`atmosphere` Module¶

Contains the following atmospheric functions:

density = atm_density(alt, mach)

mach = atm_mach(alt, velocity)

velocity = atm_velocity(alt, mach)

pressure = atm_pressure(alt)

temperature = atm_temperature(alt)

sos = atm_speed_of_sound(alt)

mu = atm_dynamic_viscosity_mu(alt)

nu = atm_kinematic_viscosity_nu(alt)

eas = atm_equivalent_airspeed(alt, mach)

rho, machs, velocity = make_flfacts_alt_sweep(

mach, alts, eas_limit=1000., alt_units=’m’, velocity_units=’m/s’, density_units=’kg/m^3’, eas_units=’m/s’)

rho, machs, velocity = make_flfacts_mach_sweep(

alt, machs, eas_limit=1000., alt_units=’m’, velocity_units=’m/s’, density_units=’kg/m^3’, eas_units=’m/s’)

All the default units are in English units because the source equations are in English units.

pyNastran.utils.atmosphere.atm_density(alt, R=1716.0, alt_units='ft', density_units='slug/ft^3')[source]¶

Freestream Density f$ rho_{infty} f$

Parameters:	alt : float altitude in feet or meters R : float; default=1716. gas constant for air in english units (???) alt_units : str; default=’ft’ the altitude units; ft, kft, m density_units : str; default=’slug/ft^3’ the density units; slug/ft^3, slinch/in^3, kg/m^3
Returns:	rho : float density f$ rho f$ in density_units Based on the formula P=pRT f[ large rho=frac{p}{R T} f]

pyNastran.utils.atmosphere.atm_dynamic_pressure(alt, mach, alt_units='ft', pressure_units='psf')[source]¶

Freestream Dynamic Pressure f$ q_{infty} f$

Parameters:	alt : float Altitude in alt_units mach : float Mach Number f$ M f$ alt_units : str; default=’ft’ the altitude units; ft, kft, m pressure_units : str; default=’psf’ the pressure units; psf, psi, Pa, kPa, MPa
Returns:	dynamic_pressure : float Returns dynamic pressure in pressure_units The common method that requires many calculations… f[ large q = frac{1}{2} rho V^2 f] f[ large p = rho R T f] f[ large M = frac{V}{a} f] f[ large a = sqrt{gamma R T} f] so… f[ large q = frac{gamma}{2} p M^2 f]

pyNastran.utils.atmosphere.atm_dynamic_viscosity_mu(alt, alt_units='ft', visc_units='(lbf*s)/ft^2')[source]¶

Freestream Dynamic Viscosity f$ mu_{infty} f$

Parameters:	alt : float Altitude in alt_units alt_units : str; default=’ft’ the altitude units; ft, kft, m visc_units : str; default=’(lbfs)/ft^2’ the viscosity units; (lbfs)/ft^2, (Ns)/m^2, Pas
Returns:	mu : float dynamic viscosity f$ mu_{infty} f$ in (lbfs)/ft^2 or (Ns)/m^2 (SI) See also sutherland_viscoscity ..

pyNastran.utils.atmosphere.atm_equivalent_airspeed(alt, mach, alt_units='ft', eas_units='ft/s')[source]¶

Freestream equivalent airspeed

Parameters:	alt : float altitude in alt_units Mach : float Mach Number $ M $ alt_units : str; default=’ft’ the altitude units; ft, kft, m eas_units : str; default=’ft/s’ the equivalent airspeed units; ft/s, m/s, in/s, knots
Returns:	eas : float equivalent airspeed in eas_units EAS = TAS * sqrt(rho/rho0) p = rho * R * T rho = p/(RT) rho/rho0 = p/T * T0/p0 TAS = a * M EAS = a * M * sqrt(p/T * T0/p0) EAS = a * M * sqrt(pT0 / (Tp0))

pyNastran.utils.atmosphere.atm_kinematic_viscosity_nu(alt, alt_units='ft', visc_units='ft^2/s')[source]¶

Freestream Kinematic Viscosity f$ nu_{infty} f$

Parameters:	alt : float Altitude in alt_units alt_units : str; default=’ft’ the altitude units; ft, kft, m visc_units : str; default=’slug/ft^3’ the kinematic viscosity units; ft^2/s, m^2/s
Returns:	nu : float kinematic viscosity f$ nu_{infty} f$ in visc_units f[ large nu = frac{mu}{rho} f] See also sutherland_viscoscity .. Todo better debug ..

pyNastran.utils.atmosphere.atm_mach(alt, V, alt_units='ft', velocity_units='ft/s')[source]¶

Freestream Mach Number

Parameters:	alt : float altitude in alt_units V : float Velocity in velocity_units alt_units : str; default=’ft’ the altitude units; ft, kft, m velocity_units : str; default=’ft/s’ the velocity units; ft/s, m/s, in/s, knots
Returns:	mach : float Mach Number f$ M f$ f[ large M = frac{V}{a} f]

pyNastran.utils.atmosphere.atm_pressure(alt, alt_units='ft', pressure_units='psf')[source]¶

