def __init__(self, h):
# Cantera Solution object
self.gas = ct.Solution('air.xml')
# Discretised altitude steps
self.h = h
# Average molecular diameter of gas
self.d = 4E-10
self.steps = len(h)
self.rho = np.zeros(self.steps)
self.p = np.zeros(self.steps)
self.T = np.zeros(self.steps)
self.a = np.zeros(self.steps)
self.k = np.zeros(self.steps)
self.mu = np.zeros(self.steps)
for index, alt in enumerate(self.h):
self.rho[index] = atm.alt2density(alt, alt_units='m', density_units='kg/m**3')
self.p[index] = atm.alt2press(alt, press_units='pa', alt_units='m')
self.T[index] = atm.alt2temp(alt, alt_units='m', temp_units='K')
self.a[index] = atm.temp2speed_of_sound(self.T[index], temp_units='K', speed_units='m/s')
for index, alt in enumerate(self.h):
self.gas.TP = self.T[index], self.p[index]
self.k[index] = self.gas.cp / self.gas.cv
self.mu[index] = self.gas.viscosity
print 'ATMOSPHERIC MODEL COMPUTED (US76)'
return None
def tip_mach(tas,
rpm,
temperature,
dia,
speed_units='kt',
temp_units='C',
dia_units='in'):
"""
Returns the mach number of the propeller blade tip, given the
true airspeed (tas), revolutions per minute (rpm), temperature and
propeller diameter.
The speed units may be specified as "kt", "mph", "km/h" or "ft/s", but
default to "kt" if not specified.
The temperature units may be specified as "C", "F", "K" or "R", but
default to deg C if not specified.
The diameter units may be specified as "in", "ft", or "m", but default
to inches if not specified.
"""
dia = U.length_conv(dia, from_units=dia_units, to_units='m')
tas = U.speed_conv(tas, from_units=speed_units, to_units='m/s')
speed_of_sound = SA.temp2speed_of_sound(temperature,
temp_units=temp_units,
speed_units='m/s')
rotation_speed = dia * rpm * np.pi / 60
tip_speed = np.sqrt(tas**2 + rotation_speed**2)
tip_mach = tip_speed / speed_of_sound
return tip_mach
def test_01(self):
# speed of sound at 5,000 ft
# Truth value from NASA RP 1046
Value = SA.temp2speed_of_sound(SA.alt2temp(5000))
Truth = 650.01
self.assertLessEqual(RE(Value, Truth), 1e-5)
def test_04(self):
# speed of sound at 10,000 m
# Truth value from NASA RP 1046
Value = SA.temp2speed_of_sound(SA.alt2temp(10000, alt_units='m'
))
Truth = 582.11
self.assertLessEqual(RE(Value, Truth), 1e-5)
def test_03(self):
# speed of sound in km/h at 2,000 m, with temp in deg R
# Truth value from NASA RP 1046
Value = SA.temp2speed_of_sound(SA.alt2temp(2000, alt_units='m',
temp_units='R'), speed_units='km/h', temp_units='R')
Truth = 1197.1
self.assertLessEqual(RE(Value, Truth), 1e-5)
def test_02(self):
# speed of sound in mph at 8,000 ft
# Truth value from NASA RP 1046
Value = SA.temp2speed_of_sound(SA.alt2temp(8000),
speed_units='mph')
Truth = 739.98
self.assertLessEqual(RE(Value, Truth), 1e-5)
def __init__(self, h, T_thermosphere):
# Cantera Solution object
self.gas = ct.Solution('air.xml')
# Discretised altitude steps
self.h = h
# Average molecular diameter of gas
self.d = 4E-10
# Ratio of specific heats
self.steps = len(h)
self.rho = np.zeros(self.steps)
self.p = np.zeros(self.steps)
self.T = np.zeros(self.steps)
self.a = np.zeros(self.steps)
self.k = np.zeros(self.steps)
self.mu = np.zeros(self.steps)
# Call Jacchia77 model
data = j77.j77sri(np.max(h), T_thermosphere)
data_np = np.array(data)
h_int = spint.griddata
T_int = spint.griddata
mw_int = spint.griddata
n = spint.griddata
for index, alt in enumerate(self.h):
self.rho[index] = atm.alt2density(alt, alt_units='m', density_units='kg/m**3')
self.p[index] = atm.alt2press(alt, press_units='pa', alt_units='m')
self.T[index] = atm.alt2temp(alt, alt_units='m', temp_units='K')
self.a[index] = atm.temp2speed_of_sound(self.T[index], temp_units='K', speed_units='m/s')
for index, alt in enumerate(self.h):
self.gas.TP = self.T[index], self.p[index]
self.k[index] = self.gas.cp / self.gas.cv
self.mu[index] = self.gas.viscosity
return None
