The Euler-Euler Model, Turbulent Flow Interface
The Euler-Euler Model, Turbulent Flow (ee) interface (), found under the Multiphase Flow>Euler-Euler Model branch () when adding a physics interface, can be used to simulate high Reynolds number flow of a two-phase mixture containing a continuous and a dispersed phase. The Euler-Euler model assumes that both phases are continuous, fully interpenetrating, and incompressible (see Theory for the Euler-Euler Model Interfaces). Typical applications for the interface are fluidized beds (solid particles in gas), sedimentation (solid particles in liquid), or transport of liquid droplets or bubbles in a liquid.
The physics interface solves two sets of Navier-Stokes equations, one for each phase, in order to calculate the velocity field for each phase. The phases interchange momentum as described by a drag model. The pressure is calculated from a mixture-averaged continuity equation and the volume fraction of the dispersed phase is tracked with a transport equation.
Two-phase turbulence is modeled using the standard two-equation k-ε model with realizability constraints. The interface includes the possibility to solve one set of k-ε equations for the two-phase mixture, or to solve two sets of k-ε equations, one for each phase. Flow close to walls is modeled using wall functions.
Except where indicated below, the settings for this physics interface are the same as for The Euler-Euler Model, Laminar Flow Interface.
Turbulence
Turbulence Model Type
The default Turbulence model type is RANS, k-ε.
Two-Phase Turbulence
By default the Two-Phase Turbulence is defined as Mixture. This implies that one set of k-ε equations are solved for. To instead solve for two sets of k-ε equations, one for each fluid phase, select Phase specific (see Turbulent Two-Phase Flow Modeling).
Edit Turbulence Model Parameters
Turbulence model parameters are optimized to fit as many flow types as possible, but for some special cases, better performance can be obtained by tuning the model parameters. For a description of the turbulence model and the included model parameters see Turbulent Two-Phase Flow Modeling.
Dependent Variables
The following dependent variables (field variables) are defined for this interface:
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Velocity field, continuous phase uc
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Velocity field, dispersed phase ud
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Pressure p
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Turbulent kinetic energy, mixture k
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Turbulent dissipation rate, mixture ep
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Turbulent kinetic energy, continuous phase kc
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Turbulent dissipation rate, continuous phase epc
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Turbulent kinetic energy, dispersed phase kd
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Turbulent dissipation rate, dispersed phase epd
The names can be changed but the names of fields and dependent variables must be unique within a component.
Advanced settings
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, k-ε.
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.