Freestream Pressure f$ p_{infty} f$

Parameters:	alt : float Altitude in alt_units alt_units : str; default=’ft’ the altitude units; ft, kft, m pressure_units : str; default=’psf’ the pressure units; psf, psi, Pa, kPa, MPa
Returns:	pressure : float Returns pressure in pressure_units Note from BAC-7006-3352-001-V1.pdf # Bell Handbook of Aerodynamic Heatingn page ~236 - Table C.1n These equations were used b/c they are valid to 300k ft.n Extrapolation is performed above that.n

pyNastran.utils.atmosphere.atm_speed_of_sound(alt, alt_units='ft', velocity_units='ft/s', gamma=1.4)[source]¶

Freestream Speed of Sound f$ a_{infty} f$

Parameters:	alt : float Altitude in alt_units alt_units : str; default=’ft’ the altitude units; ft, kft, m velocity_units : str; default=’ft/s’ the velocity units; ft/s, m/s, in/s, knots
Returns:	speed_of_sound, a : float Returns speed of sound in velocity_units f[ large a = sqrt{gamma R T} f]

pyNastran.utils.atmosphere.atm_temperature(alt, alt_units='ft', temperature_units='R')[source]¶

Freestream Temperature f$ T_{infty} f$

Parameters:	alt : float Altitude in alt_units alt_units : str; default=’ft’ the altitude units; ft, kft, m temperature_units : str; default=’R’ the altitude units; R, K
Returns:	T : float temperature in degrees Rankine or Kelvin (SI) Note from BAC-7006-3352-001-V1.pdf # Bell Handbook of Aerodynamic Heatingn page ~236 - Table C.1n These equations were used because they are valid to 300k ft.n Extrapolation is performed above that.

pyNastran.utils.atmosphere.atm_unit_reynolds_number(alt, mach, alt_units='ft', reynolds_units='1/ft')[source]¶

Returns the Reynolds Number per unit length.

Parameters:	alt : float Altitude in alt_units mach : float Mach Number f$ M f$ alt_units : str; default=’ft’ the altitude units; ft, kft, m reynolds_units : str; default=‘1/ft’ the altitude units; 1/ft, 1/m, 1/in
Returns:	ReynoldsNumber/L : float Reynolds number per unit length in reynolds_units f[ large Re = frac{ rho V L}{mu} f] f[ large Re_L = frac{ rho V }{mu} f]

pyNastran.utils.atmosphere.atm_unit_reynolds_number2(alt, mach, alt_units='ft', reynolds_units='1/ft')[source]¶

Returns the Reynolds Number per unit length.

Parameters:	alt : float Altitude in alt_units mach : float Mach Number f$ M f$ alt_units : str; default=’ft’ the altitude units; ft, kft, m reynolds_units : str; default=‘1/ft’ the altitude units; 1/ft, 1/m, 1/in
Returns:	ReynoldsNumber/L : float the Reynolds Number per unit length f[ large Re_L = frac{ rho V}{mu} = frac{p M a}{mu R T} f] Note this version of Reynolds number directly caculates the base quantities, so multiple calls to atm_press and atm_temp are not made

pyNastran.utils.atmosphere.atm_velocity(alt, mach, alt_units='ft', velocity_units='ft/s')[source]¶

Freestream Velocity f$ V_{infty} f$

Parameters:	alt : float altitude in alt_units Mach : float Mach Number f$ M f$ alt_units : str; default=’ft’ the altitude units; ft, kft, m velocity_units : str; default=’ft/s’ the velocity units; ft/s, m/s, in/s, knots
Returns:	velocity : float Returns velocity in velocity_units f[ large V = M a f]

pyNastran.utils.atmosphere.convert_altitude(alt, alt_units_in, alt_units_out)[source]¶: nominal unit is ft

pyNastran.utils.atmosphere.convert_density(density, density_units_in, density_units_out)[source]¶: nominal unit is slug/ft^3

pyNastran.utils.atmosphere.convert_pressure(pressure, pressure_units_in, pressure_units_out)[source]¶: nominal unit is psf

pyNastran.utils.atmosphere.convert_velocity(velocity, velocity_units_in, velocity_units_out)[source]¶: nominal unit is ft/s

pyNastran.utils.atmosphere.get_alt_for_density(density, density_units='slug/ft^3', alt_units='ft', nmax=20, tol=5.0)[source]¶

Gets the altitude associated with a given air density.

