PA"> 340.0 </max_overpressure> 
    <valve_coefficient unit="M4*SEC/KG"> 0.015 </valve_coefficient>
  </gas_cell>
  
  ... {other gas cells} ...
  
</buoyant_forces>

See FGGasCell for the full configuration file format for gas cells.

Author: Anders Gidenstam, Jon S. Berndt

Definition at line 98 of file FGBuoyantForces.h.

#include <FGBuoyantForces.h>

Inheritance diagram for FGBuoyantForces:

Collaboration diagram for FGBuoyantForces:

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

	~FGBuoyantForces () override
	Destructor.

std::string	GetBuoyancyStrings (const std::string &delimeter)
	Gets the strings for the current set of gas cells. More...

std::string	GetBuoyancyValues (const std::string &delimeter)
	Gets the coefficient values. More...

double	GetForces (int idx) const
	Gets a component of the total Buoyant force vector. More...

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

double	GetGasMass (void) const
	Gets the total gas mass. More...

const FGMatrix33 &	GetGasMassInertia (void)
	Gets the total moments of inertia for the gas mass in the body frame. More...

const FGColumnVector3 &	GetGasMassMoment (void)
	Gets the total moment from the gas mass. More...

double	GetMoments (int idx) const
	Gets a component of the total Buoyancy moment vector. More...

const FGColumnVector3 &	GetMoments (void) const
	Gets the total Buoyancy moment vector. More...

bool	InitModel (void) override

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

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

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
FGGasCell::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

◆ FGBuoyantForces()

FGBuoyantForces ( FGFDMExec * Executive )

Constructor.

Parameters

Executive a pointer to the parent executive object

Definition at line 51 of file FGBuoyantForces.cpp.

                                                    : FGModel(FDMExec)
 {
   Name = "FGBuoyantForces";
  
   NoneDefined = true;
  
   vTotalForces.InitMatrix();
   vTotalMoments.InitMatrix();
  
   gasCellJ.InitMatrix();
  
   Debug(0);
 }

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Member Function Documentation

◆ GetBuoyancyStrings()

string GetBuoyancyStrings ( const std::string & delimeter )

Gets the strings for the current set of gas cells.

Parameters

delimeter either a tab or comma string depending on output type

Returns: a string containing the descriptive names for all parameters

Definition at line 182 of file FGBuoyantForces.cpp.

 {
   string CoeffStrings = "";
 /*
   bool firstime = true;
   for (sd = 0; sd < variables.size(); sd++) {
     if (firstime) {
       firstime = false;
     } else {
       CoeffStrings += delimeter;
     }
     CoeffStrings += variables[sd]->GetName();
   }
  
   for (axis = 0; axis < 6; axis++) {
     for (sd = 0; sd < AeroFunctions[axis].size(); sd++) {
       if (firstime) {
         firstime = false;
       } else {
         CoeffStrings += delimeter;
       }
       CoeffStrings += AeroFunctions[axis][sd]->GetName();
     }
   }
 */
   return CoeffStrings;
 }

◆ GetBuoyancyValues()

string GetBuoyancyValues ( const std::string & delimeter )

Gets the coefficient 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 parameters

Definition at line 212 of file FGBuoyantForces.cpp.

 {
   string SDValues = "";
 /*
   bool firstime = true;
   for (sd = 0; sd < variables.size(); sd++) {
     if (firstime) {
       firstime = false;
     } else {
       SDValues += delimeter;
     }
     SDValues += variables[sd]->GetValueAsString();
   }
  
   for (unsigned int axis = 0; axis < 6; axis++) {
     for (unsigned int sd = 0; sd < AeroFunctions[axis].size(); sd++) {
       if (firstime) {
         firstime = false;
       } else {
         SDValues += delimeter;
       }
       SDValues += AeroFunctions[axis][sd]->GetValueAsString();
     }
   }
 */
   return SDValues;
 }

◆ GetForces() [1/2]

double GetForces ( int idx ) const

inline

Gets a component of the total Buoyant force vector.

Returns: a component of the force vector in lbs.

Definition at line 132 of file FGBuoyantForces.h.

132 {return vTotalForces(idx);}

◆ GetForces() [2/2]

const FGColumnVector3& GetForces ( void ) const

inline

Gets the total Buoyant force vector.

Returns: a force vector in lbs.

