Creating Phases and Selecting Phase Models

Create the phases and select the appropriate phase models.

The two phases, Liquid and Vapor, that are flowing through the section of vertical pipe represent water and steam. These phases are defined by creating phases under the Eulerian physics model, but material properties are set later once all other models have been selected.

The main modeling choices that are made at this stage are:
  • A K-Epsilon model with a two-layer wall treatment is selected for the continuous phase so that it can be used under a wide range of flow conditions.
  • The Turbulence Response model is an appropriate model for the velocity fluctuations that are experienced in the dispersed phase for this bubbly flow.
  • The S-gamma model is activated for the disperse phase so that it can track bubble size starting from bubble creation at the boiling wall, and including the effects of breakup, coalescence, and (most importantly) condensation.

To create the phases and select the phase models:

Create the liquid phase.
  1. In the Physics 1 continuum, right-click the Models > Multiphase > Phases node and create a phase.
  2. Rename the Phase 1 node to Liquid.
  3. For the Liquid phase, select the following models:

    Group Box

    Model

    Enabled Models

    Flow (Pre-selected)

    Turbulent (Pre-selected)

    Material

    Liquid

    Reynolds-Averaged Navier-Stokes (Selected automatically)

    Reynolds-Averaged Turbulence

    K-Epsilon Turbulence

    Realizable K-Epsilon Two-Layer (Selected automatically)

    Wall Distance (Selected automatically)

    Two-Layer All y+ Wall Treatment (Selected automatically)

    Equation of State

    Constant Density

    Energy

    Segregated Fluid Temperature

  4. Click Close.

Create the gas phase.

  1. Create a second phase and rename it to Vapor.
  2. For the Vapor phase, select the following models:
    Group Box Model
    Enabled Models Flow (Pre-selected)

    Turbulent (Pre-selected)

    Material Gas

    Reynolds-Averaged Navier-Stokes (Selected automatically)

    Reynolds-Averaged Turbulence Turbulence Response
    Turbulence Response Models Issa Turbulence Response Model

    Wall Distance (Selected automatically)

    Equation of State Constant Density
    Energy Segregated Fluid Temperature
    Optional Models Particle Size Distribution
  3. Deactivate Auto-select recommended models.
  4. In the Particle Size Distribution box, select S-Gamma.
  5. In the S-Gamma Closure box, select Pre-Integrated S-Gamma.
  6. Click Close.
  7. Rename the Vapor > Models > Gas > Air node to Steam.

    The Phases node appears as shown.



  8. Save the simulation.