// *************************************************************************
/// @name Temperature access functions.
/// There are several ways to get the temperature, and several modeled
/// temperature values that can be retrieved. The U.S. Standard Atmosphere
/// temperature either at a specified altitude, or at sea level can be
/// retrieved. These two temperatures do NOT include the effects of any bias
/// or delta gradient that may have been supplied by the user. The modeled
/// temperature and the modeled temperature at sea level can also be
/// retrieved. These two temperatures DO include the effects of an optionally
/// user-supplied bias or delta gradient.
// @{
/// Returns the actual modeled temperature in degrees Rankine at a specified
/// altitude.
/// @param altitude The altitude above sea level (ASL) in feet.
/// @return Modeled temperature in degrees Rankine at the specified altitude.
public override double GetTemperature(double altitude)
{
double GeoPotAlt = GeopotentialAltitude(altitude);
double T;
if (GeoPotAlt >= 0.0)
{
T = StdAtmosTemperatureTable.GetValue(GeoPotAlt);
if (GeoPotAlt <= gradientFadeoutAltitude)
{
T -= temperatureDeltaGradient * GeoPotAlt;
}
}
else
{
// We don't need to add TemperatureDeltaGradient*GeoPotAlt here because
// the lapse rate vector already accounts for the temperature gradient.
T = StdAtmosTemperatureTable.GetValue(0.0) + GeoPotAlt * LapseRates[0];
}
T += temperatureBias;
if (GeoPotAlt <= gradientFadeoutAltitude)
{
T += temperatureDeltaGradient * gradientFadeoutAltitude;
}
return(T);
}
/// Returns the standard temperature in degrees Rankine at a specified
/// altitude.
/// @param altitude The altitude in feet above sea level (ASL) to get the
/// temperature at.
/// @return The STANDARD temperature in degrees Rankine at the specified
/// altitude.
public virtual double GetStdTemperature(double altitude)
{
double GeoPotAlt = GeopotentialAltitude(altitude);
if (GeoPotAlt >= 0.0)
{
return(StdAtmosTemperatureTable.GetValue(GeoPotAlt));
}
else
{
return(StdAtmosTemperatureTable.GetValue(0.0) + GeoPotAlt * LapseRates[0]);
}
}
/// Returns the standard pressure at the specified altitude.
public virtual double GetStdPressure(double altitude)
{
double GeoPotAlt = GeopotentialAltitude(altitude);
// Iterate through the altitudes to find the current Base Altitude
// in the table. That is, if the current altitude (the argument passed in)
// is 20000 ft, then the base altitude from the table is 0.0. If the
// passed-in altitude is 40000 ft, the base altitude is 36089.2388 ft (and
// the index "b" is 2 - the second entry in the table).
double BaseAlt = StdAtmosTemperatureTable.GetElement(1, 0);
int numRows = StdAtmosTemperatureTable.GetNumRows();
int b;
for (b = 0; b < numRows - 2; ++b)
{
double testAlt = StdAtmosTemperatureTable.GetElement(b + 2, 0);
if (GeoPotAlt < testAlt)
{
break;
}
BaseAlt = testAlt;
}
double Tmb = GetStdTemperature(GeometricAltitude(BaseAlt));
double deltaH = GeoPotAlt - BaseAlt;
double Lmb = LapseRates[b];
if (Lmb != 0.0)
{
double Exp = Constants.g0 / (Rdry * Lmb);
double factor = Tmb / (Tmb + Lmb * deltaH);
return(StdPressureBreakpoints[b] * Math.Pow(factor, Exp));
}
else
{
return(StdPressureBreakpoints[b] * Math.Exp(-Constants.g0 * deltaH / (Rdry * Tmb)));
}
}
/// Destructor
//virtual ~FGStandardAtmosphere();
public override bool InitModel()
{
// Assume the altitude to fade out the gradient at is at the highest
// altitude in the table. Above that, other functions are used to
// calculate temperature.
gradientFadeoutAltitude = StdAtmosTemperatureTable.GetElement(StdAtmosTemperatureTable.GetNumRows(), 0);
temperatureDeltaGradient = 0.0;
temperatureBias = 0.0;
LapseRates = StdLapseRates;
PressureBreakpoints = StdPressureBreakpoints;
SLpressure = StdSLpressure;
SLtemperature = StdSLtemperature;
SLdensity = StdSLdensity;
SLsoundspeed = StdSLsoundspeed;
Calculate(0.0);
// PrintStandardAtmosphereTable();
return(true);
}
