Air

class Air

Bases: MaterialBase

Represents the material properties for air. This sets specific material properties for air, including dynamic viscosity, specific heat ratio, gas constant, and Prandtl number.

The thermodynamic properties are specified using NASA 9-coefficient polynomials for temperature-dependent specific heats via the thermally_perfect_gas parameter. By default, coefficients are set to reproduce a constant gamma=1.4 (calorically perfect gas).

Example

>>> fl.Air(
...     dynamic_viscosity=1.063e-05 * fl.u.Pa * fl.u.s
... )

With custom NASA 9-coefficient polynomial for single species:

>>> fl.Air(
...     thermally_perfect_gas=fl.ThermallyPerfectGas(
...         species=[
...             fl.FrozenSpecies(
...                 name="Air",
...                 nasa_9_coefficients=fl.NASA9Coefficients(
...                     temperature_ranges=[
...                         fl.NASA9CoefficientSet(
...                             temperature_range_min=200.0 * fl.u.K,
...                             temperature_range_max=1000.0 * fl.u.K,
...                             coefficients=[...],
...                         ),
...                         fl.NASA9CoefficientSet(
...                             temperature_range_min=1000.0 * fl.u.K,
...                             temperature_range_max=6000.0 * fl.u.K,
...                             coefficients=[...],
...                         ),
...                     ]
...                 ),
...                 mass_fraction=1.0,
...             )
...         ]
...     )
... )

With multi-species thermally perfect gas:

>>> fl.Air(
...     thermally_perfect_gas=fl.ThermallyPerfectGas(
...         species=[
...             fl.FrozenSpecies(name="N2", nasa_9_coefficients=..., mass_fraction=0.7555),
...             fl.FrozenSpecies(name="O2", nasa_9_coefficients=..., mass_fraction=0.2316),
...             fl.FrozenSpecies(name="Ar", nasa_9_coefficients=..., mass_fraction=0.0129),
...         ]
...     )
... )

---

Attributes

name: str

Default:

'air'

dynamic_viscosity: Sutherland | ViscosityType.NonNegative

The dynamic viscosity model or value for air. Defaults to a Sutherland model with standard atmospheric conditions.

Default:

Sutherland()

thermally_perfect_gas: ThermallyPerfectGas

Thermally perfect gas model with NASA 9-coefficient polynomials for temperature-dependent thermodynamic properties. Defaults to a single-species ‘Air’ with coefficients that reproduce constant gamma=1.4 (calorically perfect gas). For multi-species gas mixtures, specify multiple FrozenSpecies with their respective mass fractions.

Default:

ThermallyPerfectGas()

prandtl_number: float

Laminar Prandtl number. Default is 0.72 for air.

Default:

0.72

turbulent_prandtl_number: float

Turbulent Prandtl number. Default is 0.9.

Default:

0.9

Properties

gas_constant: SpecificHeatCapacityType.Positive

Returns the specific gas constant for air.

Returns:

The specific gas constant for air.

Return type:

SpecificHeatCapacityType.Positive

Additional Constructors

classmethod from_file(filename)

Loads a Flow360BaseModel from .json, or .yaml file.

Parameters:

filename (str) – Full path to the .yaml or .json file to load the Flow360BaseModel from.

Returns:

An instance of the component class calling load.

Return type:

Flow360BaseModel

Example

>>> params = Flow360BaseModel.from_file(filename='folder/sim.json') 

Methods

get_specific_heat_ratio(temperature)

Computes the specific heat ratio (gamma) at a given temperature from NASA polynomial.

For thermally perfect gas, gamma = cp/cv = (cp/R) / (cp/R - 1) varies with temperature. The cp/R is computed from the NASA 9-coefficient polynomial:

cp/R = a0*T^-2 + a1*T^-1 + a2 + a3*T + a4*T^2 + a5*T^3 + a6*T^4

Parameters:

temperature (AbsoluteTemperatureType) – The temperature at which to compute gamma.

Returns:

The specific heat ratio at the given temperature.

Return type:

pd.PositiveFloat

get_pressure(density, temperature)

Calculates the pressure of air using the ideal gas law.

Parameters:

• density (DensityType.Positive) – The density of the air.

• temperature (AbsoluteTemperatureType) – The temperature of the air.

Returns:

The calculated pressure.

Return type:

PressureType.Positive

get_speed_of_sound(temperature)

Calculates the speed of sound in air at a given temperature.

For thermally perfect gas, uses the temperature-dependent gamma from the NASA polynomial.

Parameters:

temperature (AbsoluteTemperatureType) – The temperature at which to calculate the speed of sound.

Returns:

The speed of sound at the specified temperature.

Return type:

VelocityType.Positive

get_dynamic_viscosity(temperature)

Calculates the dynamic viscosity of air at a given temperature.

Parameters:

temperature (AbsoluteTemperatureType) – The temperature at which to calculate the dynamic viscosity.

Returns:

The dynamic viscosity at the specified temperature.

Return type:

ViscosityType.NonNegative

help(methods=False)

Prints message describing the fields and methods of a Flow360BaseModel.

Parameters:

methods (bool = False) – Whether to also print out information about object’s methods.

Return type:

None

Example

>>> params.help(methods=True) 

to_file(filename, **kwargs)

Exports Flow360BaseModel instance to .json or .yaml file

Parameters:

filename (str) – Full path to the .json or .yaml or file to save the Flow360BaseModel to.

Return type:

None

Example

>>> params.to_file(filename='folder/flow360.json')