flightcondition 22.7

Airspeed conversions (true/calibrated/equivalent/Mach), atmospheric data, and more with built-in unit checking.

About

Airspeed conversions (true/calibrated/equivalent/Mach), atmospheric data, and more with built-in unit checking. Specific sub-modules include:

• flightcondition : input altitude to compute common flight condition data. Easily swap between Mach number, true airspeed, calibrated airspeed, and equivalent airspeed. Includes atmospheric data.

• atmosphere : input altitude to compute 1993 International Standard Atmosphere data. Many relevant, derived quantities are included.

• units : built-in unit-checking and conversion using pint package.

See examples below for usage!

Author

Matthew C. Jones <[e-mail]>

Installation

Install Commands

Install using the pip package-management system. The easiest method is to open the terminal and run:

pip install flightcondition

Alternatively, manually download the source code, unpack, and run:

pip install <path/to/flightcondition>

Dependencies

• numpy: package for scientific computing.

• pint: package for dealing with units.

Usage

In a Python script or an ipython notebook, import all utilities with,

from flightcondition import *

or more explicitly as shown in the following examples.

Flight Condition

The Flightcondition class can be used to compute and interact with common flight condition data. Access flight condition quantities through altitude, speed, and length objects.

Outputs include:

1. altitude (atmospheric) quantities - see atmosphere below.

2. speed quantities and conversions, for example: Mach number mach, True airspeed TAS, Calibrated airspeed CAS, and Equivalent airspeed EAS.

3. length quantities, for example: Reynolds number Re and Reynolds number per-unit-length Re_by_ell.

And other lesser-used quantities! See the source code or explore interactively.

Usage:

from flightcondition import FlightCondition, unit, dimless

# Compute flight conditions for a scalar or array of altitudes
altitudes = [0, 10, 33.5] * unit('kft')
fc = FlightCondition(altitudes, EAS=300*unit('knots'))

# Print flight condition data:
print(f"{fc}")

# Print extended output:
print(f"\n{fc.tostring(full_output=True)}")

# Access flight speed formats individually
M = fc.speed.M
U_inf, U_CAS, U_EAS = fc.speed.TAS, fc.speed.CAS, fc.speed.EAS

# Access atmospheric data alone (see Atmosphere class for options)
alt = fc.altitude  # access Atmosphere object 'altitude'
p, T, rho, nu, a = alt.p, alt.T, alt.rho, alt.nu, alt.a

# Input true/calibrated/equivalent airspeed or Mach number
fc_TAS = FlightCondition(altitudes, TAS=300*unit('knots'))
fc_CAS = FlightCondition(altitudes, CAS=300*unit('knots'))
fc_EAS = FlightCondition(altitudes, EAS=300*unit('knots'))
fc_M = FlightCondition(altitudes, M=0.4535*dimless)

# Specify desired units on input and output
altitudes_in_km = [0, 3.048, 10.2108] * unit('km')
lengthscale = 60 * unit('in')  # arbitrary length scale of interest
fc_other_units = FlightCondition(altitudes, EAS=154.33*unit('m/s'),
                                ell=lengthscale)
U_TAS = fc_other_units.speed.TAS
print(f"\nThe true airspeed in m/s is {U_TAS.to('m/s'):.5g}")
print(f"The true airspeed in km/s is {U_TAS.to('km/s'):.5g}")

# Compute additional derived quantities (see class for all options)
print(f"\nThe dynamic pressure in psi is "
    f"{fc.speed.q_inf.to('psi'):.5g}")
print(f"The Reynolds number is {fc.length.Re:.5g}")
print(f"The Reynolds number per-unit-length [1/in] is "
    f"{fc.length.Re_by_ell.to('1/in'):.5g}")

Atmosphere

The Atmosphere class can be used to compute and interact with common standard atmosphere data and derived quantities.

Outputs include:

• Pressure p

• Temperature T

• Density rho

• Sound speed a

• Dynamic viscosity mu

• Kinematic viscosity nu

• Thermal conductivity k

• Layer name layer.name

• Geometric altitude h

• Geopotential altitude H

• Acceleration due to gravity g

• Mean free path MFP

Usage:

from flightcondition import Atmosphere, unit

# Compute atmospheric data for a scalar or array of altitudes
h = [0.0, 12.7, 44.2, 81.0] * unit('km')
atm = Atmosphere(h)

# Print abbreviated output:
print(f"\n{atm}")

# Print extended output in US units:
print(f"\n{atm.tostring(full_output=True, US_units=True)}")

# See also the linspace() function from numpy, e.g.
# h = linspace(0, 81.0, 82) * unit('km')

# Access individual properties and convert to desired units: "
p, T, rho, nu, a = atm.p, atm.T, atm.rho, atm.nu, atm.a
print(f"\nThe pressure in psi is {p.to('psi'):.5g}")

# Compute additional properties such as thermal conductivity,
# mean free path, and more (see class for all options)
print(f"\nThe thermal conductivity is {atm.k:.5g}"
    f"\nThe mean free path = {atm.MFP:.5g}")

Units

Conveniently input, output, and convert units using pint units.

from flightcondition import unit, printv

h = 33 * unit('km')
print(h.to('kft'))
# >>> 108.26771653543307 kft
printv(h, to='kft')
# >>> h = 108.27 kft

U_inf = 20 * unit('knots')
rho_inf = 1.225 * unit('kg/m^3')
q_inf = 0.5*rho_inf*U_inf**2
printv(q_inf, to='psi')
# >>> q_inf = 0.0094042 psi

Note that pint does not support conflicting unit registries so avoid interactions between flightcondition.unit and a separate pint.UnitRegistry.

Command Line Interface

It is also possible to compute flight conditions from the command line for convenience but with limited functionality. Run flightcondition -h for help.

An example call is provided for the flight condition of 233 knots-equivalent-airspeed at 23 kilo-feet with a length scale of 4 feet:

flightcondition --alt 23 kft --EAS 233 kt --ell 4 ft

License

flightcondition is licensed under the MIT LICENSE. See the LICENSE document.

Disclaimer

The software is provided “as is”, without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and noninfringement. In no event shall the authors or copyright holders be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with the software or the use or other dealings in the software.