The DES RBVM, Spalart-Allmaras (spf) interface () simulates turbulent single-phase flows by resolving the largest three-dimensional unsteady eddies and modeling the effect of the smaller eddies with the residual-based variational multiscale (RBVM) method in the bulk and with the Spalart–Allmaras model near walls. The equations solved by the DES RBVM, Spalart–Allmaras interface are the continuity equation for conservation of mass, the Navier–Stokes equation, augmented by additional stress terms, for conservation of momentum, and the Spalart–Allmaras equation for the undamped kinematic viscosity. Consistent modeling is used for the additional stresses.

The DES RBVM, Spalart–Allmaras interface should only be used for three-dimensional, time-dependent analyses. The main feature is Fluid Properties, which adds the Navier–Stokes, continuity, and Spalart–Allmaras equations, and provides an interface for defining the fluid material and its properties. When this physics interface is added, the following default nodes are also added in the Model Builder: Fluid Properties, Initial Values, and Wall.

Except where included below, see The Laminar Flow Interface for all the other settings.

A different LES model can be selected under LES model. A RANS turbulence model can be selected by changing the Turbulence model type to RANS, and a LES model can be selected by changing the Turbulence model type to LES. Laminar or creeping flow may be simulated by changing the Turbulence model type to None.

The Turbulence model property disables the Neglect inertial term (Stokes flow) check box and Enable porous media domains check box.

The DES RBVM, Spalart–Allmaras model employs per default an Automatic wall treatment, which switches between a low-Reynolds-number formulation and a wall-function formulation depending on how well resolved the flow is close to the wall. The automatic wall treatment gives a robust formulation that makes the most out of the available resolution.

Select the Low Re option in order to enforce resolution all the way down to the wall. This can be more accurate that the automatic wall treatment provided that the mesh is fine enough.

For this physics interface the parameters are Cμ, for the Include synthetic turbulence option in the Velocity inlet condition and the Spalart–Allmaras parameters Cb1, Cb2, Cv1, , Cw2, Cw3, κv, B, and CDES.

To enable this section, click the Show More Options button () and select Stabilization in the Show More Options dialog box.

The Use dynamic subgrid time scale check box is not selected by default.

Select the Limit small time steps effect on stabilization time scale check box to prevent loss of stabilization at small time steps. This check box is selected by default.