// pitot.cxx - the pitot air system.
// Written by David Megginson, started 2002.
//
+// Last modified by Eric van den Berg, 24 Nov 2012
// This file is in the Public Domain and comes with no warranty.
-#include "pitot.hxx"
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <simgear/constants.h>
+
#include <Main/fg_props.hxx>
#include <Main/util.hxx>
+#include "pitot.hxx"
+
-PitotSystem::PitotSystem ()
+PitotSystem::PitotSystem ( SGPropertyNode *node )
+ :
+ _name(node->getStringValue("name", "pitot")),
+ _num(node->getIntValue("number", 0))
{
}
void
PitotSystem::init ()
{
- _serviceable_node = fgGetNode("/systems/pitot[0]/serviceable", true);
+ string branch;
+ branch = "/systems/" + _name;
+
+ SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true );
+ _serviceable_node = node->getChild("serviceable", 0, true);
_pressure_node = fgGetNode("/environment/pressure-inhg", true);
- _density_node = fgGetNode("/environment/density-slugft3", true);
- _velocity_node = fgGetNode("/velocities/airspeed-kt", true);
- _total_pressure_node =
- fgGetNode("/systems/pitot[0]/total-pressure-inhg", true);
+ _mach_node = fgGetNode("/velocities/mach", true);
+ _total_pressure_node = node->getChild("total-pressure-inhg", 0, true);
+ _measured_total_pressure_node = node->getChild("measured-total-pressure-inhg", 0, true);
}
void
{
}
-#ifndef INHGTOPSF
-# define INHGTOPSF (2116.217/29.9212)
-#endif
-
-#ifndef PSFTOINHG
-# define PSFTOINHG (1/INHGTOPSF)
-#endif
-
-#ifndef KTTOFPS
-# define KTTOFPS 1.68781
-#endif
-
-
void
PitotSystem::update (double dt)
{
if (_serviceable_node->getBoolValue()) {
- // The pitot tube sees the forward
- // velocity in the body axis.
- double p = _pressure_node->getDoubleValue() * INHGTOPSF;
- double r = _density_node->getDoubleValue();
- double v = _velocity_node->getDoubleValue() * KTTOFPS;
- double q = 0.5 * r * v * v; // dynamic
- _total_pressure_node->setDoubleValue((p + q) * PSFTOINHG);
+ double p = _pressure_node->getDoubleValue();
+ double mach = _mach_node->getDoubleValue();
+ mach = std::max( mach , 0.0 );
+ double p_t = p * pow(1 + 0.2 * mach*mach, 3.5 ); // true total pressure around aircraft
+ _total_pressure_node->setDoubleValue(p_t);
+ double p_t_meas = p_t;
+ if (mach > 1) {
+ p_t_meas = p * pow( 1.2 * mach*mach, 3.5 ) * pow( 2.8/2.4*mach*mach - 0.4 / 2.4 , -2.5 ); // measured total pressure by pitot tube (Rayleigh formula, at Mach>1, normal shockwave in front of pitot tube)
+ }
+ _measured_total_pressure_node->setDoubleValue(p_t_meas);
}
}