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

The valid combinations of multiple turbulence quantities is summarized as follows,

default

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.

viscosity_ratio alone

This applies to both SST and SA model. For SST model this is effectively an override of the above default viscosity_ratio value while keeping the default specificDissipationRate. For SA model the viscosity_ratio will be converted to the modified_viscosity_ratio.

turbulent_kinetic_energy or turbulent_intensity alone

For SST model only. specific_dissipation_rate will be set to the default value.

turbulent_length_scale alone

For SST model only. specific_dissipation_rate will be set to the default value.

modified_viscosity

For SA model only.

modified_viscosity_ratio

For SA model only.

turbulent_kinetic_energy or turbulent_intensity with specific_dissipation_rate

For SST model only.

turbulent_kinetic_energy or turbulent_intensity with viscosity_ratio

For SST model only.

turbulent_kinetic_energy or turbulent_intensity with turbulent_length_scale

For SST model only.

specific_dissipation_rate with viscosity_ratio

For SST model only.

specific_dissipation_rate with turbulent_length_scale

For SST model only.

viscosity_ratio with turbulent_length_scale

For SST model only.

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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