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:
by providing the
gas
keyword argument, the algorithm will load pre-computed values ofM
,sigma
andSigma_mu
.viscosity_chapman_enskog(T, gas="air" [optional])
by providing
M
,sigma
andSigma_mu
. This is going to disregard the value ofgas
.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