The Mixture Model, k-ε (mm) interface (
), found under the
Multiphase Flow>Mixture Model>Mixture Model, Turbulent Flow branch (
) when adding a physics interface, is used to model the flow at high Reynolds numbers of liquids containing a dispersed phase. The dispersed phase can be bubbles, liquid droplets, or solid particles, which are assumed to always travel with their terminal velocity.
The Mixture Model, k-ε interface solves one set of Navier–Stokes equations for the momentum of the mixture. The pressure distribution is calculated from a mixture averaged continuity equation and the velocity of the dispersed phase is described by a slip model. The volume fraction of the dispersed phase is tracked by solving a transport equation for the volume fraction. Turbulence effects are modeled using the standard two-equation
k-
ε model with realizability constraints. Flow close to walls is modeled using wall functions.
The default Turbulence model type is
RANS. A different turbulence model can be selected under
Turbulence model. The default turbulence model is
k-ε.
Wall treatment for the k-
ε model can only be set to
Wall functions. More options become available by selecting another option under
Turbulence model.
To display this section, click the Show More Options button (
) and select
Stabilization. The settings for this section are the same as for
The Mixture Model, Laminar Flow Interface with the addition of this section: stabilization for the turbulence variables in the
Turbulence equations area.
To display this section, click the Show More Options button (
) and select
Advanced Physics Options. The
Turbulence variables scale parameters subsection is available when the
Turbulence model type is set to
RANS.
The Jscale 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.