Source code for RCAIDE.Framework.Analyses.Atmospheric.US_Standard_1976
# US_Standard_1976.py
#
# Created:
# Modified: Feb 2016, Andrew Wendorff
# Jan 2018, W. Maier
# ----------------------------------------------------------------------
# Imports
# ----------------------------------------------------------------------
import numpy as np
from warnings import warn
import RCAIDE
from RCAIDE.Framework.Analyses.Atmospheric import Atmospheric
from RCAIDE.Framework.Mission.Common.Conditions import Conditions
from RCAIDE.Framework.Core import Units
from RCAIDE.Framework.Core.Arrays import atleast_2d_col
from RCAIDE.Library.Attributes.Gases import Air
from RCAIDE.Library.Attributes.Planets import Earth
# ----------------------------------------------------------------------
# Classes
# ----------------------------------------------------------------------
[docs]
class US_Standard_1976(Atmospheric):
""" Implements the U.S. Standard Atmosphere (1976 version)
Assumptions:
None
Source:
U.S. Standard Atmosphere, 1976, U.S. Government Printing Office, Washington, D.C., 1976
"""
def __defaults__(self):
"""This sets the default values for the analysis to function.
Assumptions:
None
Source:
N/A
Inputs:
None
Output:
None
Properties Used:
None
"""
atmo_data = RCAIDE.Library.Attributes.Atmospheres.Earth.US_Standard_1976()
self.update(atmo_data)
[docs]
def compute_values(self,altitude,temperature_deviation=0.0,var_gamma=False):
"""Computes atmospheric values.
Assumptions:
US 1976 Standard Atmosphere
Source:
U.S. Standard Atmosphere, 1976, U.S. Government Printing Office, Washington, D.C., 1976
Inputs:
altitude [m]
temperature_deviation [K]
Output:
atmo_data.
pressure [Pa]
temperature [K]
speed_of_sound [m/s]
dynamic_viscosity [kg/(m*s)]
kinematic_viscosity [m^2/s]
thermal_conductivity [W/(m*K)]
prandtl_number [-]
Properties Used:
self.
fluid_properties.gas_specific_constant [J/(kg*K)]
planet.sea_level_gravity [m/s^2]
planet.mean_radius [m]
breaks.
altitude [m]
temperature [K]
pressure [Pa]
"""
# unpack
zs = altitude
gas = self.fluid_properties
planet = self.planet
grav = self.planet.sea_level_gravity
Rad = self.planet.mean_radius
R = gas.gas_specific_constant
delta_isa = temperature_deviation
# check properties
if not gas == Air():
warn('US Standard Atmosphere not using Air fluid properties')
if not planet == Earth():
warn('US Standard Atmosphere not using Earth planet properties')
# convert input if necessary
zs = atleast_2d_col(zs)
# get model altitude bounds
zmin = self.breaks.altitude[0]
zmax = self.breaks.altitude[-1]
# convert geometric to geopotential altitude
zs = zs/(1 + zs/Rad)
# check ranges
if np.amin(zs) < zmin:
print("Warning: altitude requested below minimum for this atmospheric model; returning values for h = -2.0 km")
zs[zs < zmin] = zmin
if np.amax(zs) > zmax:
print("Warning: altitude requested above maximum for this atmospheric model; returning values for h = 86.0 km")
zs[zs > zmax] = zmax
# initialize return data
zeros = np.zeros_like(zs)
p = zeros * 0.0
T = zeros * 0.0
rho = zeros * 0.0
a = zeros * 0.0
mu = zeros * 0.0
z0 = zeros * 0.0
T0 = zeros * 0.0
p0 = zeros * 0.0
alpha = zeros * 0.0
# populate the altitude breaks
# this uses >= and <= to capture both edges and because values should be the same at the edges
for i in range( len(self.breaks.altitude)-1 ):
i_inside = (zs >= self.breaks.altitude[i]) & (zs <= self.breaks.altitude[i+1])
z0[ i_inside ] = self.breaks.altitude[i]
T0[ i_inside ] = self.breaks.temperature[i]
p0[ i_inside ] = self.breaks.pressure[i]
alpha[ i_inside ] = -(self.breaks.temperature[i+1] - self.breaks.temperature[i])/ \
(self.breaks.altitude[i+1] - self.breaks.altitude[i])
# interpolate the breaks
dz = zs-z0
i_isoth = (alpha == 0.)
i_adiab = (alpha != 0.)
p[i_isoth] = p0[i_isoth] * np.exp(-1.*dz[i_isoth]*grav/(R*T0[i_isoth]))
p[i_adiab] = p0[i_adiab] * ( (1.-alpha[i_adiab]*dz[i_adiab]/T0[i_adiab]) **(1.*grav/(alpha[i_adiab]*R)) )
T = T0 - dz*alpha + delta_isa
rho = gas.compute_density(T,p)
a = gas.compute_speed_of_sound(T,p,var_gamma)
mu = gas.compute_absolute_viscosity(T)
K = gas.compute_thermal_conductivity(T)
Pr = gas.compute_prandtl_number(T)
atmo_data = Conditions()
atmo_data.expand_rows(zs.shape[0])
atmo_data.pressure = p
atmo_data.temperature = T
atmo_data.density = rho
atmo_data.speed_of_sound = a
atmo_data.dynamic_viscosity = mu
atmo_data.kinematic_viscosity = mu/rho
atmo_data.thermal_conductivity = K
atmo_data.prandtl_number = Pr
return atmo_data
# ----------------------------------------------------------------------
# Module Tests
# ----------------------------------------------------------------------
if __name__ == '__main__':
import pylab as plt
h = np.linspace(-1.,60.,200) * Units.km
delta_isa = 0.
h = 5000.
atmosphere = US_Standard_1976()
data = atmosphere.compute_values(h,delta_isa)
p = data.pressure
T = data.temperature
rho = data.density
a = data.speed_of_sound
mu = data.dynamic_viscosity
K = data.thermal_conductivity
print(data)
