FGWinds Class Reference

Models atmospheric disturbances: winds, gusts, turbulence, downbursts, etc. More...

#include <FGWinds.h>

Inheritance diagram for FGWinds:

Collaboration diagram for FGWinds:

Classes
struct	Inputs
struct	OneMinusCosineGust
	Stores the information about a single one minus cosine gust instance. More...
struct	OneMinusCosineProfile
struct	UpDownBurst
	Stores information about a specified Up- or Down-burst. More...

Public Types
enum	eGustFrame { gfNone =0, gfBody, gfWind, gfLocal }
enum	tType {   ttNone, ttStandard, ttCulp, ttMilspec,   ttTustin }
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.

Public Member Functions
	FGWinds (FGFDMExec *)
	Constructor.
	~FGWinds ()
	Destructor.
virtual void	EndGustDuration (double dur)
	Specifies the length of time it takes for the gust to return to zero velocity.
virtual double	GetGustNED (int idx) const
	Retrieves a gust component in NED frame.
virtual const FGColumnVector3 &	GetGustNED (void) const
	Retrieves the gust components in NED frame.
virtual int	GetProbabilityOfExceedence () const
virtual double	GetRhythmicity () const
virtual const FGColumnVector3 &	GetTotalWindNED (void) const
	Retrieves the total wind components in NED frame.
virtual double	GetTotalWindNED (int idx) const
	Retrieves a total wind component in NED frame.
virtual double	GetTurbDirection (void) const
virtual double	GetTurbGain () const
virtual double	GetTurbMagnitude (void) const
virtual double	GetTurbNED (int idx) const
	Retrieves a turbulence component in NED frame.
virtual double	GetTurbPQR (int idx) const
virtual const FGColumnVector3 &	GetTurbPQR (void) const
virtual double	GetTurbRate () const
virtual tType	GetTurbType () const
virtual const FGColumnVector3 &	GetWindNED (void) const
	Retrieves the wind components in NED frame.
virtual double	GetWindNED (int idx) const
	Retrieves a wind component in NED frame.
virtual double	GetWindPsi (void) const
	Retrieves the direction that the wind is coming from. More...
virtual double	GetWindspeed (void) const
virtual double	GetWindspeed20ft () const
virtual void	GustFrame (eGustFrame gFrame)
	Specifies the frame that the gust direction vector components are specified in. More...
virtual void	GustMagnitude (double mag)
	Specifies the magnitude of the gust in feet/second.
virtual void	GustXComponent (double x)
	Specifies the X component of velocity in the specified gust frame (ft/sec).
virtual void	GustYComponent (double y)
	Specifies the Y component of velocity in the specified gust frame (ft/sec).
virtual void	GustZComponent (double z)
	Specifies the Z component of velocity in the specified gust frame (ft/sec).
bool	InitModel (void)
void	NumberOfUpDownburstCells (int num)
bool	Run (bool Holding)
	Runs the winds model; called by the Executive Can pass in a value indicating if the executive is directing the simulation to Hold. More...
virtual void	SetGustNED (int idx, double gust)
	Sets a gust component in NED frame.
virtual void	SetGustNED (double gN, double gE, double gD)
	Sets the gust components in NED frame.
virtual void	SetProbabilityOfExceedence (int idx)
	allowable range: 0-7, 3=light, 4=moderate, 6=severe turbulence
virtual void	SetRhythmicity (double r)
virtual void	SetTurbGain (double tg)
virtual void	SetTurbNED (int idx, double turb)
	Sets a turbulence component in NED frame.
virtual void	SetTurbRate (double tr)
virtual void	SetTurbType (tType tt)
	Turbulence models available: ttNone, ttStandard, ttBerndt, ttCulp, ttMilspec, ttTustin.
virtual void	SetWindNED (double wN, double wE, double wD)
	Sets the wind components in NED frame.
virtual void	SetWindNED (int idx, double wind)
	Sets a wind component in NED frame.
virtual void	SetWindNED (const FGColumnVector3 &wind)
	Sets the wind components in NED frame.
virtual void	SetWindPsi (double dir)
	Sets the direction that the wind is coming from. More...
virtual void	SetWindspeed (double speed)
virtual void	SetWindspeed20ft (double ws)
virtual void	StartGust (bool running)
	Initiates the execution of the gust.
virtual void	StartupGustDuration (double dur)
	Specifies the duration of the startup portion of the gust.
virtual void	SteadyGustDuration (double dur)
	Specifies the length of time that the gust is at a steady, full strength.
Public Member Functions inherited from FGModel
	FGModel (FGFDMExec *)
	Constructor.
virtual	~FGModel ()
	Destructor.
virtual SGPath	FindFullPathName (const SGPath &path) const
FGFDMExec *	GetExec (void)
unsigned int	GetRate (void)
	Get the output rate for the model in frames.
void	SetPropertyManager (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...
FGFunction *	GetPreFunction (const std::string &name)
	Get one of the "pre" function. More...
bool	Load (Element *el, FGPropertyManager *PropertyManager, std::string prefix="")
void	PostLoad (Element *el, FGPropertyManager *PropertyManager, std::string prefix="")
void	PreLoad (Element *el, FGPropertyManager *PropertyManager, 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.
std::string	GetVersion (void)
	Returns the version number of JSBSim. More...
void	PutMessage (const Message &msg)
	Places a Message structure on the Message queue. More...
void	PutMessage (const std::string &text)
	Creates a message with the given text and places it on the queue. More...
void	PutMessage (const std::string &text, bool bVal)
	Creates a message with the given text and boolean value and places it on the queue. More...
void	PutMessage (const std::string &text, int iVal)
	Creates a message with the given text and integer value and places it on the queue. More...
void	PutMessage (const std::string &text, double dVal)
	Creates a message with the given text and double value and places it on the queue. More...
int	SomeMessages (void)
	Reads the message on the queue (but does not delete it). More...
void	ProcessMessage (void)
	Reads the message on the queue and removes it from the queue. More...
Message *	ProcessNextMessage (void)
	Reads the next message on the queue and removes it from the queue. More...

