12.4 Steps in Using a Turbulence Model

When your ANSYS FLUENT model includes turbulence you need to activate the relevant model and options, and supply turbulent boundary conditions. These inputs are described in this section.

The procedure for setting up a turbulent flow problem is described below. (Note that this procedure includes only those steps necessary for the turbulence model itself; you will need to set up other models, boundary conditions, etc. as usual.)

1.   To activate one of the turbulence models, select either Spalart-Allmaras, k-epsilon, k-omega, Transition k-kl-omega, Transition SST, Reynolds Stress, Detached Eddy Simulation, or Large Eddy Simulation (LES) under Model in the Viscous Model dialog box (Figure  12.4.1).

Models Viscous Edit...

Figure 12.4.1: The Viscous Model Dialog Box

If you choose the k-epsilon model, select either Standard, RNG, or Realizable under the k-epsilon Model. If you choose the k-omega model, select Standard or SST under k-omega Model.

The Detached Eddy Simulation and the Large Eddy Simulation (LES) models are available only for 3D cases.

2.   If the flow involves walls, and you are using one of the $k$- $\epsilon$ models or the RSM, choose one of the following options for the Near-Wall Treatment in the Viscous Model dialog box:

• Standard Wall Functions

• Non-Equilibrium Wall Functions

• Enhanced Wall Treatment

• User-Defined Wall Functions

For more information about these near-wall options, see this section in the separate Theory Guide. By default, the standard wall function is enabled.

For more information about the automatically defined near-wall treatment for the Spalart-Allmaras model, see this section in the separate Theory Guide.

For more information about the automatically defined near-wall treatment for the $k$- $\omega$ model, see this section in the separate Theory Guide.

For more information about the automatically defined near-wall treatment for the LES model, see this section in the separate Theory Guide.

3.   Enable the appropriate turbulence modeling options in the Viscous Model dialog box. See Section  12.13 for details.

4.   Specify the boundary conditions for the solution variables.

Boundary Conditions

See Section  12.14 for details.

5.   Specify the initial guess for the solution variables.

Solution Initialization

See Section  12.15 for details. Note that Reynolds stresses are automatically initialized using $k$, and therefore need not be initialized explicitly.