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pitot tube using velocities/mach as mach norm, not the u componant

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janodesbois 2013-10-31 20:28:12 +01:00
parent 78301e95b4
commit 05fa7130fc
2 changed files with 9 additions and 2 deletions
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9
src/Systems/pitot.cxx
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@ -37,6 +37,8 @@ PitotSystem::init ()
_serviceable_node = node->getChild("serviceable", 0, true); _serviceable_node = node->getChild("serviceable", 0, true);
_pressure_node = fgGetNode("/environment/pressure-inhg", true); _pressure_node = fgGetNode("/environment/pressure-inhg", true);
_mach_node = fgGetNode("/velocities/mach", true); _mach_node = fgGetNode("/velocities/mach", true);
_alpha_deg_node = fgGetNode("/orientation/alpha-deg", true);
_beta_deg_node = fgGetNode("/orientation/side-slip-deg", true);
_total_pressure_node = node->getChild("total-pressure-inhg", 0, true); _total_pressure_node = node->getChild("total-pressure-inhg", 0, true);
_measured_total_pressure_node = node->getChild("measured-total-pressure-inhg", 0, true); _measured_total_pressure_node = node->getChild("measured-total-pressure-inhg", 0, true);
} }
@ -57,14 +59,17 @@ PitotSystem::update (double dt)
if (_serviceable_node->getBoolValue()) { if (_serviceable_node->getBoolValue()) {
double p = _pressure_node->getDoubleValue(); double p = _pressure_node->getDoubleValue();
double mach = _mach_node->getDoubleValue(); double mach = _mach_node->getDoubleValue();
mach = std::max( mach , 0.0 ); double alpha = _alpha_deg_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
double beta = _beta_deg_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
mach = mach * fabs(cos(alpha)) * cos(beta);
mach = std::max( mach , 0.0 ); // we want a mach=0 if the airflow comes from behind
double p_t = p * pow(1 + 0.2 * mach*mach, 3.5 ); // true total pressure around aircraft double p_t = p * pow(1 + 0.2 * mach*mach, 3.5 ); // true total pressure around aircraft
_total_pressure_node->setDoubleValue(p_t); _total_pressure_node->setDoubleValue(p_t);
double p_t_meas = p_t; double p_t_meas = p_t;
if (mach > 1) { 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) 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); _measured_total_pressure_node->setDoubleValue(mach);
} }
} }

2
src/Systems/pitot.hxx
View file

@ -60,6 +60,8 @@ private:
SGPropertyNode_ptr _mach_node; SGPropertyNode_ptr _mach_node;
SGPropertyNode_ptr _total_pressure_node; SGPropertyNode_ptr _total_pressure_node;
SGPropertyNode_ptr _measured_total_pressure_node; SGPropertyNode_ptr _measured_total_pressure_node;
SGPropertyNode_ptr _alpha_deg_node;
SGPropertyNode_ptr _beta_deg_node;
}; };
#endif // __SYSTEMS_PITOT_HXX #endif // __SYSTEMS_PITOT_HXX