Public Attributes
struct JSBSim::FGWinds::Inputs	in
enum JSBSim::FGWinds::tType	turbType
Public Attributes inherited from FGModel
std::string	Name

Additional Inherited Members
Static Public Member Functions inherited from FGJSBBase
static double	CelsiusToFahrenheit (double celsius)
	Converts from degrees Celsius to degrees Fahrenheit. More...
static double	CelsiusToKelvin (double celsius)
	Converts from degrees Celsius to degrees Kelvin. More...
static double	CelsiusToRankine (double celsius)
	Converts from degrees Celsius to degrees Rankine. More...
static double	Constrain (double min, double value, double max)
	Constrain a value between a minimum and a maximum value.
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 double	FahrenheitToCelsius (double fahrenheit)
	Converts from degrees Fahrenheit to degrees Celsius. More...
static double	FeetToMeters (double measure)
	Converts from feet to meters. More...
static double	GaussianRandomNumber (void)
static double	KelvinToCelsius (double kelvin)
	Converts from degrees Kelvin to degrees Celsius. More...
static double	KelvinToFahrenheit (double kelvin)
	Converts from degrees Kelvin to degrees Fahrenheit. More...
static double	KelvinToRankine (double kelvin)
	Converts from degrees Kelvin to degrees Rankine. More...
static double	MachFromVcalibrated (double vcas, double p, double psl, double rhosl)
	Calculate the Mach number from the calibrated airspeed. More...
static double	PitotTotalPressure (double mach, double p)
	Compute the total pressure in front of the Pitot tube. More...
static double	RankineToCelsius (double rankine)
	Converts from degrees Rankine to degrees Celsius. More...
static double	RankineToKelvin (double rankine)
	Converts from degrees Rankine to degrees Kelvin. More...
static double	sign (double num)
static double	VcalibratedFromMach (double mach, double p, double psl, double rhosl)
	Calculate the calibrated airspeed from the Mach number. More...
Static Public Attributes inherited from FGJSBBase
static short	debug_lvl = 1
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
Protected Member Functions inherited from FGModel
virtual bool	Load (Element *el)
	Loads this model. More...
Protected Member Functions inherited from FGJSBBase
void	Debug (int)
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
FGPropertyManager *	PropertyManager
unsigned int	rate
Protected Attributes inherited from FGModelFunctions
FGPropertyReader	LocalProperties
std::vector< FGFunction * >	PostFunctions
std::vector< FGFunction * >	PreFunctions
Static Protected Attributes inherited from FGJSBBase
static const double	degtorad = 0.017453292519943295769236907684886
static const double	fpstokts = 1.0/ktstofps
static const double	fttom = 0.3048
static int	gaussian_random_number_phase = 0
static const double	hptoftlbssec = 550.0
static const double	in3tom3 = 1.638706E-5
static const double	inchtoft = 0.08333333
static const double	inhgtopa = 3386.38
static const std::string	JSBSim_version = "1.0 " __DATE__ " " __TIME__
static const double	kgtolb = 2.20462
static const double	kgtoslug = 0.06852168
static const double	ktstofps = 1.68781
static const double	lbtoslug = 1.0/slugtolb
static Message	localMsg
static const double	m3toft3 = 1.0/(fttom*fttom*fttom)
static double	Mair = 28.9645
static unsigned int	messageId = 0
static std::queue< Message >	Messages
static const std::string	needed_cfg_version = "2.0"
static const double	psftoinhg = 0.014138
static const double	psftopa = 47.88
static const double	radtodeg = 57.295779513082320876798154814105
static double	Reng = 1716.56
static double	Rstar = 1545.348
static const double	SHRatio = 1.40
static const double	slugtolb = 32.174049

Detailed Description

Models atmospheric disturbances: winds, gusts, turbulence, downbursts, etc.

Various turbulence models are available. They are specified via the property atmosphere/turb-type. The following models are available:

• 0: ttNone (turbulence disabled)
• 1: ttStandard
• 2: ttCulp
• 3: ttMilspec (Dryden spectrum)
• 4: ttTustin (Dryden spectrum)

The Milspec and Tustin models are described in the Yeager report cited below. They both use a Dryden spectrum model whose parameters (scale lengths and intensities) are modelled according to MIL-F-8785C. Parameters are modelled differently for altitudes below 1000ft and above 2000ft, for altitudes in between they are interpolated linearly.

The two models differ in the implementation of the transfer functions described in the milspec.

To use one of these two models, set atmosphere/turb-type to 4 resp. 5, and specify values for atmosphere/turbulence/milspec/windspeed_at_20ft_AGL-fps and atmosphere/turbulence/milspec/severity (the latter corresponds to the probability of exceedence curves from Fig. 7 of the milspec, allowable range is 0 (disabled) to 7). atmosphere/psiw-rad is respected as well; note that you have to specify a positive wind magnitude to prevent psiw from being reset to zero.

Reference values (cf. figures 7 and 9 from the milspec):

Intensity	windspeed_at_20ft_AGL-fps	severity
light	25 (15 knots)	3
moderate	50 (30 knots)	4
severe	75 (45 knots)	6

See also

Yeager, Jessie C.: "Implementation and Testing of Turbulence Models for the F18-HARV" (pdf), NASA CR-1998-206937, 1998

MIL-F-8785C: Military Specification: Flying Qualities of Piloted Aircraft

Definition at line 119 of file FGWinds.h.

Member Function Documentation

GetWindPsi()

virtual double GetWindPsi ( void  ) const

inlinevirtual

Retrieves the direction that the wind is coming from.

The direction is defined as north=0 and increases counterclockwise. The wind heading is returned in radians.

Definition at line 165 of file FGWinds.h.

{ return psiw; }

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GustFrame()

virtual void GustFrame ( eGustFrame  gFrame )

inlinevirtual

Specifies the frame that the gust direction vector components are specified in.

The body frame is defined with the X direction forward, and the Y direction positive out the right wing. The wind frame is defined with the X axis pointing into the velocity vector, the Z axis perpendicular to the X axis, in the aircraft XZ plane, and the Y axis completing the system. The local axis is a navigational frame with X pointing north, Y pointing east, and Z pointing down. This is a locally vertical, locally horizontal frame, with the XY plane tangent to the geocentric surface.

Definition at line 295 of file FGWinds.h.

{oneMinusCosineGust.gustFrame = gFrame;}

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Run()

bool Run ( bool  Holding )

virtual

Runs the winds 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 142 of file FGWinds.cpp.

{
  if (FGModel::Run(Holding)) return true;
  if (Holding) return false;

  if (turbType != ttNone) Turbulence(in.AltitudeASL);
  if (oneMinusCosineGust.gustProfile.Running) CosineGust();

  vTotalWindNED = vWindNED + vGustNED + vCosineGust + vTurbulenceNED;

   // psiw (Wind heading) is the direction the wind is blowing towards
  if (vWindNED(eX) != 0.0) psiw = atan2( vWindNED(eY), vWindNED(eX) );
  if (psiw < 0) psiw += 2*M_PI;

  Debug(2);
  return false;
}

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SetWindPsi()

void SetWindPsi ( double  dir )

virtual

Sets the direction that the wind is coming from.

The direction is defined as north=0 and increases counterclockwise to 2*pi (radians). The vertical component of wind is assumed to be zero - and is forcibly set to zero. This function sets the vWindNED vector components based on the supplied direction. The magnitude of the wind set in the vector is preserved (assuming the vertical component is non-zero).

Parameters

dir	wind direction in the horizontal plane, in radians.

Definition at line 187 of file FGWinds.cpp.

{
  double mag = GetWindspeed();
  psiw = dir;
  SetWindspeed(mag);
}

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

• FGWinds.h
• FGWinds.cpp