Defining the Phase Interactions

Using the Multiphase Interaction model, you define the interaction between the continuous water phase and the dispersed hexane phase. Phase interaction models account for droplet breakup and coalescence.

For turbulent breakup, two models are available: Martinez-Bazan Fragments Breakage Rate and Tsouris and Tavlarides Breakage Rate. The Tsouris and Tavlarides Breakage Rate is the most suitable model for this tutorial case as it does not have a minimum particle diameter for breakup. The model specifies a breakup probability that decreases exponentially with droplet diameter.

The Luo Coalescence Efficiency model is the only option available within the AMUSIG model for coalescence in turbulent conditions. The model specifies a higher probability of coalescence due to the longer contact time caused by turbulence fluctuations, and a shorter bubble deformation time.

When you create a phase interaction, you select the continuous phase first, and then the dispersed phase. When you select the dispersed phase, you also choose the phase interaction type. In this simulation, the continuous phase is Water, the dispersed phase is Hexane, and the phase interaction type is Continuous-Dispersed Topology.

To define the phase interactions:

  1. In the Physics 1 continuum, right-click the Models > Multiphase Interaction > Phase Interactions node and select New > Water > Hexane (Continuous-Dispersed).
  2. Right-click Phase Interaction 1 > Models and click Select Models. Choose the following additional models:
    Group Box Model
    Optional Models

    Turbulent Breakup

    Multiple Size-Group Breakup (Selected automatically)

    Breakage Rate

    Tsouris and Tavlarides Breakage Rate

    Tsouris and Tavlarides Daughter Particle Size Distribution (Selected automatically)

    Optional Models

    Turbulent Coalescence

    Multiple Size-Group Coalescence (Selected automatically)

    Turbulent Collision Rate (Selected automatically)

    Luo Coalescence Efficiency (Selected automatically)

    Optional Models

    Turbulent Dispersion Force

    Virtual Mass Coefficient (Selected automatically)

    Optional Models

    Virtual Mass Force

  3. Click Close.

A length scale is required for interaction area and transfers. The Adaptive Multiple Size-Group Diameter method is the usual and default method for AMUSIG simulations. When this option is selected in a multi-speed simulation, each size-group automatically uses its own group diameter for the drag force and for other interaction models.

The interfacial surface tension between the hexane droplet and the surrounding water is also important. This value is used in the calculation of the Weber number—the ratio of dynamic pressure (due to turbulence) to surface tension. A high Weber number implies a higher breakup rate for the droplets.

  1. Edit the Phase Interaction 1 > Models node and set the following properties:
    Node Property Setting
    Interaction Length Scale > Interaction Length Scale Method Adaptive Multiple Size-Group Diameter
    Multiphase Material > Material Properties > Surface Tension > Constant Value 0.051 N/m


  2. Save the simulation.