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Transport Models

Viscosity models for computing temperature-dependent transport properties.

Available Models

Class Description Presets
Sutherland Standard Sutherland's law .air(), .nitrogen()
SutherlandLowTemp Low-temperature corrected .air()
SutherlandBlended Smooth polynomial blend .air()
Keyes High-temperature model .air(), .nitrogen()
PowerLaw Simple power law .air(m=0.76)

Methods

All transport models provide:

Method Returns Description
mu(temp) float Dynamic viscosity [Pa s]
nu(temp, dens) float Kinematic viscosity [m^2/s]
dmudt(temp) float Viscosity temperature derivative [Pa s / K]

Usage

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from flow_state.transport import Sutherland

# create model
model = Sutherland.air()

# compute viscosity at 300 K
T = 300.0
mu = model.mu(T)           # ~1.85e-5 Pa s
dmudt = model.dmudt(T)     # derivative for CFD applications
nu = model.nu(T, rho=1.2)  # kinematic viscosity

Custom Parameters

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from flow_state.transport import Sutherland

# custom gas
model = Sutherland.custom(
    mu_ref=1.8e-5,
    T_ref=300.0,
    S=120.0,
    name="my_gas"
)

Model Selection

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from flow_state.transport import (
    Sutherland,
    SutherlandLowTemp,
    SutherlandBlended,
    Keyes,
    PowerLaw,
)

# standard (moderate temperatures)
model = Sutherland.air()

# low-temperature flows (cryogenic, expansion tunnels)
model = SutherlandLowTemp.air()

# smooth derivative (CFD stability)
model = SutherlandBlended.air()

# high-temperature (hypersonic)
model = Keyes.air()

# simplified analysis
model = PowerLaw.air(m=0.76)

Theory

See Transport Theory for the underlying formulas.