The Turbulent Flow, k-ε (spf) interface () is used for simulating single-phase flows at high Reynolds numbers. The physics interface is suitable for incompressible flows, weakly compressible flows, and compressible flows at low Mach numbers (typically less than 0.3).

The equations solved by the Turbulent Flow, k-ε interface are the Reynolds-averaged Navier–Stokes (RANS) equations for conservation of momentum and the continuity equation for conservation of mass. Turbulence effects are modeled using the standard two-equation k-ε model with realizability constraints. The flow near walls is modeled using wall functions.

The Turbulent Flow, k-ε interface can be used for stationary and time-dependent analyses. The main feature is Fluid Properties, which adds the RANS equations and the transport equations for k and ε, 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, and Initial Values.

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

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

Wall treatment for the k-ε model can only be set to Wall functions. More options becomes available by selecting another option under Turbulence model.

The Turbulence model property disables the Neglect inertial term (Stokes flow) check box, and for 2D components also the Shallow Channel Approximation check box.

For this physics interface the parameters are Ce1, Ce2, Cμ, σk, σe, κv, and B.

To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box. The Turbulence variables scale parameters subsection is available when the Turbulence model type is set to RANS.

In addition to the settings described for the Laminar Flow interface, enter a value for Uscale and Lfact under the Turbulence variables scale parameters subsection.

The Uscale and Lfact parameters are used to calculate absolute tolerances for the turbulence variables. The scaling parameters must only contain numerical values, units or parameters defined under Global Definitions. The scaling parameters cannot contain variables. The parameters are used when a new default solver for a transient study step is generated. If you change the parameters, the new values take effect the next time you generate a new default solver