FGGasCell Class Reference

#include <FGGasCell.h>

Inherits FGForce.

List of all members.

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Detailed Description

Author:

Anders Gidenstam

Configuration File Format:

<buoyant_forces>
  <gas_cell type="{HYDROGEN | HELIUM | AIR}">
    <location unit="{M | IN}">
      <x> {number} </x>
      <y> {number} </y>
      <z> {number} </z>
    </location>
    <x_width unit="{M | IN}"> {number} </x_width>
    <y_radius unit="{M | IN}"> {number} </y_radius>
    <z_radius unit="{M | IN}"> {number} </z_radius>
    <max_overpressure unit="{PA | PSI}"> {number} </max_overpressure>
    <valve_coefficient unit="{M4*SEC/KG | FT4*SEC/SLUG}"> {number} </valve_coefficient>
    <fullness> {number} </fullness>  
    <heat>
      {heat transfer coefficients} [lbs ft / sec]
    </heat>
    <ballonet>
      <location unit="{M | IN}">
        <x> {number} </x>
        <y> {number} </y>
        <z> {number} </z>
      </location>
      <x_width unit="{M | IN}"> {number} </x_width>
      <y_radius unit="{M | IN}"> {number} </y_radius>
      <z_radius unit="{M | IN}"> {number} </z_radius>
      <max_overpressure unit="{PA | PSI}"> {number} </max_overpressure>
      <valve_coefficient unit="{M4*SEC/KG | FT4*SEC/SLUG}"> {number} </valve_coefficient>
      <fullness> {number} </fullness>  
      <heat>
       {heat transfer coefficients} [lb ft / (sec Rankine)]
      </heat>
      <blower_input>
       {input air flow function} [ft^3 / sec]
      </blower_input>
    </ballonet>
  </gas_cell>
</buoyant_forces>

Definition of the gas cell configuration file parameters:

• type - One of HYDROGEN, HELIUM or AIR.
• location - Location of cell center in the aircraft's structural frame. Currently this is were the forces of the cell is applied.
• {x|y|z}_radius - Radius along in the respective direction (both ends).
• {x|y|z}_width - Width in the respective direction. NOTE: A 'x', 'y', 'z'-radius/width combination must be specified.
• fullness - Initial fullness of the cell, normally [0,1], values >1 initialize the cell at pressure.
• max_overpressure - Maximum cell overpressure (excess is automatically valved off).
• valve_coefficient - Capacity of the manual valve. The valve is considered to be located at the top of the cell. The valve coefficient determine the flow out of the cell according to: dVolume/dt = ValveCoefficient * DeltaPressure.
• heat - Zero or more FGFunction:s describing the heat flow from the atmosphere into the gas cell. Unit: [lb ft / (sec Rankine)]. If there are no heat transfer functions at all the gas cell temperature will equal that of the surrounding atmosphere. A constant function returning 0 results in adiabatic behaviour.
• ballonet - Zero or more ballonets, i.e. air bags inside the gas cell. Ballonets are used to maintain the volume of the gas cell and keep its internal pressure higher than that of the surrounding environment.
  • location - Location of ballonet center in the aircraft's structural frame.
  • {x|y|z}_radius - Radius along in the respective direction (both ends).
  • {x|y|z}_width - Width in the respective direction.
  • max_overpressure - Maximum ballonet overpressure (excess is automatically valved off).
  • valve_coefficient - Capacity of the exit valve between the ballonet and the atmosphere. The valve coefficient determine the flow out of the cell according to: dVolume/dt = ValveCoefficient * DeltaPressure.
  • heat - Zero or more FGFunction:s describing the heat flow from the enclosing gas cell into the ballonet. Unit: [lb ft / (sec Rankine)]
  • blower_input - One FGFunction describing the air flow into the ballonet. Unit: [ft³ / sec] (at the temperature and pressure of the ballonet.)

Definition at line 176 of file FGGasCell.h.

Public Member Functions
void	Calculate (double dt)
	Runs the gas cell model; called by BuoyantForces.
	FGGasCell (FGFDMExec *exec, Element *el, int num)
	Constructor.
int	GetIndex (void) const
	Get the index of this gas cell.
const FGMatrix33 &	GetInertia (void) const
	Get the moments of inertia of the gas cell (including any ballonets).
double	GetMass (void) const
	Get the current mass of the gas cell (including any ballonets).
const FGColumnVector3 &	GetMassMoment (void) const
	Get the moment due to mass of the gas cell (including any ballonets).
double	GetPressure (void) const
	Get the current gas pressure inside the gas cell.
double	GetTemperature (void) const
	Get the current gas temperature inside the gas cell.
double	GetXYZ (int idx) const
	Get the center of gravity location of the gas cell (including any ballonets).
const FGColumnVector3 &	GetXYZ (void) const
	Get the center of gravity location of the gas cell (including any ballonets).

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Constructor & Destructor Documentation

FGGasCell	(	FGFDMExec *	exec,
		Element *	el,
		int	num
	)

Parameters:

	exec	Executive a pointer to the parent executive object
	el	Pointer to configuration file XML node
	num	Gas cell index number.

Definition at line 63 of file FGGasCell.cpp.

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Member Function Documentation

int GetIndex

(

void

)

const [inline]

Returns:

gas cell index.

Definition at line 192 of file FGGasCell.h.

const FGMatrix33& GetInertia

(

void

)

const [inline]

Returns:

moments of inertia matrix relative the gas cell location in slug ft².

Definition at line 211 of file FGGasCell.h.

double GetMass

(

void

)

const [inline]

Returns:

gas mass in slug.

Definition at line 206 of file FGGasCell.h.

const FGColumnVector3& GetMassMoment

(

void

)

const [inline]

Note that the buoyancy of the gas cell is handled separately by the FGForce part and not included here.

Returns:

moment vector in lbs ft.

Definition at line 218 of file FGGasCell.h.

double GetPressure

(

void

)

const [inline]

Returns:

gas pressure in lbs / ft².

Definition at line 226 of file FGGasCell.h.

double GetTemperature

(

void

)

const [inline]

Returns:

gas temperature in Rankine.

Definition at line 222 of file FGGasCell.h.

double GetXYZ

(

int

idx

)

const [inline]

Returns:

CoG location in the structural frame.

Definition at line 202 of file FGGasCell.h.

const FGColumnVector3& GetXYZ

(

void

)

const [inline]

Returns:

CoG location in the structural frame.

Definition at line 197 of file FGGasCell.h.

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

• FGGasCell.h
• FGGasCell.cpp