Parameters:	density : float the air density in slug/ft^3 density_units : str; default=’slug/ft^3’ the density units; slug/ft^3, slinch/in^3, kg/m^3 alt_units : str; default=’ft’ sets the units for the output altitude; ft, m, kft nmax : int; default=20 max number of iterations for convergence tol : float; default=5. tolerance in alt_units
Returns:	alt : float the altitude in feet

pyNastran.utils.atmosphere.get_alt_for_eas_with_constant_mach(equivalent_airspeed, mach, velocity_units='ft/s', alt_units='ft', nmax=20, tol=5.0)[source]¶

Gets the altitude associated with a equivalent airspeed.

Parameters:	equivalent_airspeed : float the equivalent airspeed in velocity_units mach : float the mach to hold constant alt_units : str; default=’ft’ the altitude units; ft, kft, m nmax : int; default=20 max number of iterations for convergence tol : float; default=5. tolerance in alt_units
Returns:	alt : float the altitude in alt units

pyNastran.utils.atmosphere.get_alt_for_pressure(pressure, pressure_units='psf', alt_units='ft', nmax=20, tol=5.0)[source]¶

Gets the altitude associated with a pressure.

Parameters:	pressure : float the pressure lb/ft^2 (SI=Pa) pressure_units : str; default=’psf’ the pressure units; psf, psi, Pa, kPa, MPa alt_units : str; default=’ft’ the altitude units; ft, kft, m nmax : int; default=20 max number of iterations for convergence tol : float; default=5. tolerance in alt_units
Returns:	alt : float the altitude in alt_units

pyNastran.utils.atmosphere.get_alt_for_q_with_constant_mach(q, mach, pressure_units='psf', alt_units='ft', nmax=20, tol=5.0)[source]¶

Gets the altitude associated with a dynamic pressure.

Parameters:	q : float the dynamic pressure lb/ft^2 (SI=Pa) mach : float the mach to hold constant pressure_units : str; default=’psf’ the pressure units; psf, psi, Pa, kPa, MPa alt_units : str; default=’ft’ the altitude units; ft, kft, m nmax : int; default=20 max number of iterations for convergence tol : float; default=5. tolerance in alt_units
Returns:	alt : float the altitude in alt_units

pyNastran.utils.atmosphere.make_flfacts_alt_sweep(mach, alts, eas_limit=1000.0, alt_units='m', velocity_units='m/s', density_units='kg/m^3', eas_units='m/s')[source]¶

Makes a sweep across altitude for a constant Mach number.

Parameters:

alt : List[float]

Altitude in alt_units

Mach : float: Mach Number

$ M

$

eas_limit : float: Equivalent airspeed limiter in eas_units
alt_units : str; default=’m’: the altitude units; ft, kft, m
velocity_units : str; default=’m/s’: the velocity units; ft/s, m/s, in/s, knots
density_units : str; default=’kg/m^3’: the density units; slug/ft^3, slinch/in^3, kg/m^3
eas_units : str; default=’m/s’: the equivalent airspeed units; ft/s, m/s, in/s, knots

pyNastran.utils.atmosphere.make_flfacts_eas_sweep(alt, eass, alt_units='m', velocity_units='m/s', density_units='kg/m^3', eas_units='m/s')[source]¶

Makes a sweep across equivalent airspeed for a constant altitude.

Parameters:

alt : float: Altitude in alt_units
eass : List[float]: Equivalent airspeed in eas_units
alt_units : str; default=’m’: the altitude units; ft, kft, m
velocity_units : str; default=’m/s’: the velocity units; ft/s, m/s, in/s, knots
density_units : str; default=’kg/m^3’: the density units; slug/ft^3, slinch/in^3, kg/m^3
eas_units : str; default=’m/s’: the equivalent airspeed units; ft/s, m/s, in/s, knots

pyNastran.utils.atmosphere.make_flfacts_mach_sweep(alt, machs, eas_limit=1000.0, alt_units='m', velocity_units='m/s', density_units='kg/m^3', eas_units='m/s')[source]¶

Makes a sweep across Mach number for a constant altitude.

Parameters:

alt : float

Altitude in alt_units

Machs : List[float]: Mach Number

$ M

$

eas_limit : float: Equivalent airspeed limiter in eas_units
alt_units : str; default=’m’: the altitude units; ft, kft, m
velocity_units : str; default=’m/s’: the velocity units; ft/s, m/s, in/s, knots
density_units : str; default=’kg/m^3’: the density units; slug/ft^3, slinch/in^3, kg/m^3
eas_units : str; default=’m/s’: the equivalent airspeed units; ft/s, m/s, in/s, knots

pyNastran.utils.atmosphere.sutherland_viscoscity(T)[source]¶

Helper function that calculates the dynamic viscosity f$ mu f$ of air at a given temperature.

Parameters:

T : float: Temperature T is in Rankine

Returns:

mu : float: dynamic viscosity f$ mu f$ of air in (lbf*s)/ft^2

Note

prints a warning if T>5400 deg R

Sutherland’s Equationn
From Aerodynamics for Engineers 4th Editionn
John J. Bertin 2002n
page 6 eq 1.5bn

atmosphere Module¶

`atmosphere` Module¶