Defining the Eulerian Phases

The Multiphase model controls the definition of Eulerian phases within the physics continuum. You define the bulk properties and phase composition of the fluid mixture in two separate stages.

When you activate the Multiphase model in the physics continuum, Simcenter STAR-CCM+ automatically selects the multiphase fluid model and sets up a default immiscible fluid mixture. It contains no Eulerian phases in its initial state.

Note the following:

  • The most common situation is a two-phase, liquid-gas mixture.
  • Default names, material properties, and (Constant) property values are assigned to materials retrieved from the database.

    If none of these materials correspond to the phases present in your problem, do the following:

    • Rename the appropriate materials by right-clicking its node in the tree.

    • Open the corresponding Properties node and specify new settings as necessary.

  • The order in which phases are defined is not important in principle.

    However, if you want to model surface tension in the simulation at some point, you are advised to define the liquid phase as the first component.

  • For laminar flows, it is possible to select the Non-Newtonian Generalized Power Law for the dynamic viscosity of liquid materials in a VOF simulation.

  • Simcenter STAR-CCM+ does not support multi-component VOF phases in combination with a mixing-plane interface. Single-component VOF phases only are supported.

Create the necessary phases and select the appropriate phase models.

The number of phases required depends on what you are modeling. Melting and Solidification require the liquid phase only - the solid phase is assumed to be the solid form of the liquid.

For each phase, do the following:

  1. Create a Eulerian phase and then open the Phase Model Selection dialog.
  2. From the Material group box, select the appropriate model:
    Material Notes
    Gas
    Multi-Component Gas
    Liquid
    Multi-Component Liquid Boiling is not supported.
  3. For multi-component materials only, from the Reaction Regime box, select the appropriate option:
    Reaction Regime Notes
    Non-reacting The Species model is selected automatically.
    Reacting Either:
    See:
  4. From the Equation of State group box, select the appropriate option:
    Equation of State Notes
    Constant Density
    Polynomial Density
    User Defined EOS
    Ideal Gas Gas materials only. Energy model is selected automatically.
    Real Gas Gas materials only. IAPWS-IF97 (Steam) model is selected automatically for single-component gas.
    IAPWS-IF97 (Water) Liquid materials only.
  5. From the Optional Models group box, select the appropriate options:
    Optional Model Notes
    Wall Porosity Not available for multi-component liquids.

    See Wall Porosity.

    Wall Distance Used to account for near-wall effects.

    See Wall Distance.

    Mass Error Rate Used for dealing with mass conservation errors.

    See Mass Error Rate Model Reference.

    Mass Imbalance Correction

    Enforces mass conservation of the phase. This model is useful when the flow rate of the phase through the system is very small compared to the volume of the phase in the system. That is, simulations that are characterized as a large volume that is fed and emptied though small leakage paths.

    You can activate this model in one phase only in a VOF simulation.

    See Mass Imbalance Correction Model Reference.
    Passive Scalar Used for tracking the phase material within the simulation.

    See Modeling Passive Scalars.

    Blob Detection Used to identify grid-resolved liquid droplets or gas bubbles in the VOF field.

    See Detecting Liquid Droplets or Gas Bubbles.

    Species

    Available for multi-component phases only.

    See Species.

    Melting-Solidification Available for liquid materials only.

    Adds the following models to the Optional Models group box: