15.12. Setting Up the Detached Eddy Simulation Model

When using the Detached Eddy Simulation (DES) model, the following underlying RANS turbulence models can be used:

  • Spalart-Allmaras

  • Realizable -

  • SST -

  • BSL -

  • Transition SST

Note that for the DES model, the Bounded Central Differencing scheme (available in the Solution Methods task page) is recommended for momentum discretization, and is the default setting.

For additional information, see the following sections:

 

15.12.1. Setting Up DES with the Spalart-Allmaras Model

To set up a Detached Eddy Simulation with the Spalart-Allmaras model, select Detached Eddy Simulation (DES) from the Model list in the Viscous Model dialog box and then select Spalart-Allmaras from the RANS Model list.

Ansys Fluent uses Equation 4–271 (in the Theory Guide) to compute the value of the length scale for the Spalart-Allmaras model. By default, the empirical constant is set to 0.65. You can change its value in the Cdes field under Model Constants. The following options are available for this model:

Figure 15.22: The Viscous Model Dialog Box Displaying Options for DES with the Spalart-Allmaras Model

The Viscous Model Dialog Box Displaying Options for DES with the Spalart-Allmaras Model

Additionally, you can perform the following DES-specific function by using the /define/models/viscous/detached-eddy-simulation? text command:

  • Modify only the length scales that appear in the destruction term in equation (the default is to modify all length scales within the equation)

 

15.12.2. Setting Up DES with the Realizable k-ε Model

To set up a Detached Eddy Simulation with the Realizable - model, select Detached Eddy Simulation (DES) from the Model list in the Viscous Model dialog box and then select Realizable k-epsilon from the RANS Model list.

The model-specific options for DES with the Realizable - model are the following:

The model constant is set to 0.61 for the Realizable - model (see DES with the Realizable k-ε Model in the Theory Guide). The enhanced wall treatment (EWT-) is always enabled for DES with the Realizable - model (see Enhanced Wall Treatment ε-Equation (EWT-ε) in the Theory Guide).

Figure 15.23: The Viscous Model Dialog Box Displaying Options for DES with the Realizable k-ε Model

The Viscous Model Dialog Box Displaying Options for DES with the Realizable k-ε Model

 

15.12.3. Setting Up DES with the SST k-ω Model

To set up a Detached Eddy Simulation with the SST - model, select Detached Eddy Simulation (DES) from the Model list in the Viscous Model dialog box and then select SST k-omega from the RANS Model list.

The model-specific options that you can select for DES with the SST - model are the following:

The model constant is set to 0.61 for the SST - RANS model (see DES with the BSL or SST k-ω Model in the Theory Guide).

Figure 15.24: The Viscous Model Dialog Box Displaying Options for DES with the SST k-ω Model

The Viscous Model Dialog Box Displaying Options for DES with the SST k-ω Model

 

15.12.4. Setting Up DES with the BSL k-ω Model

To set up a Detached Eddy Simulation with the BSL - model for a transient case, select k-omega from the Model list in the Viscous Model dialog box, select BSL from the k-omega Model list, and enable the Detached Eddy Simulation (DES) option in the Scale-Resolving Simulation Options group box.

The model-specific options that you can select for DES with the BSL - model are the following:

The model constant is set to 0.61 for the BSL - RANS model (see DES with the BSL or SST k-ω Model in the Theory Guide).

Figure 15.25: The Viscous Model Dialog Box Displaying Options for DES with the BSL k-ω Model

The Viscous Model Dialog Box Displaying Options for DES with the BSL k-ω Model

 

15.12.5. Setting Up DES with the Transition SST Model

To set up a Detached Eddy Simulation with the Transition SST model for a transient case, select Transition SST from the Model list in the Viscous Model dialog box and then enable the Detached Eddy Simulation (DES) option in the Scale-Resolving Simulation Options group box.

For DES with the Transition SST model, you can choose to enable the Delayed DES option in the DES Options group box (see Delayed Detached Eddy Simulation (DDES) for details). When this option is enabled you can make a selection from the Shielding Functions list, as described in Shielding Functions for the BSL / SST / Transition SST Detached Eddy Simulation Model.

Figure 15.26: The Viscous Model Dialog Box Displaying Options for DES with the Transition SST Model

The Viscous Model Dialog Box Displaying Options for DES with the Transition SST Model

Note that the y+-insensitive wall treatment of the underlying turbulence model is used. For details on the available options, see y+-Insensitive Near-Wall Treatment for ω-based Turbulence Models in the Fluent Theory Guide.