K-Epsilon Regions Reference

This section details the conditions that are required for each region type that is supported by the K-Epsilon turbulence model. In addition, information is provided about the values for each region type.

Region conditions and values are elected by the region type, and/or by methods selected in corresponding nodes in the Conditions node.

Fluid Region

Note	Region types that do not require setting any conditions or values are not listed.

Turbulence Source Option

Controls whether you want to use a turbulence source term, as well as what type.

Turbulence Source Option	Corresponding Value Nodes
None	None.
Specified	Turbulent Dissipation Rate Source Scalar profile value to specify a turbulence source for $ε$ directly. Turbulent Kinetic Energy Source Scalar profile value to specify a turbulence source for $k$ directly.
Ambient	Ambient Turbulence Specification Adds a turbulence source to counteract turbulence decay in external aero flows. The source terms are inferred from the specified Inflow Boundary. Provided that reasonable inflow turbulence is specified and that flow uniformly enters the domain at this boundary, the sources should not contaminate any boundary layers. The benefits of this feature are: Easier fine-tuning of turbulence intensity without having to have excessively large turbulent viscosity ratios. This is particularly advantageous for the transition model. The ability to properly simulate a plane or car moving through background turbulence.

Porous Region

Turbulence Specification

Controls how you define the turbulence profile within a porous region.

The K-Epsilon model requires the turbulent kinetic energy $k$ and the turbulent dissipation rate $ε$ . You can enter the corresponding values directly or have them derived from other turbulence quantities.

Method	Corresponding Value Nodes
K + Epsilon	Turbulent Kinetic Energy Scalar profile value to specify $k$ directly. Turbulent Dissipation Rate Scalar profile value to specify $ε$ directly.
Intensity + Length Scale Calculation of $k$ and $ε$ from a specified turbulence intensity $I$ and length scale $l$ using Eqn. (1356) and Eqn. (1358). Do not use this method if the velocity field is initialized to zero.	Turbulence Intensity Scalar profile value to specify $I$ . Turbulent Length Scale Scalar profile value to specify $l$ .
Intensity + Viscosity Ratio Calculation of $k$ and $ε$ from a specified turbulence intensity $I$ and viscosity ratio $μ_{t} / μ$ using Eqn. (1357) and Eqn. (1359). Do not use this method if the velocity field is initialized to zero.	Turbulence Intensity As for Intensity + Length Scale. Turbulent Viscosity Ratio Scalar profile value to specify the ratio of turbulent to laminar viscosity $μ_{t} / μ$ .

Method

Corresponding Value Nodes

K + Epsilon

Turbulent Kinetic Energy: Scalar profile value to specify $k$ directly.
Turbulent Dissipation Rate: Scalar profile value to specify $ε$ directly.

Intensity + Length Scale

Calculation of $k$ and $ε$ from a specified turbulence intensity $I$ and length scale $l$ using Eqn. (1356) and Eqn. (1358).

Do not use this method if the velocity field is initialized to zero.

Turbulence Intensity: Scalar profile value to specify $I$ .
Turbulent Length Scale: Scalar profile value to specify $l$ .

Intensity + Viscosity Ratio

Calculation of $k$ and $ε$ from a specified turbulence intensity $I$ and viscosity ratio $μ_{t} / μ$ using Eqn. (1357) and Eqn. (1359).

Do not use this method if the velocity field is initialized to zero.

Turbulence Intensity: As for Intensity + Length Scale.
Turbulent Viscosity Ratio: Scalar profile value to specify the ratio of turbulent to laminar viscosity $μ_{t} / μ$ .