Viscosity

pygasflow.atd.viscosity.viscosity_air_power_law(T)[source]

Compute air’s viscosity using a power law:

Parameters
Tfloat or array_like

Temperature of the air in [K]

Returns
mufloat or array_like

Viscosity [kg / (m * s)]

Notes

The following equation is being used:

  • mu(T) = 0.702e-07 * T for T <= 200

  • mu(T) = 0.04644e-05 * T**0.65 for T > 200

Examples

Compute air’s viscosity at T=50K:

>>> from pygasflow.atd.viscosity import viscosity_air_power_law
>>> viscosity_air_power_law(50)
3.5100000000000003e-06
pygasflow.atd.viscosity.viscosity_air_southerland(T)[source]

Compute the viscosity of air with Southerland equation.

Parameters
Tfloat or array_like

Temperature of the air in [K]

Returns
mufloat or array_like

Viscosity [kg / (m * s)]

Examples

Compute air’s viscosity at T=50K:

>>> from pygasflow.atd.viscosity import viscosity_air_southerland
>>> viscosity_air_southerland(50)
3.2137209693578125e-06
pygasflow.atd.viscosity.viscosity_chapman_enskog(T, gas='air', M=None, sigma=None, Sigma_mu=None)[source]

Compute the viscosity of pure motoatomic or polyatomic gases using Chapman-Enskog theory.

There are two mode of operation:

  1. by providing the gas keyword argument, the algorithm will load pre-computed values of M, sigma and Sigma_mu. viscosity_chapman_enskog(T, gas="air" [optional])

  2. by providing M, sigma and Sigma_mu. This is going to disregard the value of gas. viscosity_chapman_enskog(T, M=M, sigma=sigma, Sigma_mu=Sigma_mu)

Parameters
Tfloat or array_like

Temperature of the air in [K]

gasstr, optional

Possible values are: 'air', 'N2', 'O2', 'NO', 'N', 'O', 'Ar', 'He'

Mfloat or None, optional

Molecular weigth [kg / kmole]

sigmafloat or None, optional

Collision parameter (first Lennard-Jones parameter) [1e10 m]

Sigma_mufloat or None, optional

Dimensionless collision integral

Returns
mufloat or array_like

Viscosity [kg / (m * s)]

References

  • “Basic of aerothermodynamics” by Ernst Heinrich, Table 13.1

  • “Transport Phenomena” by R. Byron Bird, Warren E. Stewart, Edwing N. Lightfoot, Table E2

Examples

Compute air’s viscosity at T=50K:

>>> from pygasflow.atd.viscosity import viscosity_chapman_enskog
>>> viscosity_chapman_enskog(50)
3.4452054654966263e-06

Compute the viscosity of molecular oxygen at T=300K:

>>> viscosity_chapman_enskog(300, gas="O2")
1.8423646870376057e-05