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12.12 Steps in Using a Turbulence Model

When your 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 the turbulence model, select Spalart-Allmaras, k-epsilon, k-omega, Reynolds Stress, Detached Eddy Simulation (3D), and Large Eddy Simulation (LES) (3D) under Model in the Viscous Model panel (Figure  12.12.1).

Define $\rightarrow$ Models $\rightarrow$ Viscous...

Figure 12.12.1: The Viscous Model Panel

If you choose the k-epsilon model, select Standard, RNG, or Realizable under 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 panel:
  • Standard Wall Functions

  • Non-Equilibrium Wall Functions

  • Enhanced Wall Treatment

  • User-Defined Wall Functions
These near-wall options are described in detail in Section  12.10. By default, the standard wall function is enabled.

The near-wall treatment for the Spalart-Allmaras, $k$- $\omega$, and LES models is defined automatically, as described in Sections  12.3.7, 12.5.3, and 12.9.4, respectively.

3.   Enable the appropriate turbulence modeling options in the Viscous Model panel. See Section  12.19 for details.

4.   Specify the boundary conditions for the solution variables.

Define $\rightarrow$ Boundary Conditions...

See Section  12.20 for details.

5.   Specify the initial guess for the solution variables.

Solve $\rightarrow$ Initialize $\rightarrow$ Initialize...

See Section  12.21 for details. Note that Reynolds stresses are automatically initialized using $k$, and therefore need not be initialized.

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© Fluent Inc. 2006-09-20