flow360.TurbulenceQuantities

flow360.TurbulenceQuantities#

TurbulenceQuantities(viscosity_ratio=None, modified_viscosity_ratio=None, modified_viscosity=None, specific_dissipation_rate=None, turbulent_kinetic_energy=None, turbulent_length_scale=None, turbulent_intensity=None)[source]#

TurbulenceQuantities() function specifies turbulence conditions for the Inflow or Freestream at boundaries. The turbulence properties that can be specified are listed below. All values are dimensional. For valid specifications as well as the default values, please see the Notes section below.

Parameters:

  • viscosity_ratio (>= 0) – The ratio between the turbulent viscosity and freestream laminar viscosity. Applicable to both KOmegaSST and SpalartAllmaras. Its value will be converted to modifiedTurbulentViscosityRatio when using SpalartAllmaras model.

  • modified_viscosity_ratio (>= 0) – The ratio between the modified turbulent viscosity (in SA model) and freestream laminar viscosity. Applicable to SpalartAllmaras.

  • modified_viscosity (>=0) – The modified turbulent viscosity, aka nuHat. Applicable to SpalartAllmaras.

  • specific_dissipation_rate (>= 0) – The turbulent specific dissipation rate. Applicable to KOmegaSST.

  • turbulent_kinetic_energy (>=0) – The turbulent kinetic energy. Applicable to KOmegaSST.

  • turbulent_length_scale (> 0) – The turbulent length scale is an estimation of the size of the eddies that are modeled/not resolved. Applicable to KOmegaSST.

  • turbulent_intensity (>= 0) – The turbulent intensity is related to the turbulent kinetic energy by \(k = 1.5(U_{ref} * I)^2\) where \(k\) is the dimensional turbulent kinetic energy, \(U_{ref}\) is the reference velocity and \(I\) is the turbulent intensity. The value represents the actual magnitude of intensity instead of percentage. Applicable to KOmegaSST.

Return type:

A matching tubulence specification object.

Raises:

ValueError – If the TurbulenceQuantities inputs do not represent a valid specification.

Notes

Default Behavior

The default turbulence depends on the turbulence model. For SA model without transition model this is equivalent to set modified_viscosity_ratio = 3.0 (or effectively viscosity_ratio = 0.210438). For SA model with transition model, modified_viscosity_ratio = 0.1 (or effectively viscosity_ratio = 2.794e-7). For SST model the default turbulence is viscosity_ratio = 0.01 with default specific_dissipation_rate = \(MachRef/L_{box}\) where \(L_{box} \triangleq exp\left(\displaystyle\sum_{i=1}^{3}log(x_{i,max}-x_{i,min}\right)\). \(x_{i,max},x_{i,min}\) is the bounding box dimension for wall boundaries.

Valid Parameter Combinations

The following table shows which parameter combinations are valid for each turbulence model:

Turbulence Quantity Compatibility#

Parameter Combination

SA Model

SST Model

(default - no parameters)

✓ (default)

✓ (default)

viscosity_ratio alone

✓ (converted to modified_viscosity_ratio)

✓ (overrides default, keeps default specific_dissipation_rate)

modified_viscosity alone

✓

✗

modified_viscosity_ratio alone

✓

✗

turbulent_kinetic_energy alone

✗

✓ (specific_dissipation_rate set to default)

turbulent_intensity alone

✗

✓ (specific_dissipation_rate set to default)

turbulent_length_scale alone

✗

✓ (specific_dissipation_rate set to default)

turbulent_kinetic_energy + specific_dissipation_rate

✗

✓

turbulent_intensity + specific_dissipation_rate

✗

✓

turbulent_kinetic_energy + viscosity_ratio

✗

✓

turbulent_intensity + viscosity_ratio

✗

✓

turbulent_kinetic_energy + turbulent_length_scale

✗

✓

turbulent_intensity + turbulent_length_scale

✗

✓

specific_dissipation_rate + viscosity_ratio

✗

✓

specific_dissipation_rate + turbulent_length_scale

✗

✓

viscosity_ratio + turbulent_length_scale

✗

✓

Example

Apply modified turbulent viscosity ratio for SA model.

>>> fl.TurbulenceQuantities(modified_viscosity_ratio=10)

Apply turbulent kinetic energy and specific dissipation rate for SST model.

>>> fl.TurbulenceQuantities(
    turbulent_kinetic_energy=0.2 * fl.u.m**2 / fl.u.s**2,
    specific_dissipation_rate=100 / fl.u.s)

Apply specific dissipation rate and turbulent viscosity ratio for SST model.

>>> fl.TurbulenceQuantities(specific_dissipation_rate=150 / fl.u.s, viscosity_ratio=1000)
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