What Is the Spalart-Allmaras Detached Eddy Model?

Detached eddy simulation (DES) [27] is a modeling approach that combines features of Reynolds-Averaged (RANS) simulation in part of the flow and large eddy simulation (LES) in unsteady, separated regions. The DES version of the Spalart-Allmaras model contains modifications to the damping functions recommended by Squires et al. [29]. These modifications do not affect the predictions of fully turbulent flows, but prevent spurious upstream propagation of the eddy viscosity into attached laminar regions. In addition, recent updates by Spalart et al. [28] termed DDES (delayed detached eddy simulation) have been incorporated to enhance the ability of the model to distinguish between LES and RANS regions.

Spalart-Allmaras Detached Eddy Properties

Deformation Option	Selects the modified or standard production term.
	Modified	Selects the modified production term. This is recommended for most simulations. See Eqn. 175.
	Original	Selects the standard production term. This option allows comparison with results from other CFD codes that lack the modified production term. See Eqn. (173).
Convection	For guidance on selecting a convection, see Diffusion Term .
	1st-order	Selects the first-order convection.
	2nd-order	Selects the second-order convection.

Spalart-Allmaras Detached Eddy Expert Properties

Unless you are thoroughly familiar with the theoretical aspects of this model and the discretization techniques used in STAR-CCM+, we recommend that you not make any changes within the Expert category. The values in that category reflect both the model's design and discretization approaches that have been optimized for accuracy and performance. Tampering with them may diminish the effectiveness of the model.

Cb1	The coefficient , Eqn. 165.
Cb2	The coefficient , Eqn. 164.
Cdes	The DES length scale coefficient . Eqn. 183
CdesTimeLim	The DES blended upwind scheme time scale coefficient . Eqn. 183
Cprod	The coefficient , Eqn. 175.
Cv1	The coefficient , Eqn. 171.
Cv2	The coefficient , Eqn. 169.
Cw2	The coefficient , Eqn. 180.
Cw3	The coefficient , Eqn. 179.
Kappa	The von Karman constant , Eqns.(168) and (181).
Low Re Correction	Option to include the low Reynolds number correction factor in Eqn. 183. If checked, is computed as in Eqn. 186. If unchecked, is set to 1.
Secondary Gradients	Neglect or include the boundary secondary gradients for diffusion and/or the interior secondary gradients at mesh faces.
	On	Include both secondary gradients.
	Off	Exclude both secondary gradients.
	Interior Only	Include the interior secondary gradients only.
	Boundaries Only	Include the boundary secondary gradients only.
Sigma	The coefficient , Eqn. 164.

Field Functions Reference

The following primitive field functions are made available to the simulation when the Spalart-Allmaras turbulence model is used. These objects all have the same base properties.