Definition at line 128 of file FGBuoyantForces.h.

128 {return vTotalForces;}

◆ GetGasMass()

double GetGasMass ( void ) const

Gets the total gas mass.

The gas mass is part of the aircraft's inertia.

Returns: mass in slugs.

Definition at line 141 of file FGBuoyantForces.cpp.

 {
   double Gw = 0.0;
  
   for (unsigned int i = 0; i < Cells.size(); i++) {
     Gw += Cells[i]->GetMass();
   }
  
   return Gw;
 }

◆ GetGasMassInertia()

const FGMatrix33 & GetGasMassInertia ( void )

Gets the total moments of inertia for the gas mass in the body frame.

Returns: moments of inertia matrix in the body frame in slug ft².

Definition at line 165 of file FGBuoyantForces.cpp.

 {
   size_t size = Cells.size();
   
   if (size == 0) return gasCellJ;
  
   gasCellJ.InitMatrix();
  
   for (unsigned int i=0; i < size; i++) {
     gasCellJ += Cells[i]->GetInertia();
   }
   
   return gasCellJ;
 }

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◆ GetGasMassMoment()

const FGColumnVector3 & GetGasMassMoment ( void )

Gets the total moment from the gas mass.

Returns: a moment vector in the structural frame in lbs in.

Definition at line 154 of file FGBuoyantForces.cpp.

 {
   vXYZgasCell_arm.InitMatrix();
   for (unsigned int i = 0; i < Cells.size(); i++) {
     vXYZgasCell_arm += Cells[i]->GetMassMoment();
   }
   return vXYZgasCell_arm;
 }

◆ GetMoments() [1/2]

double GetMoments ( int idx ) const

inline

Gets a component of the total Buoyancy moment vector.

Returns: a component of the moment vector in the body frame in lbs ft.

Definition at line 140 of file FGBuoyantForces.h.

140 {return vTotalMoments(idx);}

◆ GetMoments() [2/2]

const FGColumnVector3& GetMoments ( void ) const

inline

Gets the total Buoyancy moment vector.

Returns: a moment vector in the body frame in lbs ft.

Definition at line 136 of file FGBuoyantForces.h.

136 {return vTotalMoments;}

◆ Load()

bool Load ( Element * element )

overridevirtual

Loads the Buoyant forces model.

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

Parameters

element pointer to the current XML element for Buoyant forces parameters.

Returns: true if successful

Reimplemented from FGModel.

Definition at line 113 of file FGBuoyantForces.cpp.

 {
   Element *gas_cell_element;
  
   Debug(2);
  
   // Perform base class Pre-Load
   if (!FGModel::Upload(document, true))
     return false;
  
   gas_cell_element = document->FindElement("gas_cell");
   while (gas_cell_element) {
     NoneDefined = false;
     Cells.push_back(new FGGasCell(FDMExec, gas_cell_element, Cells.size(), in));
     gas_cell_element = document->FindNextElement("gas_cell");
   }
   
   PostLoad(document, FDMExec);
  
   if (!NoneDefined) {
     bind();
   }
  
   return true;
 }

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◆ Run()

bool Run ( bool Holding )

overridevirtual

Runs the Buoyant forces 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 89 of file FGBuoyantForces.cpp.

 {
   if (FGModel::Run(Holding)) return true;
   if (Holding) return false; // if paused don't execute
   if (NoneDefined) return true;
  
   RunPreFunctions();
  
   vTotalForces.InitMatrix();
   vTotalMoments.InitMatrix();
  
   for (unsigned int i=0; i<Cells.size(); i++) {
     Cells[i]->Calculate(FDMExec->GetDeltaT());
     vTotalForces  += Cells[i]->GetBodyForces();
     vTotalMoments += Cells[i]->GetMoments();
   }
  
   RunPostFunctions();
  
   return false;
 }

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

Detailed Description

Public Member Functions

Public Attributes

Additional Inherited Members

Constructor & Destructor Documentation

◆ FGBuoyantForces()

Member Function Documentation

◆ GetBuoyancyStrings()

◆ GetBuoyancyValues()

◆ GetForces() [1/2]

◆ GetForces() [2/2]

◆ GetGasMass()

◆ GetGasMassInertia()

◆ GetGasMassMoment()

◆ GetMoments() [1/2]

◆ GetMoments() [2/2]

◆ Load()

◆ Run()