Setting Up the Phase Interactions

Phase interactions describe the mutual influence of the two materials (phases) air and water on each other. In this simulation, the continuous phase is water and the dispersed phase is air. The air bubbles have a diameter of 1 mm.

To model drag, you use the Tomiyama drag coefficient method, which is the recommended method when simulating bubbly flows. This method covers a wide range of fluid properties and bubble diameters. It requires gravity to be activated. The method determines the drag force depending on how contaminated the bulk flow is by impurities and provides three levels of system contamination. Additionally, you use the Virtual Mass Force model to account for the work done by rising bubbles to displace the surrounding fluid. To simulate the effects of the interaction between the bubbles and the surrounding turbulent eddies, you use the Turbulent Dispersion model.

To define the phase interactions:

  1. In the Physics 1 continuum, right-click the Models > Multiphase Interaction > Phase Interactions node and select New > Water > Air (Continuous-Dispersed).
  2. Rename the Phase Interaction 1 node to Water-Air.
  3. For the phase interaction Water-Air, select the following models:

    Group Box

    Model

    Optional Models

    Virtual Mass Force

    Virtual Mass Coefficient (selected automatically)

    Turbulent Dispersion Force
  4. Edit the Water-Air > Models node and set the following properties:
    Node Property Setting
    Interaction Length Scale > Interaction Length Scale Method Constant
    Value 0.001 m
    Drag Force > Drag Coefficient Method Tomiyama
    The Tomiyama method automatically activates surface tension force as a material property for the Water-Air phase interaction. The default surface tension value for the water-air interface, 0.072 N/m, is appropriate for this simulation.
  5. Save the simulation.